import { BadRequestException } from '@nestjs/common';

export const MAX_INSPECTION_SIGNATURE_BYTES = 1024 * 1024;

export interface UploadedInspectionSignatureFile {
  originalname: string;
  mimetype: string;
  size: number;
  buffer: Buffer;
}

export interface InspectedInspectionSignatureFile {
  originalName: string;
  mimeType: 'image/png';
  extension: '.png';
}

export function inspectInspectionSignatureFile(
  file: UploadedInspectionSignatureFile | undefined,
): InspectedInspectionSignatureFile {
  if (!file?.buffer?.length) {
    throw new BadRequestException({
      code: 'INSPECTION_SIGNATURE_FILE_REQUIRED',
      message: 'La firma manuscrita en formato PNG es obligatoria',
    });
  }
  if (file.buffer.length > MAX_INSPECTION_SIGNATURE_BYTES) {
    throw new BadRequestException({
      code: 'INSPECTION_SIGNATURE_FILE_TOO_LARGE',
      message: 'La firma no puede superar 1 MB',
    });
  }
  const pngSignature = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]);
  if (
    file.mimetype !== 'image/png'
    || file.buffer.length < pngSignature.length
    || !file.buffer.subarray(0, pngSignature.length).equals(pngSignature)
  ) {
    throw new BadRequestException({
      code: 'INSPECTION_SIGNATURE_PNG_REQUIRED',
      message: 'La firma debe ser una imagen PNG válida',
    });
  }
  return {
    originalName: (file.originalname || 'firma.png').slice(0, 255),
    mimeType: 'image/png',
    extension: '.png',
  };
}