/**
 * 基于 localStorage 的客户端持久化存储。
 * 提供会话、标签、图片资源的 CRUD 操作。
 */

import type { Session, Tag, ImageAsset, ChatMessage } from "./types";

const STORAGE_KEYS = {
  sessions: "epeekit-sessions",
  tags: "epeekit-tags",
  assets: "epeekit-assets",
} as const;

// --------------- 内置标签 ---------------

const BUILTIN_TAGS: Tag[] = [
  { id: "tag-ui", name: "UI", color: "#6366f1", builtin: true },
  { id: "tag-icon", name: "Icon", color: "#f59e0b", builtin: true },
  { id: "tag-illustration", name: "原画", color: "#10b981", builtin: true },
  { id: "tag-style", name: "风格探索", color: "#ec4899", builtin: true },
  { id: "tag-character", name: "立绘", color: "#8b5cf6", builtin: true },
  { id: "tag-concept", name: "概念图", color: "#06b6d4", builtin: true },
];

// --------------- 通用 helpers ---------------

function readJSON<T>(key: string, fallback: T): T {
  if (typeof window === "undefined") return fallback;
  try {
    const raw = localStorage.getItem(key);
    return raw ? (JSON.parse(raw) as T) : fallback;
  } catch {
    return fallback;
  }
}

function writeJSON<T>(key: string, data: T) {
  if (typeof window === "undefined") return;
  localStorage.setItem(key, JSON.stringify(data));
}

// --------------- ID 生成 ---------------

let counter = 0;
export function generateId(prefix = ""): string {
  counter++;
  const ts = Date.now().toString(36);
  const rand = Math.random().toString(36).slice(2, 6);
  return `${prefix}${ts}-${rand}-${counter}`;
}

// --------------- 标签 ---------------

export function loadTags(): Tag[] {
  const custom = readJSON<Tag[]>(STORAGE_KEYS.tags, []);
  const builtinIds = new Set(BUILTIN_TAGS.map((t) => t.id));
  const merged = [...BUILTIN_TAGS, ...custom.filter((t) => !builtinIds.has(t.id))];
  return merged;
}

export function saveTags(tags: Tag[]) {
  const custom = tags.filter((t) => !t.builtin);
  writeJSON(STORAGE_KEYS.tags, custom);
}

export function addTag(name: string, color: string): Tag {
  const tag: Tag = { id: generateId("tag-"), name, color, builtin: false };
  const existing = loadTags();
  saveTags([...existing, tag]);
  return tag;
}

export function deleteTag(tagId: string) {
  const tags = loadTags().filter((t) => t.id !== tagId && !t.builtin);
  saveTags(tags);
}

// --------------- 会话 ---------------

export function loadSessions(): Session[] {
  return readJSON<Session[]>(STORAGE_KEYS.sessions, []);
}

export function saveSessions(sessions: Session[]) {
  writeJSON(STORAGE_KEYS.sessions, sessions);
}

export function createSession(): Session {
  const now = Date.now();
  const session: Session = {
    id: generateId("sess-"),
    title: "新对话",
    tags: [],
    messages: [],
    createdAt: now,
    updatedAt: now,
  };
  const sessions = loadSessions();
  saveSessions([session, ...sessions]);
  return session;
}

export function updateSession(session: Session) {
  const sessions = loadSessions();
  const idx = sessions.findIndex((s) => s.id === session.id);
  if (idx >= 0) {
    sessions[idx] = { ...session, updatedAt: Date.now() };
  } else {
    sessions.unshift({ ...session, updatedAt: Date.now() });
  }
  saveSessions(sessions);
}

export function deleteSession(sessionId: string) {
  const sessions = loadSessions().filter((s) => s.id !== sessionId);
  saveSessions(sessions);
  // 同时删除关联的图片资源
  const assets = loadAssets().filter((a) => a.sessionId !== sessionId);
  saveAssets(assets);
}

// --------------- 图片资源 ---------------

export function loadAssets(): ImageAsset[] {
  return readJSON<ImageAsset[]>(STORAGE_KEYS.assets, []);
}

export function saveAssets(assets: ImageAsset[]) {
  writeJSON(STORAGE_KEYS.assets, assets);
}

export function addAsset(asset: ImageAsset) {
  const assets = loadAssets();
  assets.unshift(asset);
  saveAssets(assets);
}

export function updateAsset(assetId: string, patch: Partial<ImageAsset>) {
  const assets = loadAssets();
  const idx = assets.findIndex((a) => a.id === assetId);
  if (idx >= 0) {
    assets[idx] = { ...assets[idx], ...patch };
    saveAssets(assets);
  }
}

export function deleteAsset(assetId: string) {
  saveAssets(loadAssets().filter((a) => a.id !== assetId));
}

export function toggleFavorite(assetId: string): boolean {
  const assets = loadAssets();
  const idx = assets.findIndex((a) => a.id === assetId);
  if (idx >= 0) {
    assets[idx].favorited = !assets[idx].favorited;
    saveAssets(assets);
    return assets[idx].favorited;
  }
  return false;
}