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

import '../../core/region/region_config.dart';
import '../../core/region/region_repository.dart';
import '../../l10n/app_localizations.dart';
import '../timeline/radar_timeline.dart';

/// Sources, licences and the independence disclaimer.
///
/// Reached from Settings, which is one tap from the map. That path is what the
/// OSM attribution guidelines call for: the credit does not have to sit on the
/// map permanently, but it must stay findable from it — "an (i) button in the
/// corner of the map or an About option in a menu".
///
/// The content is driven by the region config, so a new region cannot ship
/// without its credits, plus the credit the radar manifest carries for the
/// frames actually on screen.
class SourcesScreen extends ConsumerWidget {
  const SourcesScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final l10n = AppLocalizations.of(context);
    final region = ref.watch(regionConfigProvider);

    return Scaffold(
      appBar: AppBar(title: Text(l10n.sourcesTitle)),
      body: switch (region) {
        AsyncData(:final value) => _SourcesBody(region: value),
        AsyncError(:final error) => Center(
          child: Padding(
            padding: const EdgeInsets.all(24),
            child: Text('${l10n.dataUnavailable}\n$error'),
          ),
        ),
        _ => Center(child: Text(l10n.loading)),
      },
    );
  }
}

class _SourcesBody extends ConsumerWidget {
  const _SourcesBody({required this.region});

  final RegionConfig region;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final l10n = AppLocalizations.of(context);
    final theme = Theme.of(context);
    // The frames carry their own credit, set by whoever published them. It is
    // not in the region config, so without this it would be lost when the
    // attribution bar came off the map.
    final frameCredit = ref.watch(
      radarTimelineProvider.select((state) => state.manifest?.attribution),
    );

    return ListView(
      padding: const EdgeInsets.symmetric(vertical: 8),
      children: [
        // The disclaimer comes first, before the sources it qualifies: a reader
        // who stops after the first screenful must still have seen it.
        _Card(
          icon: Icons.info_outline,
          title: l10n.sourcesDisclaimerTitle,
          body: l10n.sourcesDisclaimerBody,
        ),

        _SectionHeader(l10n.sourcesDataSection),
        for (final attribution in region.attributions)
          _AttributionTile(attribution: attribution),

        if (frameCredit != null)
          ListTile(
            leading: const Icon(Icons.radar),
            title: Text(frameCredit),
            subtitle: Text(l10n.sourcesRadarFrames),
          ),

        _Card(
          icon: Icons.copyright_outlined,
          title: l10n.sourcesShareAlikeTitle,
          body: l10n.sourcesShareAlikeBody,
        ),

        Padding(
          padding: const EdgeInsets.fromLTRB(16, 8, 16, 24),
          child: OutlinedButton.icon(
            onPressed: () => _open(region.alerts.officialBulletinUrl),
            icon: const Icon(Icons.open_in_new),
            label: Text(l10n.sourcesOfficialBulletin),
          ),
        ),

        Padding(
          padding: const EdgeInsets.fromLTRB(16, 0, 16, 24),
          child: Text(
            region.displayName,
            style: theme.textTheme.bodySmall?.copyWith(
              color: theme.colorScheme.outline,
            ),
          ),
        ),
      ],
    );
  }
}

class _AttributionTile extends StatelessWidget {
  const _AttributionTile({required this.attribution});

  final Attribution attribution;

  @override
  Widget build(BuildContext context) {
    final l10n = AppLocalizations.of(context);
    final license = attribution.license;

    return ListTile(
      title: Text(attribution.text),
      subtitle: Text(
        license == null
            ? l10n.sourcesNoLicenseStated
            : l10n.sourcesLicenseLabel(license),
      ),
      trailing: IconButton(
        icon: const Icon(Icons.open_in_new),
        tooltip: l10n.openLink,
        onPressed: () => _open(attribution.url),
      ),
      onTap: () => _open(attribution.url),
    );
  }
}

class _SectionHeader extends StatelessWidget {
  const _SectionHeader(this.title);

  final String title;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 16, 16, 8),
      child: Text(
        title,
        style: theme.textTheme.titleSmall?.copyWith(
          color: theme.colorScheme.primary,
        ),
      ),
    );
  }
}

class _Card extends StatelessWidget {
  const _Card({required this.icon, required this.title, required this.body});

  final IconData icon;
  final String title;
  final String body;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return Card(
      margin: const EdgeInsets.fromLTRB(16, 8, 16, 8),
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Row(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Icon(icon, color: theme.colorScheme.primary),
            const SizedBox(width: 12),
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(title, style: theme.textTheme.titleSmall),
                  const SizedBox(height: 4),
                  Text(body, style: theme.textTheme.bodyMedium),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

/// Opens [url] in the browser, ignoring a failure to launch.
///
/// A dead link is a poor experience but not a reason to crash the screen the
/// disclaimer lives on.
Future<void> _open(String url) async {
  final uri = Uri.tryParse(url);
  if (uri == null) return;
  await launchUrl(uri, mode: LaunchMode.externalApplication);
}