import {
  Injectable,
  Logger,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';

interface AgentApiRequest {
  conversation_id: string;
  query: string;
  sender_id: string;
}

interface AgentApiResponse {
  reply?: string;
  message?: string;
  content?: string;
  response?: string;
  text?: string;
  answer?: string;
}

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

  constructor(
    private readonly configService: ConfigService,
  ) {}

  // ==================== Mention Bot Logic ====================

  /**
   * Check if message contains a mention of the configured bot username
   */
  containsMention(content: string): boolean {
    const botUsername = this.configService.get<string>('AGENT_BOT_USERNAME') || this.configService.get<string>('agent.botUsername') || 'studybot';
    const pattern = new RegExp(`@${botUsername}\\b`, 'i');
    return pattern.test(content);
  }

  /**
   * Extract the prompt from a message by removing the bot mention
   */
  extractPrompt(content: string): string {
    const botUsername = this.configService.get<string>('AGENT_BOT_USERNAME') || this.configService.get<string>('agent.botUsername') || 'studybot';
    const pattern = new RegExp(`@${botUsername}\\b`, 'gi');
    return content.replace(pattern, '').trim();
  }

  /**
   * Get bot user ID from config
   */
  getBotUserId(): string | undefined {
    const botUserId = this.configService.get<string>('AGENT_BOT_USER_ID');
    if (botUserId) return botUserId;
    return this.configService.get<string>('agent.botUserId') || undefined;
  }

  /**
   * Call the external agent API and return the reply text
   * Returns null if agent is not configured or returns empty
   */
  async callAgent(
    roomId: string,
    userId: string,
    prompt: string,
    username?: string,
  ): Promise<string | null> {
    const baseUrl = this.configService.get<string>('AGENT_API_URL') || this.configService.get<string>('agent.apiUrl');

    if (!baseUrl) {
      this.logger.warn('AGENT_API_URL not configured, skipping agent call');
      return 'Xin lỗi, tôi đang gặp sự cố kết nối. Vui lòng thử lại sau!';
    }

    if (!prompt) {
      this.logger.debug('Empty prompt, skipping agent call');
      return null;
    }

    try {
      this.logger.log(`Calling agent API for room ${roomId}, user ${userId}`);
      const reply = await this.callAgentApi({
        conversation_id: roomId,
        query: prompt,
        sender_id: username || userId,
      });

      if (!reply || reply.trim().length === 0) {
        this.logger.warn('Agent returned empty reply');
        return 'Xin lỗi, tôi không hiểu câu hỏi của bạn. Vui lòng thử lại!';
      }

      this.logger.log(`Agent replied for room ${roomId}`);
      return reply;
    } catch (error) {
      this.logger.error(`Failed to call agent: ${error.message}`);
      return 'Xin lỗi, tôi đang gặp sự cố kỹ thuật. Vui lòng thử lại sau nhé!';
    }
  }

  /**
   * Call the external agent API at POST /api/v1/chat
   */
  private async callAgentApi(payload: AgentApiRequest): Promise<string> {
    const baseUrl = this.configService.get<string>('AGENT_API_URL') || this.configService.get<string>('agent.apiUrl');
    const apiKey = this.configService.get<string>('AGENT_API_KEY') || this.configService.get<string>('agent.apiKey');

    const url = `${baseUrl}/api/v1/chat`;

    this.logger.debug(`Agent API URL: ${url}`);
    this.logger.debug(`Agent API payload: ${JSON.stringify(payload)}`);

    const headers: Record<string, string> = {
      'Content-Type': 'application/json',
    };

    if (apiKey) {
      headers['Authorization'] = `Bearer ${apiKey}`;
    }

    const response = await fetch(url, {
      method: 'POST',
      headers,
      body: JSON.stringify(payload),
    });

    if (!response.ok) {
      throw new Error(`Agent API returned ${response.status}: ${await response.text()}`);
    }

    const data = (await response.json()) as AgentApiResponse;

    // Support multiple response formats
    return (
      data.reply ||
      data.message ||
      data.content ||
      data.response ||
      data.text ||
      data.answer ||
      ''
    );
  }
}