import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:clide/clide.dart';
import 'package:clide/kernel/kernel.dart';
import 'package:clide/widgets/widgets.dart';
import 'package:flutter/widgets.dart';
import 'package:clide/src/terminal/terminal.dart';

/// General-purpose terminal pane. Spawns the user's `$SHELL` under the
/// daemon's PTY (via `pane.spawn`), feeds the `pane.output` event
/// stream into an xterm.dart Terminal, and routes user input back
/// through `pane.write`.
///
/// Deliberately knows nothing about Claude — that's `builtin.claude`'s
/// job. The shared widget layer (ClidePtyView, ClidePaneChrome) keeps
/// the two extensions visually consistent without coupling them.
class TerminalPane extends StatefulWidget {
  const TerminalPane({super.key});

  @override
  State<TerminalPane> createState() => _TerminalPaneState();
}

class _TerminalPaneState extends State<TerminalPane> {
  static const _maxLines = 2000;

  late final Terminal _terminal;
  StreamSubscription<DaemonEvent>? _eventSub;
  String? _paneId;
  String? _error;
  int _pid = 0;

  /// Cached in didChangeDependencies — ancestor lookups are illegal in
  /// dispose(), and the old lookup-and-swallow there meant pane.close
  /// was never sent, leaking the backend PTY + daemon pane (T-366).
  KernelServices? _kernel;

  @override
  void initState() {
    super.initState();
    _terminal = Terminal(maxLines: _maxLines);
    // Route user input back through IPC once a pane id is known.
    _terminal.onOutput = _onTerminalOutput;
    _terminal.onResize = _onTerminalResize;
    // Spawn asynchronously after the first build so we have access to
    // the kernel via InheritedWidget lookup.
    WidgetsBinding.instance.addPostFrameCallback((_) => _spawn());
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _kernel = ClideKernel.of(context);
  }

  @override
  void dispose() {
    _eventSub?.cancel();
    _eventSub = null;
    final id = _paneId;
    _paneId = null;
    if (id != null) {
      // Fire-and-forget. Daemon-side pane.close is idempotent.
      unawaited(_kernel?.ipc.request('pane.close', args: {'id': id}));
    }
    super.dispose();
  }

  Future<void> _spawn() async {
    if (!mounted) return;
    final ipc = _kernel?.ipc;
    if (ipc == null || !ipc.isConnected) {
      setState(() => _error = 'Backend not connected.');
      return;
    }

    // Windows has no $SHELL convention and no login-shell flag —
    // PowerShell 7 first, classic PowerShell as the always-there
    // fallback.
    final shell = Platform.isWindows ? null : (Platform.environment['SHELL'] ?? '/bin/bash');
    final argv = shell != null ? [shell, '-l'] : ['powershell.exe', '-NoLogo'];
    // The open workspace, not Directory.current — a desktop launch starts
    // in $HOME and a project switch doesn't move the process CWD (T-381).
    final cwd = _kernel?.project.current?.path ?? Directory.current.path;

    final response = await ipc.request(
      'pane.spawn',
      args: {'argv': argv, 'kind': PaneKind.terminal.wire, 'cwd': cwd, 'cols': _terminal.viewWidth, 'rows': _terminal.viewHeight},
    );
    if (!mounted) return;
    if (!response.ok) {
      setState(() => _error = response.error?.message ?? 'spawn failed');
      return;
    }

    _paneId = response.data['id'] as String?;
    _pid = (response.data['pid'] as num?)?.toInt() ?? 0;
    _subscribeToPaneEvents();
    setState(() {}); // refresh subtitle with PID
  }

  void _subscribeToPaneEvents() {
    final kernel = _kernel;
    if (kernel == null) return;
    _eventSub = kernel.events.on<DaemonEvent>().listen((event) {
      if (event.subsystem != 'pane') return;
      if (event.data['id'] != _paneId) return;
      switch (event.kind) {
        case 'pane.output':
          final b64 = event.data['bytes_b64'];
          if (b64 is String) {
            // writeBytes keeps UTF-8 decode state across chunks — a rune
            // split across PTY reads must not become U+FFFD (T-373).
            _terminal.writeBytes(base64Decode(b64));
          }
        case 'pane.exit':
          setState(() => _error = 'Shell exited.');
        case 'pane.closed':
          // Daemon-side gone; reset state so the user can retry.
          _paneId = null;
          setState(() {});
      }
    });
  }

  void _onTerminalOutput(String text) {
    final id = _paneId;
    if (id == null) return;
    _kernel?.ipc.request('pane.write', args: {'id': id, 'text': text});
  }

  void _onTerminalResize(int cols, int rows, int pixelWidth, int pixelHeight) {
    final id = _paneId;
    if (id == null) return;
    _kernel?.ipc.request('pane.resize', args: {'id': id, 'cols': cols, 'rows': rows});
  }

  @override
  Widget build(BuildContext context) {
    final subtitle = _error != null ? _error! : (_paneId == null ? 'spawning shell…' : 'pid $_pid · ${_paneId!}');

    return ClidePaneChrome(
      title: 'terminal',
      subtitle: subtitle,
      child: _error != null ? _ErrorBody(message: _error!) : ClidePtyView(terminal: _terminal, label: 'terminal — $subtitle'),
    );
  }
}

class _ErrorBody extends StatelessWidget {
  const _ErrorBody({required this.message});
  final String message;
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(16),
      child: Align(
        alignment: Alignment.topLeft,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [const ClideText('Terminal unavailable'), const SizedBox(height: 4), ClideText(message, muted: true)],
        ),
      ),
    );
  }
}

/// Cast the Uint8List base64 source to a typed form consumers can
/// inspect in tests. Exposed via the library's barrel only because it
/// helps the extension test probe the terminal state without pulling
/// in the xterm.dart model directly.
typedef TerminalBytes = Uint8List;