feat(cli): support stdin for input handling (fixes #71)

packages/cli/src/utils.ts

@@ -0,0 +1,79 @@
+import type { InputSource } from './types'
+import * as fsp from 'node:fs/promises'
+import * as path from 'node:path'
+import process from 'node:process'
+
+export function detectMode(
+  input: InputSource,
+  encodeFlag?: boolean,
+  decodeFlag?: boolean,
+): 'encode' | 'decode' {
+  // Explicit flags take precedence
+  if (encodeFlag)
+    return 'encode'
+  if (decodeFlag)
+    return 'decode'
+
+  // Auto-detect based on file extension
+  if (input.type === 'file') {
+    if (input.path.endsWith('.json'))
+      return 'encode'
+    if (input.path.endsWith('.toon'))
+      return 'decode'
+  }
+
+  // Default to encode
+  return 'encode'
+}
+
+export async function readInput(source: InputSource): Promise<string> {
+  if (source.type === 'stdin')
+    return readFromStdin()
+
+  return fsp.readFile(source.path, 'utf-8')
+}
+
+export function formatInputLabel(source: InputSource): string {
+  if (source.type === 'stdin')
+    return 'stdin'
+
+  const relativePath = path.relative(process.cwd(), source.path)
+  return relativePath || path.basename(source.path)
+}
+
+function readFromStdin(): Promise<string> {
+  const { stdin } = process
+
+  if (stdin.readableEnded)
+    return Promise.resolve('')
+
+  return new Promise((resolve, reject) => {
+    let data = ''
+
+    const onData = (chunk: string) => {
+      data += chunk
+    }
+
+    function cleanup() {
+      stdin.off('data', onData)
+      stdin.off('error', onError)
+      stdin.off('end', onEnd)
+    }
+
+    function onError(error: Error) {
+      cleanup()
+      reject(error)
+    }
+
+    function onEnd() {
+      cleanup()
+      resolve(data)
+    }
+
+    stdin.setEncoding('utf-8')
+    stdin.on('data', onData)
+    stdin.once('error', onError)
+    stdin.once('end', onEnd)
+    stdin.resume()
+  })
+}