import { statSync, createReadStream, promises as fs } from 'node:fs'
import { basename } from 'node:path'
import { MessageChannel } from 'node:worker_threads'

import File from './file.js'
import Blob from './index.js'

const { stat } = fs

const DOMException = globalThis.DOMException || (() => {
  const port = new MessageChannel().port1
  const ab = new ArrayBuffer(0)
  try { port.postMessage(ab, [ab, ab]) } catch (err) { return err.constructor }
})()

/**
 * @param {string} path filepath on the disk
 * @param {string} [type] mimetype to use
 */
const blobFromSync = (path, type) => fromBlob(statSync(path), path, type)

/**
 * @param {string} path filepath on the disk
 * @param {string} [type] mimetype to use
 */
const blobFrom = (path, type) => stat(path).then(stat => fromBlob(stat, path, type))

/**
 * @param {string} path filepath on the disk
 * @param {string} [type] mimetype to use
 */
const fileFrom = (path, type) => stat(path).then(stat => fromFile(stat, path, type))

/**
 * @param {string} path filepath on the disk
 * @param {string} [type] mimetype to use
 */
const fileFromSync = (path, type) => fromFile(statSync(path), path, type)

// @ts-ignore
const fromBlob = (stat, path, type = '') => new Blob([new BlobDataItem({
  path,
  size: stat.size,
  lastModified: stat.mtimeMs,
  start: 0
})], { type })

// @ts-ignore
const fromFile = (stat, path, type = '') => new File([new BlobDataItem({
  path,
  size: stat.size,
  lastModified: stat.mtimeMs,
  start: 0
})], basename(path), { type, lastModified: stat.mtimeMs })

/**
 * This is a blob backed up by a file on the disk
 * with minium requirement. Its wrapped around a Blob as a blobPart
 * so you have no direct access to this.
 *
 * @private
 */
class BlobDataItem {
  #path
  #start

  constructor (options) {
    this.#path = options.path
    this.#start = options.start
    this.size = options.size
    this.lastModified = options.lastModified
  }

  /**
   * Slicing arguments is first validated and formatted
   * to not be out of range by Blob.prototype.slice
   */
  slice (start, end) {
    return new BlobDataItem({
      path: this.#path,
      lastModified: this.lastModified,
      size: end - start,
      start
    })
  }

  async * stream () {
    const { mtimeMs } = await stat(this.#path)
    if (mtimeMs > this.lastModified) {
      throw new DOMException('The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired.', 'NotReadableError')
    }
    yield * createReadStream(this.#path, {
      start: this.#start,
      end: this.#start + this.size - 1
    })
  }

  get [Symbol.toStringTag] () {
    return 'Blob'
  }
}

export default blobFromSync
export { File, Blob, blobFrom, blobFromSync, fileFrom, fileFromSync }