editor.c

// Compiler issue fixed 
#define _DEFAULT_SOURCE
#define _BSD_SOURCE
#define _GNU_SOURCE


#include <unistd.h>
#include <termios.h>
#include <stdlib.h>
#include <ctype.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <stdarg.h>


#define CTRL_KEY(k) ((k) & 0x1f)
#define ABUF_INIT {NULL,0}
#define EDITOR_VERSION "0.0.1"
#define EDITOR_TAB_STOP 8
#define EDITOR_QUIT_TIMES 1


#define HL_HIGHLIGHT_NUMBERS (1<<0)
#define HL_HIGHLIGHT_STRINGS (1<<1)


enum editorKey {

  BACKSPACE = 127,
  ARROW_LEFT = 1000,
  ARROW_RIGHT,
  ARROW_UP,
  ARROW_DOWN,
  DEL_KEY,
  HOME_KEY,
  END_KEY, 
  PAGE_UP,
  PAGE_DOWN

};

enum editorHighlight{

  HL_NORMAL = 0,
  HL_COMMENT,
  HL_MLCOMMENT,
  HL_KEYWORD1,
  HL_KEYWORD2,
  HL_STRING,
  HL_NUMBER,
  HL_MATCH

};
// To store text from editor
typedef struct erow {

	int size;
	int rsize;
	char *chars;
	char *render;
	unsigned char *hl;
	int idx;
	int hl_open_comment;

}erow;

// Syntax highlighting struct
struct editorSyntax {

  char *filetype;
  char **filematch;
  char **keywords;
  char *singleline_comment_start;
  char *multiline_comment_start;
  char *multiline_comment_end;
  int flags;

};

struct editorConfig {

	struct termios orig_termios;
	int screenrows;
	int screencols;
	int numrows;
	int cx,cy;
	int rx; // Horizontal coordinate 
	int rowoff; // For vertical screen scrolling 
	int coloff; // For horizontal scrolling
	erow *row;
	int dirty; // Dirty bit to prevent losing unsaved changes
	char *filename;
	char statusmsg[80];
	time_t statusmsg_time;
	struct editorSyntax *syntax;

};

struct editorConfig E;

// Syntax highlighting for C & CPP

char *C_HL_extensions[] = { ".c", ".h", ".cpp", NULL };

char *C_HL_keywords[] = {

  "switch", "if", "while", "for", "break", "continue", "return", "else",
  "struct", "union", "typedef", "static", "enum", "class", "case",

  "int|", "long|", "double|", "float|", "char|", "unsigned|", "signed|",
  "void|", NULL
};


struct editorSyntax HLDB[] = {

  {
    "c",
    C_HL_extensions,
    C_HL_keywords,
    "//", "/*", "*/",
    HL_HIGHLIGHT_NUMBERS | HL_HIGHLIGHT_STRINGS
  },

};

#define HLDB_ENTRIES (sizeof(HLDB) / sizeof(HLDB[0]))

// Vararg function prototype

void editorSetStatusMessage(const char *fmt, ...);
void editorRefreshScreen();
char *editorPrompt(char *prompt, void(*callback)(char *, int));

// Error handler
void die(const char *s){

	write(STDOUT_FILENO,"\x1b[2J",4); // Clear screen on exit
	write(STDOUT_FILENO, "\x1b[H",3); // Reposition on exit
	
	perror(s);
	exit(1);
}

void disableRawMode() {
  if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == -1)
  	die("tcsetattr");
}

void enableRawMode() {

  if(tcgetattr(STDIN_FILENO, &E.orig_termios) == -1) // Termos attribute setter 
  	die("tcgetattr");

  atexit(disableRawMode); // Disable raw mode at exit 

  struct termios raw = E.orig_termios;
  /*
  	 - Disable echo and canonical mode
  	 - Disable SIGINT SIGTSTP signals
  	 - Disable Ctrl-V
  */
  raw.c_lflag &= ~(ECHO | ICANON | IEXTEN |ISIG); 
  //raw.c_lflag &= ~(ICRNL | IXON); // Disable Ctrl-S, Ctrl-Q & Ctrl-M
  raw.c_oflag &= ~(OPOST); // Turn off output processing
  raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON); // Miscellaneous flags
  raw.c_cflag |= (CS8);
  raw.c_cc[VMIN] = 0; // Minimum bytes of input needed before read() can return 
  raw.c_cc[VTIME] = 1; // Maximum amount of time to wait before read() returns  
 


  if(tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1)
  	die("tcsetattr");
}

// Manage low level terminal input 
int editorReadKey(){
	int nread;
	char c;

	while((nread = read(STDIN_FILENO, &c,1)) != 1){
		if(nread == -1 && errno == EAGAIN)
			die("read");
	}

	if(c == '\x1b'){

		char seq[3];

		if(read(STDIN_FILENO, &seq[0],1) != 1)
			return '\x1b';

		if(read(STDIN_FILENO, &seq[1],1) != 1)
			return '\x1b';

		// To move cursor with arrow keys
		if(seq[0] == '['){

			if(seq[1] >= '0' && seq[1] <= '9'){
				if(read(STDIN_FILENO,&seq[2],1) != 1)
					return '\x1b';

				if(seq[2] == '~'){

					switch(seq[1]){
						case '1': return HOME_KEY;
						case '3': return DEL_KEY;
						case '4': return END_KEY;
						case '5': return PAGE_UP;
						case '6': return PAGE_DOWN;
						case '7': return HOME_KEY;
						case '8': return END_KEY;
					}
				}
			}
			else{

				switch(seq[1]){

					case 'A': return ARROW_UP;
					case 'B': return ARROW_DOWN;
					case 'C': return ARROW_RIGHT;
					case 'D': return ARROW_LEFT;
					case 'H': return HOME_KEY;
					case 'F': return END_KEY;

				}
			
			}

		}
		else if(seq[0] == 'O'){

			switch(seq[1]){

				case 'H': return HOME_KEY;
				case 'F': return END_KEY; 
			}
		}
		return '\x1b';
	}
	else{

		return c;
	}
}

int getCursorPosition(int *rows,int *cols){

	char buf[32];
	unsigned int i = 0; 



	if(write(STDOUT_FILENO, "\x1b[6n",4) != 4)
		return -1;

	while(i < sizeof(buf) - 1){
		if(read(STDIN_FILENO, &buf[i],1) != 1)
			break;

		if(buf[i] == 'R')
			break;

		i++;	

	}
	buf[i] = '\0';
	if (buf[0] != '\x1b' || buf[1] != '[') 
		return -1;

  	if (sscanf(&buf[2], "%d;%d", rows, cols) != 2)
  		return -1;

  	return 0;
}

// Utility function to get size of window
int getWindowSize(int *rows, int *cols){
	struct winsize ws;

	// ioctl syscall 
	if(ioctl(STDOUT_FILENO,TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0){

		// Escape sequence to send cursor move to right and then down (999 px)
		if(write(STDOUT_FILENO, "\x1b[999C\xb[999B",12) != 12)
			return -1;

		return getCursorPosition(rows,cols);
	}
	else{

		*cols = ws.ws_col;
		*rows = ws.ws_row;
		return 0;
	}
}

// returns true if separator character
int is_separator(int c){

	return isspace(c) || c == '\0' || strchr(",.()+-/*=~%<>[];", c) != NULL;

}

void editorUpdateSyntax(erow *row) {

  row->hl = realloc(row->hl, row->rsize);
  memset(row->hl, HL_NORMAL, row->rsize);

  if (E.syntax == NULL)
  	return;

  char **keywords = E.syntax->keywords;

  char *scs = E.syntax->singleline_comment_start;
  char *mcs = E.syntax->multiline_comment_start;
  char *mce = E.syntax->multiline_comment_end;

  int scs_len = scs ? strlen(scs) : 0;
  int mcs_len = mcs ? strlen(mcs) : 0;
  int mce_len = mce ? strlen(mce) : 0;

  int prev_sep = 1;
  int in_string = 0;
  int in_comment = (row->idx > 0 && E.row[row->idx - 1].hl_open_comment);

  int i = 0;
  while (i < row->rsize) {

    char c = row->render[i];
    unsigned char prev_hl = (i > 0) ? row->hl[i - 1] : HL_NORMAL;

    if (scs_len && !in_string && !in_comment) {

      if (!strncmp(&row->render[i], scs, scs_len)) {

        memset(&row->hl[i], HL_COMMENT, row->rsize - i);
        break;

      }

    }

    if (mcs_len && mce_len && !in_string) {

      if (in_comment) {

        row->hl[i] = HL_MLCOMMENT;

        if (!strncmp(&row->render[i], mce, mce_len)) {

          memset(&row->hl[i], HL_MLCOMMENT, mce_len);
          i += mce_len;
          in_comment = 0;
          prev_sep = 1;
          continue;

        } 
        else {

          i++;
          continue;

        }

      } 
      else if (!strncmp(&row->render[i], mcs, mcs_len)) {

        memset(&row->hl[i], HL_MLCOMMENT, mcs_len);
        i += mcs_len;
        in_comment = 1;
        continue;

      }

    }

    if (E.syntax->flags & HL_HIGHLIGHT_STRINGS) {

      if (in_string) {

        row->hl[i] = HL_STRING;

        if (c == '\\' && i + 1 < row->rsize) {

          row->hl[i + 1] = HL_STRING;
          i += 2;
          continue;

        }
        if (c == in_string)
        	in_string = 0;

        i++;
        prev_sep = 1;
        continue;

      } 
      else {

        if (c == '"' || c == '\'') {

          in_string = c;
          row->hl[i] = HL_STRING;
          i++;
          continue;

        }

      }

    }

    if (E.syntax->flags & HL_HIGHLIGHT_NUMBERS) {

      if ((isdigit(c) && (prev_sep || prev_hl == HL_NUMBER)) || (c == '.' && prev_hl == HL_NUMBER)) {

        row->hl[i] = HL_NUMBER;
        i++;
        prev_sep = 0;
        continue;

      }

    }

    if (prev_sep) {

      int j;
      for (j = 0; keywords[j]; j++) {

        int klen = strlen(keywords[j]);
        int kw2 = keywords[j][klen - 1] == '|';
        if (kw2) klen--;

        if (!strncmp(&row->render[i], keywords[j], klen) && is_separator(row->render[i + klen])) {

          memset(&row->hl[i], kw2 ? HL_KEYWORD2 : HL_KEYWORD1, klen);
          i += klen;
          break;

        }

      }
      if (keywords[j] != NULL) {

        prev_sep = 0;
        continue;
      }

    }
    prev_sep = is_separator(c);
    i++;

  }

  int changed = (row->hl_open_comment != in_comment);
  row->hl_open_comment = in_comment;

  if (changed && row->idx + 1 < E.numrows)
    editorUpdateSyntax(&E.row[row->idx + 1]);

}


int editorSyntaxToColor(int hl){

	switch(hl){

		case HL_COMMENT:

		case HL_MLCOMMENT: return 36;

		case HL_KEYWORD1: return 33;

		case HL_KEYWORD2: return 32;

		case HL_STRING: return 35;

		case HL_NUMBER: return 31; // Foreground red

		case HL_MATCH: return 34; // Foreground blue

		default: return 37; // Foreground white

	}

}

void editorSelectSyntaxHighlight() {

  E.syntax = NULL;

  if (E.filename == NULL)
  		return;

  char *ext = strrchr(E.filename, '.');

  for (unsigned int j = 0; j < HLDB_ENTRIES; j++) {

    struct editorSyntax *s = &HLDB[j];
    unsigned int i = 0;

    while (s->filematch[i]) {

      int is_ext = (s->filematch[i][0] == '.');

      if ((is_ext && ext && !strcmp(ext, s->filematch[i])) || (!is_ext && strstr(E.filename, s->filematch[i]))) {

        E.syntax = s;
        int filerow;

        for (filerow = 0; filerow < E.numrows; filerow++)
        	editorUpdateSyntax(&E.row[filerow]);
        
        return;
        
      }

      i++;

    }

  }

}



void editorUpdateRow(erow *row){

	int tabs = 0;
	int j;

	for(j = 0; j < row->size; j++)
		if(row->chars[j] == '\t')
			tabs++;

	free(row->render);
	row->render = malloc(row->size + tabs * (EDITOR_TAB_STOP - 1) + 1);

	int idx = 0;

	for(j = 0; j < row->size; j++){

		if(row->chars[j] == '\t'){

			row->render[idx++] = ' ';
			while(idx % EDITOR_TAB_STOP != 0)
				row->render[idx++] = ' ';
		}
		else
			row->render[idx++] = row->chars[j];
	}

	row->render[idx] = '\0';
	row->rsize = idx;

	editorUpdateSyntax(row);

}


void editorRowDelChar(erow *row, int at) {

  if (at < 0 || at >= row->size)
  		return;

  memmove(&row->chars[at], &row->chars[at + 1], row->size - at);

  row->size--;

  editorUpdateRow(row);

  E.dirty++;
}

// Function renaming
void editorInsertRow(int at, char *s, size_t len){

	// Adding enter key functionality

	if(at < 0 || at >  E.numrows)
		return;

	E.row = realloc(E.row, sizeof(erow) * (E.numrows + 1));
	memmove(&E.row[at + 1], &E.row[at], sizeof(erow) * (E.numrows - at));

	E.row[at].idx = at;

	E.row[at].size = len;
	E.row[at].chars = malloc(len + 1);
	memcpy(E.row[at].chars, s, len);
	
	E.row[at].chars[len] = '\0';
	E.row[at].rsize = 0;
	E.row[at].render = NULL;
	E.row[at].hl = NULL;
	E.row[at].hl_open_comment = 0;

	editorUpdateRow(&E.row[at]);

	E.numrows++;
	E.dirty++;
}

void editorFreeRow(erow *row){

	free(row->render);
	free(row->chars);
	free(row->hl);
}

void editorDelRow(int at){

	if(at < 0 || at >= E.numrows)
		return;

	editorFreeRow(&E.row[at]);
	memmove(&E.row[at], &E.row[at + 1], sizeof(erow) * (E.numrows - at - 1));

	for(int j = at; j < E.numrows - 1; j++)
		E.row[j].idx--;

	E.numrows--;
	E.dirty++;

}

void editorOpen(char *filename){

	free(E.filename);
	E.filename = strdup(filename);

	// Enable syntax highlighting
	editorSelectSyntaxHighlight();

	FILE *fp = fopen(filename, "r");
	if(!fp) 
		die("fopen");

	char *line = NULL;
	size_t linecap = 0;
	ssize_t linelen;

	// File reader read multiple lines

	while((linelen = getline(&line, &linecap, fp)) != -1){

			// Strip carriage return and newline characters
			while(linelen > 0 && (line[linelen - 1] == '\n' || line[linelen - 1] == '\r'))
				linelen--;

			editorInsertRow(E.numrows, line, linelen);
	}

	free(line);
	fclose(fp);
	E.dirty = 0; // Prevent from showing "modified" when file is opened initially

}

// Save to rows to disk 
char* editorRowsToString(int *buflen){

	int totlen = 0;
	int j;

	for(j = 0; j < E.numrows; j++)
		totlen += E.row[j].size + 1;

	*buflen = totlen;

	char *buf = malloc(totlen);
	char *p = buf;

	for(j = 0; j < E.numrows; j++){

		memcpy(p, E.row[j].chars, E.row[j].size);
		p += E.row[j].size;
		*p = '\n';
		p++;
	}

	return buf;

}


// Write to disk 
void editorSave(){


	if(E.filename == NULL){

		E.filename = editorPrompt("Save as: %s (ESC to cancel)", NULL);
		// Activate if user presses ESC
		if(E.filename == NULL){

			editorSetStatusMessage("Save aborted");
			return;
		}
		editorSelectSyntaxHighlight();
	}


	int len; 
	char *buf = editorRowsToString(&len);

	int fd = open(E.filename, O_RDWR | O_CREAT, 0644);

	// Error handling 
	if(fd != -1){
		if(ftruncate(fd,len) != -1){
			if(write(fd, buf, len) == len){
				close(fd);
				free(buf);
				E.dirty = 0;
				editorSetStatusMessage("%d bytes written to disk",len);
				return;
			}
		
		}

		close(fd);
	}

	free(buf);
	editorSetStatusMessage("Cannot save! I/O error: %s", strerror(errno));

}
// Save as prompt when new file is created 
char *editorPrompt(char *prompt, void (*callback)(char *, int)) {

  size_t bufsize = 128;
  char *buf = malloc(bufsize);
  size_t buflen = 0;
  buf[0] = '\0';

  while (1) {

    editorSetStatusMessage(prompt, buf);
    editorRefreshScreen();

    int c = editorReadKey();


    if(c == DEL_KEY || c == CTRL_KEY('h') || c == BACKSPACE){

    	if(buflen != 0)
    		buf[--buflen] = '\0';
    }
    // ESC key to cancel Save As
    else if(c == '\x1b'){

    	editorSetStatusMessage("");

    	if (callback)
    		callback(buf, c);

    	free(buf);
    	return NULL;

    }
    else if (c == '\r') {

      if (buflen != 0) {

        editorSetStatusMessage("");

        if (callback)
        	callback(buf, c);
        
        return buf;

      }

    } 
    else if (!iscntrl(c) && c < 128) {

      if (buflen == bufsize - 1) {

        bufsize *= 2;
        buf = realloc(buf, bufsize);

      }
      buf[buflen++] = c;
      buf[buflen] = '\0';

    }

    if (callback)
    	callback(buf, c);

  }

}
void editorRowInsertChar(erow *row, int at, int c){

	if(at < 0 || at > row->size)
		at = row->size;

	row->chars = realloc(row->chars,row->size + 2);
	memmove(&row->chars[at + 1], &row->chars[at], row->size - at + 1);
	row->size++;
	row->chars[at] = c;

	editorUpdateRow(row);
	E.dirty++;

}

// Handles Enter Keystrokes
void editorInsertNewline(){

	if(E.cx == 0)
		editorInsertRow(E.cy, "", 0);

	else{

		erow *row = &E.row[E.cy];
		editorInsertRow(E.cy + 1, &row->chars[E.cx], row->size - E.cx);
		row = &E.row[E.cy];
		row->size = E.cx;
		row->chars[row->size] = '\0';
		editorUpdateRow(row);

	}
	E.cy++;
	E.cx = 0;
}

void editorRowAppendString(erow *row, char *s, size_t len){

	row->chars = realloc(row->chars, row->size + len + 1);
	memcpy(&row->chars[row->size], s, len);
	row->size += len;
	row->chars[row->size] = '\0';
	editorUpdateRow(row);
	E.dirty++;

}


void editorDelChar(){

	if(E.cy == E.numrows)
		return;

	if(E.cx == 0 && E.cy == 0)
		return;

	erow * row = &E.row[E.cy];

	if(E.cx > 0){
		
		editorRowDelChar(row, E.cx - 1);
		E.cx--;

	}
	else{

		E.cx = E.row[E.cy - 1].size;
		editorRowAppendString(&E.row[E.cy - 1],row->chars, row->size);
		editorDelRow(E.cy);	
		E.cy--;

	}
	
}

void editorInsertChar(int c){

	// Cursor on tilde line after end of file
	if(E.cy == E.numrows)
		editorInsertRow(E.numrows, "", 0);

	editorRowInsertChar(&E.row[E.cy], E.cx, c);
	E.cx++;

}
// Append buffer to limit write() syscalls
struct abuf{

	char *b;
	int len;

};

void abAppend(struct abuf *ab, const char *s,int len){

	char *new = realloc(ab->b, ab->len + len);

	if(new == NULL)
		return;

	memcpy(&new[ab->len],s,len);

	ab->b = new;
	ab->len += len;
}

void abFree(struct abuf *ab){

	// Free allocated buffer
	free(ab->b);

}

int editorRowCxToRx(erow *row, int cx){

	int rx = 0;
	int j;

	for(j = 0; j < cx; j++){

		if(row->chars[j] == '\t')
			rx += (EDITOR_TAB_STOP - 1) - (rx % EDITOR_TAB_STOP);

		rx++;
	}

	return rx;
}

//  Convert the render index into a chars index
int editorRowRxToCx(erow *row, int rx) {

  int cur_rx = 0;

  int cx;

  for (cx = 0; cx < row->size; cx++) {

    if (row->chars[cx] == '\t')
      cur_rx += (EDITOR_TAB_STOP - 1) - (cur_rx % EDITOR_TAB_STOP);

    cur_rx++;

    if (cur_rx > rx)
    	return cx;

  }
  return cx;
}

// Incremental search 
void editorFindCallback(char *query, int key){


 // Searching in forward and backward direction
	static int last_match = - 1;
	static int direction = 1;


	// Restore syntax highlighting after search
	static int saved_hl_line;
	static char *saved_hl = NULL;

	if(saved_hl){

		memcpy(E.row[saved_hl_line].hl, saved_hl, E.row[saved_hl_line].rsize);
		free(saved_hl);
		saved_hl = NULL;

	}

	if (key == '\r' || key == '\x1b'){

		last_match = -1;
		direction = 1;
    	return;
	}
	else if(key == ARROW_RIGHT || key == ARROW_DOWN)
		direction = 1;

	else if(key == ARROW_LEFT  || key == ARROW_UP)
		direction = -1;

	else{

		last_match = -1;
		direction =  1;
	}

	if(last_match == -1)
		direction = 1;

	int current = last_match;
	int i;

	for (i = 0; i < E.numrows; i++) {

		current += direction;
		if(current == -1)
			current = E.numrows - 1;

		else if(current == E.numrows)
			current = 0;

	    erow *row = &E.row[current];
	    char *match = strstr(row->render, query);

	    if (match) {

	      last_match = current;
	      E.cy = current;
	      E.cx = editorRowRxToCx(row, match - row->render);
	      E.rowoff = E.numrows;

	      saved_hl_line = current;
	      
	      saved_hl = malloc(row->rsize);
	      memcpy(saved_hl, row->hl, row->rsize);
	      memset(&row->hl[match - row->render], HL_MATCH, strlen(query));
	      break;

	    }

	}	

}
// Search utility function
void editorFind(){

// Restore cursor position when search is cancelled

	int saved_cx = E.cx;
  	int saved_cy = E.cy;
  	int saved_coloff = E.coloff;
  	int saved_rowoff = E.rowoff;

	char *query = editorPrompt("Search: %s (Use ESC/Arrows/Enter)", editorFindCallback);

	if(query)
		free(query);

	else{

		E.cx = saved_cx; 
		E.cy = saved_cy;
    	E.coloff = saved_coloff;
    	E.rowoff = saved_rowoff;

	}

}
void editorScroll(){

	E.rx = 0;
	if(E.cy < E.numrows)
		E.rx = editorRowCxToRx(&E.row[E.cy], E.cx);

	if(E.cy < E.rowoff)
		E.rowoff = E.cy;

	if(E.cy >= E.rowoff + E.screenrows)
		E.rowoff = E.cy - E.screenrows + 1;

	if(E.rx < E.coloff)
		E.coloff = E.rx;

	if(E.rx >= E.coloff + E.screencols)
		E.coloff = E.rx - E.screencols + 1;

}
// Status bar drawing utility -> Inverted colors 
void editorDrawStatusBar(struct abuf *ab){

	abAppend(ab, "\x1b[7m",4);

	char status[80],rstatus[80];
	int len = snprintf(status, sizeof(status), "%.20s - %d lines %s", E.filename ? E.filename : "[No Name]", E.numrows, E.dirty ? "(modified)": "");

	int rlen = snprintf(rstatus, sizeof(rstatus), "%s | %d/%d", E.syntax ? E.syntax->filetype : "no filetype", E.cy + 1, E.numrows);

	if(len > E.screencols)
		len = E.screencols;

	abAppend(ab, status, len);

	while(len < E.screencols){

		if(E.screencols - len == rlen){

			abAppend(ab,rstatus, rlen);
			break;
		}
		else{
			abAppend(ab," ",1);
			len++;
		}
	
	}

	abAppend(ab, "\x1b[m",3);
	abAppend(ab, "\r\n",2);
}

void editorDrawMessageBar(struct abuf *ab){

	abAppend(ab,"\x1b[K",3);

	int msglen = strlen(E.statusmsg);

	if(msglen > E.screencols)
		msglen = E.screencols;

	// 5 second message flash
	if(msglen && time(NULL) - E.statusmsg_time < 5)
		abAppend(ab, E.statusmsg, msglen);

}
// Draw tildes in the buffer and not actual file 
void editorDrawRows(struct abuf *ab) {

  int y;

  for (y = 0; y < E.screenrows; y++) {

  	int filerow = y + E.rowoff;

    if (filerow >= E.numrows) {

      // Print welcome message to center of terminal 
      if (E.numrows == 0 && y == E.screenrows / 3) {

        char welcome[80];
        int welcomelen = snprintf(welcome, sizeof(welcome),
          "Editor -- version %s", EDITOR_VERSION);

        if (welcomelen > E.screencols)
        	welcomelen = E.screencols;

        int padding = (E.screencols - welcomelen) / 2;

        if (padding) {

          abAppend(ab, "~", 1);
          padding--;

        }
        while (padding--)
        	abAppend(ab, " ", 1);
        
        abAppend(ab, welcome, welcomelen);
      } 
      else {

        abAppend(ab, "~", 1);

      }

    } 
    else {

      // Wrapping lines
      int len = E.row[filerow].rsize - E.coloff;
      if(len < 0)
      	len = 0;

      if (len > E.screencols) 
      	len = E.screencols;

      char *c = &E.row[filerow].render[E.coloff];
      unsigned char *hl = &E.row[filerow].hl[E.coloff];
      int current_color = -1;
      int j;

      for(j = 0; j < len; j++){

      	  if (iscntrl(c[j])) {

      	  	char sym = (c[j] <= 26) ? '@' + c[j] : '?';
          	abAppend(ab, "\x1b[7m", 4);
          	abAppend(ab, &sym, 1);
          	abAppend(ab, "\x1b[m", 3);

          	if (current_color != -1) {

            	char buf[16];
            	int clen = snprintf(buf, sizeof(buf), "\x1b[%dm", current_color);
            	abAppend(ab, buf, clen);
          	}

          }
      		else if(hl[j] == HL_NORMAL){

      			if(current_color != -1){

      				abAppend(ab, "\x1b[39m", 5);
      				current_color = -1;
      			}
				
				abAppend(ab, &c[j],1);
      		
      		}	
      		else{

      			int color = editorSyntaxToColor(hl[j]);

      			if(color != current_color){

      				current_color = color;
      				char buf[16];
      				int clen = snprintf(buf, sizeof(buf), "\x1b[%dm", color);
      				abAppend(ab, buf, clen);

      			}
      			
  				abAppend(ab, &c[j], 1);
      		}
      
      	}
      	abAppend(ab, "\x1b[39m", 5);
    }

    abAppend(ab, "\x1b[K", 3);
    abAppend(ab, "\r\n", 2);

  }

}

/*
	Write 4 bytes 
	\x1b = Escape character <ESC>
	[ = Begining of escape sequence
	J = Erase in display
	2 = Argument of J command (Clear entire screen)
*/
void  editorRefreshScreen(){

	editorScroll();

	struct abuf ab = ABUF_INIT;

	abAppend(&ab, "\x1b[?25l",6); // To hide cursor while redrawing
	abAppend(&ab,"\x1b[H",3); // Reposition cursor to top-left corner

	editorDrawRows(&ab);
	editorDrawStatusBar(&ab);
	editorDrawMessageBar(&ab);

	char buf[32];
	snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cy - E.rowoff) + 1, (E.rx - E.coloff) + 1); // Specify exact position of cursor 
	abAppend(&ab, buf, strlen(buf));

	abAppend(&ab, "\x1b[?25h",6); // h -> set mode 

	// Finally write the buffer to STDOUT
	write(STDOUT_FILENO, ab.b, ab.len);

	abFree(&ab);

}

void editorSetStatusMessage(const char *fmt, ...){

	va_list ap;
	va_start(ap, fmt);
	vsnprintf(E.statusmsg, sizeof(E.statusmsg), fmt, ap);
	va_end(ap);

	E.statusmsg_time = time(NULL);

}

void editorMoveCursor(int key){

	// Scroll to right
	erow * row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];

	switch(key){

		case ARROW_LEFT:
			// Handle cursor from going out of screen
			if(E.cx != 0)
				E.cx--;
			else if(E.cy > 0){
				E.cy--;
				E.cx = E.row[E.cy].size;
			}
			break;

		case ARROW_RIGHT:
			if(row && E.cx < row->size)
				E.cx++;

			else if(row && E.cx == row->size){
				E.cy++;
				E.cx = 0;
			}
			break;

		case ARROW_UP:
			if(E.cy != 0)
				E.cy--;
			break;

		case ARROW_DOWN:
			if(E.cy  < E.numrows)
				E.cy++;
			break;

	}

	row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
	int rowlen = row ? row->size : 0;

	if(E.cx > rowlen)
		E.cx = rowlen;

}
void editorProcessKeypress(){

	static int quit_times = EDITOR_QUIT_TIMES;

	int c = editorReadKey();

	switch(c){

		case '\r':
			editorInsertNewline();
			break;

		case CTRL_KEY('q'):
			if(E.dirty && quit_times > 0){

				editorSetStatusMessage("Warning! File has unsaved changes. Press Ctrl-Q again to quit.", quit_times);
				quit_times--;
				return;
			}
			write(STDOUT_FILENO,"\x1b[2J",4);
			write(STDOUT_FILENO,"\x1b[H",3); 
			exit(0); 
			break;

		case CTRL_KEY('s'):
			editorSave();
			break;

		case HOME_KEY:
			E.cx = 0;
			break;

		case END_KEY:
			if(E.cy < E.numrows)
				E.cx = E.row[E.cy].size;
			break;

		case CTRL_KEY('f'):
			editorFind();
			break;

		case BACKSPACE:
		case CTRL_KEY('h'):
		case DEL_KEY:
			if(c == DEL_KEY)
				editorMoveCursor(ARROW_RIGHT);

			editorDelChar();
			break;

		case PAGE_UP:
		case PAGE_DOWN:
			/* Move cursor to top/bottom of screen 
			   Code block to create time variable in switch statement
			*/
			{
				if(c == PAGE_UP)
					E.cy = E.rowoff;

				else if(c == PAGE_DOWN){

					E.cy = E.rowoff + E.screenrows - 1;
					if(E.cy > E.numrows)
						E.cy = E.numrows;

				}

				int times = E.screenrows;
				while(times--)
					editorMoveCursor(c == PAGE_UP ? ARROW_UP : ARROW_DOWN);
			}
			break;
		case ARROW_UP:
		case ARROW_DOWN:
		case ARROW_LEFT:
		case ARROW_RIGHT:
			editorMoveCursor(c);
			break;

		case CTRL_KEY('l'):
		case '\x1b':
			break;

		default:
			editorInsertChar(c);
			break;

	}
	quit_times = EDITOR_QUIT_TIMES;

}

void initEditor(){

	// Base position of cursor
	E.cx = 0;
	E.cy = 0;
	E.rx = 0;
	E.numrows = 0;
	E.row = NULL;
	E.rowoff = 0;
	E.coloff = 0;
	E.dirty = 0;
	E.filename = NULL;
	E.statusmsg_time = 0;
	E.statusmsg[0] = '\0';
	E.syntax = NULL;


	if(getWindowSize(&E.screenrows, &E.screencols) == -1)
		die("getWindowSize");

	E.screenrows -= 2;
}

// Init code 

int main(int argc, char *argv[]){

	enableRawMode();
	initEditor();

	// Open file if provided
	if(argc >= 2){

		editorOpen(argv[1]);
	}

	editorSetStatusMessage("HELP: Ctrl-S = Save | Ctrl-F = Find | Ctrl-Q = Quit");

	while (1){

		editorRefreshScreen();
		editorProcessKeypress();
	}

	return 0;
}