import { createReadStream, existsSync } from "node:fs";
import { join } from "node:path";
import {
  HttpException,
  HttpStatus,
  Injectable,
  OnModuleInit,
} from "@nestjs/common";
import { ConfigService } from "@nestjs/config";
import axios, { AxiosRequestConfig } from "axios";
import * as FormData from "form-data";

@Injectable()
export class AiService implements OnModuleInit {
  private apiKey: string;
  private accessToken: string = null;

  // These configurations are for authentication and getting the API key.
  private readonly loginOptions: AxiosRequestConfig = {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    url: `${this.configService.get<string>("AI_URL_V2")}/auth/login`,
    data: {
      username: this.configService.get<string>("AI_USERNAME"),
      password: this.configService.get<string>("AI_PASSWORD"),
    },
    timeout: 1000, // TODO: Make this ENV
  };

  constructor(private readonly configService: ConfigService) {}

  private get profileOptions(): AxiosRequestConfig {
    return {
      method: "GET",
      url: `${this.configService.get<string>("AI_URL_V2")}/auth/profile`,
      headers: {
        Authorization: `Bearer ${this.accessToken}`,
      },
    };
  }

  // This getter dynamically creates the base options for the image processing request.
  private get imageProcessOptions(): AxiosRequestConfig {
    return {
      method: "POST",
      url: `${process.env.AI_URL_V2}/services/car-damage/detector?version=ai-v7`,
      headers: {
        Authorization: `Bearer ${this.accessToken}`,
        "gateway-api-key": `${this.apiKey}`,
      },
    };
  }

  async onModuleInit() {
    try {
      const res = await this.login();
      if (res?.accessToken) {
        this.accessToken = res.accessToken;
        await this.getApiKey();
      }
    } catch (error) {
      // Don't prevent app startup if AI service is temporarily unavailable
      // The service will attempt to re-authenticate when aiRequestImage is called
      // Reset tokens so re-authentication will be attempted
      this.accessToken = null;
      this.apiKey = null;
    }
  }

  private async login() {
    const loginResponse = await axios.request(this.loginOptions);
    return loginResponse.data;
  }

  private async getApiKey() {
    const profileResponse = await axios.request(this.profileOptions);
    this.apiKey = profileResponse.data.apiKey.key;
    return this.apiKey;
  }

  public async aiRequestImage(file: {
    path: string;
    fileName?: string;
  }): Promise<any> {
    // Ensure authentication is set up
    if (!this.accessToken || !this.apiKey) {
      try {
        const res = await this.login();
        if (res?.accessToken) {
          this.accessToken = res.accessToken;
          await this.getApiKey();
        } else {
          throw new HttpException(
            "AI Service authentication failed",
            HttpStatus.UNAUTHORIZED,
          );
        }
      } catch (error) {
        throw new HttpException(
          "AI Service authentication failed",
          HttpStatus.UNAUTHORIZED,
        );
      }
    }

    // Resolve relative paths to absolute paths
    const filePath = file.path.startsWith("/")
      ? file.path
      : join(process.cwd(), file.path.replace(/^\.\//, ""));

    // Check if file exists
    if (!existsSync(filePath)) {
      throw new HttpException(
        `File not found: ${file.path}`,
        HttpStatus.NOT_FOUND,
      );
    }

    const form = new FormData();
    const fileStream = createReadStream(filePath);

    // Append file with filename if available
    if (file.fileName) {
      form.append("images", fileStream, file.fileName);
    } else {
      // Extract filename from path if not provided
      const pathParts = filePath.split("/");
      const extractedFileName = pathParts[pathParts.length - 1];
      form.append("images", fileStream, extractedFileName);
    }

    try {
      const requestHeaders = {
        ...this.imageProcessOptions.headers,
        ...form.getHeaders(),
      };

      const fs = require("fs");
      const stats = fs.statSync(filePath);

      const response = await axios.request({
        ...this.imageProcessOptions,
        headers: requestHeaders,
        data: form,
        maxContentLength: Infinity,
        maxBodyLength: Infinity,
      });

      // Validate response structure
      if (!response.data) {
        throw new HttpException(
          "AI Service returned empty response",
          HttpStatus.BAD_GATEWAY,
        );
      }

      // Check for error in response first (AI service returns 201 with error in body)
      if (response.data.error) {
        throw new HttpException(
          `AI Service error: ${response.data.error}`,
          HttpStatus.BAD_GATEWAY,
        );
      }

      // Check for processed image (downloadLink)
      if (!response.data.downloadLink) {
        throw new HttpException(
          "AI Service did not return processed image (downloadLink missing)",
          HttpStatus.BAD_GATEWAY,
        );
      }

      return response.data;
    } catch (er) {
      // Determine error source
      let errorSource = "UNKNOWN";
      let errorMessage = er.message;
      let errorDetails = "No error details available";

      if (er.response) {
        errorSource = "AI_SERVICE_RESPONSE";
        errorMessage =
          er.response?.data?.message ||
          er.message ||
          `HTTP ${er.response.status}`;
        errorDetails = er.response?.data
          ? JSON.stringify(er.response.data, null, 2)
          : `Status: ${er.response.status}, StatusText: ${er.response.statusText}`;
      } else if (er.request) {
        errorSource = "NETWORK_ERROR";
        errorMessage = "Network error - AI service did not respond";
        errorDetails = "Request was made but no response received";
      } else {
        errorSource = "REQUEST_SETUP_ERROR";
        errorMessage = er.message || "Error setting up request";
      }

      // Re-throw with detailed error information
      throw new HttpException(
        `[${errorSource}] ${errorMessage}`,
        er.response?.status || HttpStatus.INTERNAL_SERVER_ERROR,
      );
    }
  }
}