import { Injectable } from '@angular/core';
import { BaseService } from '@common/base/base.service';
import { TranslateService } from '@ngx-translate/core';
import { Observable } from 'rxjs';
import { map, takeUntil } from 'rxjs/operators';
import { LanguageHttpService } from './language.http.service';

@Injectable()
export class LanguageService extends BaseService {
	private currentLanguage: string;
	private availableLanguageCodes: string[];

	constructor(
		private translate: TranslateService,
		private languageHttpService: LanguageHttpService
	) {
		super();
	}

	public changeLanguage(lang: string) {
		this.currentLanguage = lang;
		this.translate.use(lang);
	}

	public getCurrentLanguage() {
		if (this.currentLanguage == null) throw new Error("languages not loaded");
		return this.currentLanguage;
	}

	public loadAvailableLanguages(): Observable<string[]> {
		return this.languageHttpService.queryAvailableCodes(this.languageHttpService.buildAutocompleteLookup())
			.pipe(takeUntil(this._destroyed)).pipe(
				map((data) => {
					this.availableLanguageCodes = data.items;
					if (this.availableLanguageCodes.length > 0) this.currentLanguage = this.availableLanguageCodes[0];
					return this.availableLanguageCodes;
				})
			);
	}

	public getDefaultLanguagesCode() {
		if (this.availableLanguageCodes == null || this.availableLanguageCodes.length == 0) throw new Error("languages not loaded");
		return this.availableLanguageCodes[0];
	}

	public getAvailableLanguagesCodes() {
		if (this.availableLanguageCodes == null) throw new Error("languages not loaded");
		return this.availableLanguageCodes;
	}
}