import 'dart:convert';
import 'dart:io';

import 'package:drift/drift.dart';
import 'package:drift/native.dart';
import 'package:path/path.dart' as p;
import 'package:path_provider/path_provider.dart';
import 'package:sqlite3_flutter_libs/sqlite3_flutter_libs.dart';

import '../models/note.dart';

part 'database.g.dart';

/// Local cache of server-side Notes for offline reads.
///
/// Mirrors the shape of [Note] one-to-one. Tags are stored as a JSON-encoded
/// string because SQLite has no native list type and Drift's typed converters
/// add ceremony we don't need for a simple read cache. `cachedAt` tracks when
/// the row was last written from a successful API response.
class CachedNotes extends Table {
  IntColumn get id => integer()();
  TextColumn get title => text()();
  TextColumn get body => text()();
  TextColumn get tagsJson => text().withDefault(const Constant('[]'))();
  TextColumn get noteType => text().withDefault(const Constant('note'))();
  IntColumn get projectId => integer().nullable()();
  IntColumn get milestoneId => integer().nullable()();
  DateTimeColumn get createdAt => dateTime()();
  DateTimeColumn get updatedAt => dateTime()();
  DateTimeColumn get cachedAt =>
      dateTime().clientDefault(() => DateTime.now())();

  @override
  Set<Column> get primaryKey => {id};
}

/// Per-domain sync timestamp. Keyed by a short domain string ('notes',
/// 'tasks', 'projects', 'events', etc.) so the OfflineBanner and any
/// stale-while-revalidate logic can ask "when did we last fetch this".
class SyncMetadata extends Table {
  TextColumn get domain => text()();
  DateTimeColumn get lastSyncedAt => dateTime()();

  @override
  Set<Column> get primaryKey => {domain};
}

const String kSyncDomainNotes = 'notes';

@DriftDatabase(tables: [CachedNotes, SyncMetadata])
class FabledDatabase extends _$FabledDatabase {
  FabledDatabase() : super(_openConnection());
  FabledDatabase.forTesting(super.executor);

  @override
  int get schemaVersion => 1;

  // ── Notes ────────────────────────────────────────────────────────────────

  Future<List<Note>> getAllNotes() async {
    final rows = await (select(cachedNotes)
          ..orderBy([(t) => OrderingTerm.desc(t.updatedAt)]))
        .get();
    return rows.map(_noteFromRow).toList();
  }

  Future<Note?> getNote(int id) async {
    final row = await (select(cachedNotes)..where((t) => t.id.equals(id)))
        .getSingleOrNull();
    return row == null ? null : _noteFromRow(row);
  }

  /// Replace the entire notes cache with the latest server snapshot.
  /// Used after a successful `getAll()` so the cache reflects deletions
  /// (a row that's gone from the server should be gone locally too).
  Future<void> replaceAllNotes(List<Note> notes) async {
    await transaction(() async {
      await delete(cachedNotes).go();
      if (notes.isNotEmpty) {
        await batch((b) {
          b.insertAll(
            cachedNotes,
            notes.map(_companionFromNote).toList(),
          );
        });
      }
      await _setLastSyncIn(kSyncDomainNotes, DateTime.now());
    });
  }

  /// Upsert a single note (after a successful create / update / getOne).
  Future<void> upsertNote(Note note) async {
    await into(cachedNotes).insertOnConflictUpdate(_companionFromNote(note));
  }

  Future<void> deleteNote(int id) async {
    await (delete(cachedNotes)..where((t) => t.id.equals(id))).go();
  }

  // ── Sync metadata ────────────────────────────────────────────────────────

  Future<DateTime?> getLastSync(String domain) async {
    final row = await (select(syncMetadata)
          ..where((t) => t.domain.equals(domain)))
        .getSingleOrNull();
    return row?.lastSyncedAt;
  }

  Future<void> _setLastSyncIn(String domain, DateTime timestamp) {
    return into(syncMetadata).insertOnConflictUpdate(
      SyncMetadataCompanion(
        domain: Value(domain),
        lastSyncedAt: Value(timestamp),
      ),
    );
  }
}

CachedNotesCompanion _companionFromNote(Note note) => CachedNotesCompanion(
      id: Value(note.id),
      title: Value(note.title),
      body: Value(note.body),
      tagsJson: Value(jsonEncode(note.tags)),
      noteType: Value(note.noteType),
      projectId: Value(note.projectId),
      milestoneId: Value(note.milestoneId),
      createdAt: Value(note.createdAt),
      updatedAt: Value(note.updatedAt),
    );

Note _noteFromRow(CachedNote row) => Note(
      id: row.id,
      title: row.title,
      body: row.body,
      tags: (jsonDecode(row.tagsJson) as List<dynamic>).cast<String>(),
      noteType: row.noteType,
      projectId: row.projectId,
      milestoneId: row.milestoneId,
      createdAt: row.createdAt,
      updatedAt: row.updatedAt,
    );

LazyDatabase _openConnection() {
  return LazyDatabase(() async {
    if (Platform.isAndroid) {
      await applyWorkaroundToOpenSqlite3OnOldAndroidVersions();
    }
    final dir = await getApplicationDocumentsDirectory();
    final file = File(p.join(dir.path, 'fabled_cache.sqlite'));
    return NativeDatabase.createInBackground(file);
  });
}