feat: support watcher

docs/src/index.ts

@@ -0,0 +1,12 @@
+/**
+ * Adds two numbers together.
+ *
+ * @example
+ *
+ * ```js
+ * add(1, 2); // 3
+ * ```
+ */
+export function add(a: number, b: number) {
+  return a + b;
+}

package.json

@@ -33,6 +33,7 @@
     "test:types": "tsc --noEmit --skipLibCheck"
   },
   "dependencies": {
+    "@parcel/watcher": "^2.4.0",
     "c12": "^1.7.0",
     "citty": "^0.1.5",
     "consola": "^3.2.3",

src/automd.ts

@@ -1,16 +1,18 @@
 import { existsSync, promises as fsp } from "node:fs";
 import { resolve, relative } from "pathe";
+import type { SubscribeCallback } from "@parcel/watcher";
 import type { Config, ResolvedConfig } from "./config";
-import { TransformResult, transform } from "./transform";
+import { type TransformResult, transform } from "./transform";
 import { loadConfig } from "./config";
 
 export interface AutomdResult extends TransformResult {
-  _config: ResolvedConfig;
   input: string;
   output: string;
 }
 
-export async function automd(_config: Config = {}): Promise<AutomdResult[]> {
+export async function automd(
+  _config: Config = {},
+): Promise<{ results: AutomdResult[]; _config: ResolvedConfig; time: number }> {
   const config = await loadConfig(_config.dir, _config);
 
   let inputFiles = config.input;
@@ -20,40 +22,97 @@ export async function automd(_config: Config = {}): Promise<AutomdResult[]> {
       cwd: config.dir,
       absolute: false,
       onlyFiles: true,
-      ignore: ["node_modules", "dist", ".*", ...(config.ignore || [])],
+      ignore: config.ignore,
     });
   } else {
     inputFiles = inputFiles
       .map((i) => resolve(config.dir, i))
       .filter((i) => existsSync(i))
       .map((i) => relative(config.dir, i));
   }
+  const multiFiles = inputFiles.length > 1;
 
-  return Promise.all(
-    inputFiles.map((i) => _automd(i, config, inputFiles.length > 1)),
+  const cache: ResultCache = new Map();
+
+  const start = performance.now();
+  const results = await Promise.all(
+    inputFiles.map((i) => _automd(i, config, multiFiles, cache)),
   );
+  const time = Math.round((performance.now() - start) * 1000) / 1000;
+
+  if (config.watch) {
+    await _watch(inputFiles, config, multiFiles, cache);
+  }
+
+  return {
+    _config: config,
+    time,
+    results,
+  };
 }
 
-export async function _automd(
+// -- internal --
+
+type ResultCache = Map<string, AutomdResult>;
+
+async function _automd(
   relativeInput: string,
   config: ResolvedConfig,
-  multi: boolean,
+  multiFiles: boolean,
+  cache: ResultCache,
 ): Promise<AutomdResult> {
   const input = resolve(config.dir, relativeInput);
   const contents = await fsp.readFile(input, "utf8");
 
-  const result = await transform(contents, config);
+  const cachedResult = await cache.get(input);
+  if (cachedResult?.contents === contents) {
+    return cachedResult;
+  }
+
+  const transformResult = await transform(contents, config);
 
-  const output = multi
+  const output = multiFiles
     ? resolve(config.dir, config.output || ".", relativeInput)
     : resolve(config.dir, config.output || relativeInput);
 
-  await fsp.writeFile(output, result.contents, "utf8");
+  await fsp.writeFile(output, transformResult.contents, "utf8");
 
-  return {
-    _config: config,
+  const result: AutomdResult = {
     input,
     output,
-    ...result,
+    ...transformResult,
+  };
+  cache.set(input, result);
+  return result;
+}
+
+async function _watch(
+  inputFiles: string[],
+  config: ResolvedConfig,
+  multiFiles: boolean,
+  cache: ResultCache,
+) {
+  const watcher = await import("@parcel/watcher");
+
+  const watchCb: SubscribeCallback = async (_err, events) => {
+    const filesToUpdate = events
+      .map((e) => relative(config.dir, e.path))
+      .filter((p) => inputFiles.includes(p));
+    const start = performance.now();
+    const results = await Promise.all(
+      filesToUpdate.map((f) => _automd(f, config, multiFiles, cache)),
+    );
+    const time = performance.now() - start;
+    if (config.onWatch) {
+      config.onWatch({ results, time });
+    }
   };
+
+  const subscription = await watcher.subscribe(config.dir, watchCb, {
+    ignore: config.ignore,
+  });
+
+  process.on("SIGINT", () => {
+    subscription.unsubscribe();
+  });
 }