Adds stream API (#231)

.changeset/gentle-jokes-fail.md

@@ -0,0 +1,13 @@
+---
+"@clack/prompts": minor
+---
+
+Adds `stream` API which provides the same methods as `log`, but for iterable (even async) message streams. This is particularly useful for AI responses which are dynamically generated by LLMs.
+
+```ts
+import * as p from '@clack/prompts';
+
+await p.stream.step((async function* () {
+    yield* generateLLMResponse(question);
+})())
+```

examples/basic/package.json

@@ -10,6 +10,7 @@
   },
   "scripts": {
     "start": "jiti ./index.ts",
+    "stream": "jiti ./stream.ts",
     "spinner": "jiti ./spinner.ts",
     "spinner-ci": "npx cross-env CI=\"true\" jiti ./spinner-ci.ts"
   },

examples/basic/stream.ts

@@ -0,0 +1,34 @@
+import { setTimeout } from 'node:timers/promises';
+import * as p from '@clack/prompts';
+import color from 'picocolors';
+
+async function main() {
+	console.clear();
+
+	await setTimeout(1000);
+
+	p.intro(`${color.bgCyan(color.black(' create-app '))}`);
+
+	await p.stream.step((async function* () {
+		for (const line of lorem) {
+			for (const word of line.split(' ')) {
+				yield word;
+				yield ' ';
+				await setTimeout(200);
+			}
+			yield '\n';
+			if (line !== lorem.at(-1)) {
+				await setTimeout(1000);
+			}
+		}
+	})())
+
+	p.outro(`Problems? ${color.underline(color.cyan('https://example.com/issues'))}`);
+}
+
+const lorem = [
+	'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.', 
+	'Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.',
+]
+
+main().catch(console.error);

packages/prompts/README.md

@@ -188,4 +188,20 @@ log.error('Error!');
 log.message('Hello, World', { symbol: color.cyan('~') });
 ```
 
+
+### Stream
+
+When interacting with dynamic LLMs or other streaming message providers, use the `stream` APIs to log messages from an iterable, even an async one.
+
+```js
+import { stream } from '@clack/prompts';
+
+stream.info((function *() { yield 'Info!'; })());
+stream.success((function *() { yield 'Success!'; })());
+stream.step((function *() { yield 'Step!'; })());
+stream.warn((function *() { yield 'Warn!'; })());
+stream.error((function *() { yield 'Error!'; })());
+stream.message((function *() { yield 'Hello'; yield ", World" })(), { symbol: color.cyan('~') });
+```
+
 [clack-log-prompts](https://github.com/natemoo-re/clack/blob/main/.github/assets/clack-logs.png)

packages/prompts/src/index.ts

@@ -675,6 +675,48 @@ export const log = {
 	},
 };
 
+const prefix = `${color.gray(S_BAR)}  `;
+export const stream = {
+	message: async (iterable: Iterable<string>|AsyncIterable<string>, { symbol = color.gray(S_BAR) }: LogMessageOptions = {}) => {
+		process.stdout.write(`${color.gray(S_BAR)}\n${symbol}  `);
+		let lineWidth = 3;
+		for await (let chunk of iterable) {
+			chunk = chunk.replace(/\n/g, `\n${prefix}`);
+			if (chunk.includes('\n')) {
+				lineWidth = 3 + strip(chunk.slice(chunk.lastIndexOf('\n'))).length;
+			}
+			const chunkLen = strip(chunk).length;
+			if ((lineWidth + chunkLen) < process.stdout.columns) {
+				lineWidth += chunkLen;
+				process.stdout.write(chunk);
+			} else {
+				process.stdout.write(`\n${prefix}${chunk.trimStart()}`);
+				lineWidth = 3 + strip(chunk.trimStart()).length;
+			}
+		}
+		process.stdout.write('\n');
+	},
+	info: (iterable: Iterable<string>|AsyncIterable<string>) => {
+		return stream.message(iterable, { symbol: color.blue(S_INFO) });
+	},
+	success: (iterable: Iterable<string>|AsyncIterable<string>) => {
+		return stream.message(iterable, { symbol: color.green(S_SUCCESS) });
+	},
+	step: (iterable: Iterable<string>|AsyncIterable<string>) => {
+		return stream.message(iterable, { symbol: color.green(S_STEP_SUBMIT) });
+	},
+	warn: (iterable: Iterable<string>|AsyncIterable<string>) => {
+		return stream.message(iterable, { symbol: color.yellow(S_WARN) });
+	},
+	/** alias for `log.warn()`. */
+	warning: (iterable: Iterable<string>|AsyncIterable<string>) => {
+		return stream.warn(iterable);
+	},
+	error: (iterable: Iterable<string>|AsyncIterable<string>) => {
+		return stream.message(iterable, { symbol: color.red(S_ERROR) });
+	},
+}
+
 export const spinner = () => {
 	const frames = unicode ? ['◒', '◐', '◓', '◑'] : ['•', 'o', 'O', '0'];
 	const delay = unicode ? 80 : 120;