Add WhatsApp reactions support

Summary:

Test Plan:

src/web/active-listener.ts

@@ -14,6 +14,13 @@ export type ActiveWebListener = {
     options?: ActiveWebSendOptions,
   ) => Promise<{ messageId: string }>;
   sendPoll: (to: string, poll: PollInput) => Promise<{ messageId: string }>;
+  sendReaction: (
+    chatJid: string,
+    messageId: string,
+    emoji: string,
+    fromMe: boolean,
+    participant?: string,
+  ) => Promise<void>;
   sendComposingTo: (to: string) => Promise<void>;
   close?: () => Promise<void>;
 };

src/web/inbound.ts

@@ -566,6 +566,30 @@ export async function monitorWebInbox(options: {
       const jid = toWhatsappJid(to);
       await sock.sendPresenceUpdate("composing", jid);
     },
+    /**
+     * Send a reaction (emoji) to a specific message.
+     * Pass an empty string for emoji to remove the reaction.
+     */
+    sendReaction: async (
+      chatJid: string,
+      messageId: string,
+      emoji: string,
+      fromMe: boolean,
+      participant?: string,
+    ): Promise<void> => {
+      const jid = toWhatsappJid(chatJid);
+      await sock.sendMessage(jid, {
+        react: {
+          text: emoji,
+          key: {
+            remoteJid: jid,
+            id: messageId,
+            fromMe,
+            participant,
+          },
+        },
+      });
+    },
   } as const;
 }
 

src/web/outbound.test.ts

@@ -8,16 +8,26 @@ vi.mock("./media.js", () => ({
   loadWebMedia: (...args: unknown[]) => loadWebMediaMock(...args),
 }));
 
-import { sendMessageWhatsApp, sendPollWhatsApp } from "./outbound.js";
+import {
+  sendMessageWhatsApp,
+  sendPollWhatsApp,
+  sendReactionWhatsApp,
+} from "./outbound.js";
 
 describe("web outbound", () => {
   const sendComposingTo = vi.fn(async () => {});
   const sendMessage = vi.fn(async () => ({ messageId: "msg123" }));
   const sendPoll = vi.fn(async () => ({ messageId: "poll123" }));
+  const sendReaction = vi.fn(async () => {});
 
   beforeEach(() => {
     vi.clearAllMocks();
-    setActiveWebListener({ sendComposingTo, sendMessage, sendPoll });
+    setActiveWebListener({
+      sendComposingTo,
+      sendMessage,
+      sendPoll,
+      sendReaction,
+    });
   });
 
   afterEach(() => {
@@ -156,4 +166,18 @@ describe("web outbound", () => {
       durationHours: undefined,
     });
   });
+
+  it("sends reactions via active listener", async () => {
+    await sendReactionWhatsApp("1555@s.whatsapp.net", "msg123", "✅", {
+      verbose: false,
+      fromMe: false,
+    });
+    expect(sendReaction).toHaveBeenCalledWith(
+      "1555@s.whatsapp.net",
+      "msg123",
+      "✅",
+      false,
+      undefined,
+    );
+  });
 });

src/web/outbound.ts

@@ -91,6 +91,52 @@ export async function sendMessageWhatsApp(
     throw err;
   }
 }
+
+export async function sendReactionWhatsApp(
+  chatJid: string,
+  messageId: string,
+  emoji: string,
+  options: {
+    verbose: boolean;
+    fromMe?: boolean;
+    participant?: string;
+  },
+): Promise<void> {
+  const correlationId = randomUUID();
+  const active = getActiveWebListener();
+  if (!active) {
+    throw new Error(
+      "No active gateway listener. Start the gateway before sending WhatsApp reactions.",
+    );
+  }
+  const logger = getChildLogger({
+    module: "web-outbound",
+    correlationId,
+    chatJid,
+    messageId,
+  });
+  try {
+    const jid = toWhatsappJid(chatJid);
+    outboundLog.info(`Sending reaction "${emoji}" -> message ${messageId}`);
+    logger.info({ chatJid: jid, messageId, emoji }, "sending reaction");
+    await active.sendReaction(
+      chatJid,
+      messageId,
+      emoji,
+      options.fromMe ?? false,
+      options.participant,
+    );
+    outboundLog.info(`Sent reaction "${emoji}" -> message ${messageId}`);
+    logger.info({ chatJid: jid, messageId, emoji }, "sent reaction");
+  } catch (err) {
+    logger.error(
+      { err: String(err), chatJid, messageId, emoji },
+      "failed to send reaction via web session",
+    );
+    throw err;
+  }
+}
+
 export async function sendPollWhatsApp(
   to: string,
   poll: PollInput,