import 'package:flutter/widgets.dart';
import 'package:riverpod_annotation/riverpod_annotation.dart';

part 'page_dimensions_provider.g.dart';

/// Threshold: images with aspect ratio >= this are considered double-page spreads.
const double doublePageAspectRatio = 1.0;

/// Stores resolved dimensions for a single page image.
class PageDimension {
  final int width;
  final int height;

  const PageDimension({required this.width, required this.height});

  double get aspectRatio => height > 0 ? width / height : 0;
  bool get isDoublePage => aspectRatio >= doublePageAspectRatio;
}

/// Provider that caches page dimensions for a publication.
/// Parameterized by publication ID so each publication has its own cache.
@riverpod
class PageDimensionsNotifier extends _$PageDimensionsNotifier {
  @override
  Map<int, PageDimension> build(String publicationId) {
    return {};
  }

  /// Resolve dimensions for a page from its [imageProvider].
  /// Returns immediately if already cached. Otherwise resolves asynchronously
  /// and updates state when done.
  void resolvePage(int pageIndex, ImageProvider imageProvider) {
    if (state.containsKey(pageIndex)) return;

    final stream = imageProvider.resolve(ImageConfiguration.empty);
    late ImageStreamListener listener;
    listener = ImageStreamListener(
      (ImageInfo info, bool synchronousCall) {
        final image = info.image;
        final dim = PageDimension(
          width: image.width,
          height: image.height,
        );
        state = {...state, pageIndex: dim};
        image.dispose();
        stream.removeListener(listener);
      },
      onError: (exception, stackTrace) {
        // Failed to resolve — leave uncached, will be treated as portrait
        stream.removeListener(listener);
      },
    );
    stream.addListener(listener);
  }

  /// Check if a page's dimensions have been resolved.
  bool hasPage(int pageIndex) => state.containsKey(pageIndex);
}