import 'package:flutter/material.dart';
import 'package:flutter_alacritty/flutter_alacritty.dart';

import 'connection_bar.dart';
import 'rtty_pty_backend.dart';
import 'terminal_config.dart';
import 'theme.dart';

/// 主终端页面。
///
/// 使用 `flutter_alacritty` 的 Rust 引擎（TerminalEngine + TerminalView）渲染，
/// 通过 [RttyPtyBackend] 桥接远程 Rtty Rust 服务端的 WebSocket 数据流。
/// 断开时展示终端提示页，连接后进入实时工业级 ANSI 渲染。
class TerminalScreen extends StatefulWidget {
  const TerminalScreen({super.key});

  @override
  State<TerminalScreen> createState() => _TerminalScreenState();
}

class _TerminalScreenState extends State<TerminalScreen> {
  late final TerminalConfig _config;
  TerminalEngine? _engine;
  TerminalController _controller = TerminalController();
  final FocusNode _focus = FocusNode();

  RttyPtyBackend? _backend;

  final _host = TextEditingController(text: '127.0.0.1');
  final _port = TextEditingController(text: '8080');
  final _session = TextEditingController();

  ConnState _state = ConnState.disconnected;
  String? _sessionId;
  int _cols = 0;
  int _rows = 0;

  @override
  void initState() {
    super.initState();
    _config = RttyTerminalConfig.build();
  }

  @override
  void dispose() {
    _tearDownSession();
    _host.dispose();
    _port.dispose();
    _session.dispose();
    _controller.dispose();
    _focus.dispose();
    super.dispose();
  }

  Future<void> _connect() async {
    final host = _host.text.trim();
    final port = int.tryParse(_port.text.trim()) ?? 8080;
    final session = _session.text.trim();
    if (host.isEmpty) return;

    _tearDownSession();

    setState(() {
      _engine = TerminalEngine(config: _config);
      _controller = TerminalController()..attach(_engine!);
      _backend = RttyPtyBackend();
    });

    _backend!.onStateChanged = (s) {
      if (!mounted) return;
      setState(() => _state = s);
      if (s == ConnState.disconnected || s == ConnState.error) {
        _sessionId = null;
      }
    };
    _backend!.onReady = (id, cols, rows) {
      if (!mounted) return;
      setState(() {
        _sessionId = id;
        _cols = cols;
        _rows = rows;
      });
    };

    await _backend!.connect(host: host, port: port, session: session);
  }

  void _disconnect() => _tearDownSession();

  void _tearDownSession() {
    final b = _backend;
    if (b != null) {
      b.onStateChanged = null;
      b.onReady = null;
      b.kill();
      b.dispose();
    }
    _backend = null;
    _engine?.dispose();
    _engine = null;
    _sessionId = null;
    _state = ConnState.disconnected;
  }

  void _handlePtyResize(int cols, int rows) {
    final b = _backend;
    if (b == null) return;
    b.resize(rows, cols);
    if (mounted) {
      setState(() {
        _cols = cols;
        _rows = rows;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    final sizeText = _state == ConnState.connected ? '$_cols × $_rows' : '—';

    return Scaffold(
      backgroundColor: RttyTheme.background,
      body: Column(
        children: [
          ConnectionBar(
            state: _state,
            hostController: _host,
            portController: _port,
            sessionController: _session,
            sessionId: _sessionId,
            terminalSize: sizeText,
            onConnect: _connect,
            onDisconnect: _disconnect,
          ),
          Expanded(child: _buildBody()),
          const _StatusBar(),
        ],
      ),
    );
  }

  Widget _buildBody() {
    final engine = _engine;
    if (_state == ConnState.connected && engine != null) {
      return Container(
        color: RttyTheme.background,
        padding: const EdgeInsets.all(16),
        child: ClipRRect(
          borderRadius: BorderRadius.circular(4),
          child: Container(
            decoration: BoxDecoration(
              color: RttyTheme.background,
              border: Border.all(color: RttyTheme.border),
              borderRadius: BorderRadius.circular(4),
            ),
            padding: const EdgeInsets.fromLTRB(12, 10, 12, 10),
            child: TerminalView(
              engine,
              controller: _controller,
              focusNode: _focus,
              autofocus: true,
              onPtyResize: _handlePtyResize,
              theme: _config.theme,
              textStyle: _config.style,
              mouseCursor: SystemMouseCursors.text,
            ),
          ),
        ),
      );
    }
    return _IdlePane(state: _state);
  }
}

/// 未连接时的提示面板。
class _IdlePane extends StatelessWidget {
  const _IdlePane({required this.state});

  final ConnState state;

  @override
  Widget build(BuildContext context) {
    final (title, subtitle) = switch (state) {
      ConnState.disconnected => (
          'AWAITING CONNECTION',
          '输入服务端地址后点击 CONNECT 建立终端会话',
        ),
      ConnState.connecting => (
          'CONNECTING',
          '正在协商 WebSocket 终端会话…',
        ),
      ConnState.error => (
          'CONNECTION LOST',
          '无法建立连接，请检查服务端是否已启动',
        ),
      ConnState.connected => ('', ''),
    };

    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          _ScanlineGlyph(state: state),
          const SizedBox(height: 28),
          Text(
            title,
            style: const TextStyle(
              color: RttyTheme.textDim,
              fontSize: 18,
              fontWeight: FontWeight.w700,
              letterSpacing: 3,
            ),
          ),
          const SizedBox(height: 10),
          Text(
            subtitle,
            style: const TextStyle(color: RttyTheme.textFaint, fontSize: 12),
          ),
        ],
      ),
    );
  }
}

/// 终端提示区的装饰性扫描线字形。
class _ScanlineGlyph extends StatelessWidget {
  const _ScanlineGlyph({required this.state});

  final ConnState state;

  @override
  Widget build(BuildContext context) {
    final color = switch (state) {
      ConnState.connected => RttyTheme.primary,
      ConnState.connecting => RttyTheme.accent,
      ConnState.error => RttyTheme.danger,
      _ => RttyTheme.textFaint,
    };

    return Container(
      width: 96,
      height: 96,
      decoration: BoxDecoration(
        border: Border.all(color: color.withValues(alpha: 0.5), width: 1.5),
        borderRadius: BorderRadius.circular(12),
      ),
      child: CustomPaint(painter: _ScanlinePainter(color)),
    );
  }
}

class _ScanlinePainter extends CustomPainter {
  _ScanlinePainter(this.color);

  final Color color;

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = color.withValues(alpha: 0.18)
      ..strokeWidth = 1;
    const spacing = 6.0;
    for (double y = 0; y < size.height; y += spacing) {
      canvas.drawLine(Offset(0, y), Offset(size.width, y), paint);
    }
    final cursorPaint = Paint()
      ..color = color.withValues(alpha: 0.8)
      ..strokeWidth = 2;
    canvas.drawRect(
      Rect.fromLTWH(size.width * 0.3, size.height * 0.45, 24, 14),
      cursorPaint..style = PaintingStyle.stroke,
    );
  }

  @override
  bool shouldRepaint(covariant _ScanlinePainter old) => old.color != color;
}

/// 底部状态栏：会话 ID、连接状态、按键提示。
class _StatusBar extends StatelessWidget {
  const _StatusBar();

  @override
  Widget build(BuildContext context) {
    return Container(
      height: 26,
      decoration: BoxDecoration(
        color: RttyTheme.surface,
        border: Border(top: BorderSide(color: RttyTheme.border)),
      ),
      padding: const EdgeInsets.symmetric(horizontal: 16),
      child: Row(
        children: const [
          _StatusDot(),
          SizedBox(width: 8),
          Text(
            'RTTY DESKTOP',
            style: TextStyle(
              color: RttyTheme.textFaint,
              fontSize: 10,
              letterSpacing: 1.6,
              fontWeight: FontWeight.w600,
            ),
          ),
          SizedBox(width: 20),
          _Hint('拖选复制', RttyTheme.textFaint),
          SizedBox(width: 14),
          _Hint('Ctrl+Shift+C / V 复制粘贴', RttyTheme.textFaint),
          Spacer(),
          Text(
            'FLUTTER × ALACRITTY ENGINE',
            style: TextStyle(color: RttyTheme.textFaint, fontSize: 10),
          ),
        ],
      ),
    );
  }
}

class _StatusDot extends StatelessWidget {
  const _StatusDot();

  @override
  Widget build(BuildContext context) {
    return Container(
      width: 6,
      height: 6,
      decoration: const BoxDecoration(
        color: RttyTheme.primary,
        shape: BoxShape.circle,
      ),
    );
  }
}

class _Hint extends StatelessWidget {
  const _Hint(this.text, this.color);

  final String text;
  final Color color;

  @override
  Widget build(BuildContext context) {
    return Text(
      text,
      style: TextStyle(color: color, fontSize: 10, fontFamily: 'Consolas'),
    );
  }
}