import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';
import 'package:package_info_plus/package_info_plus.dart';
import 'package:url_launcher/url_launcher.dart';

import '../i18n/strings.g.dart';
import 'theme.dart';

/// The app's public website. Shown as a tappable row in [AboutScreen].
const String _websiteUrl = 'https://tane.comunes.org';

/// The public source repository (AGPL). Shown as a tappable row in [AboutScreen].
const String _sourceUrl = 'https://git.comunes.org/comunes/tane';

/// The translation platform where anyone can help translate Tane.
const String _translateUrl = 'https://translate.comunes.org/projects/tane/';

/// The year Tane's copyright starts. Ğ1nkgo uses its own first year (2023);
/// Tane's is 2026.
const int _copyrightStartYear = 2026;

/// A single year (`2026`) until the calendar rolls over, then a range
/// (`2026-2027`), mirroring Ğ1nkgo's legalese line.
String _copyrightYears() {
  final int now = DateTime.now().year;
  return now <= _copyrightStartYear
      ? '$_copyrightStartYear'
      : '$_copyrightStartYear-$now';
}

/// An "about" screen à la Ğ1nkgo: brand header, the human explanation of what
/// Tane is and where its name comes from, the app version, license, the
/// website, and the bundled open-source licenses page.
class AboutScreen extends StatelessWidget {
  const AboutScreen({super.key});

  @override
  Widget build(BuildContext context) {
    final t = context.t;
    return Scaffold(
      appBar: AppBar(title: Text(t.about.title)),
      body: ListView(
        padding: const EdgeInsets.only(bottom: 24),
        children: [
          const _Header(),
          Padding(
            padding: const EdgeInsets.fromLTRB(20, 4, 20, 8),
            child: Text(
              t.about.tagline,
              textAlign: TextAlign.center,
              style: Theme.of(context).textTheme.titleMedium?.copyWith(
                color: seedOnSurface,
                height: 1.35,
              ),
            ),
          ),
          const _Paragraph(),
          const Divider(height: 32),
          _InfoTile(
            icon: Icons.info_outline,
            label: t.about.version,
            valueBuilder: (context) => const _VersionText(),
          ),
          _InfoTile(
            icon: Icons.balance_outlined,
            label: t.about.license,
            value: t.about.licenseValue,
          ),
          ListTile(
            leading: const Icon(Icons.public, color: seedGreen),
            title: Text(t.about.website),
            subtitle: const Text(_websiteUrl),
            onTap: () => launchUrl(
              Uri.parse(_websiteUrl),
              mode: LaunchMode.externalApplication,
            ),
          ),
          ListTile(
            leading: const Icon(Icons.code, color: seedGreen),
            title: Text(t.about.sourceCode),
            subtitle: const Text(_sourceUrl),
            onTap: () => launchUrl(
              Uri.parse(_sourceUrl),
              mode: LaunchMode.externalApplication,
            ),
          ),
          ListTile(
            leading: const Icon(Icons.translate, color: seedGreen),
            title: Text(t.about.translate),
            subtitle: Text(t.about.translateSubtitle),
            onTap: () => launchUrl(
              Uri.parse(_translateUrl),
              mode: LaunchMode.externalApplication,
            ),
          ),
          ListTile(
            leading: const Icon(Icons.privacy_tip_outlined, color: seedGreen),
            title: Text(t.legal.title),
            subtitle: Text(t.legal.subtitle),
            trailing: const Icon(Icons.chevron_right),
            onTap: () => context.push('/legal'),
          ),
          ListTile(
            leading: const Icon(Icons.description_outlined, color: seedGreen),
            title: Text(t.about.openSourceLicenses),
            subtitle: Text(t.about.openSourceLicensesSubtitle),
            onTap: () => showLicensePage(
              context: context,
              applicationName: t.app.title,
              applicationLegalese: t.about.copyright(years: _copyrightYears()),
              applicationIcon: Padding(
                padding: const EdgeInsets.all(8),
                child: Image.asset('assets/logo.png', width: 48),
              ),
            ),
          ),
          const Divider(height: 32),
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 20),
            child: Text(
              t.about.copyright(years: _copyrightYears()),
              textAlign: TextAlign.center,
              style: Theme.of(context).textTheme.bodySmall?.copyWith(
                color: seedOnSurface.withValues(alpha: 0.7),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

/// Brand block: the logo, the app name and its 種 kanji.
class _Header extends StatelessWidget {
  const _Header();

  @override
  Widget build(BuildContext context) {
    final t = context.t;
    return Padding(
      padding: const EdgeInsets.fromLTRB(20, 24, 20, 4),
      child: Column(
        children: [
          Image.asset('assets/logo.png', width: 88),
          const SizedBox(height: 12),
          Text(
            t.app.title,
            style: const TextStyle(
              color: seedGreen,
              fontSize: 28,
              fontWeight: FontWeight.w700,
              letterSpacing: -0.2,
            ),
          ),
          Text(
            t.about.kanji,
            style: Theme.of(context).textTheme.titleLarge?.copyWith(
              color: seedGreen.withValues(alpha: 0.7),
            ),
          ),
        ],
      ),
    );
  }
}

/// The two explanatory paragraphs: what Tane is, and the heritage of its
/// name (yui / tanomoshi / the paper Plantare).
class _Paragraph extends StatelessWidget {
  const _Paragraph();

  @override
  Widget build(BuildContext context) {
    final t = context.t;
    final style = Theme.of(
      context,
    ).textTheme.bodyMedium?.copyWith(color: seedOnSurface, height: 1.5);
    return Padding(
      padding: const EdgeInsets.fromLTRB(20, 12, 20, 0),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(t.about.intro, style: style),
          const SizedBox(height: 14),
          Text(t.about.heritage, style: style),
        ],
      ),
    );
  }
}

/// A leading-icon row showing a static [value] or a [valueBuilder] widget.
class _InfoTile extends StatelessWidget {
  const _InfoTile({
    required this.icon,
    required this.label,
    this.value,
    this.valueBuilder,
  });

  final IconData icon;
  final String label;
  final String? value;
  final WidgetBuilder? valueBuilder;

  @override
  Widget build(BuildContext context) {
    return ListTile(
      leading: Icon(icon, color: seedGreen),
      title: Text(label),
      trailing: value != null
          ? Text(value!, style: Theme.of(context).textTheme.bodyMedium)
          : valueBuilder?.call(context),
    );
  }
}

/// Reads the app version from the platform and renders it as `x.y.z (build)`.
class _VersionText extends StatelessWidget {
  const _VersionText();

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<PackageInfo>(
      future: PackageInfo.fromPlatform(),
      builder: (context, snapshot) {
        final info = snapshot.data;
        final text = info == null
            ? '—'
            : '${info.version} (${info.buildNumber})';
        return Text(text, style: Theme.of(context).textTheme.bodyMedium);
      },
    );
  }
}