implement context

README.md

@@ -13,6 +13,11 @@ Re-organize files with Javascript.
 **Delete all backups and create new ones**\
 `jsmv src "f.endsWith('.backup') ? f.del() : f.mv(f + '.backup')"`
 
+**Number files**\
+`jsmv src "f.mv(ctx.i++ + '.js')" --ctx "{i: 0}"`
+
+Look at the [e2e tests](./tests/e2e) for more examples.
+
 ===
 
 ## How to Use
@@ -24,7 +29,10 @@ The command format is `jsmv dir_name snippet_or_file_name <FLAGS>`
 You can either provide a JS snippet or a file that contains a JS snippet.
 
 The JS snippet has access to the variable `f`. By default `f` is described by
-the [defaultFileObj class](./defaultFileObj.ts). It's well commented.
+the [defaultFileObj class](./defaultFileObj.ts). It's well commented. There's
+also `ctx` which is a variable that is persistent between every execution of the
+snippet. It is possible to add/delete properties on `ctx`, but re-assignment is
+impossible.
 
 _Entry_ = The current file/directory being operated on.
 
@@ -44,6 +52,25 @@ If you want `f` to have custom functionality you can implement your own
 `JSMOVE_FILEOBJ_PATH` is an optional environment variable to a file path with a
 custom FileObj class. `--fileObj` overrides `JSMOVE_FILEOBJ_PATH`.
 
+## --ctx and JSMOVE_CTX
+
+`--ctx` is a snippet of JS-object-notation (e.g `{foo: "bar"}`) that will be
+executed to create the initial context. Without it, the initial context is
+empty.
+
+`JSMOVE_CTX` operates similarly to `JSMOVE_FILEOBJ_PATH` except it's not a path.
+
+### Guidelines
+
+All custom FileObj classes should implement the `getOp` operation. File system
+operations should not be done directly inside the FileObj class. Rather, an `Op`
+should be returned by `getOp`. This has several benefits:
+
+- Atomicity (explained [here](#Atomicity))
+- jsmv can do checks like
+  - ensuring files are only deleted if `-d` is passed
+  - ensuring moves don't overwrite files unless `-o` is passed
+
 ## Order of Operations
 
 ### Atomicity

src/constants.ts

@@ -1,5 +1,5 @@
 export const HELP_MSG = `
-Usage: [binary_name] directory snippet_or_file <FLAGS> [--fileobj=<file>]
+Usage: [binary_name] directory snippet_or_file <FLAGS> [--fileobj=<file>] [--ctx=<js_snippet>]
 
 FLAGS:
 -h, --help:      Show this message
@@ -9,4 +9,5 @@ FLAGS:
 -q, --quiet      Don't print unless there's an error
 -o, --overwrite  Allow overwriting files with the copy or move operations
 --fileObj        A file with a custom "FileObj" class
+--ctx            A snippet of JS to create the initial context
 `;

src/defaultFileObj.ts

@@ -40,6 +40,7 @@ export class FileObj extends String implements IFileObj {
     isDir: boolean;
     isFile: boolean;
     cliArgs: unknown;
+    ctx: any;
   }) {
     const absPath = path.join(absDirPath, name);
     super(absPath);

src/main.ts

@@ -29,15 +29,6 @@ const optHelp = args.help || false;
 const optQuiet = args.quiet || false;
 const optOverwrite = args.overwrite || false;
 
-const configPath = Deno.env.get("JSMOVE_FILEOBJ_PATH");
-if (configPath !== undefined && !args.fileObj) {
-  if (!fs.existsSync(configPath)) {
-    console.warn(`No config at "${configPath}"`);
-  } else {
-    args.fileObj = configPath;
-  }
-}
-
 if (optHelp) {
   console.log(HELP_MSG);
   Deno.exit(0);
@@ -59,15 +50,39 @@ const snippet = fs.existsSync(snippetOrFileName)
   : snippetOrFileName;
 // Sand-boxing is decent: `this` is undefined, global variables don't seem to be mutated
 // Probably has holes though.
-const createMutation: (f: FileObj) => void = new Function("f", snippet) as any;
+const createMutation: (f: FileObj, ctx: any) => void = new Function(
+  "f",
+  "ctx",
+  snippet,
+) as any;
 
 let FileObjClass = FileObj;
 
-if (args.fileObj) {
-  if (args.fileObj === true) {
-    fatal("--fileObj requires an argument");
+function envOrOpt(
+  optName: string,
+  isPath: boolean,
+  cb: (optVal: string) => void,
+) {
+  const envName = `JSMOVE_${optName.toUpperCase()}${isPath ? "_PATH" : null}`;
+  const val = Deno.env.get(envName);
+  if (isPath && val !== undefined && !args[optName]) {
+    if (!fs.existsSync(val)) {
+      console.warn(`No file at "${val}" provided by ${envName}`);
+    } else {
+      args[optName] = val;
+    }
+  }
+
+  if (args[optName]) {
+    if (args[optName] === true) {
+      fatal(`--${optName} requires an argument`);
+    }
+    cb(args[optName]);
   }
-  const text = Deno.readTextFileSync(args.fileObj);
+}
+
+envOrOpt("fileObj", true, (p) => {
+  const text = Deno.readTextFileSync(p);
   const f = new Function("FileObj", "fs", "path", text);
   FileObjClass = f(FileObj, fs, path);
   if (typeof FileObjClass !== "function") {
@@ -76,7 +91,18 @@ if (args.fileObj) {
   if (typeof FileObjClass.prototype.getOp !== "function") {
     throw new Error(`Custom fileObj class must have a "getOp" function`);
   }
-}
+});
+
+let ctx = {};
+envOrOpt("ctx", false, (text) => {
+  const toEval = `return ${text}`;
+  try {
+    const f = new Function(toEval);
+    ctx = f();
+  } catch (e) {
+    fatal(`Could not create/execute function created from "${toEval}"`);
+  }
+});
 
 function forEach(
   dir: string,
@@ -92,6 +118,7 @@ function forEach(
         cliArgs: args,
         isDir: isDirectory,
         isFile: isFile,
+        ctx,
       }),
     );
     if (optRecursive) {
@@ -108,7 +135,7 @@ function forEach(
 const toDelete = new Set<string>();
 if (optDelete) {
   forEach(dir, (oldPath) => {
-    createMutation(oldPath);
+    createMutation(oldPath, ctx);
     if (oldPath.getOp()?.type === OpType.DELETE) {
       toDelete.add(oldPath.path);
       return true;
@@ -122,7 +149,7 @@ const newFiles = new Set<string>();
 
 forEach(dir, (oldPath) => {
   if (toDelete.has(oldPath.path)) return;
-  createMutation(oldPath);
+  createMutation(oldPath, ctx);
   const op = oldPath.getOp();
   if (op === null) return;
   if (op.type === OpType.DELETE) {

tests/e2e/number-files-with-ctx/cmd.json

@@ -0,0 +1,3 @@
+{
+  "params": ["f.mv(ctx.i++ + '.js')", "--ctx", "{i: 0}"]
+}

tests/e2e/number-files-with-ctx/expected.json

@@ -0,0 +1,21 @@
+{
+  "type": "dir",
+  "name": "temp",
+  "children": [
+    {
+      "type": "file",
+      "name": "1.js",
+      "text": ""
+    },
+    {
+      "type": "file",
+      "name": "0.js",
+      "text": ""
+    },
+    {
+      "type": "file",
+      "name": "2.js",
+      "text": ""
+    }
+  ]
+}