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

import '../downloads/download_manager.dart';
import '../state/providers.dart';
import '../theme/tokens.dart';
import '../widgets/hairline_panel.dart';

/// Manage offline downloads: what's saved, how much space it uses, and any
/// in-flight transfers. Tapping a completed track plays it.
class DownloadsScreen extends ConsumerWidget {
  const DownloadsScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final downloads = ref.watch(downloadManagerProvider);
    final controller = ref.read(downloadManagerProvider.notifier);
    final playback = ref.read(playbackCommandsProvider);

    final active = downloads.byId.values.where((d) => d.isActive).toList();
    final completed = downloads.completed;

    return Scaffold(
      appBar: AppBar(
        title: const Text('Downloads',
            style: TextStyle(fontWeight: FontWeight.w700)),
        actions: [
          if (completed.isNotEmpty)
            TextButton(
              onPressed: () => _confirmClear(context, controller),
              child: Text('Clear all',
                  style: TextStyle(color: TimbreColors.dimmed)),
            ),
        ],
      ),
      body: SafeArea(
        child: (active.isEmpty && completed.isEmpty)
            ? Center(
                child: Text('No downloads yet.',
                    style: TextStyle(color: TimbreColors.dimmed)),
              )
            : ListView(
                padding: const EdgeInsets.all(TimbreSpacing.lg),
                children: [
                  if (active.isNotEmpty) ...[
                    HairlinePanel(
                      title: 'Downloading',
                      trailing: '(${active.length})',
                      padding: const EdgeInsets.symmetric(
                          vertical: TimbreSpacing.md),
                      child: Column(
                        children: [
                          for (final d in active) _ActiveRow(info: d),
                        ],
                      ),
                    ),
                    const SizedBox(height: TimbreSpacing.xl),
                  ],
                  HairlinePanel(
                    title: 'Saved',
                    active: true,
                    trailing: completed.isEmpty
                        ? null
                        : '${completed.length} · ${_fmtBytes(downloads.totalBytes)}',
                    padding:
                        const EdgeInsets.symmetric(vertical: TimbreSpacing.md),
                    child: completed.isEmpty
                        ? Padding(
                            padding: EdgeInsets.all(TimbreSpacing.lg),
                            child: Text('Nothing saved for offline yet.',
                                style: TextStyle(color: TimbreColors.dimmed)),
                          )
                        : Column(
                            children: [
                              for (final d in completed)
                                _SavedRow(
                                  info: d,
                                  onPlay: () =>
                                      playback.playSongs([d.song]),
                                  onRemove: () => controller.remove(d.song.id),
                                ),
                            ],
                          ),
                  ),
                ],
              ),
      ),
    );
  }

  Future<void> _confirmClear(
      BuildContext context, DownloadController controller) async {
    final ok = await showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        backgroundColor: TimbreColors.surface,
        title: const Text('Remove all downloads?'),
        content: const Text(
            'This deletes every saved file for this server. It cannot be undone.'),
        actions: [
          TextButton(
              onPressed: () => Navigator.pop(ctx, false),
              child: const Text('Cancel')),
          TextButton(
              onPressed: () => Navigator.pop(ctx, true),
              child: const Text('Remove all')),
        ],
      ),
    );
    if (ok == true) await controller.clearAll();
  }
}

class _ActiveRow extends StatelessWidget {
  const _ActiveRow({required this.info});
  final DownloadInfo info;

  @override
  Widget build(BuildContext context) {
    final accent = Theme.of(context).colorScheme.primary;
    final failed = info.status == DownloadStatus.failed;
    return Padding(
      padding: const EdgeInsets.symmetric(
          horizontal: TimbreSpacing.lg, vertical: TimbreSpacing.xs),
      child: Row(
        children: [
          Expanded(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(info.song.title ?? 'Untitled',
                    maxLines: 1,
                    overflow: TextOverflow.ellipsis,
                    style: TextStyle(color: TimbreColors.foreground)),
                const SizedBox(height: TimbreSpacing.xs),
                if (failed)
                  const Text('Failed',
                      style: TextStyle(color: Color(0xFFE06C75), fontSize: 12))
                else
                  LinearProgressIndicator(
                    value: info.progress > 0 ? info.progress : null,
                    minHeight: 3,
                    backgroundColor: TimbreColors.border,
                    color: accent,
                  ),
              ],
            ),
          ),
          const SizedBox(width: TimbreSpacing.md),
          Text(
            failed
                ? '—'
                : (info.status == DownloadStatus.queued ? 'Queued' : ''),
            style: TextStyle(color: TimbreColors.dimmed, fontSize: 12),
          ),
        ],
      ),
    );
  }
}

class _SavedRow extends StatelessWidget {
  const _SavedRow({
    required this.info,
    required this.onPlay,
    required this.onRemove,
  });

  final DownloadInfo info;
  final VoidCallback onPlay;
  final VoidCallback onRemove;

  @override
  Widget build(BuildContext context) {
    final quality = info.format ??
        (info.bitRate != null ? '${info.bitRate} kbps' : 'Original');
    return InkWell(
      onTap: onPlay,
      child: Container(
        constraints:
            const BoxConstraints(minHeight: TimbreSpacing.minTouchTarget),
        padding: const EdgeInsets.only(left: TimbreSpacing.lg),
        child: Row(
          children: [
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Text(info.song.title ?? 'Untitled',
                      maxLines: 1,
                      overflow: TextOverflow.ellipsis,
                      style: TextStyle(color: TimbreColors.foreground)),
                  Text(
                    [
                      info.song.artist,
                      '$quality · ${_fmtBytes(info.sizeBytes ?? 0)}',
                    ].where((e) => e != null && e.isNotEmpty).join(' · '),
                    maxLines: 1,
                    overflow: TextOverflow.ellipsis,
                    style:
                        TextStyle(color: TimbreColors.dimmed, fontSize: 12),
                  ),
                ],
              ),
            ),
            InkWell(
              onTap: onRemove,
              customBorder: const CircleBorder(),
              child: SizedBox(
                width: TimbreSpacing.minTouchTarget,
                height: TimbreSpacing.minTouchTarget,
                child: Icon(Icons.delete_outline,
                    size: 20, color: TimbreColors.dimmed),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

String _fmtBytes(int bytes) {
  if (bytes <= 0) return '0 MB';
  const units = ['B', 'KB', 'MB', 'GB'];
  var size = bytes.toDouble();
  var i = 0;
  while (size >= 1024 && i < units.length - 1) {
    size /= 1024;
    i++;
  }
  return '${size.toStringAsFixed(size >= 10 || i == 0 ? 0 : 1)} ${units[i]}';
}