/**
 * Draft 持久化抽象层
 *
 * 默认实现：IndexedDbDraftStorage（localStorage fallback）
 *   - tiktok.drafts.index   → DraftMeta[]      列表渲染快
 *   - tiktok.draft.<id>     → 完整 PipelineDraft（按需 lazy load）
 *
 * 后续可继续升级到远端 /api/drafts，业务零改动。
 */

import { DraftMeta, PipelineDraft, toDraftMeta } from '../models/pipeline-draft.model';

export interface DraftStorage {
  list(): Promise<DraftMeta[]>;
  get(id: string): Promise<PipelineDraft | null>;
  put(draft: PipelineDraft): Promise<void>;
  delete(id: string): Promise<void>;
  /** 清空所有 drafts（仅调试 / 用户主动调用） */
  clear(): Promise<void>;
}

const INDEX_KEY = 'tiktok.drafts.index';
const DRAFT_KEY_PREFIX = 'tiktok.draft.';
const IDB_DB_NAME = 'videoWorkflow.workspaceStorage';
const IDB_DB_VERSION = 1;
const IDB_DRAFT_STORE = 'drafts';
const IDB_DRAFT_INDEX_STORE = 'draftIndex';
const IDB_SCOPE_INDEX = 'scope';
const IDB_MIGRATION_KEY_PREFIX = 'videoWorkflow.storageMigration.draftsIndexedDb.v1.';

export class LocalStorageDraftStorage implements DraftStorage {
  constructor(private readonly scope = '') {}

  private key(base: string): string {
    if (!this.scope) return base;
    const safeScope = this.scope.replace(/[^a-zA-Z0-9_.:-]/g, '_');
    return `${base}.${safeScope}`;
  }

  private draftKey(id: string): string {
    if (!this.scope) return DRAFT_KEY_PREFIX + id;
    const safeScope = this.scope.replace(/[^a-zA-Z0-9_.:-]/g, '_');
    return `${DRAFT_KEY_PREFIX}${safeScope}.${id}`;
  }

  async list(): Promise<DraftMeta[]> {
    try {
      const raw = localStorage.getItem(this.key(INDEX_KEY));
      if (!raw) return [];
      const arr = JSON.parse(raw);
      return Array.isArray(arr) ? arr : [];
    } catch (e) {
      console.warn('[DraftStorage] list parse failed', e);
      return [];
    }
  }

  async get(id: string): Promise<PipelineDraft | null> {
    try {
      const raw = localStorage.getItem(this.draftKey(id));
      if (!raw) return null;
      return JSON.parse(raw) as PipelineDraft;
    } catch (e) {
      console.warn('[DraftStorage] get parse failed', id, e);
      return null;
    }
  }

  async put(draft: PipelineDraft): Promise<void> {
    try {
      localStorage.setItem(this.draftKey(draft.id), JSON.stringify(draft));
    } catch (e) {
      // 配额溢出：尝试清最旧的草稿后重试一次
      console.warn('[DraftStorage] put failed, trying to evict oldest', e);
      await this.evictOldest();
      try {
        localStorage.setItem(this.draftKey(draft.id), JSON.stringify(draft));
      } catch (e2) {
        console.error('[DraftStorage] put failed after evict', e2);
        throw e2;
      }
    }
    // 同步更新索引
    const list = await this.list();
    const idx = list.findIndex((m) => m.id === draft.id);
    const meta = toDraftMeta(draft);
    if (idx >= 0) list[idx] = meta;
    else list.unshift(meta);
    list.sort((a, b) => b.updatedAt - a.updatedAt);
    try {
      localStorage.setItem(this.key(INDEX_KEY), JSON.stringify(list));
    } catch (e) {
      console.warn('[DraftStorage] index update failed', e);
    }
  }

  async delete(id: string): Promise<void> {
    try {
      localStorage.removeItem(this.draftKey(id));
    } catch {}
    const list = await this.list();
    const next = list.filter((m) => m.id !== id);
    try {
      localStorage.setItem(this.key(INDEX_KEY), JSON.stringify(next));
    } catch (e) {
      console.warn('[DraftStorage] index delete failed', e);
    }
  }

  async clear(): Promise<void> {
    const list = await this.list();
    for (const m of list) {
      try {
        localStorage.removeItem(this.draftKey(m.id));
      } catch {}
    }
    try {
      localStorage.removeItem(this.key(INDEX_KEY));
    } catch {}
  }

  /** 配额溢出回收：移除最旧的非 running draft */
  private async evictOldest(): Promise<void> {
    const list = await this.list();
    const evictable = list
      .filter((m) => m.status !== 'running')
      .sort((a, b) => a.updatedAt - b.updatedAt);
    if (!evictable.length) return;
    const victim = evictable[0];
    try {
      localStorage.removeItem(this.draftKey(victim.id));
      const next = list.filter((m) => m.id !== victim.id);
      localStorage.setItem(this.key(INDEX_KEY), JSON.stringify(next));
      console.warn('[DraftStorage] evicted oldest draft', victim.id);
    } catch {}
  }
}

interface ScopedDraftRecord {
  storageKey: string;
  scope: string;
  draft: PipelineDraft;
}

interface ScopedDraftMetaRecord {
  storageKey: string;
  scope: string;
  meta: DraftMeta;
}

export class IndexedDbDraftStorage implements DraftStorage {
  private dbPromise: Promise<IDBDatabase> | null = null;
  private readonly fallback: LocalStorageDraftStorage;
  private readonly safeScope: string;

  constructor(private readonly scope = '') {
    this.safeScope = this.normalizeScope(scope);
    this.fallback = new LocalStorageDraftStorage(scope);
  }

  async list(): Promise<DraftMeta[]> {
    try {
      await this.ensureMigrated();
      const db = await this.openDb();
      const records = await this.getAllByScope<ScopedDraftMetaRecord>(db, IDB_DRAFT_INDEX_STORE);
      return records
        .map((record) => record.meta)
        .sort((a, b) => b.updatedAt - a.updatedAt);
    } catch (error) {
      console.warn('[IndexedDbDraftStorage] list failed, using localStorage fallback', error);
      return this.fallback.list();
    }
  }

  async get(id: string): Promise<PipelineDraft | null> {
    try {
      await this.ensureMigrated();
      const db = await this.openDb();
      const record = await this.requestToPromise<ScopedDraftRecord | undefined>(
        db.transaction(IDB_DRAFT_STORE, 'readonly').objectStore(IDB_DRAFT_STORE).get(this.storageKey(id)),
      );
      return record?.draft || null;
    } catch (error) {
      console.warn('[IndexedDbDraftStorage] get failed, using localStorage fallback', id, error);
      return this.fallback.get(id);
    }
  }

  async put(draft: PipelineDraft): Promise<void> {
    try {
      await this.ensureMigrated();
      const db = await this.openDb();
      await this.putRecord(db, draft);
    } catch (error) {
      console.warn('[IndexedDbDraftStorage] put failed, using localStorage fallback', error);
      await this.fallback.put(draft);
    }
  }

  async delete(id: string): Promise<void> {
    try {
      await this.ensureMigrated();
      const db = await this.openDb();
      const tx = db.transaction([IDB_DRAFT_STORE, IDB_DRAFT_INDEX_STORE], 'readwrite');
      tx.objectStore(IDB_DRAFT_STORE).delete(this.storageKey(id));
      tx.objectStore(IDB_DRAFT_INDEX_STORE).delete(this.storageKey(id));
      await this.transactionDone(tx);
    } catch (error) {
      console.warn('[IndexedDbDraftStorage] delete failed, using localStorage fallback', id, error);
      await this.fallback.delete(id);
    }
  }

  async clear(): Promise<void> {
    try {
      await this.ensureMigrated();
      const db = await this.openDb();
      const drafts = await this.getAllByScope<ScopedDraftMetaRecord>(db, IDB_DRAFT_INDEX_STORE);
      const tx = db.transaction([IDB_DRAFT_STORE, IDB_DRAFT_INDEX_STORE], 'readwrite');
      for (const record of drafts) {
        tx.objectStore(IDB_DRAFT_STORE).delete(record.storageKey);
        tx.objectStore(IDB_DRAFT_INDEX_STORE).delete(record.storageKey);
      }
      await this.transactionDone(tx);
    } catch (error) {
      console.warn('[IndexedDbDraftStorage] clear failed, using localStorage fallback', error);
      await this.fallback.clear();
    }
  }

  private async ensureMigrated(): Promise<void> {
    if (this.hasMigrationMarker()) return;
    const db = await this.openDb();
    const existingCount = await this.countByScope(db, IDB_DRAFT_INDEX_STORE);
    if (existingCount === 0) {
      const metas = await this.fallback.list();
      for (const meta of metas) {
        const draft = await this.fallback.get(meta.id);
        if (draft) await this.putRecord(db, draft);
      }
    }
    this.setMigrationMarker();
  }

  private async putRecord(db: IDBDatabase, draft: PipelineDraft): Promise<void> {
    const storageKey = this.storageKey(draft.id);
    const tx = db.transaction([IDB_DRAFT_STORE, IDB_DRAFT_INDEX_STORE], 'readwrite');
    tx.objectStore(IDB_DRAFT_STORE).put({
      storageKey,
      scope: this.safeScope,
      draft,
    } satisfies ScopedDraftRecord);
    tx.objectStore(IDB_DRAFT_INDEX_STORE).put({
      storageKey,
      scope: this.safeScope,
      meta: toDraftMeta(draft),
    } satisfies ScopedDraftMetaRecord);
    await this.transactionDone(tx);
  }

  private openDb(): Promise<IDBDatabase> {
    if (this.dbPromise) return this.dbPromise;
    if (!('indexedDB' in window)) return Promise.reject(new Error('IndexedDB 不可用'));
    this.dbPromise = new Promise((resolve, reject) => {
      const req = indexedDB.open(IDB_DB_NAME, IDB_DB_VERSION);
      req.onupgradeneeded = () => {
        const db = req.result;
        if (!db.objectStoreNames.contains(IDB_DRAFT_STORE)) {
          const store = db.createObjectStore(IDB_DRAFT_STORE, { keyPath: 'storageKey' });
          store.createIndex(IDB_SCOPE_INDEX, 'scope', { unique: false });
        }
        if (!db.objectStoreNames.contains(IDB_DRAFT_INDEX_STORE)) {
          const store = db.createObjectStore(IDB_DRAFT_INDEX_STORE, { keyPath: 'storageKey' });
          store.createIndex(IDB_SCOPE_INDEX, 'scope', { unique: false });
        }
      };
      req.onsuccess = () => resolve(req.result);
      req.onerror = () => reject(req.error || new Error('IndexedDB 打开失败'));
      req.onblocked = () => reject(new Error('IndexedDB 被其他页面占用，请关闭旧页面后重试'));
    });
    return this.dbPromise;
  }

  private async getAllByScope<T>(db: IDBDatabase, storeName: string): Promise<T[]> {
    const store = db.transaction(storeName, 'readonly').objectStore(storeName);
    const index = store.index(IDB_SCOPE_INDEX);
    return this.requestToPromise<T[]>(index.getAll(this.safeScope));
  }

  private async countByScope(db: IDBDatabase, storeName: string): Promise<number> {
    const store = db.transaction(storeName, 'readonly').objectStore(storeName);
    return this.requestToPromise<number>(store.index(IDB_SCOPE_INDEX).count(this.safeScope));
  }

  private requestToPromise<T>(request: IDBRequest<T>): Promise<T> {
    return new Promise((resolve, reject) => {
      request.onsuccess = () => resolve(request.result);
      request.onerror = () => reject(request.error);
    });
  }

  private transactionDone(tx: IDBTransaction): Promise<void> {
    return new Promise((resolve, reject) => {
      tx.oncomplete = () => resolve();
      tx.onerror = () => reject(tx.error);
      tx.onabort = () => reject(tx.error || new Error('IndexedDB 事务已中止'));
    });
  }

  private storageKey(id: string): string {
    return `${this.safeScope}::${id}`;
  }

  private normalizeScope(scope: string): string {
    return (scope || 'default').replace(/[^a-zA-Z0-9_.:-]/g, '_');
  }

  private hasMigrationMarker(): boolean {
    try {
      return localStorage.getItem(IDB_MIGRATION_KEY_PREFIX + this.safeScope) === 'done';
    } catch {
      return false;
    }
  }

  private setMigrationMarker(): void {
    try {
      localStorage.setItem(IDB_MIGRATION_KEY_PREFIX + this.safeScope, 'done');
    } catch {}
  }
}