import 'dart:typed_data';

import 'package:path/path.dart' as p;
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';

import '../models/datalog_session.dart';

/// SQLite database wrapper for sessions and raw ECU frames.
class DatalogDb {
  static const _dbName = 'hvbt_datalog.db';
  static const _version = 1;

  Database? _db;

  Future<Database> get _database async {
    _db ??= await _open();
    return _db!;
  }

  Future<Database> _open() async {
    final dir = await getApplicationDocumentsDirectory();
    final path = p.join(dir.path, _dbName);
    return openDatabase(
      path,
      version: _version,
      onCreate: (db, _) async {
        await db.execute('''
          CREATE TABLE sessions (
            id         INTEGER PRIMARY KEY AUTOINCREMENT,
            ecu_type   TEXT    NOT NULL,
            start_time INTEGER NOT NULL,
            end_time   INTEGER,
            frame_count INTEGER NOT NULL DEFAULT 0
          )
        ''');
        await db.execute('''
          CREATE TABLE frames (
            id         INTEGER PRIMARY KEY AUTOINCREMENT,
            session_id INTEGER NOT NULL,
            timestamp  INTEGER NOT NULL,
            data       BLOB    NOT NULL,
            FOREIGN KEY(session_id) REFERENCES sessions(id) ON DELETE CASCADE
          )
        ''');
        await db.execute(
            'CREATE INDEX idx_frames_session ON frames(session_id)');
      },
    );
  }

  // ── Sessions ──────────────────────────────────────────────────────────────

  /// Inserts a new session row. Returns the assigned id.
  Future<int> insertSession(DatalogSession session) async {
    final db = await _database;
    return db.insert('sessions', session.toMap()..remove('id'));
  }

  /// Updates end_time and frame_count for an existing session.
  Future<void> closeSession(int sessionId, DateTime endTime, int frameCount) async {
    final db = await _database;
    await db.update(
      'sessions',
      {
        'end_time': endTime.millisecondsSinceEpoch,
        'frame_count': frameCount,
      },
      where: 'id = ?',
      whereArgs: [sessionId],
    );
  }

  /// Returns all sessions ordered newest first.
  Future<List<DatalogSession>> getSessions() async {
    final db = await _database;
    final rows = await db.query('sessions', orderBy: 'start_time DESC');
    return rows.map(DatalogSession.fromMap).toList();
  }

  /// Deletes a session and all its frames (CASCADE).
  Future<void> deleteSession(int sessionId) async {
    final db = await _database;
    await db.delete('sessions', where: 'id = ?', whereArgs: [sessionId]);
  }

  // ── Frames ────────────────────────────────────────────────────────────────

  /// Batch-inserts multiple frames in a single transaction.
  Future<void> insertFrames(
      int sessionId, List<PendingFrame> frames) async {
    if (frames.isEmpty) return;
    final db = await _database;
    await db.transaction((txn) async {
      final batch = txn.batch();
      for (final f in frames) {
        batch.insert('frames', {
          'session_id': sessionId,
          'timestamp': f.timestamp.millisecondsSinceEpoch,
          'data': f.data,
        });
      }
      await batch.commit(noResult: true);
    });
  }

  /// Returns all raw frames for a session, ordered by timestamp.
  Future<List<StoredFrame>> getFrames(int sessionId) async {
    final db = await _database;
    final rows = await db.query(
      'frames',
      where: 'session_id = ?',
      whereArgs: [sessionId],
      orderBy: 'timestamp ASC',
    );
    return rows
        .map((r) => StoredFrame(
              timestamp: DateTime.fromMillisecondsSinceEpoch(
                  r['timestamp'] as int),
              data: r['data'] as Uint8List,
            ))
        .toList();
  }

  Future<void> close() async => _db?.close();
}

// ─── DTOs ─────────────────────────────────────────────────────────────────────

class PendingFrame {
  final DateTime timestamp;
  final Uint8List data;
  const PendingFrame(this.timestamp, this.data);
}

class StoredFrame {
  final DateTime timestamp;
  final Uint8List data;
  const StoredFrame({required this.timestamp, required this.data});
}