import { Injectable } from '@angular/core';
import { TranslateService } from '@ngx-translate/core';
import { firstValueFrom } from 'rxjs';
import 'dayjs/locale/en';
import 'dayjs/locale/de';
import dayjs, { Dayjs } from 'dayjs';
import { DateAdapter } from '@angular/material/core';
import arraySupport from 'dayjs/plugin/arraySupport';
import localeData from 'dayjs/plugin/localeData';
import { registerLocaleData } from '@angular/common';
import localeDe from '@angular/common/locales/de';
import { BaseUserPreferenceService } from './base-user-preference.service';

dayjs.extend(arraySupport);
dayjs.extend(localeData);

@Injectable({
    providedIn: 'root',
})
export class LanguageService {
    constructor(
        private readonly _translateService: TranslateService,
        private readonly _userPreferenceService: BaseUserPreferenceService,
        private readonly _dateAdapter: DateAdapter<Dayjs>,
    ) {
        registerLocaleData(localeDe);
        _translateService.addLangs(['en', 'de']);
        _translateService.setDefaultLang('en');
    }

    get currentLanguage() {
        return this._translateService.currentLang;
    }

    async set(language: string): Promise<void> {
        dayjs.locale(language);
        this._dateAdapter.setLocale(language);
        await firstValueFrom(this._translateService.use(language));
    }

    isAvailable(language: string): boolean {
        return this._translateService.getLangs().includes(language);
    }

    async setInitialLanguage(): Promise<void> {
        const defaultLang = this.#getDefaultLanguage();
        document.documentElement.lang = defaultLang;
        this._translateService.setDefaultLang(defaultLang);
        await this.set(defaultLang);
    }

    async change(language: string) {
        await this._userPreferenceService.saveLanguage(language);
        document.documentElement.lang = language;
        await this.set(language);
    }

    #getDefaultLanguage() {
        const preferredLang = this._userPreferenceService.getLanguage();

        return this.isAvailable(preferredLang) ? preferredLang : 'en';
    }
}