worldhopper/lib/services/epub_download_service.dart

import 'dart:io';
import 'package:dio/dio.dart';
import 'package:flutter_cache_manager/flutter_cache_manager.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart' as path;
import 'package:worldhopper/models/entry.dart';
import 'package:worldhopper/models/server.dart';
import 'package:worldhopper/services/auth_service.dart';

/// Service for downloading and caching EPUB files
class EpubDownloadService {
  final AuthService _authService;
  final CacheManager _cacheManager;

  EpubDownloadService({
    AuthService? authService,
    CacheManager? cacheManager,
  })  : _authService = authService ?? AuthService(),
        _cacheManager = cacheManager ?? DefaultCacheManager();

  /// Download EPUB file from server with authentication
  /// Returns the local file path of the downloaded EPUB
  Future<File> downloadEpub(
    Entry entry,
    Server server, {
    String? savePath,
    void Function(double progress)? onProgress,
    CancelToken? cancelToken,
  }) async {
    final acquisitionLink = entry.acquisitionLink;
    if (acquisitionLink == null) {
      throw Exception('No acquisition link found for entry: ${entry.title}');
    }

    final url = acquisitionLink.href;
    if (url.isEmpty) {
      throw Exception('Invalid acquisition link URL');
    }

    // When a specific savePath is requested, bypass the in-memory cache and
    // write directly — the caller owns the destination file's lifecycle.
    if (savePath != null) {
      final dio = _authService.createAuthenticatedClient(server);
      await dio.download(
        url,
        savePath,
        cancelToken: cancelToken,
        onReceiveProgress: (received, total) {
          if (total != -1 && onProgress != null) {
            onProgress(received / total);
          }
        },
      );
      return File(savePath);
    }

    final fileInfo = await _cacheManager.getFileFromCache(url);
    if (fileInfo != null && await fileInfo.file.exists()) {
      return fileInfo.file;
    }

    final dio = _authService.createAuthenticatedClient(server);

    final cacheDir = await getTemporaryDirectory();
    final fileName = '${entry.id}.epub';
    final filePath = path.join(cacheDir.path, fileName);
    final file = File(filePath);

    await dio.download(
      url,
      filePath,
      cancelToken: cancelToken,
      onReceiveProgress: (received, total) {
        if (total != -1 && onProgress != null) {
          final progress = received / total;
          onProgress(progress);
        }
      },
    );

    await _cacheManager.putFile(
      url,
      await file.readAsBytes(),
      fileExtension: 'epub',
    );

    return file;
  }

  /// Get cached EPUB file if it exists
  Future<File?> getCachedEpub(Entry entry) async {
    final acquisitionLink = entry.acquisitionLink;
    if (acquisitionLink == null) return null;

    final url = acquisitionLink.href;
    if (url.isEmpty) return null;

    final fileInfo = await _cacheManager.getFileFromCache(url);
    if (fileInfo != null && await fileInfo.file.exists()) {
      return fileInfo.file;
    }

    return null;
  }

  /// Remove cached EPUB file
  Future<void> removeCachedEpub(Entry entry) async {
    final acquisitionLink = entry.acquisitionLink;
    if (acquisitionLink == null) return;

    final url = acquisitionLink.href;
    if (url.isEmpty) return;

    await _cacheManager.removeFile(url);
  }

  /// Check if EPUB is cached
  Future<bool> isEpubCached(Entry entry) async {
    final acquisitionLink = entry.acquisitionLink;
    if (acquisitionLink == null) return false;

    final url = acquisitionLink.href;
    if (url.isEmpty) return false;

    final fileInfo = await _cacheManager.getFileFromCache(url);
    return fileInfo != null && await fileInfo.file.exists();
  }

  /// Get download progress for an EPUB
  Stream<double> getDownloadProgress(Entry entry, Server server) async* {
    final acquisitionLink = entry.acquisitionLink;
    if (acquisitionLink == null) {
      throw Exception('No acquisition link found for entry: ${entry.title}');
    }

    final url = acquisitionLink.href;
    if (url.isEmpty) {
      throw Exception('Invalid acquisition link URL');
    }

    double progress = 0.0;
    yield progress;

    await downloadEpub(
      entry,
      server,
      onProgress: (p) {
        progress = p;
      },
    );

    yield progress;
  }
}