import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';

import '../data/database.dart';
import '../providers/providers.dart';
import '../sources/source.dart';
import 'widgets/comic_cover.dart';

class DownloadsPage extends ConsumerWidget {
  const DownloadsPage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final queue = ref.watch(downloadQueueProvider);
    final queueAsync = ref.watch(queueJobsProvider);
    final downloadedAsync = ref.watch(downloadedSeriesProvider);

    return Scaffold(
      appBar: AppBar(title: const Text('Downloads')),
      body: queueAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (e, _) => Center(child: Text('$e')),
        data: (queueJobs) {
          return downloadedAsync.when(
            loading: () => const Center(child: CircularProgressIndicator()),
            error: (e, _) => Center(child: Text('$e')),
            data: (groups) {
              final queued =
                  queueJobs.where((j) => j.status == 'queued').length;
              final failed =
                  queueJobs.where((j) => j.status == 'failed').length;
              final pendingTotal = queued + failed;
              final hasDownloads = groups.isNotEmpty;
              final showRunning = queue.isRunning;
              if (!showRunning && !hasDownloads && pendingTotal == 0) {
                return const Center(
                  child: Padding(
                    padding: EdgeInsets.all(24),
                    child: Text(
                      'No downloads yet.\nSelect chapters on a series and tap Download.',
                      textAlign: TextAlign.center,
                    ),
                  ),
                );
              }

              final queueLabel = failed > 0
                  ? 'Queue ($pendingTotal · $failed failed)'
                  : 'Queue ($pendingTotal)';

              return CustomScrollView(
                slivers: [
                  if (showRunning)
                    SliverToBoxAdapter(
                      child: Padding(
                        padding: const EdgeInsets.fromLTRB(16, 12, 16, 4),
                        child: Column(
                          crossAxisAlignment: CrossAxisAlignment.stretch,
                          children: [
                            Text(
                              queue.message.isEmpty
                                  ? 'Downloading…'
                                  : queue.message,
                              style: Theme.of(context).textTheme.bodyMedium,
                              maxLines: 2,
                              overflow: TextOverflow.ellipsis,
                            ),
                            const SizedBox(height: 8),
                            LinearProgressIndicator(
                              value: queue.progress.clamp(0.0, 1.0),
                            ),
                          ],
                        ),
                      ),
                    ),
                  if (pendingTotal > 0)
                    SliverToBoxAdapter(
                      child: ListTile(
                        leading: const Icon(Icons.queue),
                        title: Text(queueLabel),
                        trailing: const Icon(Icons.chevron_right),
                        onTap: () => context.push('/downloads/queue'),
                      ),
                    ),
                  if (groups.isNotEmpty) ...[
                    SliverToBoxAdapter(
                      child: Padding(
                        padding: const EdgeInsets.fromLTRB(16, 16, 16, 8),
                        child: Text(
                          'Downloaded',
                          style: Theme.of(context).textTheme.titleMedium,
                        ),
                      ),
                    ),
                    SliverList.builder(
                      itemCount: groups.length,
                      itemBuilder: (context, i) {
                        return _DownloadedSeriesTile(group: groups[i]);
                      },
                    ),
                  ],
                  const SliverToBoxAdapter(child: SizedBox(height: 24)),
                ],
              );
            },
          );
        },
      ),
    );
  }
}

class DownloadsQueuePage extends ConsumerWidget {
  const DownloadsQueuePage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final queueAsync = ref.watch(queueJobsProvider);
    return Scaffold(
      appBar: AppBar(title: const Text('Queue')),
      body: queueAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (e, _) => Center(child: Text('$e')),
        data: (jobs) {
          final list = jobs
              .where((j) => j.status == 'queued' || j.status == 'failed')
              .toList();
          if (list.isEmpty) {
            return const Center(child: Text('Queue is empty.'));
          }
          return ListView.builder(
            itemCount: list.length,
            itemBuilder: (context, i) => _QueueJobTile(job: list[i]),
          );
        },
      ),
    );
  }
}

class _QueueJobTile extends ConsumerWidget {
  const _QueueJobTile({required this.job});

  final QueueJobView job;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final statusLabel = switch (job.status) {
      'running' => 'Downloading',
      'queued' => 'Queued',
      'failed' => 'Failed',
      _ => job.status,
    };

    return ListTile(
      leading: Icon(_iconFor(job.status)),
      title: Text(
        job.seriesTitle,
        maxLines: 1,
        overflow: TextOverflow.ellipsis,
      ),
      subtitle: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            '${job.chapterLabel} · $statusLabel',
            maxLines: 1,
            overflow: TextOverflow.ellipsis,
          ),
          if (job.status == 'failed' && job.error != null) ...[
            const SizedBox(height: 2),
            Text(
              job.error!,
              maxLines: 2,
              overflow: TextOverflow.ellipsis,
              style: TextStyle(
                color: Theme.of(context).colorScheme.error,
                fontSize: 12,
              ),
            ),
          ],
        ],
      ),
      isThreeLine: job.status == 'failed',
      trailing: job.status == 'failed'
          ? IconButton(
              tooltip: 'Retry',
              icon: const Icon(Icons.refresh),
              onPressed: job.chapterId == null
                  ? null
                  : () => ref
                      .read(downloadQueueProvider)
                      .retryChapter(job.chapterId!),
            )
          : job.status == 'queued'
              ? IconButton(
                  tooltip: 'Cancel',
                  icon: const Icon(Icons.cancel_outlined),
                  onPressed: job.chapterId == null
                      ? null
                      : () => ref
                          .read(downloadQueueProvider)
                          .cancelChapter(job.chapterId!),
                )
              : null,
      onTap: job.titleId == null
          ? null
          : () => context.push('/title/${job.titleId}'),
    );
  }

  IconData _iconFor(String status) {
    switch (status) {
      case 'failed':
        return Icons.error_outline;
      case 'queued':
        return Icons.hourglass_empty;
      default:
        return Icons.download_outlined;
    }
  }
}

class _DownloadedSeriesTile extends ConsumerWidget {
  const _DownloadedSeriesTile({required this.group});

  final DownloadedSeriesGroup group;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final sourceId = SourceId.tryParse(group.source);
    return ExpansionTile(
      leading: SizedBox(
        width: 40,
        height: 56,
        child: ClipRRect(
          borderRadius: BorderRadius.circular(4),
          child: ComicCover(url: group.coverUrl, sourceId: sourceId),
        ),
      ),
      title: Text(
        group.seriesTitle,
        maxLines: 1,
        overflow: TextOverflow.ellipsis,
      ),
      subtitle: Text(
        '${group.chapters.length} chapter${group.chapters.length == 1 ? '' : 's'}',
      ),
      children: [
        for (final ch in group.chapters)
          Dismissible(
            key: ValueKey('dl-${ch.chapterId}'),
            direction: DismissDirection.endToStart,
            background: Container(
              color: Theme.of(context).colorScheme.error,
              alignment: Alignment.centerRight,
              padding: const EdgeInsets.symmetric(horizontal: 16),
              child: const Icon(Icons.delete_outline, color: Colors.white),
            ),
            confirmDismiss: (_) async {
              final ok = await showDialog<bool>(
                context: context,
                builder: (ctx) => AlertDialog(
                  title: const Text('Delete download?'),
                  content: Text(
                    'Remove “${ch.chapterLabel}” from Downloads and delete the CBZ file.',
                  ),
                  actions: [
                    TextButton(
                      onPressed: () => Navigator.pop(ctx, false),
                      child: const Text('Cancel'),
                    ),
                    FilledButton(
                      onPressed: () => Navigator.pop(ctx, true),
                      child: const Text('Delete'),
                    ),
                  ],
                ),
              );
              return ok == true;
            },
            onDismissed: (_) {
              ref.read(downloadQueueProvider).deleteDownload(ch.chapterId);
            },
            child: ListTile(
              contentPadding: const EdgeInsets.only(left: 72, right: 8),
              title: Text(ch.chapterLabel),
              subtitle: ch.downloadedAt == null
                  ? null
                  : Text(_formatDate(ch.downloadedAt!)),
              trailing: PopupMenuButton<String>(
                onSelected: (v) {
                  if (v == 'delete') {
                    ref
                        .read(downloadQueueProvider)
                        .deleteDownload(ch.chapterId);
                  }
                },
                itemBuilder: (context) => const [
                  PopupMenuItem(value: 'delete', child: Text('Delete')),
                ],
              ),
              onTap: () {
                context.push('/read/${ch.titleId}/${ch.chapterId}');
              },
            ),
          ),
      ],
    );
  }

  String _formatDate(DateTime dt) {
    final local = dt.toLocal();
    final y = local.year.toString().padLeft(4, '0');
    final m = local.month.toString().padLeft(2, '0');
    final d = local.day.toString().padLeft(2, '0');
    return 'Downloaded $y-$m-$d';
  }
}