fix(media): sniff mime and keep extensions

src/media/mime.ts

@@ -0,0 +1,130 @@
+import path from "node:path";
+
+import { mediaKindFromMime, type MediaKind } from "./constants.js";
+
+// Map common mimes to preferred file extensions.
+const EXT_BY_MIME: Record<string, string> = {
+  "image/jpeg": ".jpg",
+  "image/png": ".png",
+  "image/webp": ".webp",
+  "image/gif": ".gif",
+  "audio/ogg": ".ogg",
+  "audio/mpeg": ".mp3",
+  "video/mp4": ".mp4",
+  "application/pdf": ".pdf",
+  "text/plain": ".txt",
+};
+
+const MIME_BY_EXT: Record<string, string> = Object.fromEntries(
+  Object.entries(EXT_BY_MIME).map(([mime, ext]) => [ext, mime]),
+);
+
+function normalizeHeaderMime(mime?: string | null): string | undefined {
+  if (!mime) return undefined;
+  const cleaned = mime.split(";")[0]?.trim().toLowerCase();
+  return cleaned || undefined;
+}
+
+function sniffMime(buffer?: Buffer): string | undefined {
+  if (!buffer || buffer.length < 4) return undefined;
+
+  // JPEG: FF D8 FF
+  if (buffer[0] === 0xff && buffer[1] === 0xd8 && buffer[2] === 0xff) {
+    return "image/jpeg";
+  }
+
+  // PNG: 89 50 4E 47 0D 0A 1A 0A
+  if (
+    buffer.length >= 8 &&
+    buffer[0] === 0x89 &&
+    buffer[1] === 0x50 &&
+    buffer[2] === 0x4e &&
+    buffer[3] === 0x47 &&
+    buffer[4] === 0x0d &&
+    buffer[5] === 0x0a &&
+    buffer[6] === 0x1a &&
+    buffer[7] === 0x0a
+  ) {
+    return "image/png";
+  }
+
+  // GIF: GIF87a / GIF89a
+  if (buffer.length >= 6) {
+    const sig = buffer.subarray(0, 6).toString("ascii");
+    if (sig === "GIF87a" || sig === "GIF89a") return "image/gif";
+  }
+
+  // WebP: RIFF....WEBP
+  if (
+    buffer.length >= 12 &&
+    buffer.subarray(0, 4).toString("ascii") === "RIFF" &&
+    buffer.subarray(8, 12).toString("ascii") === "WEBP"
+  ) {
+    return "image/webp";
+  }
+
+  // PDF: %PDF-
+  if (buffer.subarray(0, 5).toString("ascii") === "%PDF-") {
+    return "application/pdf";
+  }
+
+  // Ogg / Opus: OggS
+  if (buffer.subarray(0, 4).toString("ascii") === "OggS") {
+    return "audio/ogg";
+  }
+
+  // MP3: ID3 tag or frame sync FF E0+.
+  if (buffer.subarray(0, 3).toString("ascii") === "ID3") {
+    return "audio/mpeg";
+  }
+  if (buffer[0] === 0xff && (buffer[1] & 0xe0) === 0xe0) {
+    return "audio/mpeg";
+  }
+
+  // MP4: "ftyp" at offset 4.
+  if (buffer.length >= 12 && buffer.subarray(4, 8).toString("ascii") === "ftyp") {
+    return "video/mp4";
+  }
+
+  return undefined;
+}
+
+function extFromPath(filePath?: string): string | undefined {
+  if (!filePath) return undefined;
+  try {
+    if (/^https?:\/\//i.test(filePath)) {
+      const url = new URL(filePath);
+      return path.extname(url.pathname).toLowerCase() || undefined;
+    }
+  } catch {
+    // fall back to plain path parsing
+  }
+  const ext = path.extname(filePath).toLowerCase();
+  return ext || undefined;
+}
+
+export function detectMime(opts: {
+  buffer?: Buffer;
+  headerMime?: string | null;
+  filePath?: string;
+}): string | undefined {
+  const sniffed = sniffMime(opts.buffer);
+  if (sniffed) return sniffed;
+
+  const headerMime = normalizeHeaderMime(opts.headerMime);
+  if (headerMime) return headerMime;
+
+  const ext = extFromPath(opts.filePath);
+  if (ext && MIME_BY_EXT[ext]) return MIME_BY_EXT[ext];
+
+  return undefined;
+}
+
+export function extensionForMime(mime?: string | null): string | undefined {
+  if (!mime) return undefined;
+  return EXT_BY_MIME[mime.toLowerCase()];
+}
+
+export function kindFromMime(mime?: string | null): MediaKind {
+  return mediaKindFromMime(mime);
+}

src/media/store.test.ts

@@ -2,6 +2,7 @@ import fs from "node:fs/promises";
 import path from "node:path";
 
 import { afterAll, beforeAll, describe, expect, it, vi } from "vitest";
+import sharp from "sharp";
 
 const realOs = await vi.importActual<typeof import("node:os")>("node:os");
 const HOME = path.join(realOs.tmpdir(), "warelay-home-test");
@@ -35,6 +36,16 @@ describe("media store", () => {
     const savedStat = await fs.stat(saved.path);
     expect(savedStat.size).toBe(buf.length);
     expect(saved.contentType).toBe("text/plain");
+    expect(saved.path.endsWith(".txt")).toBe(true);
+
+    const jpeg = await sharp({
+      create: { width: 2, height: 2, channels: 3, background: "#123456" },
+    })
+      .jpeg({ quality: 80 })
+      .toBuffer();
+    const savedJpeg = await store.saveMediaBuffer(jpeg, "image/jpeg");
+    expect(savedJpeg.contentType).toBe("image/jpeg");
+    expect(savedJpeg.path.endsWith(".jpg")).toBe(true);
 
     const huge = Buffer.alloc(5 * 1024 * 1024 + 1);
     await expect(store.saveMediaBuffer(huge)).rejects.toThrow(
@@ -50,6 +61,7 @@ describe("media store", () => {
     expect(saved.size).toBe(10);
     const savedStat = await fs.stat(saved.path);
     expect(savedStat.isFile()).toBe(true);
+    expect(path.extname(saved.path)).toBe(".txt");
 
     // make the file look old and ensure cleanOldMedia removes it
     const past = Date.now() - 10_000;
@@ -57,4 +69,21 @@ describe("media store", () => {
     await store.cleanOldMedia(1);
     await expect(fs.stat(saved.path)).rejects.toThrow();
   });
+
+  it("renames media based on detected mime even when extension is wrong", async () => {
+    const pngBytes = await sharp({
+      create: { width: 2, height: 2, channels: 3, background: "#00ff00" },
+    })
+      .png()
+      .toBuffer();
+    const bogusExt = path.join(HOME, "image-wrong.bin");
+    await fs.writeFile(bogusExt, pngBytes);
+
+    const saved = await store.saveMediaSource(bogusExt);
+    expect(saved.contentType).toBe("image/png");
+    expect(path.extname(saved.path)).toBe(".png");
+
+    const buf = await fs.readFile(saved.path);
+    expect(buf.equals(pngBytes)).toBe(true);
+  });
 });

src/media/store.ts

@@ -6,6 +6,8 @@ import os from "node:os";
 import path from "node:path";
 import { pipeline } from "node:stream/promises";
 
+import { detectMime, extensionForMime } from "./mime.js";
+
 const MEDIA_DIR = path.join(os.homedir(), ".warelay", "media");
 const MAX_BYTES = 5 * 1024 * 1024; // 5MB
 const DEFAULT_TTL_MS = 2 * 60 * 1000; // 2 minutes
@@ -43,23 +45,42 @@ async function downloadToFile(
   url: string,
   dest: string,
   headers?: Record<string, string>,
-) {
+): Promise<{ headerMime?: string; sniffBuffer: Buffer; size: number }>
-  await new Promise<void>((resolve, reject) => {
+/**
+ * Download media to disk while capturing the first few KB for mime sniffing.
+ */
+{
+  return await new Promise((resolve, reject) => {
     const req = request(url, { headers }, (res) => {
       if (!res.statusCode || res.statusCode >= 400) {
         reject(new Error(`HTTP ${res.statusCode ?? "?"} downloading media`));
         return;
       }
       let total = 0;
+      const sniffChunks: Buffer[] = [];
+      let sniffLen = 0;
       const out = createWriteStream(dest);
       res.on("data", (chunk) => {
         total += chunk.length;
+        if (sniffLen < 16384) {
+          sniffChunks.push(chunk);
+          sniffLen += chunk.length;
+        }
         if (total > MAX_BYTES) {
           req.destroy(new Error("Media exceeds 5MB limit"));
         }
       });
       pipeline(res, out)
-        .then(() => resolve())
+        .then(() => {
+          const sniffBuffer = Buffer.concat(sniffChunks, Math.min(sniffLen, 16384));
+          const rawHeader = res.headers["content-type"];
+          const headerMime = Array.isArray(rawHeader) ? rawHeader[0] : rawHeader;
+          resolve({
+            headerMime,
+            sniffBuffer,
+            size: total,
+          });
+        })
         .catch(reject);
     });
     req.on("error", reject);
@@ -83,11 +104,22 @@ export async function saveMediaSource(
   await fs.mkdir(dir, { recursive: true });
   await cleanOldMedia();
   const id = crypto.randomUUID();
-  const dest = path.join(dir, id);
   if (looksLikeUrl(source)) {
-    await downloadToFile(source, dest, headers);
+    const tempDest = path.join(dir, `${id}.tmp`);
-    const stat = await fs.stat(dest);
+    const { headerMime, sniffBuffer, size } = await downloadToFile(
-    return { id, path: dest, size: stat.size };
+      source,
+      tempDest,
+      headers,
+    );
+    const mime = detectMime({
+      buffer: sniffBuffer,
+      headerMime,
+      filePath: source,
+    });
+    const ext = extensionForMime(mime) ?? path.extname(new URL(source).pathname);
+    const finalDest = path.join(dir, ext ? `${id}${ext}` : id);
+    await fs.rename(tempDest, finalDest);
+    return { id, path: finalDest, size, contentType: mime };
   }
   // local path
   const stat = await fs.stat(source);
@@ -97,8 +129,12 @@ export async function saveMediaSource(
   if (stat.size > MAX_BYTES) {
     throw new Error("Media exceeds 5MB limit");
   }
-  await fs.copyFile(source, dest);
+  const buffer = await fs.readFile(source);
-  return { id, path: dest, size: stat.size };
+  const mime = detectMime({ buffer, filePath: source });
+  const ext = extensionForMime(mime) ?? path.extname(source);
+  const dest = path.join(dir, ext ? `${id}${ext}` : id);
+  await fs.writeFile(dest, buffer);
+  return { id, path: dest, size: stat.size, contentType: mime };
 }
 
 export async function saveMediaBuffer(
@@ -112,7 +148,9 @@ export async function saveMediaBuffer(
   const dir = path.join(MEDIA_DIR, subdir);
   await fs.mkdir(dir, { recursive: true });
   const id = crypto.randomUUID();
-  const dest = path.join(dir, id);
+  const mime = detectMime({ buffer, headerMime: contentType });
+  const ext = extensionForMime(mime);
+  const dest = path.join(dir, ext ? `${id}${ext}` : id);
   await fs.writeFile(dest, buffer);
-  return { id, path: dest, size: buffer.byteLength, contentType };
+  return { id, path: dest, size: buffer.byteLength, contentType: mime };
 }

src/web/inbound.media.test.ts

@@ -0,0 +1,93 @@
+import crypto from "node:crypto";
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+
+import { afterAll, beforeAll, describe, expect, it, vi } from "vitest";
+
+const HOME = path.join(os.tmpdir(), `warelay-inbound-media-${crypto.randomUUID()}`);
+process.env.HOME = HOME;
+
+vi.mock("@whiskeysockets/baileys", async () => {
+  const actual = await vi.importActual<typeof import("@whiskeysockets/baileys")>(
+    "@whiskeysockets/baileys",
+  );
+  const jpegBuffer = Buffer.from([
+    0xff, 0xd8, 0xff, 0xdb, 0x00, 0x43, 0x00, 0x03, 0x02, 0x02, 0x02, 0x02, 0x02, 0x03, 0x02, 0x02, 0x02, 0x03, 0x03,
+    0x03, 0x03, 0x04, 0x06, 0x04, 0x04, 0x04, 0x04, 0x04, 0x08, 0x06, 0x06, 0x05, 0x06, 0x09, 0x08, 0x0a, 0x0a, 0x09,
+    0x08, 0x09, 0x09, 0x0a, 0x0c, 0x0f, 0x0c, 0x0a, 0x0b, 0x0e, 0x0b, 0x09, 0x09, 0x0d, 0x11, 0x0d, 0x0e, 0x0f, 0x10,
+    0x10, 0x11, 0x10, 0x0a, 0x0c, 0x12, 0x13, 0x12, 0x10, 0x13, 0x0f, 0x10, 0x10, 0x10, 0xff, 0xc0, 0x00, 0x11, 0x08,
+    0x00, 0x01, 0x00, 0x01, 0x03, 0x01, 0x11, 0x00, 0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xff, 0xc4, 0x00, 0x14, 0x00,
+    0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xc4, 0x00,
+    0x14, 0x10, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xda, 0x00,
+    0x0c, 0x03, 0x01, 0x00, 0x02, 0x11, 0x03, 0x11, 0x00, 0x3f, 0x00, 0xff, 0xd9,
+  ]);
+  return {
+    ...actual,
+    downloadMediaMessage: vi.fn().mockResolvedValue(jpegBuffer),
+  };
+});
+
+vi.mock("./session.js", () => {
+  const { EventEmitter } = require("node:events");
+  const ev = new EventEmitter();
+  const sock = {
+    ev,
+    ws: { close: vi.fn() },
+    sendPresenceUpdate: vi.fn().mockResolvedValue(undefined),
+    sendMessage: vi.fn().mockResolvedValue(undefined),
+    readMessages: vi.fn().mockResolvedValue(undefined),
+    updateMediaMessage: vi.fn(),
+    logger: {},
+    user: { id: "me@s.whatsapp.net" },
+  };
+  return {
+    createWaSocket: vi.fn().mockResolvedValue(sock),
+    waitForWaConnection: vi.fn().mockResolvedValue(undefined),
+    getStatusCode: vi.fn(() => 200),
+  };
+});
+
+import { monitorWebInbox } from "./inbound.js";
+
+describe("web inbound media saves with extension", () => {
+  beforeAll(async () => {
+    await fs.rm(HOME, { recursive: true, force: true });
+  });
+
+  afterAll(async () => {
+    await fs.rm(HOME, { recursive: true, force: true });
+  });
+
+  it("stores inbound image with jpeg extension", async () => {
+    const onMessage = vi.fn();
+    const listener = await monitorWebInbox({ verbose: false, onMessage });
+    const { createWaSocket } = await import("./session.js");
+    const realSock = await (createWaSocket as unknown as () => Promise<{
+      ev: import("node:events").EventEmitter;
+    }>)();
+
+    const upsert = {
+      type: "notify",
+      messages: [
+        {
+          key: { id: "img1", fromMe: false, remoteJid: "111@s.whatsapp.net" },
+          message: { imageMessage: { mimetype: "image/jpeg" } },
+          messageTimestamp: 1_700_000_001,
+        },
+      ],
+    };
+
+    realSock.ev.emit("messages.upsert", upsert);
+    await new Promise((resolve) => setTimeout(resolve, 5));
+
+    expect(onMessage).toHaveBeenCalledTimes(1);
+    const msg = onMessage.mock.calls[0][0];
+    expect(msg.mediaPath).toBeDefined();
+    expect(path.extname(msg.mediaPath!)).toBe(".jpg");
+    const stat = await fs.stat(msg.mediaPath!);
+    expect(stat.size).toBeGreaterThan(0);
+
+    await listener.close();
+  });
+});

src/web/media.test.ts

@@ -38,4 +38,20 @@ describe("web media loading", () => {
     expect(result.buffer.length).toBeLessThanOrEqual(cap);
     expect(result.buffer.length).toBeLessThan(buffer.length);
   });
+
+  it("sniffs mime before extension when loading local files", async () => {
+    const pngBuffer = await sharp({
+      create: { width: 2, height: 2, channels: 3, background: "#00ff00" },
+    })
+      .png()
+      .toBuffer();
+    const wrongExt = path.join(os.tmpdir(), `warelay-media-${Date.now()}.bin`);
+    tmpFiles.push(wrongExt);
+    await fs.writeFile(wrongExt, pngBuffer);
+
+    const result = await loadWebMedia(wrongExt, 1024 * 1024);
+
+    expect(result.kind).toBe("image");
+    expect(result.contentType).toBe("image/jpeg");
+  });
 });

src/web/media.ts

@@ -1,5 +1,4 @@
 import fs from "node:fs/promises";
-import path from "node:path";
 import sharp from "sharp";
 
 import { isVerbose, logVerbose } from "../globals.js";
@@ -8,6 +7,7 @@ import {
   maxBytesForKind,
   mediaKindFromMime,
 } from "../media/constants.js";
+import { detectMime } from "../media/mime.js";
 
 export async function loadWebMedia(
   mediaUrl: string,
@@ -45,7 +45,11 @@ export async function loadWebMedia(
       throw new Error(`Failed to fetch media: HTTP ${res.status}`);
     }
     const array = Buffer.from(await res.arrayBuffer());
-    const contentType = res.headers.get("content-type");
+    const contentType = detectMime({
+      buffer: array,
+      headerMime: res.headers.get("content-type"),
+      filePath: mediaUrl,
+    });
     const kind = mediaKindFromMime(contentType);
     const cap = Math.min(
       maxBytes ?? maxBytesForKind(kind),
@@ -66,24 +70,7 @@ export async function loadWebMedia(
 
   // Local path
   const data = await fs.readFile(mediaUrl);
-  const ext = path.extname(mediaUrl);
+  const mime = detectMime({ buffer: data, filePath: mediaUrl });
-  const mime =
-    (ext &&
-      (
-        {
-          ".jpg": "image/jpeg",
-          ".jpeg": "image/jpeg",
-          ".png": "image/png",
-          ".webp": "image/webp",
-          ".gif": "image/gif",
-          ".ogg": "audio/ogg",
-          ".opus": "audio/ogg",
-          ".mp3": "audio/mpeg",
-          ".mp4": "video/mp4",
-          ".pdf": "application/pdf",
-        } as Record<string, string | undefined>
-      )[ext.toLowerCase()]) ??
-    undefined;
   const kind = mediaKindFromMime(mime);
   const cap = Math.min(
     maxBytes ?? maxBytesForKind(kind),