worldhopper/lib/screens/reader/two_page_reader.dart

import 'package:flutter/material.dart';
import 'package:cached_network_image/cached_network_image.dart';
import 'package:photo_view/photo_view.dart';
import 'package:worldhopper/screens/reader/page_grouping.dart';

/// Renders a two-page spread reader using a PageView.
///
/// Each "page" in the PageView corresponds to one [PageSpread] — either a
/// single page (cover, landscape, or unpaired) or a pair of portrait pages.
class TwoPageReader extends StatelessWidget {
  final List<PageSpread> spreads;
  final PageController pageController;
  final String Function(int pageIndex) getPageUrl;
  final Map<String, String> headers;
  final FilterQuality filterQuality;
  final bool reverse;
  final bool einkMode;
  final ValueChanged<int> onPageChanged;
  final VoidCallback onTap;

  const TwoPageReader({
    super.key,
    required this.spreads,
    required this.pageController,
    required this.getPageUrl,
    required this.headers,
    required this.filterQuality,
    required this.reverse,
    this.einkMode = false,
    required this.onPageChanged,
    required this.onTap,
  });

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: onTap,
      child: PageView.builder(
        controller: pageController,
        reverse: reverse,
        itemCount: spreads.length,
        onPageChanged: onPageChanged,
        physics: einkMode
            ? const NeverScrollableScrollPhysics()
            : const BouncingScrollPhysics(),
        itemBuilder: (context, spreadIndex) {
          final spread = spreads[spreadIndex];

          if (spread.isSingle) {
            return _buildSinglePage(spread.pages[0]);
          } else {
            return _buildPairedPages(spread.pages[0], spread.pages[1]);
          }
        },
      ),
    );
  }

  /// Single page: use PhotoView for full zoom/pan support.
  Widget _buildSinglePage(int pageIndex) {
    return PhotoView(
      imageProvider: CachedNetworkImageProvider(
        getPageUrl(pageIndex),
        headers: headers,
      ),
      filterQuality: filterQuality,
      minScale: PhotoViewComputedScale.contained,
      maxScale: PhotoViewComputedScale.covered * 3,
      backgroundDecoration: const BoxDecoration(color: Colors.black),
      loadingBuilder: (context, event) => Center(
        child: CircularProgressIndicator(
          value: event == null
              ? 0
              : event.cumulativeBytesLoaded / (event.expectedTotalBytes ?? 1),
          color: Colors.white,
        ),
      ),
      heroAttributes: PhotoViewHeroAttributes(tag: 'page-$pageIndex'),
    );
  }

  /// Paired pages: InteractiveViewer wrapping two images centered together.
  Widget _buildPairedPages(int leftPageIndex, int rightPageIndex) {
    return LayoutBuilder(
      builder: (context, constraints) {
        final halfWidth = constraints.maxWidth / 2;
        final maxHeight = constraints.maxHeight;

        return InteractiveViewer(
          minScale: 1.0,
          maxScale: 3.0,
          child: SizedBox(
            width: constraints.maxWidth,
            height: maxHeight,
            child: Row(
              mainAxisAlignment: MainAxisAlignment.center,
              mainAxisSize: MainAxisSize.min,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                _buildHalfPage(
                    leftPageIndex, halfWidth, maxHeight, Alignment.centerRight),
                _buildHalfPage(
                    rightPageIndex, halfWidth, maxHeight, Alignment.centerLeft),
              ],
            ),
          ),
        );
      },
    );
  }

  Widget _buildHalfPage(
      int pageIndex, double width, double height, Alignment alignment) {
    return SizedBox(
      width: width,
      height: height,
      child: CachedNetworkImage(
        imageUrl: getPageUrl(pageIndex),
        httpHeaders: headers,
        filterQuality: filterQuality,
        fit: BoxFit.contain,
        alignment: alignment,
        placeholder: (context, url) => const Center(
          child: CircularProgressIndicator(color: Colors.white),
        ),
        errorWidget: (context, url, error) => const Center(
          child: Icon(Icons.error, color: Colors.white),
        ),
      ),
    );
  }
}