/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import {
  MergeStrategy,
  Rule,
  Tree,
  apply,
  chain,
  filter,
  mergeWith,
  move,
  url,
} from '@angular-devkit/schematics';
import { createHash } from 'crypto';
import * as ts from '../../third_party/github.com/Microsoft/TypeScript/lib/typescript';
import { getWorkspace } from '../../utility/workspace';

const toDrop: {[importName: string]: true} = {
  'core-js/es6/symbol': true,
  'core-js/es6/object': true,
  'core-js/es6/function': true,
  'core-js/es6/parse-int': true,
  'core-js/es6/parse-float': true,
  'core-js/es6/number': true,
  'core-js/es6/math': true,
  'core-js/es6/string': true,
  'core-js/es6/date': true,
  'core-js/es6/array': true,
  'core-js/es6/regexp': true,
  'core-js/es6/map': true,
  'core-js/es6/set': true,
  'core-js/es6/weak-map': true,
};

const header = `/**
 * This file includes polyfills needed by Angular and is loaded before the app.
 * You can add your own extra polyfills to this file.
 *
 * This file is divided into 2 sections:
 *   1. Browser polyfills. These are applied before loading ZoneJS and are sorted by browsers.
 *   2. Application imports. Files imported after ZoneJS that should be loaded before your main
 *      file.
 *
 * The current setup is for so-called "evergreen" browsers; the last versions of browsers that
 * automatically update themselves. This includes Safari >= 10, Chrome >= 55 (including Opera),
 * Edge >= 13 on the desktop, and iOS 10 and Chrome on mobile.
 *
 * Learn more in https://angular.io/guide/browser-support
 */

/***************************************************************************************************
* BROWSER POLYFILLS
*/
`;

const applicationPolyfillsHeader = 'APPLICATION IMPORTS';
const browserPolyfillsHeader = 'BROWSER POLYFILLS';

const knownPolyfillHashes = [
  '3dba718d7afe009e112e10d69073d2a2', // 6.0 - unmodified
  'fccdb76b06ea636933f8b99b1c8d9725', // 6.0 - all core-js uncommented
  '97e16639be1de06153695f5fefde745d', // 7.0 - unmodified
  'd6c13d6dcf94ff3749283f33dd0d4864', // 7.0 - all core-js uncommented
  '79bf0fd46c215e5f4145e15641c325f3', // 7.2 - unmodified
  '6fe8080c7e38ee0ce677fdbc3884377a', // 7.2 - all core-js uncommented
  '8e7f6abb3d2dca03b4dbb300e400a880', // 7.3 - unmodified
];

function dropES2015PolyfillsFromFile(polyfillPath: string): Rule {
  return (tree: Tree) => {
    const source = tree.read(polyfillPath);
    if (!source) {
      return;
    }

    const content = source.toString();
    // Check if file is unmodified, if so then replace and return
    const hash = createHash('md5');
    // normalize line endings to increase hash match chances
    hash.update(content.replace(/\r\n|\r/g, '\n'));
    const digest = hash.digest('hex');
    if (knownPolyfillHashes.includes(digest)) {
      // Replace with new project polyfills file
      // This removes the need to parse and also updates all included comments

      // mergeWith overwrite doesn't work so clear out existing file
      tree.delete(polyfillPath);

      return mergeWith(
        apply(url('../../application/files/src'), [
          filter(path => path === '/polyfills.ts.template'),
          move('/polyfills.ts.template', polyfillPath),
        ]),
        MergeStrategy.Overwrite,
      );
    }

    if (!content.includes('core-js')) {
      // no action required if no mention of core-js
      return;
    }

    const sourceFile = ts.createSourceFile(polyfillPath,
      content.replace(/^\uFEFF/, ''),
      ts.ScriptTarget.Latest,
      true,
    );
    const imports = sourceFile.statements
      .filter(s => s.kind === ts.SyntaxKind.ImportDeclaration) as ts.ImportDeclaration[];

    if (imports.length === 0) { return; }

    // Start the update of the file.
    const recorder = tree.beginUpdate(polyfillPath);

    const applicationPolyfillsStart = content.indexOf(applicationPolyfillsHeader);
    const browserPolyfillsStart = content.indexOf(browserPolyfillsHeader);

    let addHeader = false;
    for (const i of imports) {
      const module = ts.isStringLiteral(i.moduleSpecifier) && i.moduleSpecifier.text;
      // We do not want to remove imports which are after the "APPLICATION IMPORTS" header.
      if (module && toDrop[module] && applicationPolyfillsStart > i.getFullStart()) {
        recorder.remove(i.getFullStart(), i.getFullWidth());
        if (i.getFullStart() <= browserPolyfillsStart) {
          addHeader = true;
        }
      }
    }

    // We've removed the header since it's part of the JSDoc of the nodes we dropped
    if (addHeader) {
      recorder.insertLeft(0, header);
    }

    tree.commitUpdate(recorder);
  };
}

/**
 * Drop ES2015 polyfills from all application projects
 */
export function dropES2015Polyfills(): Rule {
  return async (tree) => {
    let workspace;
    try {
      workspace = await getWorkspace(tree);
    } catch {
      return;
    }

    const rules = [];
    for (const [, project] of workspace.projects) {
      if (project.extensions.projectType !== 'application') {
        continue;
      }

      const buildTarget = project.targets.get('build');
      const polyfills = buildTarget?.options?.polyfills;

      if (polyfills && typeof polyfills === 'string') {
        rules.push(dropES2015PolyfillsFromFile(polyfills));
      }
    }

    return chain(rules);
  };
}
