worldhopper/lib/services/offline_content_checker.dart

import 'package:worldhopper/models/opds_entry.dart';
import 'package:worldhopper/services/epub_download_service.dart';

/// Service for checking if content is available offline
///
/// Determines whether a given OPDS entry can be accessed without
/// an internet connection.
class OfflineContentChecker {
  final EpubDownloadService _epubService;

  OfflineContentChecker({
    required EpubDownloadService epubService,
  }) : _epubService = epubService;

  /// Check if the given content is available offline
  ///
  /// Returns true if:
  /// - For EPUBs: The file is cached locally
  /// - For OPDS-PS streams: Always returns false (pages are streamed from server)
  ///
  /// Returns false otherwise.
  Future<bool> isContentAvailableOffline(OPDSEntry entry) async {
    // EPUB publications can be cached
    if (entry.isEpub) {
      return await _epubService.isEpubCached(entry);
    }

    // Image streams (OPDS-PS) require server connection
    // Pages are streamed and not fully cached
    if (entry.isImageStream) {
      return false;
    }

    // Default to false for unknown content types
    return false;
  }

  /// Get a detailed status message about offline availability
  ///
  /// Returns a user-friendly message explaining whether the content
  /// is available offline and why.
  Future<String> getOfflineStatusMessage(OPDSEntry entry) async {
    if (entry.isEpub) {
      final isCached = await _epubService.isEpubCached(entry);
      if (isCached) {
        return 'This EPUB is cached and available offline.';
      } else {
        return 'This EPUB is not cached. Connect to internet to download.';
      }
    }

    if (entry.isImageStream) {
      return 'Image streams require an internet connection. Pages may not load offline.';
    }

    return 'This content requires an internet connection.';
  }
}