fix(chat): stabilize message identities

src/stores/chat/ui-message.ts

@@ -1,7 +1,9 @@
 import { z } from "zod";
 
 export const UiMessageSchema = z.object({
-  id: z.string().optional(),
+  displayId: z.string().min(1),
+  remoteId: z.string().min(1).optional(),
+  clientId: z.string().min(1).optional(),
   content: z.string(),
   isFromAI: z.boolean(),
   date: z.string(),
@@ -18,6 +20,41 @@ export const UiMessageSchema = z.object({
 
 export type UiMessage = z.infer<typeof UiMessageSchema>;
 
+let fallbackClientId = 0;
+
+export function createRemoteUiMessageIdentity(
+  remoteId: string,
+  isFromAI: boolean,
+  occurrence = 0,
+): Pick<UiMessage, "displayId" | "remoteId"> {
+  const role = isFromAI ? "assistant" : "user";
+  const base = `server:${encodeURIComponent(remoteId)}:${role}`;
+  return {
+    displayId: occurrence > 0 ? `${base}:${occurrence}` : base,
+    remoteId,
+  };
+}
+
+export function createLegacyUiMessageIdentity(
+  fingerprint: string,
+  occurrence = 0,
+): Pick<UiMessage, "displayId"> {
+  const base = `legacy:${hashIdentity(fingerprint)}`;
+  return {
+    displayId: occurrence > 0 ? `${base}:${occurrence}` : base,
+  };
+}
+
+export function createClientUiMessageIdentity(
+  kind: "message" | "image" | "reply" | "error",
+): Pick<UiMessage, "displayId" | "clientId"> {
+  const clientId = createClientId();
+  return {
+    clientId,
+    displayId: `client:${kind}:${clientId}`,
+  };
+}
+
 export const UiMessage = {
   create(input: Omit<UiMessage, "date"> & { date?: string }): UiMessage {
     return UiMessageSchema.parse({
@@ -31,3 +68,20 @@ export const UiMessage = {
     });
   },
 };
+
+function createClientId(): string {
+  if (typeof globalThis.crypto?.randomUUID === "function") {
+    return globalThis.crypto.randomUUID();
+  }
+  fallbackClientId += 1;
+  return `${Date.now().toString(36)}-${fallbackClientId.toString(36)}`;
+}
+
+function hashIdentity(value: string): string {
+  let hash = 0x811c9dc5;
+  for (let index = 0; index < value.length; index += 1) {
+    hash ^= value.charCodeAt(index);
+    hash = Math.imul(hash, 0x01000193);
+  }
+  return (hash >>> 0).toString(36);
+}