feat: Add --watch support (#107)

fixes #104

<!-- ps-id: 9ee09974-f388-4657-a4ae-4b2ebb490df5 -->

generator/gen.bin.ts

@@ -1,27 +1,37 @@
 #!/usr/bin/env node
 import yargs from 'yargs';
 
-// @ts-ignore
 import { hideBin } from 'yargs/helpers';
 import gen from './gen';
 import { glob } from 'glob';
+import { watcher } from './watcher';
 
 yargs(hideBin(process.argv))
-  .command<{ files: string }>(
+  .command(
     'gen [files]',
     'Generates json schemas next to corresponding ts files',
-    (yargs) => {
+    (yargs) =>
       yargs
         .positional('files', {
           describe: 'glob pattern of files',
           type: 'string',
           demandOption: true,
         })
-        .demandOption(['files']);
-    },
+        .option('watch', {
+          alias: 'w',
+          type: 'boolean',
+          description: 'Watch files for changes',
+        })
+        .demandOption(['files']),
     async (argv) => {
-      const files = await glob(argv.files);
+      if (argv.watch) {
+        console.log('Watching for changes...');
+        watcher(argv.files);
+        return;
+      }
 
+      console.log('Generating schemas...');
+      const files = await glob(argv.files);
       await gen({ files });
     },
   )

generator/watcher.ts

@@ -0,0 +1,30 @@
+import chokidar from 'chokidar';
+import gen from './gen';
+import path from 'node:path';
+import fsp from 'node:fs/promises';
+
+export function watcher(files: string | string[]) {
+  const watcher = chokidar.watch(files);
+  watcher.on('change', async (file: string) => {
+    await gen({ files: [file] });
+  });
+  watcher.on('add', async (file: string) => {
+    await gen({ files: [file] });
+  });
+  watcher.on('unlink', async (file: string) => {
+    const jsonFile = path.parse(file);
+    const schema = path.format({
+      ...jsonFile,
+      base: path.basename(jsonFile.base, jsonFile.ext) + '.gen.json',
+      ext: '.json',
+    });
+    const exists = await fsp
+      .stat(schema)
+      .then(() => true)
+      .catch(() => false);
+
+    if (exists) {
+      await fsp.rm(schema);
+    }
+  });
+}

package.json

@@ -8,6 +8,7 @@
   },
   "dependencies": {
     "@types/json-schema": "^7.0.13",
+    "chokidar": "3.5.3",
     "crypto-js": "^4.1.1",
     "glob": "^10.3.4",
     "json-schema-merge-allof": "^0.8.1",