file-system-access/src/adapters/sandbox.ts

File System Access API implementation (ponyfill) with pluggable storage adapters via IndexedDB, Cache API, in-memory etc.

import { Adapter, FileSystemFileHandleAdapter, FileSystemFolderHandleAdapter, WriteChunk } from '../interfaces.js'
import { errors, isChunkObject } from '../util.js'

const { INVALID, GONE, SYNTAX, DISALLOWED } = errors

class Sink implements UnderlyingSink<WriteChunk> {
  private file: File
  private size: number
  private position: number

  constructor (private fileHandle: FileHandle, file: File, private writer: FileWriter, keepExistingData: boolean) {
    this.file = keepExistingData ? file : new File([], file.name, file)
    this.size = keepExistingData ? file.size : 0
    this.position = 0
  }

  async write (chunk: WriteChunk) {
    try {
      // This ensures an error is thrown if the file has been deleted
      await this.fileHandle.getFile()
    } catch (err) {
      throw new DOMException(...GONE)
    }

    let file = this.file

    if (isChunkObject(chunk)) {
      if (chunk.type === 'write') {
        if (typeof chunk.position === 'number' && chunk.position >= 0) {
          this.position = chunk.position
          if (this.size < chunk.position) {
            this.file = new File(
              [this.file, new ArrayBuffer(chunk.position - this.size)],
              this.file.name,
              this.file
            )
          }
        }
        if (!('data' in chunk)) {
          throw new DOMException(...SYNTAX('write requires a data argument'))
        }
        chunk = chunk.data
      } else if (chunk.type === 'seek') {
        if (Number.isInteger(chunk.position) && chunk.position >= 0) {
          if (this.size < chunk.position) {
            throw new DOMException(...INVALID)
          }
          this.position = chunk.position
          return
        } else {
          throw new DOMException(...SYNTAX('seek requires a position argument'))
        }
      } else if (chunk.type === 'truncate') {
        if (Number.isInteger(chunk.size) && chunk.size >= 0) {
          file = chunk.size < this.size
            ? new File([file.slice(0, chunk.size)], file.name, file)
            : new File([file, new Uint8Array(chunk.size - this.size)], file.name, file)

          this.size = file.size
          if (this.position > file.size) {
            this.position = file.size
          }
          this.file = file
          return
        } else {
          throw new DOMException(...SYNTAX('truncate requires a size argument'))
        }
      }
    }

    chunk = new Blob([chunk])

    let blob = this.file
    // Calc the head and tail fragments
    const head = blob.slice(0, this.position)
    const tail = blob.slice(this.position + chunk.size)

    // Calc the padding
    let padding = this.position - head.size
    if (padding < 0) {
      padding = 0
    }
    blob = new File([
      head,
      new Uint8Array(padding),
      chunk,
      tail
    ], blob.name)

    this.size = blob.size
    this.position += chunk.size

    this.file = blob
  }

  async close () {
    try {
      // This ensures an error is thrown if the file has been deleted
      await this.fileHandle.getFile()
    } catch (err) {
      throw new DOMException(...GONE)
    }

    // We need to work with a cloned file because writer.truncate() will destroy our original data
    const bufferCopy = await new Promise<ArrayBuffer>((resolve, reject) => {
      const reader = new FileReader()
      reader.onload = () => resolve(reader.result as ArrayBuffer)
      reader.onerror = reject
      reader.readAsArrayBuffer(this.file)
    })
    this.file = new File([bufferCopy], this.file.name, this.file)

    await new Promise((resolve, reject) => {
      this.writer.onwriteend = resolve
      this.writer.onerror = reject
      this.writer.truncate(0)
    })

    await new Promise((resolve, reject) => {
      this.writer.onwriteend = resolve
      this.writer.onerror = reject
      this.writer.write(this.file)
    })

    this.writer.onwriteend = null!
    this.writer.onerror = null!

    this.file = this.position = this.size = null!
  }
}

export class FileHandle implements FileSystemFileHandleAdapter {
  readonly kind = 'file'
  file: FileEntry
  writable: boolean
  readable = true

  constructor (file: FileEntry, writable = true) {
    this.file = file
    this.writable = writable
  }

  get name () {
    return this.file.name
  }

  async isSameEntry (other: FileHandle) {
    return this.file.toURL() === other.file.toURL()
  }

  getFile () {
    return new Promise(this.file.file.bind(this.file))
  }

  async createWritable (opts: FileSystemCreateWritableOptions) {
    if (!this.writable) throw new DOMException(...DISALLOWED)

    const file = await this.getFile()

    return new Promise<Sink>((resolve, reject) =>
      this.file.createWriter(fileWriter => {
        resolve(new Sink(this, file, fileWriter, !!opts.keepExistingData))
      }, reject)
    )
  }
}

export class FolderHandle implements FileSystemFolderHandleAdapter {
  readonly kind = 'directory'
  readonly name
  private dir: FileSystemDirectoryEntry
  writable: boolean
  readable = true

  constructor (dir: FileSystemDirectoryEntry, writable = true) {
    this.dir = dir
    this.writable = writable
    this.name = dir.name
  }

  async isSameEntry (other: FolderHandle) {
    return this.dir.fullPath === other.dir.fullPath
  }

  async * entries () {
    const reader = this.dir.createReader()
    const entries = await new Promise(reader.readEntries.bind(reader))
    for (const x of entries) {
      yield [
        x.name,
        x.isFile ?
          new FileHandle(x as FileEntry, this.writable) :
          new FolderHandle(x as FileSystemDirectoryEntry, this.writable)
      ] as [string, FileHandle | FolderHandle]
    }
  }

  getDirectoryHandle (name: string, opts: Flags = {}) {
    return new Promise<FolderHandle>((resolve, reject) => {
      this.dir.getDirectory(name, opts, dir => {
        resolve(new FolderHandle(dir))
      }, reject)
    })
  }

  getFileHandle (name: string, opts: Flags = {}) {
    return new Promise<FileHandle>((resolve, reject) =>
      this.dir.getFile(name, opts, file => resolve(new FileHandle(file)), reject)
    )
  }

  async removeEntry (name: string, opts?: { recursive?: boolean}) {
    let entry: FolderHandle | FileHandle
    try {
      entry = await this.getDirectoryHandle(name)
    } catch (err) {
      if (err.name === 'TypeMismatchError') {
        entry = await this.getFileHandle(name)
      } else {
        throw err
      }
    }

    return new Promise<void>((resolve, reject) => {
      if (entry instanceof FolderHandle) {
        opts?.recursive
          ? entry.dir.removeRecursively(() => resolve(), reject)
          : entry.dir.remove(() => resolve(), reject)
      } else if (entry.file) {
        entry.file.remove(() => resolve(), reject)
      }
    })
  }
}

export interface SandboxOptions {
  _persistent?: 0 | 1
}

const adapter: Adapter<SandboxOptions> = ({ _persistent = 0 }) => new Promise((resolve, reject) =>
  window.webkitRequestFileSystem(
    _persistent, 0,
    e => resolve(new FolderHandle(e.root)),
    reject
  )
)

export default adapter