import {HttpClient} from '@angular/common/http';
import {TranslateLoader} from '@ngx-translate/core';
import {Observable, forkJoin} from 'rxjs';
import {map} from 'rxjs/operators';
// 这种语法只有在tsconfig.json中新增"esModuleInterop": true, 才不会报错
import merge from 'deepmerge';
import { Injector, InjectionToken } from '@angular/core';

export interface ITranslationResource {
  prefix: string;
  suffix: string;
}
/**
 * 其他翻译资源
 */
export const NA_TRANSLATE_RESOURCES = new InjectionToken<TranslateLoader[]>(
  'NA_TRANSLATE_RESOURCES'
);

export class MultiTranslateHttpLoader implements TranslateLoader {
  constructor(
    private http: HttpClient,
    private resources: ITranslationResource[],
    private injector: Injector
  ) {}

  /**
   * 获取翻译资源
   *
   * @param lang 语言
   */
  public getTranslation(lang: string): Observable<any> {
    const obs: Observable<any>[] = [];
    const translateResources = this.injector.get(NA_TRANSLATE_RESOURCES, []);
    translateResources.forEach(tr => {
      obs.push(tr.getTranslation(lang));
    });

    const requests = this.resources.map(resource => {
      return this.http.get(resource.prefix + lang + resource.suffix);
    });
    obs.push(...requests);
    // const merge = require('deepmerge').default;
    return forkJoin(obs).pipe(map(response => {
      const mergeResponse = [];
      response.forEach(item => {
        if (item) {
          mergeResponse.push(item);
        }
      });
      // 如果response数组内存在null，这里会报错
      return merge.all(mergeResponse);
    }));
  }
}