const fs = require('fs');

const removalAi = {
  cookies: new Map(),

  headers: {
    'user-agent': 'Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/150.0.0.0 Mobile Safari/537.36',
    'accept-language': 'ar-EG,ar;q=0.9,en-US;q=0.8,en;q=0.7',
    'sec-ch-ua': '"Not;A=Brand";v="8", "Chromium";v="150", "Google Chrome";v="150"',
    'sec-ch-ua-mobile': '?1',
    'sec-ch-ua-platform': '"Android"'
  },

  isImageBuffer(buf) {
    if (!buf || !(buf instanceof Uint8Array || Buffer.isBuffer(buf)) || buf.length < 4) {
      return false;
    }
    // PNG: 89 50 4E 47
    if (buf[0] === 0x89 && buf[1] === 0x50 && buf[2] === 0x4E && buf[3] === 0x47) return true;
    // JPEG: FF D8 FF
    if (buf[0] === 0xFF && buf[1] === 0xD8 && buf[2] === 0xFF) return true;
    // GIF: 47 49 46 38 ("GIF8")
    if (buf[0] === 0x47 && buf[1] === 0x49 && buf[2] === 0x46 && buf[3] === 0x38) return true;
    // WEBP: RIFF...WEBP
    if (buf.length >= 12 &&
        buf[0] === 0x52 && buf[1] === 0x49 && buf[2] === 0x46 && buf[3] === 0x46 &&
        buf[8] === 0x57 && buf[9] === 0x45 && buf[10] === 0x42 && buf[11] === 0x50) return true;
    // BMP: 42 4D ("BM")
    if (buf[0] === 0x42 && buf[1] === 0x4D) return true;

    return false;
  },

  saveCookies(res) {
    const setCookies = res.headers.getSetCookie?.() ?? [];
    for (const item of setCookies) {
      const [pair] = item.split(';');
      const [key, ...val] = pair.split('=');
      if (key && val.length) this.cookies.set(key.trim(), val.join('=').trim());
    }
  },

  getCookieHeader() {
    return Array.from(this.cookies.entries()).map(([k, v]) => `${k}=${v}`).join('; ');
  },

  async getSecurity() {
    const headers = {
      ...this.headers,
      'Connection': 'keep-alive',
      'Upgrade-Insecure-Requests': '1',
      'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7',
      'Sec-Fetch-Site': 'none',
      'Sec-Fetch-Mode': 'navigate',
      'Sec-Fetch-User': '?1',
      'Sec-Fetch-Dest': 'document',
      'Accept-Encoding': 'gzip, deflate, br, zstd'
    };
    const cookie = this.getCookieHeader();
    if (cookie) headers['Cookie'] = cookie;

    const res = await fetch('https://removal.ai/', { headers });
    this.saveCookies(res);

    const html = await res.text();
    const match = html.match(/var\s+ajax_upload_object\s*=\s*(\{[\s\S]*?\});/);
    if (!match) throw new Error('ajax_upload_object not found');
    return Function(`return (${match[1]})`)().security;
  },

  async getWebToken(security) {
    const headers = {
      ...this.headers,
      'Connection': 'keep-alive',
      'X-Requested-With': 'XMLHttpRequest',
      'Accept': '*/*',
      'Sec-Fetch-Site': 'same-origin',
      'Sec-Fetch-Mode': 'cors',
      'Sec-Fetch-Dest': 'empty',
      'Referer': 'https://removal.ai/upload/',
      'Accept-Encoding': 'gzip, deflate, br, zstd'
    };
    const cookie = this.getCookieHeader();
    if (cookie) headers['Cookie'] = cookie;

    const res = await fetch(`https://removal.ai/wp-admin/admin-ajax.php?action=ajax_get_webtoken&security=${security}`, { headers });
    this.saveCookies(res);

    const json = await res.json();
    if (!json.success) throw new Error(JSON.stringify(json));
    return json.data.webtoken;
  },

  /**
   * Remove background from image (accepts file path string or Buffer).
   * @param {string|Buffer|Uint8Array} input - Image file path or Buffer data.
   * @returns {Promise<{
   *   status: number,
   *   url: string,
   *   preview_demo: string,
   *   low_resolution: string,
   *   original: string,
   *   original_width: number,
   *   original_height: number,
   *   preview_width: number,
   *   preview_height: number
   * }>} Expected API response object containing processed image URLs.
   */
  async removeBackground(input) {
    let buffer;
    let filename = 'image.png';

    if (typeof input === 'string') {
      if (!fs.existsSync(input)) {
        throw new Error(`File not found at path: ${input}`);
      }
      buffer = fs.readFileSync(input);
      filename = input.split('/').pop() || 'image.png';
    } else if (Buffer.isBuffer(input) || input instanceof Uint8Array) {
      buffer = Buffer.from(input);
    } else {
      throw new Error('Invalid input: Must be a file path (string) or Buffer.');
    }

    if (!this.isImageBuffer(buffer)) {
      throw new Error('Invalid file format: File is not a supported image (PNG, JPEG, WEBP, GIF, BMP).');
    }

    const security = await this.getSecurity();
    const token = await this.getWebToken(security);

    const form = new FormData();
    form.append('image_file', new Blob([buffer], { type: 'image/png' }), filename);

    const headers = {
      ...this.headers,
      'web-token': token,
      'accept': '*/*',
      'origin': 'https://removal.ai',
      'sec-fetch-site': 'same-site',
      'sec-fetch-mode': 'cors',
      'sec-fetch-dest': 'empty',
      'accept-encoding': 'gzip, deflate, br, zstd',
      'priority': 'u=1, i'
    };
    const cookie = this.getCookieHeader();
    if (cookie) headers['Cookie'] = cookie;

    const res = await fetch('https://api.removal.ai/3.0/remove', {
      method: 'POST',
      headers,
      body: form
    });
    this.saveCookies(res);

    return await res.json();
  }
};

module.exports = removalAi;