import { Injectable, NotFoundException, Logger, Optional } from '@nestjs/common';
import { PrismaService } from '../../infrastructure/database/prisma.service';
import { ContentSafetyService } from '../content-safety/content-safety.service';

@Injectable()
export class RagChatService {
  private readonly logger = new Logger(RagChatService.name);

  constructor(
    private readonly prisma: PrismaService,
    @Optional() private readonly safety?: ContentSafetyService,
  ) {}

  async createSession(userId: string, knowledgeBaseId: string, title?: string) {
    return this.prisma.chatSession.create({
      data: { userId, knowledgeBaseId, title: title || '新对话' },
    });
  }

  async listSessions(userId: string, kbId?: string) {
    return this.prisma.chatSession.findMany({
      where: { userId, ...(kbId ? { knowledgeBaseId: kbId } : {}) },
      orderBy: { updatedAt: 'desc' },
    });
  }

  async getMessages(sessionId: string) {
    return this.prisma.chatMessage.findMany({
      where: { sessionId },
      orderBy: { createdAt: 'asc' },
      include: { citations: true },
    });
  }

  async sendMessage(userId: string, sessionId: string, content: string) {
    const session = await this.prisma.chatSession.findUnique({ where: { id: sessionId } });
    if (!session || session.userId !== userId) throw new NotFoundException('对话不存在');

    // Content safety check on user input
    const inputCheck = await this.safety?.check(content, { userId, contentType: 'rag_input' });
    if (inputCheck && !inputCheck.safe) {
      return { blocked: true, message: '输入包含违规内容，请修改后重试' };
    }

    // Save user message
    await this.prisma.chatMessage.create({
      data: { sessionId, role: 'user', content },
    });

    // Generate AI response (simplified — real RAG pipeline in M3)
    const reply = `感谢提问。基于知识库内容，我暂时无法生成完整回答（RAG 检索管道将在后续版本完善）。`;
    const aiMsg = await this.prisma.chatMessage.create({
      data: { sessionId, role: 'ai', content: reply, tokens: reply.length },
    });

    // Update session timestamp
    await this.prisma.chatSession.update({ where: { id: sessionId }, data: { updatedAt: new Date() } });

    return { message: aiMsg, citations: [] };
  }

  async deleteSession(sessionId: string) {
    await this.prisma.chatCitation.deleteMany({ where: { message: { sessionId } } });
    await this.prisma.chatMessage.deleteMany({ where: { sessionId } });
    await this.prisma.chatSession.delete({ where: { id: sessionId } });
    return { success: true };
  }
}