feat: Add Line plugin (#1630)

* feat: add LINE plugin (#1630) (thanks @plum-dawg)

* feat: complete LINE plugin (#1630) (thanks @plum-dawg)

* chore: drop line plugin node_modules (#1630) (thanks @plum-dawg)

* test: mock /context report in commands test (#1630) (thanks @plum-dawg)

* test: limit macOS CI workers to avoid OOM (#1630) (thanks @plum-dawg)

* test: reduce macOS CI vitest workers (#1630) (thanks @plum-dawg)

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/line/download.ts

@@ -0,0 +1,120 @@
+import fs from "node:fs";
+import path from "node:path";
+import os from "node:os";
+import { messagingApi } from "@line/bot-sdk";
+import { logVerbose } from "../globals.js";
+
+interface DownloadResult {
+  path: string;
+  contentType?: string;
+  size: number;
+}
+
+export async function downloadLineMedia(
+  messageId: string,
+  channelAccessToken: string,
+  maxBytes = 10 * 1024 * 1024,
+): Promise<DownloadResult> {
+  const client = new messagingApi.MessagingApiBlobClient({
+    channelAccessToken,
+  });
+
+  const response = await client.getMessageContent(messageId);
+
+  // response is a Readable stream
+  const chunks: Buffer[] = [];
+  let totalSize = 0;
+
+  for await (const chunk of response as AsyncIterable<Buffer>) {
+    totalSize += chunk.length;
+    if (totalSize > maxBytes) {
+      throw new Error(`Media exceeds ${Math.round(maxBytes / (1024 * 1024))}MB limit`);
+    }
+    chunks.push(chunk);
+  }
+
+  const buffer = Buffer.concat(chunks);
+
+  // Determine content type from magic bytes
+  const contentType = detectContentType(buffer);
+  const ext = getExtensionForContentType(contentType);
+
+  // Write to temp file
+  const tempDir = os.tmpdir();
+  const fileName = `line-media-${messageId}-${Date.now()}${ext}`;
+  const filePath = path.join(tempDir, fileName);
+
+  await fs.promises.writeFile(filePath, buffer);
+
+  logVerbose(`line: downloaded media ${messageId} to ${filePath} (${buffer.length} bytes)`);
+
+  return {
+    path: filePath,
+    contentType,
+    size: buffer.length,
+  };
+}
+
+function detectContentType(buffer: Buffer): string {
+  // Check magic bytes
+  if (buffer.length >= 2) {
+    // JPEG
+    if (buffer[0] === 0xff && buffer[1] === 0xd8) {
+      return "image/jpeg";
+    }
+    // PNG
+    if (buffer[0] === 0x89 && buffer[1] === 0x50 && buffer[2] === 0x4e && buffer[3] === 0x47) {
+      return "image/png";
+    }
+    // GIF
+    if (buffer[0] === 0x47 && buffer[1] === 0x49 && buffer[2] === 0x46) {
+      return "image/gif";
+    }
+    // WebP
+    if (
+      buffer[0] === 0x52 &&
+      buffer[1] === 0x49 &&
+      buffer[2] === 0x46 &&
+      buffer[3] === 0x46 &&
+      buffer[8] === 0x57 &&
+      buffer[9] === 0x45 &&
+      buffer[10] === 0x42 &&
+      buffer[11] === 0x50
+    ) {
+      return "image/webp";
+    }
+    // MP4
+    if (buffer[4] === 0x66 && buffer[5] === 0x74 && buffer[6] === 0x79 && buffer[7] === 0x70) {
+      return "video/mp4";
+    }
+    // M4A/AAC
+    if (buffer[0] === 0x00 && buffer[1] === 0x00 && buffer[2] === 0x00) {
+      if (buffer[4] === 0x66 && buffer[5] === 0x74 && buffer[6] === 0x79 && buffer[7] === 0x70) {
+        return "audio/mp4";
+      }
+    }
+  }
+
+  return "application/octet-stream";
+}
+
+function getExtensionForContentType(contentType: string): string {
+  switch (contentType) {
+    case "image/jpeg":
+      return ".jpg";
+    case "image/png":
+      return ".png";
+    case "image/gif":
+      return ".gif";
+    case "image/webp":
+      return ".webp";
+    case "video/mp4":
+      return ".mp4";
+    case "audio/mp4":
+      return ".m4a";
+    case "audio/mpeg":
+      return ".mp3";
+    default:
+      return ".bin";
+  }
+}