import type { SyncEvent } from './types.js';
import { parseEventFilename } from './utils.js';

const EVENTS_DIR = 'events';

export class FolderStore {
  private dirHandle: FileSystemDirectoryHandle | null = null;

  // ── Handle management ──────────────────────────────────────

  get hasHandle(): boolean {
    return this.dirHandle !== null;
  }

  getHandle(): FileSystemDirectoryHandle | null {
    return this.dirHandle;
  }

  setHandle(handle: FileSystemDirectoryHandle): void {
    this.dirHandle = handle;
  }

  async selectFolder(): Promise<FileSystemDirectoryHandle> {
    if (typeof window.showDirectoryPicker !== 'function') {
      throw new Error(
        'File System Access API is not supported in this browser. ' +
          'Use a Chromium-based browser (Chrome, Edge, Brave, etc.).',
      );
    }
    this.dirHandle = await window.showDirectoryPicker({
      mode: 'readwrite',
    });
    // Ensure events directory exists
    await this.dirHandle.getDirectoryHandle(EVENTS_DIR, { create: true });
    return this.dirHandle;
  }

  // ── Permission checks ─────────────────────────────────────

  async hasPermission(): Promise<boolean> {
    if (!this.dirHandle) return false;
    try {
      const perm = await this.dirHandle.queryPermission({ mode: 'readwrite' });
      return perm === 'granted';
    } catch {
      return false;
    }
  }

  async requestPermission(): Promise<boolean> {
    if (!this.dirHandle) return false;
    try {
      const perm = await this.dirHandle.requestPermission({
        mode: 'readwrite',
      });
      return perm === 'granted';
    } catch {
      return false;
    }
  }

  // ── Write event file ──────────────────────────────────────

  async writeEvent(filename: string, event: SyncEvent): Promise<void> {
    const eventsDir = await this.getEventsDir();
    const fileHandle = await eventsDir.getFileHandle(filename, {
      create: true,
    });
    const writable = await fileHandle.createWritable();
    try {
      await writable.write(JSON.stringify(event, null, 2));
    } finally {
      await writable.close();
    }
  }

  // ── Scan events ────────────────────────────────────────────

  async scanEventFilenames(): Promise<string[]> {
    const eventsDir = await this.getEventsDir();
    const names: string[] = [];

    for await (const [name, handle] of eventsDir.entries()) {
      if (handle.kind === 'file' && name.endsWith('.json')) {
        if (parseEventFilename(name)) {
          names.push(name);
        }
      }
    }

    // Sort by (timestamp, full filename) for deterministic ordering
    names.sort((a, b) => {
      const pa = parseEventFilename(a)!;
      const pb = parseEventFilename(b)!;
      if (pa.ts !== pb.ts) return pa.ts - pb.ts;
      return a.localeCompare(b);
    });

    return names;
  }

  async readEventFile(filename: string): Promise<SyncEvent | null> {
    const eventsDir = await this.getEventsDir();
    try {
      const fh = await eventsDir.getFileHandle(filename);
      const file = await fh.getFile();
      const text = await file.text();
      return JSON.parse(text) as SyncEvent;
    } catch {
      return null;
    }
  }

  // ── Data files (SQLite database persistence) ────────────────

  async writeDataFile(filename: string, data: Uint8Array): Promise<void> {
    const dataDir = await this.getDataDir();
    const fh = await dataDir.getFileHandle(filename, { create: true });
    const writable = await fh.createWritable();
    try {
      await writable.write(data.buffer as ArrayBuffer);
    } finally {
      await writable.close();
    }
  }

  async readDataFile(filename: string): Promise<Uint8Array | null> {
    try {
      const dataDir = await this.getDataDir();
      const fh = await dataDir.getFileHandle(filename);
      const file = await fh.getFile();
      const buf = await file.arrayBuffer();
      return new Uint8Array(buf);
    } catch {
      return null;
    }
  }

  // ── Internals ──────────────────────────────────────────────

  private async getEventsDir(): Promise<FileSystemDirectoryHandle> {
    if (!this.dirHandle) {
      throw new Error('No folder selected. Call selectFolder() first.');
    }
    return this.dirHandle.getDirectoryHandle(EVENTS_DIR, { create: true });
  }

  private async getDataDir(): Promise<FileSystemDirectoryHandle> {
    if (!this.dirHandle) {
      throw new Error('No folder selected. Call selectFolder() first.');
    }
    return this.dirHandle.getDirectoryHandle('data', { create: true });
  }
}