/**
 * Copyright 2020 Google Inc. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import { promises as fs } from 'fs';

import { lookup as lookupMime } from 'mime-types';

const prefix = 'data-url:';

export default function dataURLPlugin() {
  return {
    name: 'data-url-plugin',
    async resolveId(id, importer) {
      if (!id.startsWith(prefix)) return;
      return (
        prefix + (await this.resolve(id.slice(prefix.length), importer)).id
      );
    },
    async load(id) {
      if (!id.startsWith(prefix)) return;
      const realId = id.slice(prefix.length);
      this.addWatchFile(realId);

      const source = await fs.readFile(realId);
      const type = lookupMime(realId) || 'text/plain';

      return `export default 'data:${type};base64,${source.toString(
        'base64',
      )}';`;
    },
  };
}
