import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class FileUploadService {
  //Check uploaded file size should be less than or equal to specified size
  isValidFileMaxSize(file, maxSize: Number): boolean {
    if (file) {
      return file.size <= maxSize;
    }
    return false;
  }

  //Check uploaded file mime type
  isValidJpegMimeType(file): boolean {
    if (file) {
      return file.type === new String("image/jpeg").toLowerCase();
    }
    return false;
  }

  //Check uploaded image file dimension
  isValidImageDimension(file, height: Number, width: Number, callback) {
    if (file) {
      const reader: FileReader = new FileReader();
      reader.readAsDataURL(file);
      reader.onload = (e:any) => {
        var img = new Image();
        img.src = e.target.result.toString();
        img.onload = () => {
          const isValid = img.height === height && img.width === width;
          callback(isValid);
        };
      };
    }
  }

  //Check valid image file for specific dimension(height and width) and max file size.
  isValidImageFile(file, callback) {
    const isValidMime = this.isValidJpegMimeType(file);
     this.isValidJpegContentType(file,(isValidContent)=>{
        //const isValidImage = isValidMime && isValidMaxSize && isValidContent && isValidDimension;
        const isValidImage = isValidMime && isValidContent;
        callback(isValidImage);
     });
  }

  //Check uploaded image file content type for valid jpeg file.
  isValidJpegContentType(file, callback) {
    const reader: FileReader = new FileReader();
    reader.readAsArrayBuffer(file);
    reader.onload =  (e:any) => {
      var arr = (new Uint8Array(e.target.result).subarray(0, 4));
      var header = '';
      for (var i = 0; i < arr.length; i++) {
        header += arr[i].toString(16);
      }
      // Magic numbers: http://www.garykessler.net/library/file_sigs.html
      switch (header) {
        case "ffd8ffDB":
        case "ffd8ffe0":
        case "ffd8ffe1":
        case "ffd8ffe2":
        case "ffd8ffe3":
        case "ffd8ffe8":
          return callback(true);
        default:
          return callback(false);
      }
    }
  }

  //Get uploaded image binary string
  getImageBinaryString(file, callback) {
    const reader: FileReader = new FileReader();
    reader.readAsBinaryString(file);
    reader.onload = (e: any) => {
      callback(e.target.result.toString());
    };
  }
}