feat(payment): add chat support discounts and gratitude

(cherry picked from commit ef9b79bc83)

src/stores/chat/__tests__/chat-commercial-message.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vitest";
+
+import { appendCommercialMessage } from "../helper/commercial-message";
+
+describe("chat commercial message", () => {
+  const incoming = {
+    messageId: "payment-thanks-1",
+    message: "Thank you for supporting me.",
+    characterId: "maya-tan",
+    createdAt: "2026-07-28T08:30:00.000Z",
+  };
+
+  it("appends one persisted payment thank-you to the matching character chat", () => {
+    const messages = appendCommercialMessage([], "maya-tan", incoming);
+
+    expect(messages).toHaveLength(1);
+    expect(messages[0]).toMatchObject({
+      remoteId: "payment-thanks-1",
+      content: "Thank you for supporting me.",
+      isFromAI: true,
+    });
+  });
+
+  it("ignores duplicate delivery and a message for another character", () => {
+    const messages = appendCommercialMessage([], "maya-tan", incoming);
+
+    expect(appendCommercialMessage(messages, "maya-tan", incoming)).toEqual(
+      messages,
+    );
+    expect(appendCommercialMessage(messages, "elio", incoming)).toEqual(
+      messages,
+    );
+  });
+});

src/stores/chat/chat-events.ts

@@ -28,6 +28,15 @@ export type ChatEvent =
     }
   | { type: "ChatOlderHistoryLoadFailed"; error: unknown }
   | { type: "ChatHistoryRefreshRequested" }
+  | {
+      type: "ChatCommercialMessageReceived";
+      message: {
+        messageId: string;
+        message: string;
+        characterId: string;
+        createdAt: string;
+      };
+    }
   // Chat domain events.
   | { type: "ChatSendMessage"; content: string }
   | { type: "ChatSendImage"; imageBase64: string }

src/stores/chat/helper/commercial-message.ts

@@ -0,0 +1,30 @@
+import { createRemoteUiMessageIdentity, type UiMessage } from "../ui-message";
+import { todayString } from "@/utils/date";
+
+export interface IncomingCommercialMessage {
+  messageId: string;
+  message: string;
+  characterId: string;
+  createdAt: string;
+}
+
+export function appendCommercialMessage(
+  messages: readonly UiMessage[],
+  activeCharacterId: string,
+  incoming: IncomingCommercialMessage,
+): UiMessage[] {
+  if (incoming.characterId !== activeCharacterId) return [...messages];
+  if (messages.some((message) => message.remoteId === incoming.messageId)) {
+    return [...messages];
+  }
+  const createdAt = new Date(incoming.createdAt);
+  return [
+    ...messages,
+    {
+      ...createRemoteUiMessageIdentity(incoming.messageId, true),
+      content: incoming.message,
+      isFromAI: true,
+      date: todayString(Number.isNaN(createdAt.getTime()) ? new Date() : createdAt),
+    },
+  ];
+}

src/stores/chat/machine/session-flow.ts

@@ -1,4 +1,5 @@
 import { createChatPromotionState } from "../helper/promotion";
+import { appendCommercialMessage } from "../helper/commercial-message";
 import { shouldPromptUnlockHistory } from "../helper/unlock";
 import { createInitialChatState } from "../chat-state";
 import {
@@ -53,6 +54,19 @@ const injectPromotionAction = unlockMachineSetup.assign(({ event }) => {
 
 const clearPromotionAction = unlockMachineSetup.assign({ promotion: null });
 
+const appendCommercialMessageAction = unlockMachineSetup.assign(
+  ({ context, event }) => {
+    if (event.type !== "ChatCommercialMessageReceived") return {};
+    return {
+      messages: appendCommercialMessage(
+        context.messages,
+        context.characterId,
+        event.message,
+      ),
+    };
+  },
+);
+
 export const chatMachineSetup = unlockMachineSetup.extend({
   actions: {
     startGuestSession: startGuestSessionAction,
@@ -60,6 +74,7 @@ export const chatMachineSetup = unlockMachineSetup.extend({
     clearChatSession: clearChatSessionAction,
     injectPromotion: injectPromotionAction,
     clearPromotion: clearPromotionAction,
+    appendCommercialMessage: appendCommercialMessageAction,
   },
 });
 
@@ -258,6 +273,7 @@ export const chatRootStateConfig = chatMachineSetup.createStateConfig({
   on: {
     ChatPromotionInjected: { actions: "injectPromotion" },
     ChatPromotionCleared: { actions: "clearPromotion" },
+    ChatCommercialMessageReceived: { actions: "appendCommercialMessage" },
   },
   states: {
     idle: idleState,