import { randomUUID } from 'node:crypto'
import { mkdir, readFile, rm, writeFile } from 'node:fs/promises'
import { join } from 'node:path'

const KEY_PATTERN = /^[0-9a-f-]{36}\.[a-z]{3,4}$/

/** Stores uploaded files on local disk under random names. */
export class FileStorage {
  readonly dir: string

  constructor(dir: string) {
    this.dir = dir
  }

  async save(data: Uint8Array, extension: string): Promise<string> {
    await mkdir(this.dir, { recursive: true })
    const key = `${randomUUID()}.${extension}`
    await writeFile(this.path(key), data, { flag: 'wx' })
    return key
  }

  read(key: string): Promise<Buffer> {
    return readFile(this.path(key))
  }

  async remove(key: string): Promise<void> {
    await rm(this.path(key), { force: true })
  }

  private path(key: string) {
    if (!KEY_PATTERN.test(key)) throw new Error(`Invalid storage key: ${key}`)
    return join(this.dir, key)
  }
}