import 'dart:async';
import 'dart:collection';
import 'dart:io';
import 'dart:math';
import 'dart:typed_data';

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:just_audio/just_audio.dart';
import 'package:path_provider/path_provider.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:vad/vad.dart';

import 'api_client_provider.dart';

// ── Public helpers (also used by tests) ──────────────────────────────────────

class SentenceResult {
  final List<String> sentences;
  final String remainder;
  const SentenceResult({required this.sentences, required this.remainder});
}

/// Extract completed sentences from [text] at `.`, `!`, `?` boundaries.
/// Returns the completed sentences and the unconsumed remainder.
SentenceResult extractSentences(String text) {
  final boundary = RegExp(r'[.!?]+(?=\s|$)');
  final sentences = <String>[];
  var remaining = text;
  RegExpMatch? match;
  while ((match = boundary.firstMatch(remaining)) != null) {
    final end = match!.end;
    final sentence = remaining.substring(0, end).trim();
    if (sentence.isNotEmpty) sentences.add(sentence);
    remaining = remaining.substring(end).trimLeft();
  }
  return SentenceResult(sentences: sentences, remainder: remaining);
}

/// Strip markdown formatting before sending text to TTS.
String stripMarkdownForTts(String text) {
  return text
      .replaceAll(RegExp(r'```[\s\S]*?```'), '') // fenced code blocks
      .replaceAllMapped(RegExp(r'`([^`]+)`'), (m) => m[1]!) // inline code
      .replaceAll(RegExp(r'#{1,6}\s+'), '') // headings
      .replaceAllMapped(RegExp(r'\*\*([^*]+)\*\*'), (m) => m[1]!) // bold
      .replaceAllMapped(RegExp(r'\*([^*]+)\*'), (m) => m[1]!) // italic
      .replaceAllMapped(
          RegExp(r'\[([^\]]+)\]\([^)]+\)'), (m) => m[1]!) // links → text
      .replaceAll(RegExp(r'^\s*[-*+]\s+', multiLine: true), '') // list markers
      .replaceAll(RegExp(r'\n{2,}'), ' ') // multiple newlines → space
      .replaceAll('\n', ' ')
      .trim();
}

/// Encode float PCM samples (-1..1) as a 16-bit mono WAV at 16 kHz.
Uint8List encodeWav(List<double> samples, {int sampleRate = 16000}) {
  final numSamples = samples.length;
  final dataSize = numSamples * 2;
  final fileSize = 44 + dataSize;
  final buf = ByteData(fileSize);

  // RIFF header
  buf.setUint8(0, 0x52); // R
  buf.setUint8(1, 0x49); // I
  buf.setUint8(2, 0x46); // F
  buf.setUint8(3, 0x46); // F
  buf.setUint32(4, fileSize - 8, Endian.little);
  buf.setUint8(8, 0x57); // W
  buf.setUint8(9, 0x41); // A
  buf.setUint8(10, 0x56); // V
  buf.setUint8(11, 0x45); // E

  // fmt chunk
  buf.setUint8(12, 0x66); // f
  buf.setUint8(13, 0x6D); // m
  buf.setUint8(14, 0x74); // t
  buf.setUint8(15, 0x20); // (space)
  buf.setUint32(16, 16, Endian.little); // chunk size
  buf.setUint16(20, 1, Endian.little); // PCM format
  buf.setUint16(22, 1, Endian.little); // mono
  buf.setUint32(24, sampleRate, Endian.little);
  buf.setUint32(28, sampleRate * 2, Endian.little); // byte rate
  buf.setUint16(32, 2, Endian.little); // block align
  buf.setUint16(34, 16, Endian.little); // bits per sample

  // data chunk
  buf.setUint8(36, 0x64); // d
  buf.setUint8(37, 0x61); // a
  buf.setUint8(38, 0x74); // t
  buf.setUint8(39, 0x61); // a
  buf.setUint32(40, dataSize, Endian.little);

  for (var i = 0; i < numSamples; i++) {
    final clamped = samples[i].clamp(-1.0, 1.0);
    final int16 = (clamped * 32767).round().clamp(-32768, 32767);
    buf.setInt16(44 + i * 2, int16, Endian.little);
  }

  return buf.buffer.asUint8List();
}

// ── State ─────────────────────────────────────────────────────────────────────

enum VoiceMode { idle, recording, transcribing, playing }

class VoiceState {
  final VoiceMode mode;
  final bool voiceModeActive;
  final bool available;
  /// Normalized mic amplitude 0.0–1.0 while recording.
  final double amplitude;

  const VoiceState({
    this.mode = VoiceMode.idle,
    this.voiceModeActive = false,
    this.available = true,
    this.amplitude = 0.0,
  });

  VoiceState copyWith({
    VoiceMode? mode,
    bool? voiceModeActive,
    bool? available,
    double? amplitude,
  }) =>
      VoiceState(
        mode: mode ?? this.mode,
        voiceModeActive: voiceModeActive ?? this.voiceModeActive,
        available: available ?? this.available,
        amplitude: amplitude ?? this.amplitude,
      );
}

// ── Provider ──────────────────────────────────────────────────────────────────

final voiceProvider =
    NotifierProvider.autoDispose<VoiceNotifier, VoiceState>(VoiceNotifier.new);

// ── Notifier ──────────────────────────────────────────────────────────────────

class VoiceNotifier extends Notifier<VoiceState> {
  // Audio playback
  AudioPlayer? _player;

  // VAD — sole owner of the microphone
  VadHandler? _vadHandler;
  StreamSubscription<void>? _vadSpeechStartSub;
  StreamSubscription<List<double>>? _vadSpeechEndSub;
  StreamSubscription<({double isSpeech, double notSpeech, List<double> frame})>?
      _vadFrameSub;
  StreamSubscription<String>? _vadErrorSub;
  bool _speechDetected = false;
  int _speechStartMs = 0;
  static const _vadGraceMs = 1500;
  bool _disposed = false;

  // Voice mode callbacks
  Future<void> Function(String transcript)? _onTranscript;
  void Function(String message)? _onError;
  bool _enableTts = false;

  // Streaming TTS state
  String _sentenceBuffer = '';
  int _lastSeenLength = 0;
  bool _streamComplete = false;

  // Whisper context hint
  String _lastAssistantContent = '';

  // Empty transcript counter
  int _emptyTranscriptCount = 0;

  // TTS playback queue
  final _ttsQueue = Queue<Uint8List>();
  bool _ttsPlaying = false;
  int _ttsCounter = 0;
  Directory? _tempDir;

  @override
  VoiceState build() {
    _disposed = false;
    _player = AudioPlayer();
    ref.onDispose(() {
      _disposed = true;
      _cancelSubscriptions();
      _vadHandler?.dispose();
      _vadHandler = null;
      _player?.dispose();
      _player = null;
    });
    return const VoiceState();
  }

  // ── Public API ──────────────────────────────────────────────────────────────

  Future<void> enterVoiceMode({
    required Future<void> Function(String transcript) onTranscript,
    bool enableTts = false,
    required void Function(String message) onError,
  }) async {
    if (state.voiceModeActive) {
      if (state.mode == VoiceMode.recording && !_speechDetected) {
        onError('No speech detected');
      }
      exitVoiceMode();
      return;
    }

    try {
      final status = await ref.read(voiceRepositoryProvider).checkStatus();
      if (!status.enabled || !status.stt) {
        onError('Speech-to-text not available on this server');
        return;
      }
      if (!status.tts) enableTts = false;
    } catch (_) {
      onError('Could not reach voice service');
      return;
    }

    var permStatus = await Permission.microphone.request();
    if (permStatus == PermissionStatus.permanentlyDenied) {
      onError('Microphone blocked — opening settings');
      final opened = await openAppSettings();
      if (!opened) return;
      permStatus = await Permission.microphone.status;
    }
    if (!permStatus.isGranted) {
      onError('Microphone permission required');
      return;
    }

    _onTranscript = onTranscript;
    _onError = onError;
    _enableTts = enableTts;
    _emptyTranscriptCount = 0;
    _tempDir = await getTemporaryDirectory();

    state = state.copyWith(voiceModeActive: true, available: true);
    await _startListening();
  }

  void exitVoiceMode() {
    _cleanup();
    if (!_disposed) state = const VoiceState();
  }

  void feedContent(String fullContent, {required bool isComplete}) {
    if (!state.voiceModeActive || !_enableTts) return;

    final delta = fullContent.length > _lastSeenLength
        ? fullContent.substring(_lastSeenLength)
        : '';
    _lastSeenLength = fullContent.length;
    _sentenceBuffer += delta;

    _dispatchSentences(flush: isComplete);

    if (isComplete) {
      _lastAssistantContent = fullContent;
      _streamComplete = true;
      _checkRestartListening();
    }
  }

  // ── Internal helpers ────────────────────────────────────────────────────────

  void _cleanup() {
    _cancelSubscriptions();
    final handler = _vadHandler;
    _vadHandler = null;
    handler?.dispose();
    _player?.stop();
    _ttsQueue.clear();
    _ttsPlaying = false;
    _sentenceBuffer = '';
    _lastSeenLength = 0;
    _streamComplete = false;
    _speechDetected = false;
    _onTranscript = null;
    _onError = null;
  }

  void _cancelSubscriptions() {
    _vadSpeechStartSub?.cancel();
    _vadSpeechStartSub = null;
    _vadSpeechEndSub?.cancel();
    _vadSpeechEndSub = null;
    _vadFrameSub?.cancel();
    _vadFrameSub = null;
    _vadErrorSub?.cancel();
    _vadErrorSub = null;
  }

  // ── Internal recording ──────────────────────────────────────────────────────

  Future<void> _startListening() async {
    if (_disposed || !state.voiceModeActive) return;

    _speechDetected = false;
    _speechStartMs = 0;

    try {
      await _stopVad();
      _vadHandler = VadHandler.create();

      _vadSpeechStartSub = _vadHandler!.onSpeechStart.listen((_) {
        if (_disposed || !state.voiceModeActive) return;
        if (!_speechDetected) {
          _speechDetected = true;
          _speechStartMs = DateTime.now().millisecondsSinceEpoch;
        }
      });

      _vadSpeechEndSub = _vadHandler!.onSpeechEnd.listen((audioSamples) {
        if (_disposed || !state.voiceModeActive) return;
        final now = DateTime.now().millisecondsSinceEpoch;
        final sinceStart = _speechStartMs > 0 ? now - _speechStartMs : 0;
        if (_speechDetected && sinceStart >= _vadGraceMs) {
          _stopVad();
          _handleSpeechEnd(audioSamples);
        }
      });

      _vadFrameSub = _vadHandler!.onFrameProcessed.listen((event) {
        if (_disposed || !state.voiceModeActive) return;
        final frame = event.frame;
        if (frame.isEmpty) return;
        double sumSq = 0;
        for (final s in frame) {
          sumSq += s * s;
        }
        final rms = sqrt(sumSq / frame.length);
        final norm = (rms * 4.0).clamp(0.0, 1.0);
        if ((norm - state.amplitude).abs() > 0.02) {
          state = state.copyWith(amplitude: norm);
        }
      });

      _vadErrorSub = _vadHandler!.onError.listen((msg) {
        if (_disposed) return;
        _onError?.call('VAD error: $msg');
      });

      await _vadHandler!.startListening(model: 'v5');

      // Only show recording UI after the mic is actually open.
      if (!_disposed && state.voiceModeActive) {
        state = state.copyWith(mode: VoiceMode.recording, amplitude: 0.0);
      }
    } catch (e) {
      _onError?.call('Microphone error: $e');
      _cleanup();
      if (!_disposed) state = const VoiceState();
    }
  }

  Future<void> _stopVad() async {
    _cancelSubscriptions();
    if (_vadHandler != null) {
      final handler = _vadHandler!;
      _vadHandler = null;
      await handler.dispose();
    }
  }

  Future<void> _handleSpeechEnd(List<double> audioSamples) async {
    if (_disposed || !state.voiceModeActive) return;
    state = state.copyWith(mode: VoiceMode.transcribing);

    try {
      final wavBytes = encodeWav(audioSamples);

      if (_disposed || !state.voiceModeActive) return;

      final transcript = await ref.read(voiceRepositoryProvider).transcribe(
            wavBytes,
            context:
                _lastAssistantContent.isNotEmpty ? _lastAssistantContent : null,
          );

      if (_disposed || !state.voiceModeActive) return;

      if (transcript.isEmpty) {
        _emptyTranscriptCount++;
        if (_emptyTranscriptCount >= 3) {
          _onError?.call('No speech detected — tap the mic to try again');
          _cleanup();
          if (!_disposed) state = const VoiceState();

          return;
        }
        await _startListening();
        return;
      }
      _emptyTranscriptCount = 0;

      _sentenceBuffer = '';
      _lastSeenLength = 0;
      _streamComplete = false;

      if (_enableTts && !_disposed) {
        state = state.copyWith(mode: VoiceMode.playing);
      }

      await _onTranscript?.call(transcript);

      // In STT-only mode (no TTS), return to idle after transcript is sent.
      // The user taps the mic again to record another message.
      if (!_enableTts && !_disposed && state.voiceModeActive) {
        state = state.copyWith(mode: VoiceMode.idle);
      }
    } catch (e) {
      _onError?.call('Voice error: transcription failed');
      _cleanup();
      if (!_disposed) state = const VoiceState();
    }
  }

  // ── Internal TTS ────────────────────────────────────────────────────────────

  void _dispatchSentences({required bool flush}) {
    final result = extractSentences(_sentenceBuffer);
    _sentenceBuffer = flush ? '' : result.remainder;

    for (final sentence in result.sentences) {
      _enqueueSentence(sentence);
    }
    if (flush && result.remainder.trim().length >= 3) {
      _enqueueSentence(result.remainder.trim());
    }
  }

  void _enqueueSentence(String sentence) {
    final stripped = stripMarkdownForTts(sentence);
    if (stripped.length < 3) return;
    _synthesiseSentence(stripped);
  }

  Future<void> _synthesiseSentence(String text) async {
    try {
      final wavBytes =
          await ref.read(voiceRepositoryProvider).synthesise(text);
      if (_disposed || !state.voiceModeActive) return;
      _ttsQueue.add(wavBytes);
      if (!_ttsPlaying) _drainTtsQueue();
    } catch (_) {
      // Skip failed sentence — TTS errors are non-fatal
    }
  }

  Future<void> _drainTtsQueue() async {
    if (_ttsPlaying) return;
    _ttsPlaying = true;
    final dir = _tempDir ?? await getTemporaryDirectory();

    try {
      while (_ttsQueue.isNotEmpty && state.voiceModeActive) {
        final wavBytes = _ttsQueue.removeFirst();
        final path = '${dir.path}/tts_${_ttsCounter++}.wav';
        final file = File(path);
        await file.writeAsBytes(wavBytes);

        try {
          await _player!.setFilePath(path);
          await _player!.play();
          await _player!.processingStateStream.firstWhere(
            (s) =>
                s == ProcessingState.completed || s == ProcessingState.idle,
          );
        } finally {
          await file.delete().catchError((_) => file);
        }
      }
    } finally {
      _ttsPlaying = false;
    }

    _checkRestartListening();
  }

  void _checkRestartListening() {
    if (_disposed) return;
    if (_streamComplete &&
        _ttsQueue.isEmpty &&
        !_ttsPlaying &&
        state.voiceModeActive) {
      _streamComplete = false;
      _lastSeenLength = 0;
      _sentenceBuffer = '';
      _startListening();
    }
  }
}