import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:plezy/widgets/app_icon.dart';
import 'package:material_symbols_icons/symbols.dart';
import '../../widgets/focused_scroll_scaffold.dart';
import '../../widgets/loading_indicator_box.dart';
import '../../i18n/strings.g.dart';

class MergedLicenseEntry {
  final String packageName;
  final List<LicenseEntry> licenseEntries;
  final Set<String> allPackageNames;

  MergedLicenseEntry({required this.packageName, required this.licenseEntries, required this.allPackageNames});
}

class LicensesScreen extends StatelessWidget {
  const LicensesScreen({super.key});

  static final Future<List<MergedLicenseEntry>> _licensesFuture = _loadLicenses();

  static Future<List<MergedLicenseEntry>> _loadLicenses() async {
    final licenseMap = <String, List<LicenseEntry>>{};
    final allPackageNames = <String, Set<String>>{};

    await for (final license in LicenseRegistry.licenses) {
      for (final packageName in license.packages) {
        if (!licenseMap.containsKey(packageName)) {
          licenseMap[packageName] = [];
          allPackageNames[packageName] = <String>{};
        }
        licenseMap[packageName]!.add(license);
        allPackageNames[packageName]!.addAll(license.packages);
      }
    }

    final mergedLicenses = licenseMap.entries.map((entry) {
      return MergedLicenseEntry(
        packageName: entry.key,
        licenseEntries: entry.value,
        allPackageNames: allPackageNames[entry.key]!,
      );
    }).toList();

    mergedLicenses.sort((a, b) => a.packageName.compareTo(b.packageName));
    return mergedLicenses;
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<List<MergedLicenseEntry>>(
      future: _licensesFuture,
      builder: (context, snapshot) {
        final mergedLicenses = snapshot.data;
        if (mergedLicenses == null) {
          return FocusedScrollScaffold(title: Text(t.screens.licenses), slivers: [LoadingIndicatorBox.sliver]);
        }

        return FocusedScrollScaffold(
          title: Text(t.screens.licenses),
          slivers: [
            SliverPadding(
              padding: const EdgeInsets.all(16),
              sliver: SliverList(
                delegate: SliverChildBuilderDelegate((context, index) {
                  final mergedLicense = mergedLicenses[index];
                  final packageName = mergedLicense.packageName;

                  return Card(
                    margin: const EdgeInsets.only(bottom: 8),
                    child: ListTile(
                      title: Text(
                        packageName,
                        style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: .bold),
                      ),
                      subtitle: mergedLicense.licenseEntries.length > 1
                          ? Text(t.licenses.licensesCount(count: mergedLicense.licenseEntries.length))
                          : null,
                      trailing: const AppIcon(Symbols.chevron_right_rounded, fill: 1),
                      onTap: () => _showLicenseDetail(context, mergedLicense),
                    ),
                  );
                }, childCount: mergedLicenses.length),
              ),
            ),
          ],
        );
      },
    );
  }

  void _showLicenseDetail(BuildContext context, MergedLicenseEntry mergedLicense) {
    Navigator.push(
      context,
      MaterialPageRoute(builder: (context) => _LicenseDetailScreen(mergedLicense: mergedLicense)),
    );
  }
}

class _LicenseDetailScreen extends StatelessWidget {
  final MergedLicenseEntry mergedLicense;

  const _LicenseDetailScreen({required this.mergedLicense});

  @override
  Widget build(BuildContext context) {
    final packageName = mergedLicense.packageName;
    final licenseEntries = mergedLicense.licenseEntries;

    return FocusedScrollScaffold(
      title: Text(packageName),
      slivers: [
        SliverPadding(
          padding: const EdgeInsets.all(16),
          sliver: SliverList(
            delegate: SliverChildListDelegate([
              if (mergedLicense.allPackageNames.length > 1)
                Card(
                  child: Padding(
                    padding: const EdgeInsets.all(16),
                    child: Column(
                      crossAxisAlignment: .start,
                      children: [
                        Text(
                          t.licenses.relatedPackages,
                          style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: .bold),
                        ),
                        const SizedBox(height: 8),
                        Text(mergedLicense.allPackageNames.join(', '), style: Theme.of(context).textTheme.bodyMedium),
                      ],
                    ),
                  ),
                ),
              if (mergedLicense.allPackageNames.length > 1) const SizedBox(height: 16),

              ...licenseEntries.asMap().entries.map((entry) {
                final index = entry.key;
                final license = entry.value;
                final isMultipleLicenses = licenseEntries.length > 1;

                return Column(
                  children: [
                    Card(
                      child: Padding(
                        padding: const EdgeInsets.all(16),
                        child: Column(
                          crossAxisAlignment: .start,
                          children: [
                            Text(
                              isMultipleLicenses ? t.licenses.licenseNumber(number: index + 1) : t.licenses.license,
                              style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: .bold),
                            ),
                            const SizedBox(height: 16),
                            ...license.paragraphs.map((paragraph) {
                              return Padding(
                                padding: const EdgeInsets.only(bottom: 16),
                                child: SelectableText(
                                  paragraph.text,
                                  style: TextStyle(fontFamily: paragraph.indent > 0 ? 'monospace' : null, fontSize: 14),
                                ),
                              );
                            }),
                          ],
                        ),
                      ),
                    ),
                    if (index < licenseEntries.length - 1) const SizedBox(height: 16),
                  ],
                );
              }),
            ]),
          ),
        ),
      ],
    );
  }
}