import {Inject, Injectable} from '@angular/core';
import { HttpClient } from '@angular/common/http';
import {EnaioConfig} from '../service/config/config.interface';
import {Config} from '../service/config/config.service';
import {AuthService} from '../service/auth/auth.service';
import {of as observableOf, forkJoin} from 'rxjs';
import {mergeMap, map, catchError} from 'rxjs/operators';
import {Logger} from '../service/logger/logger';
import {CoreConfig} from './core-config';
import {CORE_CONFIG} from './core-init.tokens';

/**
 * Main initialization service of the eoFrameworkCore module. The `load()` function will contain
 * all steps that needs to be executed before the application starts. Therefore it will be used
 * as `APP_INITIALIZER` from the providers section of the app module.
 *
 * Later on this service can be used by other components or services to fetch the result of the
 * initialization process (e.g. infos on the current user).
 */

@Injectable()
export class CoreInit {

  /**
   * @ignore
   */
  constructor(@Inject(CORE_CONFIG) private coreConfig: CoreConfig, private logger: Logger,
    private http: HttpClient, private configService: Config, private authService: AuthService) {
  }

  /**
   * Initializes core module. Executed in context of `APP_INITIALIZER`.
   * @returns Promise that resolves after yuuvis<sup>&reg;</sup> RAD core has been initialized
   */
  public initialize(): Promise<boolean> {

    return new Promise((resolve, reject) => {

      /**
       * getting a string means that we got an URL to load the config from
       */
      let config = !Array.isArray(this.coreConfig.main) ? observableOf([this.coreConfig.main]) :
        forkJoin(this.coreConfig.main.map(c => this.http.get(c, {
          withCredentials: this.coreConfig.withCredentials
        }).pipe(
          catchError(e => {
            this.logger.error('failed to catch config file', e);
            return observableOf({});
          })
        )));

      config.pipe(
        map((res) => res.reduce((acc, x) => {
          // merge object values on 2nd level
          Object.keys(x).forEach(k => !acc[k] || Array.isArray(x[k]) || typeof x[k] !== 'object' ? acc[k] = x[k] : Object.assign(acc[k], x[k]));
          return acc;
        }, {})
        ),
        mergeMap((res: EnaioConfig) => {
          this.configService.set(res);
          return this.authService.initUser()
            .pipe(catchError(e => observableOf(true)));
        })
      ).subscribe(res => {
        resolve(true);
      }, err => {
        this.logger.error(err);
        reject();
      });
    });
  }
}