file-commons/src/dataUriToBlob.ts

import NodeBlob from 'node-blob'

type DataUriToBlob = (dataUri: string, name?: string) => Blob

const DATA_URI_PREFIX = 'data:'
const DATA_TYPE_DELIMITER = ';'
const DATA_START = ','

interface NodeFileConfig {
  lastModified: number
}

class NodeFile extends NodeBlob {
  public readonly name: string
  public readonly lastModified: number
  constructor(blobParts: unknown[], name: string, config: Partial<NodeFileConfig>) {
    super(blobParts, config)
    this.name = name
    this.lastModified = typeof config.lastModified! === 'number' ? config.lastModified : Date.now()
  }
}

const dataUriToBlob: DataUriToBlob = (dataUri, name?) => {
  if ((typeof dataUri as unknown) !== 'string') {
    throw TypeError('Argument should be a string.')
  }

  const [encoding, base64] = dataUri.slice(DATA_URI_PREFIX.length).split(DATA_START)
  const binary = atob(base64)
  const [type] = encoding.split(DATA_TYPE_DELIMITER)
  const ab = new ArrayBuffer(binary.length)
  const ia = new Uint8Array(ab)
  for (let i = 0; i < binary.length; i++) {
    ia[i] = binary.charCodeAt(i)
  }
  if (typeof name! === 'string') {
    const FileCtor = typeof window !== 'undefined' ? window.File : NodeFile
    return new FileCtor([ab], name, { type })
  }
  const BlobCtor = typeof window !== 'undefined' ? window.Blob : NodeBlob
  return new BlobCtor([ab], { type })
}

export default dataUriToBlob