/**
 * Phase II — 统一对话 API 路由
 *
 * POST /sessions/:id/chat       — 统一对话入口（SSE 流式）
 * GET  /sessions/:id/chat/history — 获取对话历史
 * GET  /sessions/:id/chat/conversation — 获取 conversation 元信息
 *
 * SSE 格式：OpenAI Compatible（与前端 useAIStream 兼容）
 * 心跳：5 秒（H1）
 * 竞态保护：placeholder 占位（H3）
 */

import { FastifyInstance, FastifyRequest } from 'fastify';
import { logger } from '../../../common/logging/index.js';
import { prisma } from '../../../config/database.js';
import { conversationService } from '../services/ConversationService.js';
import { intentRouterService } from '../services/IntentRouterService.js';
import { chatHandlerService } from '../services/ChatHandlerService.js';
import { askUserService } from '../services/AskUserService.js';

function getUserId(request: FastifyRequest): string {
  const userId = (request as any).user?.userId;
  if (!userId) throw new Error('User not authenticated');
  return userId;
}

export default async function chatRoutes(app: FastifyInstance) {

  /**
   * POST /sessions/:id/chat
   * 统一对话入口 — SSE 流式响应
   */
  app.post('/:id/chat', async (req, reply) => {
    const { id: sessionId } = req.params as { id: string };
    const userId = getUserId(req);
    const { content, enableDeepThinking, metadata } = req.body as {
      content: string;
      enableDeepThinking?: boolean;
      metadata?: Record<string, any>;
    };

    if (!content?.trim()) {
      return reply.status(400).send({ error: '消息内容不能为空' });
    }

    // SSE 响应头
    reply.raw.writeHead(200, {
      'Content-Type': 'text/event-stream',
      'Cache-Control': 'no-cache',
      'Connection': 'keep-alive',
      'Access-Control-Allow-Origin': '*',
      'X-Accel-Buffering': 'no',
    });

    const writer = {
      write: (data: string) => {
        try {
          return reply.raw.write(data);
        } catch {
          return false;
        }
      },
      end: () => {
        try { reply.raw.end(); } catch { /* ignore */ }
      },
      on: (event: string, handler: () => void) => {
        req.raw.on(event, handler);
      },
    };

    try {
      // 1. 获取或创建 Conversation（延迟创建）
      const conversationId = await conversationService.getOrCreateConversation(sessionId, userId);

      // 2. 保存用户消息
      await conversationService.saveUserMessage(conversationId, content.trim());

      // ── H1 全局打断判定 ──
      const pending = await askUserService.getPending(sessionId);
      if (pending) {
        const askUserResponse = metadata?.askUserResponse
          ? askUserService.parseResponse(metadata)
          : null;

        if (askUserResponse) {
          // 正常回答问题（含 skip）
          const placeholderMsgId = await conversationService.createAssistantPlaceholder(
            conversationId, 'chat',
          );

          const metaEvent = JSON.stringify({
            type: 'intent_classified',
            intent: 'chat',
            confidence: 1,
            source: 'ask_user_response',
            guardTriggered: false,
          });
          writer.write(`data: ${metaEvent}\n\n`);

          const result = await chatHandlerService.handleAskUserResponse(
            sessionId, conversationId, askUserResponse, writer, placeholderMsgId,
          );

          logger.info('[SSA:Chat] AskUser response handled', {
            sessionId, action: askUserResponse.action, success: result.success,
          });

          writer.end();
          return;
        } else {
          // 用户无视卡片，强行打字转移话题
          await askUserService.clearPending(sessionId);
          logger.info('[SSA:Chat] 用户转移话题，已取消挂起的 ask_user 状态', { sessionId });
        }
      }
      // ── H1 结束 ──

      // 3. 执行模式：统一使用 Agent 通道（QPER 已废弃 UI 入口）
      const executionMode = 'agent';

      // ── Agent 通道分流 ──
      if (executionMode === 'agent') {
        const placeholderMsgId = await conversationService.createAssistantPlaceholder(
          conversationId, 'chat',
        );

        const metaEvent = JSON.stringify({
          type: 'intent_classified',
          intent: 'analyze',
          confidence: 1,
          source: 'agent_mode',
          guardTriggered: false,
        });
        writer.write(`data: ${metaEvent}\n\n`);

        const result = await chatHandlerService.handleAgentMode(
          sessionId, conversationId, content.trim(), writer, placeholderMsgId,
          metadata,
        );

        logger.info('[SSA:Chat] Agent mode request completed', {
          sessionId, success: result.success,
        });

        writer.end();
        return;
      }
      // ── QPER 通道（现有逻辑） ──

      // 3. 意图分类
      const intentResult = await intentRouterService.classify(content.trim(), sessionId);

      // 发送意图元数据事件（前端可用于 UI 切换）
      const metaEvent = JSON.stringify({
        type: 'intent_classified',
        intent: intentResult.intent,
        confidence: intentResult.confidence,
        source: intentResult.source,
        guardTriggered: intentResult.guardTriggered || false,
        guardMessage: intentResult.guardMessage,
      });
      writer.write(`data: ${metaEvent}\n\n`);

      // 4. 创建 assistant placeholder（H3 竞态保护）
      const placeholderMsgId = await conversationService.createAssistantPlaceholder(
        conversationId, intentResult.intent,
      );

      // 5. 分发到意图处理器
      const result = await chatHandlerService.handle(
        sessionId, conversationId, content.trim(),
        intentResult, writer, placeholderMsgId,
      );

      logger.info('[SSA:Chat] Request completed', {
        sessionId,
        intent: result.intent,
        success: result.success,
      });

    } catch (error: any) {
      logger.error('[SSA:Chat] Unhandled error', {
        sessionId,
        error: error.message,
      });

      const errorEvent = JSON.stringify({
        type: 'error',
        code: 'CHAT_ERROR',
        message: error.message || '处理消息时发生错误',
      });
      try {
        writer.write(`data: ${errorEvent}\n\n`);
      } catch { /* ignore */ }
    } finally {
      writer.end();
    }
  });

  /**
   * GET /sessions/:id/chat/history
   * 获取对话历史消息
   */
  app.get('/:id/chat/history', async (req, reply) => {
    const { id: sessionId } = req.params as { id: string };

    const conversation = await conversationService.getConversationBySession(sessionId);
    if (!conversation) {
      return reply.send({ messages: [], conversationId: null });
    }

    const messages = await conversationService.getMessages(conversation.id);

    return reply.send({
      conversationId: conversation.id,
      messages: messages.map(m => ({
        id: m.id,
        role: m.role,
        content: m.content,
        thinkingContent: m.thinkingContent,
        intent: (m.metadata as any)?.intent,
        status: (m.metadata as any)?.status,
        createdAt: m.createdAt,
      })),
    });
  });

  /**
   * GET /sessions/:id/chat/conversation
   * 获取 conversation 元信息
   */
  app.get('/:id/chat/conversation', async (req, reply) => {
    const { id: sessionId } = req.params as { id: string };

    const conversation = await conversationService.getConversationBySession(sessionId);
    if (!conversation) {
      return reply.send({ conversation: null });
    }

    return reply.send({
      conversation: {
        id: conversation.id,
        title: conversation.title,
        messageCount: conversation.messageCount,
        createdAt: conversation.createdAt,
        updatedAt: conversation.updatedAt,
      },
    });
  });
}