XCDesktop/api/utils/file.ts

import fs from 'fs/promises'
import path from 'path'
import { InternalError, ValidationError } from '../../shared/errors/index.js'

export const getUniqueFilename = async (imagesDirFullPath: string, baseName: string, ext: string) => {
  const maxAttempts = 1000
  for (let i = 0; i < maxAttempts; i++) {
    const suffix = i === 0 ? '' : `-${i + 1}`
    const filename = `${baseName}${suffix}${ext}`
    const fullPath = path.join(imagesDirFullPath, filename)
    try {
      await fs.access(fullPath)
    } catch {
      return filename
    }
  }
  throw new InternalError('Failed to generate unique filename')
}

export const mimeToExt: Record<string, string> = {
  'image/png': '.png',
  'image/jpeg': '.jpg',
  'image/jpg': '.jpg',
  'image/gif': '.gif',
  'image/webp': '.webp',
}

const IMAGE_MAGIC_BYTES: Record<string, { bytes: number[]; offset?: number }> = {
  'image/png': { bytes: [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a] },
  'image/jpeg': { bytes: [0xff, 0xd8, 0xff] },
  'image/gif': { bytes: [0x47, 0x49, 0x46, 0x38] },
  'image/webp': { bytes: [0x52, 0x49, 0x46, 0x46], offset: 0 },
}

const WEBP_RIFF_HEADER = [0x52, 0x49, 0x46, 0x46]
const WEBP_WEBP_MARKER = [0x57, 0x45, 0x42, 0x50]

const MIN_IMAGE_SIZE = 16
const MAX_IMAGE_SIZE = 8 * 1024 * 1024

export const validateImageBuffer = (buffer: Buffer, claimedMimeType: string): void => {
  if (buffer.byteLength < MIN_IMAGE_SIZE) {
    throw new ValidationError('Image file is too small or corrupted')
  }

  if (buffer.byteLength > MAX_IMAGE_SIZE) {
    throw new ValidationError('Image file is too large')
  }

  const magicInfo = IMAGE_MAGIC_BYTES[claimedMimeType]
  if (!magicInfo) {
    throw new ValidationError('Unsupported image type for content validation')
  }

  const offset = magicInfo.offset || 0
  const expectedBytes = magicInfo.bytes

  for (let i = 0; i < expectedBytes.length; i++) {
    if (buffer[offset + i] !== expectedBytes[i]) {
      throw new ValidationError('Image content does not match the claimed file type')
    }
  }

  if (claimedMimeType === 'image/webp') {
    if (buffer.byteLength < 12) {
      throw new ValidationError('WebP image is corrupted')
    }
    for (let i = 0; i < WEBP_WEBP_MARKER.length; i++) {
      if (buffer[8 + i] !== WEBP_WEBP_MARKER[i]) {
        throw new ValidationError('WebP image content is invalid')
      }
    }
  }
}

export const detectImageMimeType = (buffer: Buffer): string | null => {
  if (buffer.byteLength < 8) return null

  if (
    buffer[0] === 0x89 &&
    buffer[1] === 0x50 &&
    buffer[2] === 0x4e &&
    buffer[3] === 0x47 &&
    buffer[4] === 0x0d &&
    buffer[5] === 0x0a &&
    buffer[6] === 0x1a &&
    buffer[7] === 0x0a
  ) {
    return 'image/png'
  }

  if (buffer[0] === 0xff && buffer[1] === 0xd8 && buffer[2] === 0xff) {
    return 'image/jpeg'
  }

  if (buffer[0] === 0x47 && buffer[1] === 0x49 && buffer[2] === 0x46 && buffer[3] === 0x38) {
    return 'image/gif'
  }

  if (
    buffer[0] === 0x52 &&
    buffer[1] === 0x49 &&
    buffer[2] === 0x46 &&
    buffer[3] === 0x46 &&
    buffer[8] === 0x57 &&
    buffer[9] === 0x45 &&
    buffer[10] === 0x42 &&
    buffer[11] === 0x50
  ) {
    return 'image/webp'
  }

  return null
}

export const sanitizeFilename = (filename: string): string => {
  let sanitized = filename.replace(/[<>:"/\\|?*\x00-\x1f]/g, '_')
  sanitized = sanitized.replace(/^\.+|\.+$/g, '')
  sanitized = sanitized.replace(/\.{2,}/g, '.')
  if (sanitized.length > 200) {
    const ext = path.extname(filename)
    const baseName = path.basename(filename, ext)
    sanitized = baseName.substring(0, 200 - ext.length) + ext
  }
  return sanitized || 'unnamed'
}