/**
 * 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 fsp, readFileSync } from 'fs';
import { createHash } from 'crypto';
import { promisify } from 'util';
import { parse as parsePath, resolve as resolvePath, dirname } from 'path';

import postcss from 'postcss';
import postCSSNested from 'postcss-nested';
import postCSSUrl from 'postcss-url';
import postCSSModules from 'postcss-modules';
import postCSSImport from 'postcss-import';
import postCSSSimpleVars from 'postcss-simple-vars';
import cssNano from 'cssnano';
import camelCase from 'lodash.camelcase';
import glob from 'glob';

const globP = promisify(glob);

const moduleSuffix = '.css';
const prefix = 'css-bundle:';
const assetRe = new RegExp('/fake/path/to/asset/([^/]+)/', 'g');

export default function (resolveFileUrl) {
  /** @type {string[]} */
  let emittedCSSIds;
  /** @type {Map<string, string>} */
  let hashToId;
  /** @type {Map<string, { module: string, css: string }>} */
  let pathToResult;

  async function loadBundledCSS(path, rollupContext) {
    const parsedPath = parsePath(path);

    if (!pathToResult.has(path)) {
      throw Error(`Cannot find ${path} in pathToResult`);
    }

    const file = pathToResult.get(path).css;

    const cssResult = await postcss([
      postCSSImport({
        path: ['./', 'static-build/'],
        load(path) {
          if (!pathToResult.has(path)) {
            throw Error(`Cannot find ${path} in pathToResult`);
          }
          return pathToResult.get(path).css;
        },
      }),
      postCSSUrl({
        url: ({ relativePath, url }) => {
          if (/^https?:\/\//.test(url)) return url;
          const parsedPath = parsePath(relativePath);
          const source = readFileSync(resolvePath(dirname(path), relativePath));
          const fileId = rollupContext.emitFile({
            type: 'asset',
            name: parsedPath.base,
            source,
          });
          const hash = createHash('md5');
          hash.update(source);
          const md5 = hash.digest('hex');
          hashToId.set(md5, fileId);
          return `/fake/path/to/asset/${md5}/`;
        },
      }),
      cssNano,
    ]).process(file, {
      from: path,
    });

    const fileId = rollupContext.emitFile({
      type: 'asset',
      source: cssResult.css,
      name: parsedPath.base,
    });

    emittedCSSIds.push(fileId);

    return [
      `export default import.meta.ROLLUP_FILE_URL_${fileId}`,
      `export const inline = ${JSON.stringify(cssResult.css)}`,
    ].join('\n');
  }

  return {
    name: 'css',
    async buildStart() {
      emittedCSSIds = [];
      hashToId = new Map();
      pathToResult = new Map();

      const cssPaths = await globP('src/static-build/**/*.css', {
        nodir: true,
        absolute: true,
      });

      await Promise.all(
        cssPaths.map(async (path) => {
          this.addWatchFile(path);
          const file = await fsp.readFile(path);
          let moduleJSON;

          const cssResult = await postcss([
            postCSSNested,
            postCSSSimpleVars(),
            postCSSModules({
              getJSON(_, json) {
                moduleJSON = json;
              },
            }),
          ]).process(file, {
            from: undefined,
          });

          const cssClassExports = Object.entries(moduleJSON).map(
            ([key, val]) =>
              `export const $${camelCase(key)} = ${JSON.stringify(val)};`,
          );

          const defs = Object.keys(moduleJSON)
            .map((key) => `export const $${camelCase(key)}: string;`)
            .join('\n');

          const defPath = path + '.d.ts';
          const currentDefFileContent = await fsp
            .readFile(defPath, { encoding: 'utf8' })
            .catch(() => undefined);

          // Only write the file if contents have changed, otherwise it causes a loop with
          // TypeScript's file watcher.
          if (defs !== currentDefFileContent) {
            await fsp.writeFile(defPath, defs);
          }

          pathToResult.set(path, {
            module: cssClassExports.join('\n'),
            css: cssResult.css,
          });
        }),
      );
    },
    async resolveId(id, importer) {
      if (!id.startsWith(prefix)) return;
      const resolved = await this.resolve(id.slice(prefix.length), importer);
      if (!resolved) throw Error(`Couldn't resolve ${id} from ${importer}`);
      return prefix + resolved.id;
    },
    async load(id) {
      if (id.startsWith(prefix)) {
        return loadBundledCSS(id.slice(prefix.length), this);
      }
      if (id.endsWith(moduleSuffix)) {
        if (!pathToResult.has(id)) {
          throw Error(`Cannot find ${id} in pathToResult`);
        }

        return pathToResult.get(id).module;
      }
    },
    async generateBundle(options, bundle) {
      const cssAssets = emittedCSSIds.map((id) => this.getFileName(id));

      for (const cssAsset of cssAssets) {
        bundle[cssAsset].source = bundle[cssAsset].source.replace(
          assetRe,
          (_, p1) =>
            resolveFileUrl({
              fileName: this.getFileName(hashToId.get(p1)),
            }),
        );
      }

      for (const item of Object.values(bundle)) {
        if (item.type === 'asset') continue;
        item.code = item.code.replace(assetRe, (match, p1) =>
          resolveFileUrl({
            fileName: this.getFileName(hashToId.get(p1)),
          }),
        );
      }
    },
  };
}