/**
 * @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 { existsSync } from 'fs';
import { join } from 'path';
import { RuleFactory } from '../src';
import { FileSystemCollectionDesc, FileSystemSchematicDesc } from './description';
import { ExportStringRef } from './export-ref';
import {
  CollectionCannotBeResolvedException,
  CollectionMissingSchematicsMapException,
  FileSystemEngineHostBase,
  SchematicMissingFieldsException,
} from './file-system-engine-host-base';


/**
 * A simple EngineHost that uses a root with one directory per collection inside of it. The
 * collection declaration follows the same rules as the regular FileSystemEngineHostBase.
 */
export class FileSystemEngineHost extends FileSystemEngineHostBase {
  constructor(protected _root: string) { super(); }

  protected _resolveCollectionPath(name: string): string {
    // Allow `${_root}/${name}.json` as a collection.
    if (existsSync(join(this._root, name + '.json'))) {
      return join(this._root, name + '.json');
    }

    // Allow `${_root}/${name}/collection.json.
    if (existsSync(join(this._root, name, 'collection.json'))) {
      return join(this._root, name, 'collection.json');
    }

    throw new CollectionCannotBeResolvedException(name);
  }

  protected _resolveReferenceString(refString: string, parentPath: string) {
    // Use the same kind of export strings as NodeModule.
    const ref = new ExportStringRef<RuleFactory<{}>>(refString, parentPath);
    if (!ref.ref) {
      return null;
    }

    return { ref: ref.ref, path: ref.module };
  }

  protected _transformCollectionDescription(
    name: string,
    desc: Partial<FileSystemCollectionDesc>,
  ): FileSystemCollectionDesc {
    if (!desc.schematics || typeof desc.schematics != 'object') {
      throw new CollectionMissingSchematicsMapException(name);
    }

    return desc as FileSystemCollectionDesc;
  }

  protected _transformSchematicDescription(
    name: string,
    _collection: FileSystemCollectionDesc,
    desc: Partial<FileSystemSchematicDesc>,
  ): FileSystemSchematicDesc {
    if (!desc.factoryFn || !desc.path || !desc.description) {
      throw new SchematicMissingFieldsException(name);
    }

    return desc as FileSystemSchematicDesc;
  }
}