mpc.c

#include "mpc.h"

/*
 ** State Type
 */

static mpc_state_t mpc_state_invalid(void) {
    mpc_state_t s;
    s.pos = -1;
    s.row = -1;
    s.col = -1;
    return s;
}

static mpc_state_t mpc_state_new(void) {
    mpc_state_t s;
    s.pos = 0;
    s.row = 0;
    s.col = 0;
    return s;
}

static mpc_state_t *mpc_state_copy(mpc_state_t s) {
    mpc_state_t *r = malloc(sizeof(mpc_state_t));
    memcpy(r, &s, sizeof(mpc_state_t));
    return r;
}

/*
 ** Error Type
 */

static mpc_err_t *mpc_err_new(const char *filename, mpc_state_t s, const char *expected, char recieved) {
    mpc_err_t *x = malloc(sizeof(mpc_err_t));
    x->filename = malloc(strlen(filename) + 1);
    strcpy(x->filename, filename);
    x->state = s;
    x->expected_num = 1;
    x->expected = malloc(sizeof(char*));
    x->expected[0] = malloc(strlen(expected) + 1);
    strcpy(x->expected[0], expected);
    x->failure = NULL;
    x->recieved = recieved;
    return x;
}

static mpc_err_t *mpc_err_fail(const char *filename, mpc_state_t s, const char *failure) {
    mpc_err_t *x = malloc(sizeof(mpc_err_t));
    x->filename = malloc(strlen(filename) + 1);
    strcpy(x->filename, filename);
    x->state = s;
    x->expected_num = 0;
    x->expected = NULL;
    x->failure = malloc(strlen(failure) + 1);
    strcpy(x->failure, failure);
    x->recieved = ' ';
    return x;
}

void mpc_err_delete(mpc_err_t *x) {

    int i;
    for (i = 0; i < x->expected_num; i++) {
        free(x->expected[i]);
    }

    free(x->expected);
    free(x->filename);
    free(x->failure);
    free(x);
}

static int mpc_err_contains_expected(mpc_err_t *x, char *expected) {

    int i;
    for (i = 0; i < x->expected_num; i++) {
        if (strcmp(x->expected[i], expected) == 0) { return 1; }
    }

    return 0;
}

static void mpc_err_add_expected(mpc_err_t *x, char *expected) {

    x->expected_num++;
    x->expected = realloc(x->expected, sizeof(char*) * x->expected_num);
    x->expected[x->expected_num-1] = malloc(strlen(expected) + 1);
    strcpy(x->expected[x->expected_num-1], expected);

}

static void mpc_err_clear_expected(mpc_err_t *x, char *expected) {

    int i;
    for (i = 0; i < x->expected_num; i++) {
        free(x->expected[i]);
    }
    x->expected_num = 1;
    x->expected = realloc(x->expected, sizeof(char*) * x->expected_num);
    x->expected[0] = malloc(strlen(expected) + 1);
    strcpy(x->expected[0], expected);

}

void mpc_err_print(mpc_err_t *x) {
    mpc_err_print_to(x, stdout);
}

void mpc_err_print_to(mpc_err_t *x, FILE *f) {
    char *str = mpc_err_string(x);
    fprintf(f, "%s", str);
    free(str);
}

void mpc_err_string_cat(char *buffer, int *pos, int *max, char *fmt, ...) {
    /* TODO: Error Checking on Length */
    int left = ((*max) - (*pos));
    va_list va;
    va_start(va, fmt);
    if (left < 0) { left = 0;}
    (*pos) += vsprintf(buffer + (*pos), fmt, va);
    va_end(va);
}

static char char_unescape_buffer[3];

static char *mpc_err_char_unescape(char c) {

    char_unescape_buffer[0] = '\'';
    char_unescape_buffer[1] = ' ';
    char_unescape_buffer[2] = '\'';

    switch (c) {

        case '\a': return "bell";
        case '\b': return "backspace";
        case '\f': return "formfeed";
        case '\r': return "carriage return";
        case '\v': return "vertical tab";
        case '\0': return "end of input";
        case '\n': return "newline";
        case '\t': return "tab";
        case ' ' : return "space";
        default:
                   char_unescape_buffer[1] = c;
                   return char_unescape_buffer;
    }

}

char *mpc_err_string(mpc_err_t *x) {

    char *buffer = calloc(1, 1024);
    int max = 1023;
    int pos = 0; 
    int i;

    if (x->failure) {
        mpc_err_string_cat(buffer, &pos, &max,
                "%s: error: %s\n", 
                x->filename, x->failure);
        return buffer;
    }

    mpc_err_string_cat(buffer, &pos, &max, 
            "%s:%i:%i: error: expected ", x->filename, x->state.row+1, x->state.col+1);

    if (x->expected_num == 0) { mpc_err_string_cat(buffer, &pos, &max, "ERROR: NOTHING EXPECTED"); }
    if (x->expected_num == 1) { mpc_err_string_cat(buffer, &pos, &max, "%s", x->expected[0]); }
    if (x->expected_num >= 2) {

        for (i = 0; i < x->expected_num-2; i++) {
            mpc_err_string_cat(buffer, &pos, &max, "%s, ", x->expected[i]);
        } 

        mpc_err_string_cat(buffer, &pos, &max, "%s or %s", 
                x->expected[x->expected_num-2], 
                x->expected[x->expected_num-1]);
    }

    mpc_err_string_cat(buffer, &pos, &max, " at ");
    mpc_err_string_cat(buffer, &pos, &max, mpc_err_char_unescape(x->recieved));
    mpc_err_string_cat(buffer, &pos, &max, "\n");

    return realloc(buffer, strlen(buffer) + 1);
}

static mpc_err_t *mpc_err_or(mpc_err_t** x, int n) {

    int i, j;
    mpc_err_t *e = malloc(sizeof(mpc_err_t));
    e->state = mpc_state_invalid();
    e->expected_num = 0;
    e->expected = NULL;
    e->failure = NULL;
    e->filename = malloc(strlen(x[0]->filename)+1);
    strcpy(e->filename, x[0]->filename);

    for (i = 0; i < n; i++) {
        if (x[i]->state.pos > e->state.pos) { e->state = x[i]->state; }
    }

    for (i = 0; i < n; i++) {

        if (x[i]->state.pos < e->state.pos) { continue; }

        if (x[i]->failure) {
            e->failure = malloc(strlen(x[i]->failure)+1);
            strcpy(e->failure, x[i]->failure);
            break;
        }

        e->recieved = x[i]->recieved;

        for (j = 0; j < x[i]->expected_num; j++) {
            if (!mpc_err_contains_expected(e, x[i]->expected[j])) { mpc_err_add_expected(e, x[i]->expected[j]); }
        }
    }

    for (i = 0; i < n; i++) {
        mpc_err_delete(x[i]);
    }

    return e;
}

static mpc_err_t *mpc_err_repeat(mpc_err_t *x, const char *prefix) {

    int i;
    char *expect = malloc(strlen(prefix) + 1);
    strcpy(expect, prefix);

    if (x->expected_num == 1) {
        expect = realloc(expect, strlen(expect) + strlen(x->expected[0]) + 1);
        strcat(expect, x->expected[0]);
    }

    if (x->expected_num > 1) {

        for (i = 0; i < x->expected_num-2; i++) {
            expect = realloc(expect, strlen(expect) + strlen(x->expected[i]) + strlen(", ") + 1);
            strcat(expect, x->expected[i]);
            strcat(expect, ", ");
        }

        expect = realloc(expect, strlen(expect) + strlen(x->expected[x->expected_num-2]) + strlen(" or ") + 1);
        strcat(expect, x->expected[x->expected_num-2]);
        strcat(expect, " or ");
        expect = realloc(expect, strlen(expect) + strlen(x->expected[x->expected_num-1]) + 1);
        strcat(expect, x->expected[x->expected_num-1]);

    }

    mpc_err_clear_expected(x, expect);
    free(expect);

    return x;

}

static mpc_err_t *mpc_err_many1(mpc_err_t *x) {
    return mpc_err_repeat(x, "one or more of ");
}

static mpc_err_t *mpc_err_count(mpc_err_t *x, int n) {
    mpc_err_t *y;
    int digits = n/10 + 1;
    char *prefix = malloc(digits + strlen(" of ") + 1);
    sprintf(prefix, "%i of ", n);
    y = mpc_err_repeat(x, prefix);
    free(prefix);
    return y;
}

/*
 ** Input Type
 */

/*
 ** In mpc the input type has three modes of 
 ** operation: String, File and Pipe.
 **
 ** String is easy. The whole contents are 
 ** loaded into a buffer and scanned through.
 ** The cursor can jump around at will making 
 ** backtracking easy.
 **
 ** The second is a File which is also somewhat
 ** easy. The contents are never loaded into 
 ** memory but backtracking can still be achieved
 ** by seeking in the file at different positions.
 **
 ** The final mode is Pipe. This is the difficult
 ** one. As we assume pipes cannot be seeked - and 
 ** only support a single character lookahead at 
 ** any point, when the input is marked for a 
 ** potential backtracking we start buffering any 
 ** input.
 **
 ** This means that if we are requested to seek
 ** back we can simply start reading from the
 ** buffer instead of the input.
 **
 ** Of course using `mpc_predictive` will disable
 ** backtracking and make LL(1) grammars easy
 ** to parse for all input methods.
 **
 */

enum {
    MPC_INPUT_STRING = 0,
    MPC_INPUT_FILE   = 1,
    MPC_INPUT_PIPE   = 2
};

typedef struct {

    int type;
    char *filename;  
    mpc_state_t state;

    char *string;
    char *buffer;
    FILE *file;

    int backtrack;
    int marks_num;
    mpc_state_t* marks;
    char* lasts;

    char last;

} mpc_input_t;

static mpc_input_t *mpc_input_new_string(const char *filename, const char *string) {

    mpc_input_t *i = malloc(sizeof(mpc_input_t));

    i->filename = malloc(strlen(filename) + 1);
    strcpy(i->filename, filename);
    i->type = MPC_INPUT_STRING;

    i->state = mpc_state_new();

    i->string = malloc(strlen(string) + 1);
    strcpy(i->string, string);
    i->buffer = NULL;
    i->file = NULL;

    i->backtrack = 1;
    i->marks_num = 0;
    i->marks = NULL;
    i->lasts = NULL;

    i->last = '\0';

    return i;
}

static mpc_input_t *mpc_input_new_pipe(const char *filename, FILE *pipe) {

    mpc_input_t *i = malloc(sizeof(mpc_input_t));

    i->filename = malloc(strlen(filename) + 1);
    strcpy(i->filename, filename);

    i->type = MPC_INPUT_PIPE;
    i->state = mpc_state_new();

    i->string = NULL;
    i->buffer = NULL;
    i->file = pipe;

    i->backtrack = 1;
    i->marks_num = 0;
    i->marks = NULL;
    i->lasts = NULL;

    i->last = '\0';

    return i;

}

static mpc_input_t *mpc_input_new_file(const char *filename, FILE *file) {

    mpc_input_t *i = malloc(sizeof(mpc_input_t));

    i->filename = malloc(strlen(filename) + 1);
    strcpy(i->filename, filename);
    i->type = MPC_INPUT_FILE;
    i->state = mpc_state_new();

    i->string = NULL;
    i->buffer = NULL;
    i->file = file;

    i->backtrack = 1;
    i->marks_num = 0;
    i->marks = NULL;
    i->lasts = NULL;

    i->last = '\0';

    return i;
}

static void mpc_input_delete(mpc_input_t *i) {

    free(i->filename);

    if (i->type == MPC_INPUT_STRING) { free(i->string); }
    if (i->type == MPC_INPUT_PIPE) { free(i->buffer); }

    free(i->marks);
    free(i->lasts);
    free(i);
}

static void mpc_input_backtrack_disable(mpc_input_t *i) { i->backtrack--; }
static void mpc_input_backtrack_enable(mpc_input_t *i) { i->backtrack++; }

static void mpc_input_mark(mpc_input_t *i) {

    if (i->backtrack < 1) { return; }

    i->marks_num++;
    i->marks = realloc(i->marks, sizeof(mpc_state_t) * i->marks_num);
    i->lasts = realloc(i->lasts, sizeof(char) * i->marks_num);
    i->marks[i->marks_num-1] = i->state;
    i->lasts[i->marks_num-1] = i->last;

    if (i->type == MPC_INPUT_PIPE && i->marks_num == 1) {
        i->buffer = calloc(1, 1);
    }

}

static void mpc_input_unmark(mpc_input_t *i) {

    if (i->backtrack < 1) { return; }

    i->marks_num--;
    i->marks = realloc(i->marks, sizeof(mpc_state_t) * i->marks_num);
    i->lasts = realloc(i->lasts, sizeof(char) * i->marks_num);

    if (i->type == MPC_INPUT_PIPE && i->marks_num == 0) {
        free(i->buffer);
        i->buffer = NULL;
    }

}

static void mpc_input_rewind(mpc_input_t *i) {

    if (i->backtrack < 1) { return; }

    i->state = i->marks[i->marks_num-1];
    i->last  = i->lasts[i->marks_num-1];

    if (i->type == MPC_INPUT_FILE) {
        fseek(i->file, i->state.pos, SEEK_SET);
    }

    mpc_input_unmark(i);
}

static int mpc_input_buffer_in_range(mpc_input_t *i) {
    return i->state.pos < (strlen(i->buffer) + i->marks[0].pos);
}

static char mpc_input_buffer_get(mpc_input_t *i) {
    return i->buffer[i->state.pos - i->marks[0].pos];
}

static int mpc_input_terminated(mpc_input_t *i) {
    if (i->type == MPC_INPUT_STRING && i->state.pos == strlen(i->string)) { return 1; }
    if (i->type == MPC_INPUT_FILE && feof(i->file)) { return 1; }
    if (i->type == MPC_INPUT_PIPE && feof(i->file)) { return 1; }
    return 0;
}

static char mpc_input_getc(mpc_input_t *i) {

    char c = '\0';

    switch (i->type) {

        case MPC_INPUT_STRING: return i->string[i->state.pos];
        case MPC_INPUT_FILE: c = fgetc(i->file); return c;
        case MPC_INPUT_PIPE:

                             if (!i->buffer) { c = getc(i->file); return c; }

                             if (i->buffer && mpc_input_buffer_in_range(i)) {
                                 c = mpc_input_buffer_get(i);
                                 return c;
                             } else {
                                 c = getc(i->file);
                                 return c;
                             }

        default: return c;
    }
}

static char mpc_input_peekc(mpc_input_t *i) {

    char c = '\0';

    switch (i->type) {
        case MPC_INPUT_STRING: return i->string[i->state.pos];
        case MPC_INPUT_FILE: 

                               c = fgetc(i->file);
                               if (feof(i->file)) { return '\0'; }

                               fseek(i->file, -1, SEEK_CUR);
                               return c;

        case MPC_INPUT_PIPE:

                               if (!i->buffer) {
                                   c = getc(i->file);
                                   if (feof(i->file)) { return '\0'; }
                                   ungetc(c, i->file);
                                   return c;
                               }

                               if (i->buffer && mpc_input_buffer_in_range(i)) {
                                   return mpc_input_buffer_get(i);
                               } else {
                                   c = getc(i->file);
                                   if (feof(i->file)) { return '\0'; }
                                   ungetc(c, i->file);
                                   return c;
                               }

        default: return c;
    }

}

static int mpc_input_failure(mpc_input_t *i, char c) {

    switch (i->type) {
        case MPC_INPUT_STRING: break;
        case MPC_INPUT_FILE: fseek(i->file, -1, SEEK_CUR); break;
        case MPC_INPUT_PIPE:

                             if (!i->buffer) { ungetc(c, i->file); break; }

                             if (i->buffer && mpc_input_buffer_in_range(i)) {
                                 break;
                             } else {
                                 ungetc(c, i->file); 
                             }

    }

    return 0;
}

static int mpc_input_success(mpc_input_t *i, char c, char **o) {

    if (i->type == MPC_INPUT_PIPE &&
            i->buffer &&
            !mpc_input_buffer_in_range(i)) {

        i->buffer = realloc(i->buffer, strlen(i->buffer) + 2);
        i->buffer[strlen(i->buffer) + 1] = '\0';
        i->buffer[strlen(i->buffer) + 0] = c;
    }

    i->last = c;
    i->state.pos++;
    i->state.col++;

    if (c == '\n') {
        i->state.col = 0;
        i->state.row++;
    }

    if (o) {
        (*o) = malloc(2);
        (*o)[0] = c;
        (*o)[1] = '\0';
    }

    return 1;
}

static int mpc_input_any(mpc_input_t *i, char **o) {
    char x = mpc_input_getc(i);
    if (mpc_input_terminated(i)) { return 0; }
    return mpc_input_success(i, x, o);
}

static int mpc_input_char(mpc_input_t *i, char c, char **o) {
    char x = mpc_input_getc(i);
    if (mpc_input_terminated(i)) { return 0; }
    return x == c ? mpc_input_success(i, x, o) : mpc_input_failure(i, x);
}

static int mpc_input_range(mpc_input_t *i, char c, char d, char **o) {
    char x = mpc_input_getc(i);
    if (mpc_input_terminated(i)) { return 0; }
    return x >= c && x <= d ? mpc_input_success(i, x, o) : mpc_input_failure(i, x);  
}

static int mpc_input_oneof(mpc_input_t *i, const char *c, char **o) {
    char x = mpc_input_getc(i);
    if (mpc_input_terminated(i)) { return 0; }
    return strchr(c, x) != 0 ? mpc_input_success(i, x, o) : mpc_input_failure(i, x);  
}

static int mpc_input_noneof(mpc_input_t *i, const char *c, char **o) {
    char x = mpc_input_getc(i);
    if (mpc_input_terminated(i)) { return 0; }
    return strchr(c, x) == 0 ? mpc_input_success(i, x, o) : mpc_input_failure(i, x);  
}

static int mpc_input_satisfy(mpc_input_t *i, int(*cond)(char), char **o) {
    char x = mpc_input_getc(i);
    if (mpc_input_terminated(i)) { return 0; }
    return cond(x) ? mpc_input_success(i, x, o) : mpc_input_failure(i, x);  
}

static int mpc_input_string(mpc_input_t *i, const char *c, char **o) {

    char *co = NULL;
    const char *x = c;

    mpc_input_mark(i);
    while (*x) {
        if (mpc_input_char(i, *x, &co)) {
            free(co);
        } else {
            mpc_input_rewind(i);
            return 0;
        }
        x++;
    }
    mpc_input_unmark(i);

    *o = malloc(strlen(c) + 1);
    strcpy(*o, c);
    return 1;
}

static int mpc_input_anchor(mpc_input_t* i, int(*f)(char,char)) {
    return f(i->last, mpc_input_peekc(i));
}

/*
 ** Parser Type
 */

enum {
    MPC_TYPE_UNDEFINED = 0,
    MPC_TYPE_PASS      = 1,
    MPC_TYPE_FAIL      = 2,
    MPC_TYPE_LIFT      = 3,
    MPC_TYPE_LIFT_VAL  = 4,
    MPC_TYPE_EXPECT    = 5,
    MPC_TYPE_ANCHOR    = 6,
    MPC_TYPE_STATE     = 7,

    MPC_TYPE_ANY       = 8,
    MPC_TYPE_SINGLE    = 9,
    MPC_TYPE_ONEOF     = 10,
    MPC_TYPE_NONEOF    = 11,
    MPC_TYPE_RANGE     = 12,
    MPC_TYPE_SATISFY   = 13,
    MPC_TYPE_STRING    = 14,

    MPC_TYPE_APPLY     = 15,
    MPC_TYPE_APPLY_TO  = 16,
    MPC_TYPE_PREDICT   = 17,
    MPC_TYPE_NOT       = 18,
    MPC_TYPE_MAYBE     = 19,
    MPC_TYPE_MANY      = 20,
    MPC_TYPE_MANY1     = 21,
    MPC_TYPE_COUNT     = 22,

    MPC_TYPE_OR        = 23,
    MPC_TYPE_AND       = 24
};

typedef struct { char *m; } mpc_pdata_fail_t;
typedef struct { mpc_ctor_t lf; void *x; } mpc_pdata_lift_t;
typedef struct { mpc_parser_t *x; char *m; } mpc_pdata_expect_t;
typedef struct { int(*f)(char,char); } mpc_pdata_anchor_t;
typedef struct { char x; } mpc_pdata_single_t;
typedef struct { char x; char y; } mpc_pdata_range_t;
typedef struct { int(*f)(char); } mpc_pdata_satisfy_t;
typedef struct { char *x; } mpc_pdata_string_t;
typedef struct { mpc_parser_t *x; mpc_apply_t f; } mpc_pdata_apply_t;
typedef struct { mpc_parser_t *x; mpc_apply_to_t f; void *d; } mpc_pdata_apply_to_t;
typedef struct { mpc_parser_t *x; } mpc_pdata_predict_t;
typedef struct { mpc_parser_t *x; mpc_dtor_t dx; mpc_ctor_t lf; } mpc_pdata_not_t;
typedef struct { int n; mpc_fold_t f; mpc_parser_t *x; mpc_dtor_t dx; } mpc_pdata_repeat_t;
typedef struct { int n; mpc_parser_t **xs; } mpc_pdata_or_t;
typedef struct { int n; mpc_fold_t f; mpc_parser_t **xs; mpc_dtor_t *dxs;  } mpc_pdata_and_t;

typedef union {
    mpc_pdata_fail_t fail;
    mpc_pdata_lift_t lift;
    mpc_pdata_expect_t expect;
    mpc_pdata_anchor_t anchor;
    mpc_pdata_single_t single;
    mpc_pdata_range_t range;
    mpc_pdata_satisfy_t satisfy;
    mpc_pdata_string_t string;
    mpc_pdata_apply_t apply;
    mpc_pdata_apply_to_t apply_to;
    mpc_pdata_predict_t predict;
    mpc_pdata_not_t not;
    mpc_pdata_repeat_t repeat;
    mpc_pdata_and_t and;
    mpc_pdata_or_t or;
} mpc_pdata_t;

struct mpc_parser_t {
    char retained;
    char *name;
    char type;
    mpc_pdata_t data;
};

/*
 ** Stack Type
 */

typedef struct {

    int parsers_num;
    int parsers_slots;
    mpc_parser_t **parsers;
    int *states;

    int results_num;
    int results_slots;
    mpc_result_t *results;
    int *returns;

    mpc_err_t *err;

} mpc_stack_t;

static mpc_stack_t *mpc_stack_new(const char *filename) {
    mpc_stack_t *s = malloc(sizeof(mpc_stack_t));

    s->parsers_num = 0;
    s->parsers_slots = 0;
    s->parsers = NULL;
    s->states = NULL;

    s->results_num = 0;
    s->results_slots = 0;
    s->results = NULL;
    s->returns = NULL;

    s->err = mpc_err_fail(filename, mpc_state_invalid(), "Unknown Error");

    return s;
}

static void mpc_stack_err(mpc_stack_t *s, mpc_err_t* e) {
    mpc_err_t *errs[2];
    errs[0] = s->err;
    errs[1] = e;
    s->err = mpc_err_or(errs, 2);
}

static int mpc_stack_terminate(mpc_stack_t *s, mpc_result_t *r) {
    int success = s->returns[0];

    if (success) {
        r->output = s->results[0].output;
        mpc_err_delete(s->err);
    } else {
        mpc_stack_err(s, s->results[0].error);
        r->error = s->err;
    }

    free(s->parsers);
    free(s->states);
    free(s->results);
    free(s->returns);
    free(s);

    return success;
}

/* Stack Parser Stuff */

static void mpc_stack_set_state(mpc_stack_t *s, int x) {
    s->states[s->parsers_num-1] = x;
}

static void mpc_stack_parsers_reserve_more(mpc_stack_t *s) {
    if (s->parsers_num > s->parsers_slots) {
        s->parsers_slots = ceil((s->parsers_slots+1) * 1.5);
        s->parsers = realloc(s->parsers, sizeof(mpc_parser_t*) * s->parsers_slots);
        s->states = realloc(s->states, sizeof(int) * s->parsers_slots);
    }
}

static void mpc_stack_parsers_reserve_less(mpc_stack_t *s) {
    if (s->parsers_slots > pow(s->parsers_num+1, 1.5)) {
        s->parsers_slots = floor((s->parsers_slots-1) * (1.0/1.5));
        s->parsers = realloc(s->parsers, sizeof(mpc_parser_t*) * s->parsers_slots);
        s->states = realloc(s->states, sizeof(int) * s->parsers_slots);
    }
}

static void mpc_stack_pushp(mpc_stack_t *s, mpc_parser_t *p) {
    s->parsers_num++;
    mpc_stack_parsers_reserve_more(s);
    s->parsers[s->parsers_num-1] = p;
    s->states[s->parsers_num-1] = 0;
}

static void mpc_stack_popp(mpc_stack_t *s, mpc_parser_t **p, int *st) {
    *p = s->parsers[s->parsers_num-1];
    *st = s->states[s->parsers_num-1];
    s->parsers_num--;
    mpc_stack_parsers_reserve_less(s);
}

static void mpc_stack_peepp(mpc_stack_t *s, mpc_parser_t **p, int *st) {
    *p = s->parsers[s->parsers_num-1];
    *st = s->states[s->parsers_num-1];
}

static int mpc_stack_empty(mpc_stack_t *s) {
    return s->parsers_num == 0;
}

/* Stack Result Stuff */

static mpc_result_t mpc_result_err(mpc_err_t *e) {
    mpc_result_t r;
    r.error = e;
    return r;
}

static mpc_result_t mpc_result_out(mpc_val_t *x) {
    mpc_result_t r;
    r.output = x;
    return r;
}

static void mpc_stack_results_reserve_more(mpc_stack_t *s) {
    if (s->results_num > s->results_slots) {
        s->results_slots = ceil((s->results_slots + 1) * 1.5);
        s->results = realloc(s->results, sizeof(mpc_result_t) * s->results_slots);
        s->returns = realloc(s->returns, sizeof(int) * s->results_slots);
    }
}

static void mpc_stack_results_reserve_less(mpc_stack_t *s) {
    if ( s->results_slots > pow(s->results_num+1, 1.5)) {
        s->results_slots = floor((s->results_slots-1) * (1.0/1.5));
        s->results = realloc(s->results, sizeof(mpc_result_t) * s->results_slots);
        s->returns = realloc(s->returns, sizeof(int) * s->results_slots);
    }
}

static void mpc_stack_pushr(mpc_stack_t *s, mpc_result_t x, int r) {
    s->results_num++;
    mpc_stack_results_reserve_more(s);
    s->results[s->results_num-1] = x;
    s->returns[s->results_num-1] = r;
}

static int mpc_stack_popr(mpc_stack_t *s, mpc_result_t *x) {
    int r;
    *x = s->results[s->results_num-1];
    r = s->returns[s->results_num-1];
    s->results_num--;
    mpc_stack_results_reserve_less(s);
    return r;
}

static int mpc_stack_peekr(mpc_stack_t *s, mpc_result_t *x) {
    *x = s->results[s->results_num-1];
    return s->returns[s->results_num-1];
}

static void mpc_stack_popr_err(mpc_stack_t *s, int n) {
    mpc_result_t x;
    while (n) {
        mpc_stack_popr(s, &x);
        mpc_stack_err(s, x.error);
        n--;
    }
}

static void mpc_stack_popr_out(mpc_stack_t *s, int n, mpc_dtor_t *ds) {
    mpc_result_t x;
    while (n) {
        mpc_stack_popr(s, &x);
        ds[n-1](x.output);
        n--;
    }
}

static void mpc_stack_popr_out_single(mpc_stack_t *s, int n, mpc_dtor_t dx) {
    mpc_result_t x;
    while (n) {
        mpc_stack_popr(s, &x);
        dx(x.output);
        n--;
    }
}

static void mpc_stack_popr_n(mpc_stack_t *s, int n) {
    mpc_result_t x;
    while (n) {
        mpc_stack_popr(s, &x);
        n--;
    }
}

static mpc_val_t *mpc_stack_merger_out(mpc_stack_t *s, int n, mpc_fold_t f) {
    mpc_val_t *x = f(n, (mpc_val_t**)(&s->results[s->results_num-n]));
    mpc_stack_popr_n(s, n);
    return x;
}

static mpc_err_t *mpc_stack_merger_err(mpc_stack_t *s, int n) {
    mpc_err_t *x = mpc_err_or((mpc_err_t**)(&s->results[s->results_num-n]), n);
    mpc_stack_popr_n(s, n);
    return x;
}

/*
 ** This is rather pleasant. The core parsing routine
 ** is written in about 200 lines of C.
 **
 ** I also love the way in which each parsing type
 ** concisely matches some construct or pattern.
 **
 ** Particularly nice are the `or` and `and`
 ** types which have a broken but mirrored structure
 ** with return value and error reflected.
 **
 ** When this function was written in recursive form
 ** it looked pretty nice. But I've since switched
 ** it around to an awkward while loop. It was an
 ** unfortunate change for code simplicity but it
 ** is noble in the name of performance (and 
 ** not smashing the stack).
 **
 ** But it is now a pretty ugly beast...
 */

#define MPC_CONTINUE(st, x) mpc_stack_set_state(stk, st); mpc_stack_pushp(stk, x); continue
#define MPC_SUCCESS(x) mpc_stack_popp(stk, &p, &st); mpc_stack_pushr(stk, mpc_result_out(x), 1); continue
#define MPC_FAILURE(x) mpc_stack_popp(stk, &p, &st); mpc_stack_pushr(stk, mpc_result_err(x), 0); continue
#define MPC_PRIMATIVE(x, f) if (f) { MPC_SUCCESS(x); } else { MPC_FAILURE(mpc_err_fail(i->filename, i->state, "Incorrect Input")); }

int mpc_parse_input(mpc_input_t *i, mpc_parser_t *init, mpc_result_t *final) {

    /* Stack */
    int st = 0;
    mpc_parser_t *p = NULL;
    mpc_stack_t *stk = mpc_stack_new(i->filename);

    /* Variables */
    char *s;
    mpc_result_t r;

    /* Go! */
    mpc_stack_pushp(stk, init);

    while (!mpc_stack_empty(stk)) {

        mpc_stack_peepp(stk, &p, &st);

        switch (p->type) {

            /* Basic Parsers */

            case MPC_TYPE_ANY:       MPC_PRIMATIVE(s, mpc_input_any(i, &s));
            case MPC_TYPE_SINGLE:    MPC_PRIMATIVE(s, mpc_input_char(i, p->data.single.x, &s));
            case MPC_TYPE_RANGE:     MPC_PRIMATIVE(s, mpc_input_range(i, p->data.range.x, p->data.range.y, &s));
            case MPC_TYPE_ONEOF:     MPC_PRIMATIVE(s, mpc_input_oneof(i, p->data.string.x, &s));
            case MPC_TYPE_NONEOF:    MPC_PRIMATIVE(s, mpc_input_noneof(i, p->data.string.x, &s));
            case MPC_TYPE_SATISFY:   MPC_PRIMATIVE(s, mpc_input_satisfy(i, p->data.satisfy.f, &s));
            case MPC_TYPE_STRING:    MPC_PRIMATIVE(s, mpc_input_string(i, p->data.string.x, &s));

                                     /* Other parsers */

            case MPC_TYPE_UNDEFINED: MPC_FAILURE(mpc_err_fail(i->filename, i->state, "Parser Undefined!"));      
            case MPC_TYPE_PASS:      MPC_SUCCESS(NULL);
            case MPC_TYPE_FAIL:      MPC_FAILURE(mpc_err_fail(i->filename, i->state, p->data.fail.m));
            case MPC_TYPE_LIFT:      MPC_SUCCESS(p->data.lift.lf());
            case MPC_TYPE_LIFT_VAL:  MPC_SUCCESS(p->data.lift.x);
            case MPC_TYPE_STATE:     MPC_SUCCESS(mpc_state_copy(i->state));

            case MPC_TYPE_ANCHOR:
                                     if (mpc_input_anchor(i, p->data.anchor.f)) {
                                         MPC_SUCCESS(NULL);
                                     } else {
                                         MPC_FAILURE(mpc_err_new(i->filename, i->state, "anchor", mpc_input_peekc(i)));
                                     }

                                     /* Application Parsers */

            case MPC_TYPE_EXPECT:
                                     if (st == 0) { MPC_CONTINUE(1, p->data.expect.x); }
                                     if (st == 1) {
                                         if (mpc_stack_popr(stk, &r)) {
                                             MPC_SUCCESS(r.output);
                                         } else {
                                             mpc_err_delete(r.error); 
                                             MPC_FAILURE(mpc_err_new(i->filename, i->state, p->data.expect.m, mpc_input_peekc(i)));
                                         }
                                     }

            case MPC_TYPE_APPLY:
                                     if (st == 0) { MPC_CONTINUE(1, p->data.apply.x); }
                                     if (st == 1) {
                                         if (mpc_stack_popr(stk, &r)) {
                                             MPC_SUCCESS(p->data.apply.f(r.output));
                                         } else {
                                             MPC_FAILURE(r.error);
                                         }
                                     }

            case MPC_TYPE_APPLY_TO:
                                     if (st == 0) { MPC_CONTINUE(1, p->data.apply_to.x); }
                                     if (st == 1) {
                                         if (mpc_stack_popr(stk, &r)) {
                                             MPC_SUCCESS(p->data.apply_to.f(r.output, p->data.apply_to.d));
                                         } else {
                                             MPC_FAILURE(r.error);
                                         }
                                     }

            case MPC_TYPE_PREDICT:
                                     if (st == 0) { mpc_input_backtrack_disable(i); MPC_CONTINUE(1, p->data.predict.x); }
                                     if (st == 1) {
                                         mpc_input_backtrack_enable(i);
                                         mpc_stack_popp(stk, &p, &st);
                                         continue;
                                     }

                                     /* Optional Parsers */

                                     /* TODO: Update Not Error Message */

            case MPC_TYPE_NOT:
                                     if (st == 0) { mpc_input_mark(i); MPC_CONTINUE(1, p->data.not.x); }
                                     if (st == 1) {
                                         if (mpc_stack_popr(stk, &r)) {
                                             mpc_input_rewind(i);
                                             p->data.not.dx(r.output);
                                             MPC_FAILURE(mpc_err_new(i->filename, i->state, "opposite", mpc_input_peekc(i)));
                                         } else {
                                             mpc_input_unmark(i);
                                             mpc_stack_err(stk, r.error);
                                             MPC_SUCCESS(p->data.not.lf());
                                         }
                                     }

            case MPC_TYPE_MAYBE:
                                     if (st == 0) { MPC_CONTINUE(1, p->data.not.x); }
                                     if (st == 1) {
                                         if (mpc_stack_popr(stk, &r)) {
                                             MPC_SUCCESS(r.output);
                                         } else {
                                             mpc_stack_err(stk, r.error);
                                             MPC_SUCCESS(p->data.not.lf());
                                         }
                                     }

                                     /* Repeat Parsers */

            case MPC_TYPE_MANY:
                                     if (st == 0) { MPC_CONTINUE(st+1, p->data.repeat.x); }
                                     if (st >  0) {
                                         if (mpc_stack_peekr(stk, &r)) {
                                             MPC_CONTINUE(st+1, p->data.repeat.x);
                                         } else {
                                             mpc_stack_popr(stk, &r);
                                             mpc_stack_err(stk, r.error);
                                             MPC_SUCCESS(mpc_stack_merger_out(stk, st-1, p->data.repeat.f));
                                         }
                                     }

            case MPC_TYPE_MANY1:
                                     if (st == 0) { MPC_CONTINUE(st+1, p->data.repeat.x); }
                                     if (st >  0) {
                                         if (mpc_stack_peekr(stk, &r)) {
                                             MPC_CONTINUE(st+1, p->data.repeat.x);
                                         } else {
                                             if (st == 1) {
                                                 mpc_stack_popr(stk, &r);
                                                 MPC_FAILURE(mpc_err_many1(r.error));
                                             } else {
                                                 mpc_stack_popr(stk, &r);
                                                 mpc_stack_err(stk, r.error);
                                                 MPC_SUCCESS(mpc_stack_merger_out(stk, st-1, p->data.repeat.f));
                                             }
                                         }
                                     }

            case MPC_TYPE_COUNT:
                                     if (st == 0) { mpc_input_mark(i); MPC_CONTINUE(st+1, p->data.repeat.x); }
                                     if (st >  0) {
                                         if (mpc_stack_peekr(stk, &r)) {
                                             MPC_CONTINUE(st+1, p->data.repeat.x);
                                         } else {
                                             if (st != (p->data.repeat.n+1)) {
                                                 mpc_stack_popr(stk, &r);
                                                 mpc_stack_popr_out_single(stk, st-1, p->data.repeat.dx);
                                                 mpc_input_rewind(i);
                                                 MPC_FAILURE(mpc_err_count(r.error, p->data.repeat.n));
                                             } else {
                                                 mpc_stack_popr(stk, &r);
                                                 mpc_stack_err(stk, r.error);
                                                 mpc_input_unmark(i);
                                                 MPC_SUCCESS(mpc_stack_merger_out(stk, st-1, p->data.repeat.f));
                                             }
                                         }
                                     }

                                     /* Combinatory Parsers */

            case MPC_TYPE_OR:

                                     if (p->data.or.n == 0) { MPC_SUCCESS(NULL); }

                                     if (st == 0) { MPC_CONTINUE(st+1, p->data.or.xs[st]); }
                                     if (st <= p->data.or.n) {
                                         if (mpc_stack_peekr(stk, &r)) {
                                             mpc_stack_popr(stk, &r);
                                             mpc_stack_popr_err(stk, st-1);
                                             MPC_SUCCESS(r.output);
                                         }
                                         if (st <  p->data.or.n) { MPC_CONTINUE(st+1, p->data.or.xs[st]); }
                                         if (st == p->data.or.n) { MPC_FAILURE(mpc_stack_merger_err(stk, p->data.or.n)); }
                                     }

            case MPC_TYPE_AND:

                                     if (p->data.or.n == 0) { MPC_SUCCESS(p->data.and.f(0, NULL)); }

                                     if (st == 0) { mpc_input_mark(i); MPC_CONTINUE(st+1, p->data.and.xs[st]); }
                                     if (st <= p->data.and.n) {
                                         if (!mpc_stack_peekr(stk, &r)) {
                                             mpc_input_rewind(i);
                                             mpc_stack_popr(stk, &r);
                                             mpc_stack_popr_out(stk, st-1, p->data.and.dxs);
                                             MPC_FAILURE(r.error);
                                         }
                                         if (st <  p->data.and.n) { MPC_CONTINUE(st+1, p->data.and.xs[st]); }
                                         if (st == p->data.and.n) { mpc_input_unmark(i); MPC_SUCCESS(mpc_stack_merger_out(stk, p->data.and.n, p->data.and.f)); }
                                     }

                                     /* End */

            default:

                                     MPC_FAILURE(mpc_err_fail(i->filename, i->state, "Unknown Parser Type Id!"));
        }
    }

    return mpc_stack_terminate(stk, final);

}

#undef MPC_CONTINUE
#undef MPC_SUCCESS
#undef MPC_FAILURE
#undef MPC_PRIMATIVE

int mpc_parse(const char *filename, const char *string, mpc_parser_t *p, mpc_result_t *r) {
    int x;
    mpc_input_t *i = mpc_input_new_string(filename, string);
    x = mpc_parse_input(i, p, r);
    mpc_input_delete(i);
    return x;
}

int mpc_parse_file(const char *filename, FILE *file, mpc_parser_t *p, mpc_result_t *r) {
    int x;
    mpc_input_t *i = mpc_input_new_file(filename, file);
    x = mpc_parse_input(i, p, r);
    mpc_input_delete(i);
    return x;
}

int mpc_parse_pipe(const char *filename, FILE *pipe, mpc_parser_t *p, mpc_result_t *r) {
    int x;
    mpc_input_t *i = mpc_input_new_pipe(filename, pipe);
    x = mpc_parse_input(i, p, r);
    mpc_input_delete(i);
    return x;
}

int mpc_parse_contents(const char *filename, mpc_parser_t *p, mpc_result_t *r) {

    FILE *f = fopen(filename, "rb");
    int res;

    if (f == NULL) {
        r->output = NULL;
        r->error = mpc_err_fail(filename, mpc_state_new(), "Unable to open file!");
        return 0;
    }

    res = mpc_parse_file(filename, f, p, r);
    fclose(f);
    return res;
}

/*
 ** Building a Parser
 */

static void mpc_undefine_unretained(mpc_parser_t *p, int force);

static void mpc_undefine_or(mpc_parser_t *p) {

    int i;
    for (i = 0; i < p->data.or.n; i++) {
        mpc_undefine_unretained(p->data.or.xs[i], 0);
    }
    free(p->data.or.xs);

}

static void mpc_undefine_and(mpc_parser_t *p) {

    int i;
    for (i = 0; i < p->data.and.n; i++) {
        mpc_undefine_unretained(p->data.and.xs[i], 0);
    }
    free(p->data.and.xs);
    free(p->data.and.dxs);

}

static void mpc_undefine_unretained(mpc_parser_t *p, int force) {

    if (p->retained && !force) { return; }

    switch (p->type) {

        case MPC_TYPE_FAIL: free(p->data.fail.m); break;

        case MPC_TYPE_ONEOF: 
        case MPC_TYPE_NONEOF:
        case MPC_TYPE_STRING:
                            free(p->data.string.x); 
                            break;

        case MPC_TYPE_APPLY:    mpc_undefine_unretained(p->data.apply.x, 0);    break;
        case MPC_TYPE_APPLY_TO: mpc_undefine_unretained(p->data.apply_to.x, 0); break;
        case MPC_TYPE_PREDICT:  mpc_undefine_unretained(p->data.predict.x, 0);  break;

        case MPC_TYPE_MAYBE:
        case MPC_TYPE_NOT:
                                mpc_undefine_unretained(p->data.not.x, 0);
                                break;

        case MPC_TYPE_EXPECT:
                                mpc_undefine_unretained(p->data.expect.x, 0);
                                free(p->data.expect.m);
                                break;

        case MPC_TYPE_MANY:
        case MPC_TYPE_MANY1:
        case MPC_TYPE_COUNT:
                                mpc_undefine_unretained(p->data.repeat.x, 0);
                                break;

        case MPC_TYPE_OR:  mpc_undefine_or(p);  break;
        case MPC_TYPE_AND: mpc_undefine_and(p); break;

        default: break;
    }

    if (!force) {
        free(p->name);
        free(p);
    }

}

void mpc_delete(mpc_parser_t *p) {
    if (p->retained) {

        if (p->type != MPC_TYPE_UNDEFINED) {
            mpc_undefine_unretained(p, 0);
        } 

        free(p->name);
        free(p);

    } else {
        mpc_undefine_unretained(p, 0);  
    }
}

static void mpc_soft_delete(mpc_val_t *x) {
    mpc_undefine_unretained(x, 0);
}

static mpc_parser_t *mpc_undefined(void) {
    mpc_parser_t *p = calloc(1, sizeof(mpc_parser_t));
    p->retained = 0;
    p->type = MPC_TYPE_UNDEFINED;
    p->name = NULL;
    return p;
}

mpc_parser_t *mpc_new(const char *name) {
    mpc_parser_t *p = mpc_undefined();
    p->retained = 1;
    p->name = realloc(p->name, strlen(name) + 1);
    strcpy(p->name, name);
    return p;
}

mpc_parser_t *mpc_undefine(mpc_parser_t *p) {
    mpc_undefine_unretained(p, 1);
    p->type = MPC_TYPE_UNDEFINED;
    return p;
}

mpc_parser_t *mpc_define(mpc_parser_t *p, mpc_parser_t *a) {

    if (p->retained) {
        p->type = a->type;
        p->data = a->data;
    } else {
        mpc_parser_t *a2 = mpc_failf("Attempt to assign to Unretained Parser!");
        p->type = a2->type;
        p->data = a2->data;
        free(a2);
    }

    free(a);
    return p;  
}

void mpc_cleanup(int n, ...) {
    int i;
    mpc_parser_t **list = malloc(sizeof(mpc_parser_t*) * n);

    va_list va;
    va_start(va, n);
    for (i = 0; i < n; i++) { list[i] = va_arg(va, mpc_parser_t*); }
    for (i = 0; i < n; i++) { mpc_undefine(list[i]); }
    for (i = 0; i < n; i++) { mpc_delete(list[i]); }  
    va_end(va);  

    free(list);
}

mpc_parser_t *mpc_pass(void) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_PASS;
    return p;
}

mpc_parser_t *mpc_fail(const char *m) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_FAIL;
    p->data.fail.m = malloc(strlen(m) + 1);
    strcpy(p->data.fail.m, m);
    return p;
}

/*
 ** As `snprintf` is not ANSI standard this 
 ** function `mpc_failf` should be considered
 ** unsafe.
 **
 ** You have a few options if this is going to be
 ** trouble.
 **
 ** - Ensure the format string does not exceed
 **   the buffer length using precision specifiers
 **   such as `%.512s`.
 **
 ** - Patch this function in your code base to 
 **   use `snprintf` or whatever variant your
 **   system supports.
 **
 ** - Avoid it altogether.
 **
 */

mpc_parser_t *mpc_failf(const char *fmt, ...) {

    va_list va;
    char *buffer;

    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_FAIL;

    va_start(va, fmt);
    buffer = malloc(2048);
    vsprintf(buffer, fmt, va);
    va_end(va);

    buffer = realloc(buffer, strlen(buffer) + 1);
    p->data.fail.m = buffer;
    return p;

}

mpc_parser_t *mpc_lift_val(mpc_val_t *x) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_LIFT_VAL;
    p->data.lift.x = x;
    return p;
}

mpc_parser_t *mpc_lift(mpc_ctor_t lf) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_LIFT;
    p->data.lift.lf = lf;
    return p;
}

mpc_parser_t *mpc_anchor(int(*f)(char,char)) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_ANCHOR;
    p->data.anchor.f = f;
    return p;
}

mpc_parser_t *mpc_state(void) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_STATE;
    return p;
}

mpc_parser_t *mpc_expect(mpc_parser_t *a, const char *expected) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_EXPECT;
    p->data.expect.x = a;
    p->data.expect.m = malloc(strlen(expected) + 1);
    strcpy(p->data.expect.m, expected);
    return p;
}

/*
 ** As `snprintf` is not ANSI standard this 
 ** function `mpc_expectf` should be considered
 ** unsafe.
 **
 ** You have a few options if this is going to be
 ** trouble.
 **
 ** - Ensure the format string does not exceed
 **   the buffer length using precision specifiers
 **   such as `%.512s`.
 **
 ** - Patch this function in your code base to 
 **   use `snprintf` or whatever variant your
 **   system supports.
 **
 ** - Avoid it altogether.
 **
 */

mpc_parser_t *mpc_expectf(mpc_parser_t *a, const char *fmt, ...) {
    va_list va;
    char *buffer;

    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_EXPECT;

    va_start(va, fmt);
    buffer = malloc(2048);
    vsprintf(buffer, fmt, va);
    va_end(va);

    buffer = realloc(buffer, strlen(buffer) + 1);
    p->data.expect.x = a;
    p->data.expect.m = buffer;
    return p;
}

/*
 ** Basic Parsers
 */

mpc_parser_t *mpc_any(void) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_ANY;
    return mpc_expect(p, "any character");
}

mpc_parser_t *mpc_char(char c) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_SINGLE;
    p->data.single.x = c;
    return mpc_expectf(p, "'%c'", c);
}

mpc_parser_t *mpc_range(char s, char e) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_RANGE;
    p->data.range.x = s;
    p->data.range.y = e;
    return mpc_expectf(p, "character between '%c' and '%c'", s, e);
}

mpc_parser_t *mpc_oneof(const char *s) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_ONEOF;
    p->data.string.x = malloc(strlen(s) + 1);
    strcpy(p->data.string.x, s);
    return mpc_expectf(p, "one of '%s'", s);
}

mpc_parser_t *mpc_noneof(const char *s) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_NONEOF;
    p->data.string.x = malloc(strlen(s) + 1);
    strcpy(p->data.string.x, s);
    return mpc_expectf(p, "one of '%s'", s);

}

mpc_parser_t *mpc_satisfy(int(*f)(char)) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_SATISFY;
    p->data.satisfy.f = f;
    return mpc_expectf(p, "character satisfying function %p", f);
}

mpc_parser_t *mpc_string(const char *s) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_STRING;
    p->data.string.x = malloc(strlen(s) + 1);
    strcpy(p->data.string.x, s);
    return mpc_expectf(p, "\"%s\"", s);
}

/*
 ** Core Parsers
 */

mpc_parser_t *mpc_apply(mpc_parser_t *a, mpc_apply_t f) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_APPLY;
    p->data.apply.x = a;
    p->data.apply.f = f;
    return p;
}

mpc_parser_t *mpc_apply_to(mpc_parser_t *a, mpc_apply_to_t f, void *x) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_APPLY_TO;
    p->data.apply_to.x = a;
    p->data.apply_to.f = f;
    p->data.apply_to.d = x;
    return p;
}

mpc_parser_t *mpc_predictive(mpc_parser_t *a) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_PREDICT;
    p->data.predict.x = a;
    return p;
}

mpc_parser_t *mpc_not_lift(mpc_parser_t *a, mpc_dtor_t da, mpc_ctor_t lf) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_NOT;
    p->data.not.x = a;
    p->data.not.dx = da;
    p->data.not.lf = lf;
    return p;
}

mpc_parser_t *mpc_not(mpc_parser_t *a, mpc_dtor_t da) {
    return mpc_not_lift(a, da, mpcf_ctor_null);
}

mpc_parser_t *mpc_maybe_lift(mpc_parser_t *a, mpc_ctor_t lf) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_MAYBE;
    p->data.not.x = a;
    p->data.not.lf = lf;
    return p;
}

mpc_parser_t *mpc_maybe(mpc_parser_t *a) {
    return mpc_maybe_lift(a, mpcf_ctor_null);
}

mpc_parser_t *mpc_many(mpc_fold_t f, mpc_parser_t *a) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_MANY;
    p->data.repeat.x = a;
    p->data.repeat.f = f;
    return p;
}

mpc_parser_t *mpc_many1(mpc_fold_t f, mpc_parser_t *a) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_MANY1;
    p->data.repeat.x = a;
    p->data.repeat.f = f;
    return p;
}

mpc_parser_t *mpc_count(int n, mpc_fold_t f, mpc_parser_t *a, mpc_dtor_t da) {
    mpc_parser_t *p = mpc_undefined();
    p->type = MPC_TYPE_COUNT;
    p->data.repeat.n = n;
    p->data.repeat.f = f;
    p->data.repeat.x = a;
    p->data.repeat.dx = da;
    return p;
}

mpc_parser_t *mpc_or(int n, ...) {

    int i;
    va_list va;

    mpc_parser_t *p = mpc_undefined();

    p->type = MPC_TYPE_OR;
    p->data.or.n = n;
    p->data.or.xs = malloc(sizeof(mpc_parser_t*) * n);

    va_start(va, n);  
    for (i = 0; i < n; i++) {
        p->data.or.xs[i] = va_arg(va, mpc_parser_t*);
    }
    va_end(va);

    return p;
}

mpc_parser_t *mpc_and(int n, mpc_fold_t f, ...) {

    int i;
    va_list va;

    mpc_parser_t *p = mpc_undefined();

    p->type = MPC_TYPE_AND;
    p->data.and.n = n;
    p->data.and.f = f;
    p->data.and.xs = malloc(sizeof(mpc_parser_t*) * n);
    p->data.and.dxs = malloc(sizeof(mpc_dtor_t) * (n-1));

    va_start(va, f);  
    for (i = 0; i < n; i++) {
        p->data.and.xs[i] = va_arg(va, mpc_parser_t*);
    }
    for (i = 0; i < (n-1); i++) {
        p->data.and.dxs[i] = va_arg(va, mpc_dtor_t);
    }  
    va_end(va);

    return p;
}

/*
 ** Common Parsers
 */

static int mpc_soi_anchor(char prev, char next) { return (prev == '\0'); }
static int mpc_eoi_anchor(char prev, char next) { return (next == '\0'); }

mpc_parser_t *mpc_soi(void) { return mpc_expect(mpc_anchor(mpc_soi_anchor), "start of input"); }
mpc_parser_t *mpc_eoi(void) { return mpc_expect(mpc_anchor(mpc_eoi_anchor), "end of input"); }

static int mpc_boundary_anchor(char prev, char next) {
    char* word = "abcdefghijklmnopqrstuvwxyz"
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "0123456789_";
    if ( strchr(word, next) &&  prev == '\0') { return 1; }
    if ( strchr(word, prev) &&  next == '\0') { return 1; }
    if ( strchr(word, next) && !strchr(word, prev)) { return 1; }
    if (!strchr(word, next) &&  strchr(word, prev)) { return 1; }
    return 0;
}

mpc_parser_t *mpc_boundary(void) { return mpc_expect(mpc_anchor(mpc_boundary_anchor), "boundary"); }

mpc_parser_t *mpc_whitespace(void) { return mpc_expect(mpc_oneof(" \f\n\r\t\v"), "whitespace"); }
mpc_parser_t *mpc_whitespaces(void) { return mpc_expect(mpc_many(mpcf_strfold, mpc_whitespace()), "spaces"); }
mpc_parser_t *mpc_blank(void) { return mpc_expect(mpc_apply(mpc_whitespaces(), mpcf_free), "whitespace"); }

mpc_parser_t *mpc_newline(void) { return mpc_expect(mpc_char('\n'), "newline"); }
mpc_parser_t *mpc_tab(void) { return mpc_expect(mpc_char('\t'), "tab"); }
mpc_parser_t *mpc_escape(void) { return mpc_and(2, mpcf_strfold, mpc_char('\\'), mpc_any(), free); }

mpc_parser_t *mpc_digit(void) { return mpc_expect(mpc_oneof("0123456789"), "digit"); }
mpc_parser_t *mpc_hexdigit(void) { return mpc_expect(mpc_oneof("0123456789ABCDEFabcdef"), "hex digit"); }
mpc_parser_t *mpc_octdigit(void) { return mpc_expect(mpc_oneof("01234567"), "oct digit"); }
mpc_parser_t *mpc_digits(void) { return mpc_expect(mpc_many1(mpcf_strfold, mpc_digit()), "digits"); }
mpc_parser_t *mpc_hexdigits(void) { return mpc_expect(mpc_many1(mpcf_strfold, mpc_hexdigit()), "hex digits"); }
mpc_parser_t *mpc_octdigits(void) { return mpc_expect(mpc_many1(mpcf_strfold, mpc_octdigit()), "oct digits"); }

mpc_parser_t *mpc_lower(void) { return mpc_expect(mpc_oneof("abcdefghijklmnopqrstuvwxyz"), "lowercase letter"); }
mpc_parser_t *mpc_upper(void) { return mpc_expect(mpc_oneof("ABCDEFGHIJKLMNOPQRSTUVWXYZ"), "uppercase letter"); }
mpc_parser_t *mpc_alpha(void) { return mpc_expect(mpc_oneof("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), "letter"); }
mpc_parser_t *mpc_underscore(void) { return mpc_expect(mpc_char('_'), "underscore"); }
mpc_parser_t *mpc_alphanum(void) { return mpc_expect(mpc_or(3, mpc_alpha(), mpc_digit(), mpc_underscore()), "alphanumeric"); }

mpc_parser_t *mpc_int(void) { return mpc_expect(mpc_apply(mpc_digits(), mpcf_int), "integer"); }
mpc_parser_t *mpc_hex(void) { return mpc_expect(mpc_apply(mpc_hexdigits(), mpcf_hex), "hexadecimal"); }
mpc_parser_t *mpc_oct(void) { return mpc_expect(mpc_apply(mpc_octdigits(), mpcf_oct), "octadecimal"); }
mpc_parser_t *mpc_number(void) { return mpc_expect(mpc_or(3, mpc_int(), mpc_hex(), mpc_oct()), "number"); }

mpc_parser_t *mpc_real(void) {

    /* [+-]?\d+(\.\d+)?([eE][+-]?[0-9]+)? */

    mpc_parser_t *p0, *p1, *p2, *p30, *p31, *p32, *p3;

    p0 = mpc_maybe_lift(mpc_oneof("+-"), mpcf_ctor_str);
    p1 = mpc_digits();
    p2 = mpc_maybe_lift(mpc_and(2, mpcf_strfold, mpc_char('.'), mpc_digits(), free), mpcf_ctor_str);
    p30 = mpc_oneof("eE");
    p31 = mpc_maybe_lift(mpc_oneof("+-"), mpcf_ctor_str);
    p32 = mpc_digits();
    p3 = mpc_maybe_lift(mpc_and(3, mpcf_strfold, p30, p31, p32, free, free), mpcf_ctor_str);

    return mpc_expect(mpc_and(4, mpcf_strfold, p0, p1, p2, p3, free, free, free), "real");

}

mpc_parser_t *mpc_float(void) {
    return mpc_expect(mpc_apply(mpc_real(), mpcf_float), "float");
}

mpc_parser_t *mpc_char_lit(void) {
    return mpc_expect(mpc_between(mpc_or(2, mpc_escape(), mpc_any()), free, "'", "'"), "char");
}

mpc_parser_t *mpc_string_lit(void) {
    mpc_parser_t *strchar = mpc_or(2, mpc_escape(), mpc_noneof("\""));
    return mpc_expect(mpc_between(mpc_many(mpcf_strfold, strchar), free, "\"", "\""), "string");
}

mpc_parser_t *mpc_regex_lit(void) {  
    mpc_parser_t *regexchar = mpc_or(2, mpc_escape(), mpc_noneof("/"));
    return mpc_expect(mpc_between(mpc_many(mpcf_strfold, regexchar), free, "/", "/"), "regex");
}

mpc_parser_t *mpc_ident(void) {
    mpc_parser_t *p0, *p1; 
    p0 = mpc_or(2, mpc_alpha(), mpc_underscore());
    p1 = mpc_many(mpcf_strfold, mpc_alphanum()); 
    return mpc_and(2, mpcf_strfold, p0, p1, free);
}

/*
 ** Useful Parsers
 */

mpc_parser_t *mpc_startwith(mpc_parser_t *a) { return mpc_and(2, mpcf_snd, mpc_soi(), a, mpcf_dtor_null); }
mpc_parser_t *mpc_endwith(mpc_parser_t *a, mpc_dtor_t da) { return mpc_and(2, mpcf_fst, a, mpc_eoi(), da); }
mpc_parser_t *mpc_whole(mpc_parser_t *a, mpc_dtor_t da) { return mpc_and(3, mpcf_snd, mpc_soi(), a, mpc_eoi(), mpcf_dtor_null, da); }

mpc_parser_t *mpc_stripl(mpc_parser_t *a) { return mpc_and(2, mpcf_snd, mpc_blank(), a, mpcf_dtor_null); }
mpc_parser_t *mpc_stripr(mpc_parser_t *a) { return mpc_and(2, mpcf_fst, a, mpc_blank(), mpcf_dtor_null); }
mpc_parser_t *mpc_strip(mpc_parser_t *a) { return mpc_and(3, mpcf_snd, mpc_blank(), a, mpc_blank(), mpcf_dtor_null, mpcf_dtor_null); }
mpc_parser_t *mpc_tok(mpc_parser_t *a) { return mpc_and(2, mpcf_fst, a, mpc_blank(), mpcf_dtor_null); }
mpc_parser_t *mpc_sym(const char *s) { return mpc_tok(mpc_string(s)); }

mpc_parser_t *mpc_total(mpc_parser_t *a, mpc_dtor_t da) { return mpc_whole(mpc_strip(a), da); }

mpc_parser_t *mpc_between(mpc_parser_t *a, mpc_dtor_t ad, const char *o, const char *c) {
    return mpc_and(3, mpcf_snd_free,
            mpc_string(o), a, mpc_string(c),
            free, ad);
}

mpc_parser_t *mpc_parens(mpc_parser_t *a, mpc_dtor_t ad)   { return mpc_between(a, ad, "(", ")"); }
mpc_parser_t *mpc_braces(mpc_parser_t *a, mpc_dtor_t ad)   { return mpc_between(a, ad, "<", ">"); }
mpc_parser_t *mpc_brackets(mpc_parser_t *a, mpc_dtor_t ad) { return mpc_between(a, ad, "{", "}"); }
mpc_parser_t *mpc_squares(mpc_parser_t *a, mpc_dtor_t ad)  { return mpc_between(a, ad, "[", "]"); }

mpc_parser_t *mpc_tok_between(mpc_parser_t *a, mpc_dtor_t ad, const char *o, const char *c) {
    return mpc_and(3, mpcf_snd_free,
            mpc_sym(o), mpc_tok(a), mpc_sym(c),
            free, ad);
}

mpc_parser_t *mpc_tok_parens(mpc_parser_t *a, mpc_dtor_t ad)   { return mpc_tok_between(a, ad, "(", ")"); }
mpc_parser_t *mpc_tok_braces(mpc_parser_t *a, mpc_dtor_t ad)   { return mpc_tok_between(a, ad, "<", ">"); }
mpc_parser_t *mpc_tok_brackets(mpc_parser_t *a, mpc_dtor_t ad) { return mpc_tok_between(a, ad, "{", "}"); }
mpc_parser_t *mpc_tok_squares(mpc_parser_t *a, mpc_dtor_t ad)  { return mpc_tok_between(a, ad, "[", "]"); }

/*
 ** Regular Expression Parsers
 */

/*
 ** So here is a cute bootstrapping.
 **
 ** I'm using the previously defined
 ** mpc constructs and functions to
 ** parse the user regex string and
 ** construct a parser from it.
 **
 ** As it turns out lots of the standard
 ** mpc functions look a lot like `fold`
 ** functions and so can be used indirectly
 ** by many of the parsing functions to build
 ** a parser directly - as we are parsing.
 **
 ** This is certainly something that
 ** would be less elegant/interesting 
 ** in a two-phase parser which first
 ** builds an AST and then traverses it
 ** to generate the object.
 **
 ** This whole thing acts as a great
 ** case study for how trivial it can be
 ** to write a great parser in a few
 ** lines of code using mpc.
 */

/*
 **
 **  ### Regular Expression Grammar
 **
 **      <regex> : <term> | (<term> "|" <regex>)
 **     
 **      <term> : <factor>*
 **
 **      <factor> : <base>
 **               | <base> "*"
 **               | <base> "+"
 **               | <base> "?"
 **               | <base> "{" <digits> "}"
 **           
 **      <base> : <char>
 **             | "\" <char>
 **             | "(" <regex> ")"
 **             | "[" <range> "]"
 */

static mpc_val_t *mpcf_re_or(int n, mpc_val_t **xs) {
    if (xs[1] == NULL) { return xs[0]; }
    else { return mpc_or(2, xs[0], xs[1]); }
}

static mpc_val_t *mpcf_re_and(int n, mpc_val_t **xs) {
    int i;
    mpc_parser_t *p = mpc_lift(mpcf_ctor_str);
    for (i = 0; i < n; i++) {
        p = mpc_and(2, mpcf_strfold, p, xs[i], free);
    }
    return p;
}

static mpc_val_t *mpcf_re_repeat(int n, mpc_val_t **xs) {

    int num;
    if (xs[1] == NULL) { return xs[0]; }
    if (strcmp(xs[1], "*") == 0) { free(xs[1]); return mpc_many(mpcf_strfold, xs[0]); }
    if (strcmp(xs[1], "+") == 0) { free(xs[1]); return mpc_many1(mpcf_strfold, xs[0]); }
    if (strcmp(xs[1], "?") == 0) { free(xs[1]); return mpc_maybe_lift(xs[0], mpcf_ctor_str); }
    num = *(int*)xs[1];
    free(xs[1]);

    return mpc_count(num, mpcf_strfold, xs[0], free);
}

static mpc_parser_t *mpc_re_escape_char(char c) {
    switch (c) {
        case 'a': return mpc_char('\a');
        case 'f': return mpc_char('\f');
        case 'n': return mpc_char('\n');
        case 'r': return mpc_char('\r');
        case 't': return mpc_char('\t');
        case 'v': return mpc_char('\v');
        case 'b': return mpc_and(2, mpcf_snd, mpc_boundary(), mpc_lift(mpcf_ctor_str), free);
        case 'B': return mpc_not_lift(mpc_boundary(), free, mpcf_ctor_str);
        case 'A': return mpc_and(2, mpcf_snd, mpc_soi(), mpc_lift(mpcf_ctor_str), free);
        case 'Z': return mpc_and(2, mpcf_snd, mpc_eoi(), mpc_lift(mpcf_ctor_str), free);
        case 'd': return mpc_digit();
        case 'D': return mpc_not_lift(mpc_digit(), free, mpcf_ctor_str);
        case 's': return mpc_whitespace();
        case 'S': return mpc_not_lift(mpc_whitespace(), free, mpcf_ctor_str);
        case 'w': return mpc_alphanum();
        case 'W': return mpc_not_lift(mpc_alphanum(), free, mpcf_ctor_str);
        default: return NULL;
    }
}

static mpc_val_t *mpcf_re_escape(mpc_val_t *x) {

    char *s = x;
    mpc_parser_t *p;

    /* Regex Special Characters */
    if (s[0] == '.') { free(s); return mpc_any(); }
    if (s[0] == '^') { free(s); return mpc_and(2, mpcf_snd, mpc_soi(), mpc_lift(mpcf_ctor_str), free); }
    if (s[0] == '$') { free(s); return mpc_and(2, mpcf_snd, mpc_eoi(), mpc_lift(mpcf_ctor_str), free); }

    /* Regex Escape */
    if (s[0] == '\\') {
        p = mpc_re_escape_char(s[1]);
        p = (p == NULL) ? mpc_char(s[1]) : p;
        free(s);
        return p;
    }

    /* Regex Standard */
    p = mpc_char(s[0]);
    free(s);
    return p;
}

static char *mpc_re_range_escape_char(char c) {
    switch (c) {
        case '-': return "-";
        case 'a': return "\a";
        case 'f': return "\f";
        case 'n': return "\n";
        case 'r': return "\r";
        case 't': return "\t";
        case 'v': return "\v";
        case 'b': return "\b";
        case 'd': return "0123456789";
        case 's': return " \f\n\r\t\v";
        case 'w': return "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_";
        default: return NULL;
    }
}

static mpc_val_t *mpcf_re_range(mpc_val_t *x) {

    mpc_parser_t *out;
    char *range = calloc(1,1);
    char *tmp = NULL;
    char *s = x;
    char start, end;
    int i, j;
    int comp = 0;

    if (s[0] == '\0') { free(x); return mpc_fail("Invalid Regex Range Expression"); } 
    if (s[0] == '^' && 
            s[1] == '\0') { free(x); return mpc_fail("Invalid Regex Range Expression"); }

    if (s[0] == '^') { comp = 1;}

    for (i = comp; i < strlen(s); i++){

        /* Regex Range Escape */
        if (s[i] == '\\') {
            tmp = mpc_re_range_escape_char(s[i+1]);
            if (tmp != NULL) {
                range = realloc(range, strlen(range) + strlen(tmp) + 1);
                strcat(range, tmp);
            } else {
                range = realloc(range, strlen(range) + 1 + 1);
                range[strlen(range) + 1] = '\0';
                range[strlen(range) + 0] = s[i+1];      
            }
            i++;
        }

        /* Regex Range...Range */
        else if (s[i] == '-') {
            if (s[i+1] == '\0' || i == 0) {
                range = realloc(range, strlen(range) + strlen("-") + 1);
                strcat(range, "-");
            } else {
                start = s[i-1]+1;
                end = s[i+1]-1;
                for (j = start; j <= end; j++) {
                    range = realloc(range, strlen(range) + 1 + 1);
                    range[strlen(range) + 1] = '\0';
                    range[strlen(range) + 0] = j;
                }        
            }
        }

        /* Regex Range Normal */
        else {
            range = realloc(range, strlen(range) + 1 + 1);
            range[strlen(range) + 1] = '\0';
            range[strlen(range) + 0] = s[i];
        }

    }

    out = comp ? mpc_noneof(range) : mpc_oneof(range);

    free(x);
    free(range);

    return out;
}

mpc_parser_t *mpc_re(const char *re) {

    char *err_msg;
    mpc_parser_t *err_out;
    mpc_result_t r;
    mpc_parser_t *Regex, *Term, *Factor, *Base, *Range, *RegexEnclose; 

    Regex  = mpc_new("regex");
    Term   = mpc_new("term");
    Factor = mpc_new("factor");
    Base   = mpc_new("base");
    Range  = mpc_new("range");

    mpc_define(Regex, mpc_and(2, mpcf_re_or,
                Term, 
                mpc_maybe(mpc_and(2, mpcf_snd_free, mpc_char('|'), Regex, free)),
                (mpc_dtor_t)mpc_delete
                ));

    mpc_define(Term, mpc_many(mpcf_re_and, Factor));

    mpc_define(Factor, mpc_and(2, mpcf_re_repeat,
                Base,
                mpc_or(5,
                    mpc_char('*'), mpc_char('+'), mpc_char('?'),
                    mpc_brackets(mpc_int(), free),
                    mpc_pass()),
                (mpc_dtor_t)mpc_delete
                ));

    mpc_define(Base, mpc_or(4,
                mpc_parens(Regex, (mpc_dtor_t)mpc_delete),
                mpc_squares(Range, (mpc_dtor_t)mpc_delete),
                mpc_apply(mpc_escape(), mpcf_re_escape),
                mpc_apply(mpc_noneof(")|"), mpcf_re_escape)
                ));

    mpc_define(Range, mpc_apply(
                mpc_many(mpcf_strfold, mpc_or(2, mpc_escape(), mpc_noneof("]"))),
                mpcf_re_range
                ));

    RegexEnclose = mpc_whole(mpc_predictive(Regex), (mpc_dtor_t)mpc_delete);

    if(!mpc_parse("<mpc_re_compiler>", re, RegexEnclose, &r)) {
        err_msg = mpc_err_string(r.error);
        err_out = mpc_failf("Invalid Regex: %s", err_msg);
        mpc_err_delete(r.error);  
        free(err_msg);
        r.output = err_out;
    }

    mpc_delete(RegexEnclose);
    mpc_cleanup(5, Regex, Term, Factor, Base, Range);

    return r.output;

}

/*
 ** Common Fold Functions
 */

void mpcf_dtor_null(mpc_val_t *x) { return; }

mpc_val_t *mpcf_ctor_null(void) { return NULL; }
mpc_val_t *mpcf_ctor_str(void) { return calloc(1, 1); }
mpc_val_t *mpcf_free(mpc_val_t *x) { free(x); return NULL; }

mpc_val_t *mpcf_int(mpc_val_t *x) {
    int *y = malloc(sizeof(int));
    *y = strtol(x, NULL, 10);
    free(x);
    return y;
}

mpc_val_t *mpcf_hex(mpc_val_t *x) {
    int *y = malloc(sizeof(int));
    *y = strtol(x, NULL, 16);
    free(x);
    return y;
}

mpc_val_t *mpcf_oct(mpc_val_t *x) {
    int *y = malloc(sizeof(int));
    *y = strtol(x, NULL, 8);
    free(x);
    return y;
}

mpc_val_t *mpcf_float(mpc_val_t *x) {
    float* y = malloc(sizeof(float));
    *y = strtod(x, NULL);
    free(x);
    return y;
}

static char mpc_escape_input_c[]  = {
    '\a', '\b', '\f', '\n', '\r',
    '\t', '\v', '\\', '\'', '\"', '\0'};

static char *mpc_escape_output_c[] = {
    "\\a", "\\b", "\\f", "\\n", "\\r", "\\t", 
    "\\v", "\\\\", "\\'", "\\\"", "\\0", NULL};

static char mpc_escape_input_raw_re[] = { '/' };
static char *mpc_escape_output_raw_re[] = { "\\/", NULL };

static char mpc_escape_input_raw_cstr[] = { '"' };
static char *mpc_escape_output_raw_cstr[] = { "\\\"", NULL };

static char mpc_escape_input_raw_cchar[] = { '\'' };
static char *mpc_escape_output_raw_cchar[] = { "\\'", NULL };

static mpc_val_t *mpcf_escape_new(mpc_val_t *x, char *input, char **output) {

    int i;
    int found;
    char *s = x;
    char *y = calloc(1, 1);
    char buff[2];

    while (*s) {

        i = 0;
        found = 0;

        while (output[i]) {
            if (*s == input[i]) {
                y = realloc(y, strlen(y) + strlen(output[i]) + 1);
                strcat(y, output[i]);
                found = 1;
                break;
            }
            i++;
        }

        if (!found) {
            y = realloc(y, strlen(y) + 2);
            buff[0] = *s; buff[1] = '\0';
            strcat(y, buff);
        }

        s++;
    }


    return y;
}

static mpc_val_t *mpcf_unescape_new(mpc_val_t *x, char *input, char **output) {

    int i;
    int found = 0;
    char *s = x;
    char *y = calloc(1, 1);
    char buff[2];

    while (*s) {

        i = 0;
        found = 0;

        while (output[i]) {
            if ((*(s+0)) == output[i][0] &&
                    (*(s+1)) == output[i][1]) {
                y = realloc(y, strlen(y) + 2);
                buff[0] = input[i]; buff[1] = '\0';
                strcat(y, buff);
                found = 1;
                s++;
                break;
            }
            i++;
        }

        if (!found) {
            y = realloc(y, strlen(y) + 2);
            buff[0] = *s; buff[1] = '\0';
            strcat(y, buff);
        }

        if (*s == '\0') { break; }
        else { s++; }
    }

    return y;

}

mpc_val_t *mpcf_escape(mpc_val_t *x) {
    mpc_val_t *y = mpcf_escape_new(x, mpc_escape_input_c, mpc_escape_output_c);
    free(x);
    return y;
}

mpc_val_t *mpcf_unescape(mpc_val_t *x) {
    mpc_val_t *y = mpcf_unescape_new(x, mpc_escape_input_c, mpc_escape_output_c);
    free(x);
    return y;
}

mpc_val_t *mpcf_unescape_regex(mpc_val_t *x) {
    mpc_val_t *y = mpcf_unescape_new(x, mpc_escape_input_raw_re, mpc_escape_output_raw_re);
    free(x);
    return y;  
}

mpc_val_t *mpcf_escape_string_raw(mpc_val_t *x) {
    mpc_val_t *y = mpcf_escape_new(x, mpc_escape_input_raw_cstr, mpc_escape_output_raw_cstr);
    free(x);
    return y;
}

mpc_val_t *mpcf_unescape_string_raw(mpc_val_t *x) {
    mpc_val_t *y = mpcf_unescape_new(x, mpc_escape_input_raw_cstr, mpc_escape_output_raw_cstr);
    free(x);
    return y;
}

mpc_val_t *mpcf_escape_char_raw(mpc_val_t *x) {
    mpc_val_t *y = mpcf_escape_new(x, mpc_escape_input_raw_cchar, mpc_escape_output_raw_cchar);
    free(x);
    return y;
}

mpc_val_t *mpcf_unescape_char_raw(mpc_val_t *x) {
    mpc_val_t *y = mpcf_unescape_new(x, mpc_escape_input_raw_cchar, mpc_escape_output_raw_cchar);
    free(x);
    return y;
}

mpc_val_t *mpcf_null(int n, mpc_val_t** xs) { return NULL; }
mpc_val_t *mpcf_fst(int n, mpc_val_t **xs) { return xs[0]; }
mpc_val_t *mpcf_snd(int n, mpc_val_t **xs) { return xs[1]; }
mpc_val_t *mpcf_trd(int n, mpc_val_t **xs) { return xs[2]; }

static mpc_val_t *mpcf_nth_free(int n, mpc_val_t **xs, int x) {
    int i;
    for (i = 0; i < n; i++) {
        if (i != x) { free(xs[i]); }
    }
    return xs[x];
}

mpc_val_t *mpcf_fst_free(int n, mpc_val_t **xs) { return mpcf_nth_free(n, xs, 0); }
mpc_val_t *mpcf_snd_free(int n, mpc_val_t **xs) { return mpcf_nth_free(n, xs, 1); }
mpc_val_t *mpcf_trd_free(int n, mpc_val_t **xs) { return mpcf_nth_free(n, xs, 2); }

mpc_val_t *mpcf_strfold(int n, mpc_val_t **xs) {
    char *x = calloc(1, 1);
    int i;
    for (i = 0; i < n; i++) {
        x = realloc(x, strlen(x) + strlen(xs[i]) + 1);
        strcat(x, xs[i]);
        free(xs[i]);
    }
    return x;
}

mpc_val_t *mpcf_maths(int n, mpc_val_t **xs) {

    int **vs = (int**)xs;

    if (strcmp(xs[1], "*") == 0) { *vs[0] *= *vs[2]; }
    if (strcmp(xs[1], "/") == 0) { *vs[0] /= *vs[2]; }
    if (strcmp(xs[1], "%") == 0) { *vs[0] %= *vs[2]; }
    if (strcmp(xs[1], "+") == 0) { *vs[0] += *vs[2]; }
    if (strcmp(xs[1], "-") == 0) { *vs[0] -= *vs[2]; }

    free(xs[1]); free(xs[2]);

    return xs[0];
}

/*
 ** Printing
 */

static void mpc_print_unretained(mpc_parser_t *p, int force) {

    /* TODO: Print Everything Escaped */

    int i;
    char *s, *e;
    char buff[2];

    if (p->retained && !force) {;
        if (p->name) { printf("<%s>", p->name); }
        else { printf("<anon>"); }
        return;
    }

    if (p->type == MPC_TYPE_UNDEFINED) { printf("<?>"); }
    if (p->type == MPC_TYPE_PASS)   { printf("<:>"); }
    if (p->type == MPC_TYPE_FAIL)   { printf("<!>"); }
    if (p->type == MPC_TYPE_LIFT)   { printf("<#>"); }
    if (p->type == MPC_TYPE_STATE)  { printf("<S>"); }
    if (p->type == MPC_TYPE_ANCHOR) { printf("<@>"); }
    if (p->type == MPC_TYPE_EXPECT) {
        printf("%s", p->data.expect.m);
        /*mpc_print_unretained(p->data.expect.x, 0);*/
    }

    if (p->type == MPC_TYPE_ANY) { printf("<.>"); }
    if (p->type == MPC_TYPE_SATISFY) { printf("<f>"); }

    if (p->type == MPC_TYPE_SINGLE) {
        buff[0] = p->data.single.x; buff[1] = '\0';
        s = mpcf_escape_new(
                buff,
                mpc_escape_input_c,
                mpc_escape_output_c);
        printf("'%s'", s);
        free(s);
    }

    if (p->type == MPC_TYPE_RANGE) {
        buff[0] = p->data.range.x; buff[1] = '\0';
        s = mpcf_escape_new(
                buff,
                mpc_escape_input_c,
                mpc_escape_output_c);
        buff[0] = p->data.range.y; buff[1] = '\0';
        e = mpcf_escape_new(
                buff,
                mpc_escape_input_c,
                mpc_escape_output_c);
        printf("[%s-%s]", s, e);
        free(s);
        free(e);
    }

    if (p->type == MPC_TYPE_ONEOF) {
        s = mpcf_escape_new(
                p->data.string.x,
                mpc_escape_input_c,
                mpc_escape_output_c);
        printf("[%s]", s);
        free(s);
    }

    if (p->type == MPC_TYPE_NONEOF) {
        s = mpcf_escape_new(
                p->data.string.x,
                mpc_escape_input_c,
                mpc_escape_output_c);
        printf("[^%s]", s);
        free(s);
    }

    if (p->type == MPC_TYPE_STRING) {
        s = mpcf_escape_new(
                p->data.string.x,
                mpc_escape_input_c,
                mpc_escape_output_c);
        printf("\"%s\"", s);
        free(s);
    }

    if (p->type == MPC_TYPE_APPLY)    { mpc_print_unretained(p->data.apply.x, 0); }
    if (p->type == MPC_TYPE_APPLY_TO) { mpc_print_unretained(p->data.apply_to.x, 0); }
    if (p->type == MPC_TYPE_PREDICT)  { mpc_print_unretained(p->data.predict.x, 0); }

    if (p->type == MPC_TYPE_NOT)   { mpc_print_unretained(p->data.not.x, 0); printf("!"); }
    if (p->type == MPC_TYPE_MAYBE) { mpc_print_unretained(p->data.not.x, 0); printf("?"); }

    if (p->type == MPC_TYPE_MANY)  { mpc_print_unretained(p->data.repeat.x, 0); printf("*"); }
    if (p->type == MPC_TYPE_MANY1) { mpc_print_unretained(p->data.repeat.x, 0); printf("+"); }
    if (p->type == MPC_TYPE_COUNT) { mpc_print_unretained(p->data.repeat.x, 0); printf("{%i}", p->data.repeat.n); }

    if (p->type == MPC_TYPE_OR) {
        printf("(");
        for(i = 0; i < p->data.or.n-1; i++) {
            mpc_print_unretained(p->data.or.xs[i], 0);
            printf(" | ");
        }
        mpc_print_unretained(p->data.or.xs[p->data.or.n-1], 0);
        printf(")");
    }

    if (p->type == MPC_TYPE_AND) {
        printf("(");
        for(i = 0; i < p->data.and.n-1; i++) {
            mpc_print_unretained(p->data.and.xs[i], 0);
            printf(" ");
        }
        mpc_print_unretained(p->data.and.xs[p->data.and.n-1], 0);
        printf(")");
    }

}

void mpc_print(mpc_parser_t *p) {
    mpc_print_unretained(p, 1);
    printf("\n");
}

/*
 ** Testing
 */

/*
 ** These functions are slightly unwieldy and
 ** also the whole of the testing suite for mpc
 ** mpc is pretty shaky.
 **
 ** It could do with a lot more tests and more
 ** precision. Currently I am only really testing
 ** changes off of the examples.
 **
 */

int mpc_test_fail(mpc_parser_t *p, const char *s, void *d,
        int(*tester)(void*, void*),
        mpc_dtor_t destructor,
        void(*printer)(void*)) {

    mpc_result_t r;  
    if (mpc_parse("<test>", s, p, &r)) {

        if (tester(r.output, d)) {
            destructor(r.output);
            return 0;
        } else {
            destructor(r.output);
            return 1;
        }

    } else {
        mpc_err_delete(r.error);
        return 1;
    }

}

int mpc_test_pass(mpc_parser_t *p, const char *s, void *d,
        int(*tester)(void*, void*), 
        mpc_dtor_t destructor, 
        void(*printer)(void*)) {

    mpc_result_t r;  
    if (mpc_parse("<test>", s, p, &r)) {

        if (tester(r.output, d)) {
            destructor(r.output);
            return 1;
        } else {
            printf("Got "); printer(r.output); printf("\n");
            printf("Expected "); printer(d); printf("\n");
            destructor(r.output);
            return 0;
        }

    } else {    
        mpc_err_print(r.error);
        mpc_err_delete(r.error);
        return 0;

    }

}


/*
 ** AST
 */

void mpc_ast_delete(mpc_ast_t *a) {

    int i;

    if (a == NULL) { return; }
    for (i = 0; i < a->children_num; i++) {
        mpc_ast_delete(a->children[i]);
    }

    free(a->children);
    free(a->tag);
    free(a->contents);
    free(a);

}

static void mpc_ast_delete_no_children(mpc_ast_t *a) {
    free(a->children);
    free(a->tag);
    free(a->contents);
    free(a);
}

mpc_ast_t *mpc_ast_new(const char *tag, const char *contents) {

    mpc_ast_t *a = malloc(sizeof(mpc_ast_t));

    a->tag = malloc(strlen(tag) + 1);
    strcpy(a->tag, tag);

    a->contents = malloc(strlen(contents) + 1);
    strcpy(a->contents, contents);

    a->state = mpc_state_new();

    a->children_num = 0;
    a->children = NULL;
    return a;

}

mpc_ast_t *mpc_ast_build(int n, const char *tag, ...) {

    mpc_ast_t *a = mpc_ast_new(tag, "");

    int i;
    va_list va;
    va_start(va, tag);

    for (i = 0; i < n; i++) {
        mpc_ast_add_child(a, va_arg(va, mpc_ast_t*));
    }

    va_end(va);

    return a;

}

mpc_ast_t *mpc_ast_add_root(mpc_ast_t *a) {

    mpc_ast_t *r;

    if (a == NULL) { return a; }
    if (a->children_num == 0) { return a; }
    if (a->children_num == 1) { return a; }

    r = mpc_ast_new(">", "");
    mpc_ast_add_child(r, a);
    return r;
}

int mpc_ast_eq(mpc_ast_t *a, mpc_ast_t *b) {

    int i;

    if (strcmp(a->tag, b->tag) != 0) { return 0; }
    if (strcmp(a->contents, b->contents) != 0) { return 0; }
    if (a->children_num != b->children_num) { return 0; }

    for (i = 0; i < a->children_num; i++) {
        if (!mpc_ast_eq(a->children[i], b->children[i])) { return 0; }
    }

    return 1;
}

mpc_ast_t *mpc_ast_add_child(mpc_ast_t *r, mpc_ast_t *a) {
    r->children_num++;
    r->children = realloc(r->children, sizeof(mpc_ast_t*) * r->children_num);
    r->children[r->children_num-1] = a;
    return r;
}

mpc_ast_t *mpc_ast_add_tag(mpc_ast_t *a, const char *t) {
    if (a == NULL) { return a; }
    a->tag = realloc(a->tag, strlen(t) + 1 + strlen(a->tag) + 1);
    memmove(a->tag + strlen(t) + 1, a->tag, strlen(a->tag)+1);
    memmove(a->tag, t, strlen(t));
    memmove(a->tag + strlen(t), "|", 1);
    return a;
}

mpc_ast_t *mpc_ast_tag(mpc_ast_t *a, const char *t) {
    a->tag = realloc(a->tag, strlen(t) + 1);
    strcpy(a->tag, t);
    return a;
}

mpc_ast_t *mpc_ast_state(mpc_ast_t *a, mpc_state_t s) {
    if (a == NULL) { return a; }
    a->state = s;
    return a;
}

static void mpc_ast_print_depth(mpc_ast_t *a, int d) {

    int i;
    for (i = 0; i < d; i++) { printf("  "); }

    if (strlen(a->contents)) {
        printf("%s:%i:%i '%s'\n", a->tag, a->state.row+1, a->state.col+1, a->contents);
    } else {
        printf("%s \n", a->tag);
    }

    for (i = 0; i < a->children_num; i++) {
        mpc_ast_print_depth(a->children[i], d+1);
    }

}

void mpc_ast_print(mpc_ast_t *a) {
    mpc_ast_print_depth(a, 0);
}

mpc_val_t *mpcf_fold_ast(int n, mpc_val_t **xs) {

    int i, j;
    mpc_ast_t** as = (mpc_ast_t**)xs;
    mpc_ast_t *r;

    if (n == 0) { return NULL; }
    if (n == 1) { return xs[0]; }
    if (n == 2 && xs[1] == NULL) { return xs[0]; }
    if (n == 2 && xs[0] == NULL) { return xs[1]; }

    r = mpc_ast_new(">", "");

    for (i = 0; i < n; i++) {

        if (as[i] == NULL) { continue; }

        if (as[i] && as[i]->children_num > 0) {

            for (j = 0; j < as[i]->children_num; j++) {
                mpc_ast_add_child(r, as[i]->children[j]);
            }

            mpc_ast_delete_no_children(as[i]);

        } else if (as[i] && as[i]->children_num == 0) {
            mpc_ast_add_child(r, as[i]);
        }

    }

    if (r->children_num) {
        r->state = r->children[0]->state;
    }

    return r;
}

mpc_val_t *mpcf_str_ast(mpc_val_t *c) {
    mpc_ast_t *a = mpc_ast_new("", c);
    free(c);
    return a;
}

mpc_val_t *mpcf_state_ast(int n, mpc_val_t **xs) {
    mpc_state_t *s = ((mpc_state_t**)xs)[0];
    mpc_ast_t *a = ((mpc_ast_t**)xs)[1];
    a = mpc_ast_state(a, *s);
    free(s);
    return a;
}

mpc_parser_t *mpca_state(mpc_parser_t *a) {
    return mpc_and(2, mpcf_state_ast, mpc_state(), a, free);
}

mpc_parser_t *mpca_tag(mpc_parser_t *a, const char *t) {
    return mpc_apply_to(a, (mpc_apply_to_t)mpc_ast_tag, (void*)t);
}

mpc_parser_t *mpca_add_tag(mpc_parser_t *a, const char *t) {
    return mpc_apply_to(a, (mpc_apply_to_t)mpc_ast_add_tag, (void*)t);
}

mpc_parser_t *mpca_root(mpc_parser_t *a) {
    return mpc_apply(a, (mpc_apply_t)mpc_ast_add_root);
}

mpc_parser_t *mpca_not(mpc_parser_t *a) { return mpc_not(a, (mpc_dtor_t)mpc_ast_delete); }
mpc_parser_t *mpca_maybe(mpc_parser_t *a) { return mpc_maybe(a); }
mpc_parser_t *mpca_many(mpc_parser_t *a) { return mpc_many(mpcf_fold_ast, a); }
mpc_parser_t *mpca_many1(mpc_parser_t *a) { return mpc_many1(mpcf_fold_ast, a); }
mpc_parser_t *mpca_count(int n, mpc_parser_t *a) { return mpc_count(n, mpcf_fold_ast, a, (mpc_dtor_t)mpc_ast_delete); }

mpc_parser_t *mpca_or(int n, ...) {

    int i;
    va_list va;

    mpc_parser_t *p = mpc_undefined();

    p->type = MPC_TYPE_OR;
    p->data.or.n = n;
    p->data.or.xs = malloc(sizeof(mpc_parser_t*) * n);

    va_start(va, n);  
    for (i = 0; i < n; i++) {
        p->data.or.xs[i] = va_arg(va, mpc_parser_t*);
    }
    va_end(va);

    return p;

}

mpc_parser_t *mpca_and(int n, ...) {

    int i;
    va_list va;

    mpc_parser_t *p = mpc_undefined();

    p->type = MPC_TYPE_AND;
    p->data.and.n = n;
    p->data.and.f = mpcf_fold_ast;
    p->data.and.xs = malloc(sizeof(mpc_parser_t*) * n);
    p->data.and.dxs = malloc(sizeof(mpc_dtor_t) * (n-1));

    va_start(va, n);
    for (i = 0; i < n; i++) {
        p->data.and.xs[i] = va_arg(va, mpc_parser_t*);
    }
    for (i = 0; i < (n-1); i++) {
        p->data.and.dxs[i] = (mpc_dtor_t)mpc_ast_delete;
    }    
    va_end(va);

    return p;  
}

mpc_parser_t *mpca_total(mpc_parser_t *a) { return mpc_total(a, (mpc_dtor_t)mpc_ast_delete); }

/*
 ** Grammar Parser
 */

/*
 ** This is another interesting bootstrapping.
 **
 ** Having a general purpose AST type allows
 ** users to specify the grammar alone and
 ** let all fold rules be automatically taken
 ** care of by existing functions.
 **
 ** You don't get to control the type spat
 ** out but this means you can make a nice
 ** parser to take in some grammar in nice
 ** syntax and spit out a parser that works.
 **
 ** The grammar for this looks surprisingly
 ** like regex but the main difference is that
 ** it is now whitespace insensitive and the
 ** base type takes literals of some form.
 */

/*
 **
 **  ### Grammar Grammar
 **
 **      <grammar> : (<term> "|" <grammar>) | <term>
 **     
 **      <term> : <factor>*
 **
 **      <factor> : <base>
 **               | <base> "*"
 **               | <base> "+"
 **               | <base> "?"
 **               | <base> "{" <digits> "}"
 **           
 **      <base> : "<" (<digits> | <ident>) ">"
 **             | <string_lit>
 **             | <char_lit>
 **             | <regex_lit>
 **             | "(" <grammar> ")"
 */

typedef struct {
    va_list *va;
    int parsers_num;
    mpc_parser_t **parsers;
    int flags;
} mpca_grammar_st_t;

static mpc_val_t *mpcaf_grammar_or(int n, mpc_val_t **xs) {
    if (xs[1] == NULL) { return xs[0]; }
    else { return mpca_or(2, xs[0], xs[1]); }
}

static mpc_val_t *mpcaf_grammar_and(int n, mpc_val_t **xs) {
    int i;
    mpc_parser_t *p = mpc_pass();  
    for (i = 0; i < n; i++) {
        if (xs[i] != NULL) { p = mpca_and(2, p, xs[i]); }
    }
    return p;
}

static mpc_val_t *mpcaf_grammar_repeat(int n, mpc_val_t **xs) {

    int num;
    if (xs[1] == NULL) { return xs[0]; }  
    if (strcmp(xs[1], "*") == 0) { free(xs[1]); return mpca_many(xs[0]); }
    if (strcmp(xs[1], "+") == 0) { free(xs[1]); return mpca_many1(xs[0]); }
    if (strcmp(xs[1], "?") == 0) { free(xs[1]); return mpca_maybe(xs[0]); }
    if (strcmp(xs[1], "!") == 0) { free(xs[1]); return mpca_not(xs[0]); }
    num = *((int*)xs[1]);
    free(xs[1]);
    return mpca_count(num, xs[0]);
}

static mpc_val_t *mpcaf_grammar_string(mpc_val_t *x, void *s) {
    mpca_grammar_st_t *st = s;
    char *y = mpcf_unescape(x);
    mpc_parser_t *p = (st->flags & MPCA_LANG_WHITESPACE_SENSITIVE) ? mpc_string(y) : mpc_tok(mpc_string(y));
    free(y);
    return mpca_state(mpca_tag(mpc_apply(p, mpcf_str_ast), "string"));
}

static mpc_val_t *mpcaf_grammar_char(mpc_val_t *x, void *s) {
    mpca_grammar_st_t *st = s;
    char *y = mpcf_unescape(x);
    mpc_parser_t *p = (st->flags & MPCA_LANG_WHITESPACE_SENSITIVE) ? mpc_char(y[0]) : mpc_tok(mpc_char(y[0]));
    free(y);
    return mpca_state(mpca_tag(mpc_apply(p, mpcf_str_ast), "char"));
}

static mpc_val_t *mpcaf_grammar_regex(mpc_val_t *x, void *s) {
    mpca_grammar_st_t *st = s;
    char *y = mpcf_unescape_regex(x);
    mpc_parser_t *p = (st->flags & MPCA_LANG_WHITESPACE_SENSITIVE) ? mpc_re(y) : mpc_tok(mpc_re(y));
    free(y);
    return mpca_state(mpca_tag(mpc_apply(p, mpcf_str_ast), "regex"));
}

/* Should this just use `isdigit` instead */
static int is_number(const char* s) {
    int i;
    for (i = 0; i < strlen(s); i++) { if (!strchr("0123456789", s[i])) { return 0; } }
    return 1;
}

static mpc_parser_t *mpca_grammar_find_parser(char *x, mpca_grammar_st_t *st) {

    int i;
    mpc_parser_t *p;

    /* Case of Number */
    if (is_number(x)) {

        i = strtol(x, NULL, 10);

        while (st->parsers_num <= i) {
            st->parsers_num++;
            st->parsers = realloc(st->parsers, sizeof(mpc_parser_t*) * st->parsers_num);
            st->parsers[st->parsers_num-1] = va_arg(*st->va, mpc_parser_t*);
            if (st->parsers[st->parsers_num-1] == NULL) {
                return mpc_failf("No Parser in position %i! Only supplied %i Parsers!", i, st->parsers_num);
            }
        }

        return st->parsers[st->parsers_num-1];

        /* Case of Identifier */
    } else {

        /* Search Existing Parsers */
        for (i = 0; i < st->parsers_num; i++) {
            mpc_parser_t *p = st->parsers[i];
            if (p == NULL) { return mpc_failf("Unknown Parser '%s'!", x); }
            if (p->name && strcmp(p->name, x) == 0) { return p; }
        }

        /* Search New Parsers */
        while (1) {

            p = va_arg(*st->va, mpc_parser_t*);

            st->parsers_num++;
            st->parsers = realloc(st->parsers, sizeof(mpc_parser_t*) * st->parsers_num);
            st->parsers[st->parsers_num-1] = p;

            if (p == NULL) { return mpc_failf("Unknown Parser '%s'!", x); }
            if (p->name && strcmp(p->name, x) == 0) { return p; }

        }

    }  

}

static mpc_val_t *mpcaf_grammar_id(mpc_val_t *x, void *s) {

    mpca_grammar_st_t *st = s;
    mpc_parser_t *p = mpca_grammar_find_parser(x, st);
    free(x);

    if (p->name) {
        return mpca_state(mpca_root(mpca_add_tag(p, p->name)));
    } else {
        return mpca_state(mpca_root(p));
    }
}

mpc_parser_t *mpca_grammar_st(const char *grammar, mpca_grammar_st_t *st) {

    char *err_msg;
    mpc_parser_t *err_out;
    mpc_result_t r;
    mpc_parser_t *GrammarTotal, *Grammar, *Term, *Factor, *Base;

    GrammarTotal = mpc_new("grammar_total");
    Grammar = mpc_new("grammar");
    Term = mpc_new("term");
    Factor = mpc_new("factor");
    Base = mpc_new("base");

    mpc_define(GrammarTotal,
            mpc_predictive(mpc_total(Grammar, mpc_soft_delete))
            );

    mpc_define(Grammar, mpc_and(2, mpcaf_grammar_or,
                Term,
                mpc_maybe(mpc_and(2, mpcf_snd_free, mpc_sym("|"), Grammar, free)),
                mpc_soft_delete
                ));

    mpc_define(Term, mpc_many1(mpcaf_grammar_and, Factor));

    mpc_define(Factor, mpc_and(2, mpcaf_grammar_repeat,
                Base,
                mpc_or(6,
                    mpc_sym("*"),
                    mpc_sym("+"),
                    mpc_sym("?"),
                    mpc_sym("!"),
                    mpc_tok_brackets(mpc_int(), free),
                    mpc_pass()),
                mpc_soft_delete
                ));

    mpc_define(Base, mpc_or(5,
                mpc_apply_to(mpc_tok(mpc_string_lit()), mpcaf_grammar_string, st),
                mpc_apply_to(mpc_tok(mpc_char_lit()),   mpcaf_grammar_char, st),
                mpc_apply_to(mpc_tok(mpc_regex_lit()),  mpcaf_grammar_regex, st),
                mpc_apply_to(mpc_tok_braces(mpc_or(2, mpc_digits(), mpc_ident()), free), mpcaf_grammar_id, st),
                mpc_tok_parens(Grammar, mpc_soft_delete)
                ));

    if(!mpc_parse("<mpc_grammar_compiler>", grammar, GrammarTotal, &r)) {
        err_msg = mpc_err_string(r.error);
        err_out = mpc_failf("Invalid Grammar: %s", err_msg);
        mpc_err_delete(r.error);
        free(err_msg);
        r.output = err_out;
    }

    mpc_cleanup(5, GrammarTotal, Grammar, Term, Factor, Base);

    return (st->flags & MPCA_LANG_PREDICTIVE) ? mpc_predictive(r.output) : r.output;

}

mpc_parser_t *mpca_grammar(int flags, const char *grammar, ...) {
    mpca_grammar_st_t st;
    mpc_parser_t *res;
    va_list va;
    va_start(va, grammar);

    st.va = &va;
    st.parsers_num = 0;
    st.parsers = NULL;
    st.flags = flags;

    res = mpca_grammar_st(grammar, &st);  
    free(st.parsers);
    va_end(va);
    return res;
}

typedef struct {
    char *ident;
    char *name;
    mpc_parser_t *grammar;
} mpca_stmt_t;

static mpc_val_t *mpca_stmt_afold(int n, mpc_val_t **xs) {

    mpca_stmt_t *stmt = malloc(sizeof(mpca_stmt_t));
    stmt->ident = ((char**)xs)[0];
    stmt->name = ((char**)xs)[1];
    stmt->grammar = ((mpc_parser_t**)xs)[3];

    free(((char**)xs)[2]);
    free(((char**)xs)[4]);

    return stmt;
}

static mpc_val_t *mpca_stmt_fold(int n, mpc_val_t **xs) {

    int i;
    mpca_stmt_t **stmts = malloc(sizeof(mpca_stmt_t*) * (n+1));

    for (i = 0; i < n; i++) {
        stmts[i] = xs[i];
    }
    stmts[n] = NULL;  

    return stmts;
}

static void mpca_stmt_list_delete(mpc_val_t *x) {

    mpca_stmt_t **stmts = x;

    while(*stmts) {
        mpca_stmt_t *stmt = *stmts; 
        free(stmt->ident);
        free(stmt->name);
        mpc_soft_delete(stmt->grammar);
        free(stmt);  
        stmts++;
    }
    free(x);

}

static mpc_val_t *mpca_stmt_list_apply_to(mpc_val_t *x, void *s) {

    mpca_grammar_st_t *st = s;
    mpca_stmt_t *stmt;
    mpca_stmt_t **stmts = x;
    mpc_parser_t *left;

    while(*stmts) {
        stmt = *stmts;
        left = mpca_grammar_find_parser(stmt->ident, st);
        if (st->flags & MPCA_LANG_PREDICTIVE) { stmt->grammar = mpc_predictive(stmt->grammar); }
        if (stmt->name) { stmt->grammar = mpc_expect(stmt->grammar, stmt->name); }
        mpc_define(left, stmt->grammar);
        free(stmt->ident);
        free(stmt->name);
        free(stmt);
        stmts++;
    }
    free(x);

    return NULL;
}

static mpc_err_t *mpca_lang_st(mpc_input_t *i, mpca_grammar_st_t *st) {

    mpc_result_t r;
    mpc_err_t *e;
    mpc_parser_t *Lang, *Stmt, *Grammar, *Term, *Factor, *Base; 

    Lang    = mpc_new("lang");
    Stmt    = mpc_new("stmt");
    Grammar = mpc_new("grammar");
    Term    = mpc_new("term");
    Factor  = mpc_new("factor");
    Base    = mpc_new("base");

    mpc_define(Lang, mpc_apply_to(
                mpc_total(mpc_predictive(mpc_many(mpca_stmt_fold, Stmt)), mpca_stmt_list_delete),
                mpca_stmt_list_apply_to, st
                ));

    mpc_define(Stmt, mpc_and(5, mpca_stmt_afold,
                mpc_tok(mpc_ident()), mpc_maybe(mpc_tok(mpc_string_lit())), mpc_sym(":"), Grammar, mpc_sym(";"),
                free, free, free, mpc_soft_delete
                ));

    mpc_define(Grammar, mpc_and(2, mpcaf_grammar_or,
                Term,
                mpc_maybe(mpc_and(2, mpcf_snd_free, mpc_sym("|"), Grammar, free)),
                mpc_soft_delete
                ));

    mpc_define(Term, mpc_many1(mpcaf_grammar_and, Factor));

    mpc_define(Factor, mpc_and(2, mpcaf_grammar_repeat,
                Base,
                mpc_or(6,
                    mpc_sym("*"),
                    mpc_sym("+"),
                    mpc_sym("?"),
                    mpc_sym("!"),
                    mpc_tok_brackets(mpc_int(), free),
                    mpc_pass()),
                mpc_soft_delete
                ));

    mpc_define(Base, mpc_or(5,
                mpc_apply_to(mpc_tok(mpc_string_lit()), mpcaf_grammar_string, st),
                mpc_apply_to(mpc_tok(mpc_char_lit()),   mpcaf_grammar_char, st),
                mpc_apply_to(mpc_tok(mpc_regex_lit()),  mpcaf_grammar_regex, st),
                mpc_apply_to(mpc_tok_braces(mpc_or(2, mpc_digits(), mpc_ident()), free), mpcaf_grammar_id, st),
                mpc_tok_parens(Grammar, mpc_soft_delete)
                ));


    if (!mpc_parse_input(i, Lang, &r)) {
        e = r.error;
    } else {
        e = NULL;
    }

    mpc_cleanup(6, Lang, Stmt, Grammar, Term, Factor, Base);

    return e;
}

mpc_err_t *mpca_lang_file(int flags, FILE *f, ...) {
    mpca_grammar_st_t st;
    mpc_input_t *i;
    mpc_err_t *err;

    va_list va;  
    va_start(va, f);

    st.va = &va;
    st.parsers_num = 0;
    st.parsers = NULL;
    st.flags = flags;

    i = mpc_input_new_file("<mpca_lang_file>", f);
    err = mpca_lang_st(i, &st);
    mpc_input_delete(i);

    free(st.parsers);
    va_end(va);
    return err;
}

mpc_err_t *mpca_lang_pipe(int flags, FILE *p, ...) {
    mpca_grammar_st_t st;
    mpc_input_t *i;
    mpc_err_t *err;

    va_list va;  
    va_start(va, p);

    st.va = &va;
    st.parsers_num = 0;
    st.parsers = NULL;
    st.flags = flags;

    i = mpc_input_new_pipe("<mpca_lang_pipe>", p);
    err = mpca_lang_st(i, &st);
    mpc_input_delete(i);

    free(st.parsers);
    va_end(va);
    return err;
}

mpc_err_t *mpca_lang(int flags, const char *language, ...) {

    mpca_grammar_st_t st;
    mpc_input_t *i;
    mpc_err_t *err;

    va_list va;  
    va_start(va, language);

    st.va = &va;
    st.parsers_num = 0;
    st.parsers = NULL;
    st.flags = flags;

    i = mpc_input_new_string("<mpca_lang>", language);
    err = mpca_lang_st(i, &st);
    mpc_input_delete(i);

    free(st.parsers);
    va_end(va);
    return err;
}

mpc_err_t *mpca_lang_contents(int flags, const char *filename, ...) {

    mpca_grammar_st_t st;
    mpc_input_t *i;
    mpc_err_t *err;

    va_list va;

    FILE *f = fopen(filename, "rb");

    if (f == NULL) {
        return mpc_err_fail(filename, mpc_state_new(), "Unable to open file!");
    }

    va_start(va, filename);

    st.va = &va;
    st.parsers_num = 0;
    st.parsers = NULL;
    st.flags = flags;

    i = mpc_input_new_file(filename, f);
    err = mpca_lang_st(i, &st);
    mpc_input_delete(i);

    free(st.parsers);
    va_end(va);  

    fclose(f);

    return err;
}