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

import { createImageStorageContract } from './image-storage.js';

function safePath(rootDirectory, key) {
  if (typeof key !== 'string' || key.length === 0 || path.isAbsolute(key)) {
    throw new Error('Image storage key must be a relative non-empty path.');
  }

  const root = path.resolve(rootDirectory);
  const target = path.resolve(root, key);
  if (target !== root && !target.startsWith(`${root}${path.sep}`)) {
    throw new Error('Image storage key escapes the storage root.');
  }

  return target;
}

export function createLocalImageStorage(rootDirectory) {
  if (typeof rootDirectory !== 'string' || rootDirectory.length === 0) {
    throw new TypeError('Image storage root directory is required.');
  }

  return createImageStorageContract({
    async put({ key, data }) {
      if (!Buffer.isBuffer(data)) {
        throw new TypeError('Image storage data must be a Buffer.');
      }

      const target = safePath(rootDirectory, key);
      await mkdir(path.dirname(target), { recursive: true });
      await writeFile(target, data, { flag: 'wx' });
      return { key };
    },

    async get(key) {
      return readFile(safePath(rootDirectory, key));
    },

    async delete(key) {
      await rm(safePath(rootDirectory, key), { force: true });
    },
  });
}