import 'dart:convert';

import 'package:flutter/widgets.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../ai/tools/tool_definition.dart';
import '../ai/tools/tool_dispatcher.dart';
import '../ai/tools/tool_envelope.dart';
import '../ai/tools/tool_registry.dart';
import '../core/constants.dart';
import '../data/ai/llm_service.dart';
import 'ai_providers.dart';
import 'catalog_providers.dart';
import 'providers.dart';

/// Multi-turn safety cap. ADR-0005 §C — guards against tool-call loops.
const int kChatMaxTurns = 4;

/// Soft warning threshold for chat history bloat (OQ-2).
const int kChatSoftHistoryLimit = 8;

sealed class ChatMessage {
  const ChatMessage();
}

final class UserChatMessage extends ChatMessage {
  final String text;
  const UserChatMessage(this.text);
}

final class ModelChatMessage extends ChatMessage {
  final String text;
  const ModelChatMessage(this.text);
}

final class ToolCallChatMessage extends ChatMessage {
  final String name;
  final Map<String, dynamic> args;
  final ToolResult result;
  const ToolCallChatMessage(this.name, this.args, this.result);
}

final class SystemChatMessage extends ChatMessage {
  final String text;
  const SystemChatMessage(this.text);
}

class ChatSessionState {
  final List<ChatMessage> messages;
  final bool isStreaming;
  final String? streamingText;
  final String? error;

  const ChatSessionState({
    this.messages = const [],
    this.isStreaming = false,
    this.streamingText,
    this.error,
  });

  ChatSessionState copyWith({
    List<ChatMessage>? messages,
    bool? isStreaming,
    String? streamingText,
    String? error,
    bool clearStreamingText = false,
    bool clearError = false,
  }) {
    return ChatSessionState(
      messages: messages ?? this.messages,
      isStreaming: isStreaming ?? this.isStreaming,
      streamingText: clearStreamingText
          ? null
          : (streamingText ?? this.streamingText),
      error: clearError ? null : (error ?? this.error),
    );
  }
}

final toolRegistryProvider = Provider<ToolRegistry>((ref) {
  return ToolRegistry.defaults();
});

final toolDepsProvider = FutureProvider<ToolDeps>((ref) async {
  // bootstrap 가 끝나야 seed 가 채워진 framePatterns 를 신뢰할 수 있음.
  await ref.watch(bootstrapProvider.future);
  final framePatterns = await ref.watch(framePatternsProvider.future);
  return ToolDeps(
    habitDao: ref.watch(habitDaoProvider),
    trackerDao: ref.watch(trackerDaoProvider),
    catalog: ref.watch(catalogRepositoryProvider),
    framePatterns: framePatterns,
    userId: kLocalDefaultUserId,
  );
});

final toolDispatcherProvider = Provider<ToolDispatcher>((ref) {
  return ToolDispatcher(registry: ref.watch(toolRegistryProvider));
});

class ChatSessionController extends StateNotifier<ChatSessionState> {
  ChatSessionController({
    required this.llm,
    required this.dispatcher,
    required this.deps,
    required this.tools,
  }) : super(const ChatSessionState());

  final LlmService llm;
  final ToolDispatcher dispatcher;
  final ToolDeps deps;
  final List<ToolDefinition> tools;

  LlmChatSession? _session;

  Future<void> userTurn(String text, BuildContext context) async {
    final trimmed = text.trim();
    if (trimmed.isEmpty) return;
    if (state.isStreaming) return;

    state = state.copyWith(
      messages: [...state.messages, UserChatMessage(trimmed)],
      isStreaming: true,
      streamingText: '',
      clearError: true,
    );

    try {
      // 1회 lazy load.
      if (!llm.isLoaded) {
        await llm.load();
      }
      _session ??= await llm.startChat(tools: tools);

      String? pendingToolName;
      Map<String, dynamic>? pendingToolResult;
      Stream<LlmChatEvent> Function() nextStream = () =>
          _session!.sendUser(trimmed);

      for (var turn = 0; turn < kChatMaxTurns; turn++) {
        var accumulated = '';
        LlmFunctionCall? toolCall;

        await for (final event in nextStream()) {
          if (event is LlmTextChunk) {
            accumulated += event.text;
            if (!mounted) return;
            state = state.copyWith(streamingText: accumulated);
          } else if (event is LlmFunctionCall) {
            toolCall = event;
            break;
          }
        }

        if (toolCall == null) {
          // 자연어 응답으로 종료.
          if (!mounted) return;
          state = state.copyWith(
            messages: [
              ...state.messages,
              ModelChatMessage(accumulated),
            ],
            isStreaming: false,
            clearStreamingText: true,
          );
          _maybeWarnHistory();
          return;
        }

        // Tool 처리.
        if (!mounted) return;
        final result = await dispatcher.dispatch(
          toolName: toolCall.name,
          rawArgs: toolCall.args,
          confirmContext: context.mounted ? context : null,
          deps: deps,
        );
        if (!mounted) return;
        state = state.copyWith(
          messages: [
            ...state.messages,
            ToolCallChatMessage(toolCall.name, toolCall.args, result),
          ],
          streamingText: '',
        );

        pendingToolName = toolCall.name;
        // ADR-0005 / OQ-2: hard-cap tool result at 2KB so LLM context window
        // can't be blown by a runaway ToolOk payload. encodeToolResult applies
        // truncate-with-hint when needed; jsonDecode round-trips back to a Map
        // because the chat session API expects Map<String, dynamic>.
        final capped = jsonDecode(encodeToolResult(result)) as Map<String, dynamic>;
        pendingToolResult = capped;
        final capturedName = pendingToolName;
        final capturedResult = pendingToolResult;
        nextStream = () => _session!.sendToolResult(
              toolName: capturedName,
              result: capturedResult,
            );
      }

      // MAX_TURNS 초과 안전 종료.
      if (!mounted) return;
      state = state.copyWith(
        isStreaming: false,
        clearStreamingText: true,
        error: '도구 호출 루프가 너무 길어 중단했습니다.',
      );
    } catch (e, st) {
      if (!mounted) return;
      // 개발 단계 (#342) — 실 단말 진단을 위해 release 빌드에서도 full
      // message + stack 노출. 사용자 친화 메시지로 다시 좁히는 작업은
      // #342 종료 후 follow-up.
      final detail = 'LLM 응답 실패: ${e.runtimeType}\n$e\n\n--- STACK ---\n$st';
      state = state.copyWith(
        isStreaming: false,
        clearStreamingText: true,
        error: detail,
      );
    }
  }

  void clear() {
    state = const ChatSessionState();
  }

  void _maybeWarnHistory() {
    final turnCount = state.messages
        .whereType<UserChatMessage>()
        .length;
    if (turnCount == kChatSoftHistoryLimit) {
      state = state.copyWith(
        messages: [
          ...state.messages,
          const SystemChatMessage(
            '대화가 길어졌어요. 다시 시작하면 모델이 더 빠르게 답할 수 있어요. (오른쪽 위 ↻ 버튼)',
          ),
        ],
      );
    }
  }

  @override
  void dispose() {
    _session?.close();
    super.dispose();
  }
}

final chatSessionControllerProvider = StateNotifierProvider.autoDispose<
    ChatSessionController, ChatSessionState>((ref) {
  final llm = ref.watch(llmServiceProvider);
  final dispatcher = ref.watch(toolDispatcherProvider);
  final deps = ref.watch(toolDepsProvider).requireValue;
  final tools = ref.watch(toolRegistryProvider).all.toList(growable: false);
  return ChatSessionController(
    llm: llm,
    dispatcher: dispatcher,
    deps: deps,
    tools: tools,
  );
});