refactor(stores): standardize state machine structure

src/stores/private-room/helper/unlock.ts

@@ -0,0 +1,41 @@
+import type { PrivateAlbumUnlockResponse } from "@/data/dto/private-room";
+
+import type { PrivateRoomUnlockPaywallRequest } from "../private-room-state";
+
+export function toPrivateRoomErrorMessage(error: unknown): string {
+  if (error instanceof Error && error.message) return error.message;
+  return "Private room is temporarily unavailable. Please try again.";
+}
+
+export function toUnlockErrorMessage(
+  response: PrivateAlbumUnlockResponse,
+): string | null {
+  switch (response.reason) {
+    case "cost_changed":
+      return "Unlock price changed. Please confirm again.";
+    case "unlock_in_progress":
+      return "This album is already unlocking. Please try again shortly.";
+    case "deduct_failed":
+      return "Credit deduction failed. Please try again.";
+    case "persist_failed_refunded":
+      return "Unlock failed and your credits were refunded. Please try again.";
+    case "not_found":
+      return "This private album is no longer available.";
+    default:
+      return response.unlocked && !response.locked
+        ? null
+        : "Unlock failed. Please try again.";
+  }
+}
+
+export function toPaywallRequest(
+  response: PrivateAlbumUnlockResponse,
+): PrivateRoomUnlockPaywallRequest {
+  return {
+    albumId: response.albumId,
+    reason: response.reason,
+    requiredCredits: response.requiredCredits || response.unlockCost,
+    currentCredits: response.creditBalance,
+    shortfallCredits: response.shortfallCredits,
+  };
+}