/**
 * @license
 * Copyright 2021 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import {createContext, FunctionComponent} from 'preact';
import {useContext, useMemo} from 'preact/hooks';

import {formatMessage} from '../../../shared/localization/format';
import {I18nFormatter} from '../../../report/renderer/i18n-formatter';
import {UIStrings} from './ui-strings';
import {useFlowResult} from '../util';
import strings from './localized-strings.js';
import {UIStrings as ReportUIStrings} from '../../../report/renderer/report-utils.js';
import {Globals} from '../../../report/renderer/report-globals.js';

const I18nContext = createContext({
  formatter: new I18nFormatter('en-US'),
  strings: {...ReportUIStrings, ...UIStrings},
});

function useLhrLocale() {
  const flowResult = useFlowResult();
  const firstLhr = flowResult.steps[0].lhr;
  const locale = firstLhr.configSettings.locale;

  if (flowResult.steps.some(step => step.lhr.configSettings.locale !== locale)) {
    // eslint-disable-next-line no-console
    console.warn('LHRs have inconsistent locales');
  }

  return {
    locale,
    lhrStrings: firstLhr.i18n.rendererFormattedStrings,
  };
}

function useI18n() {
  return useContext(I18nContext);
}

function useLocalizedStrings() {
  const i18n = useI18n();
  return i18n.strings;
}

function useStringFormatter() {
  const {locale} = useLhrLocale();
  return (str: string, values?: Record<string, string|number>) => {
    return formatMessage(str, values, locale);
  };
}

const I18nProvider: FunctionComponent = ({children}) => {
  const {locale, lhrStrings} = useLhrLocale();

  const i18n = useMemo(() => {
    Globals.apply({
      providedStrings: {
        // Preload with strings from the first lhr.
        // Used for legacy report components imported into the flow report.
        ...lhrStrings,
        // Set any missing flow strings to default (english) values.
        ...UIStrings,
        // `strings` is generated in build/build-report.js
        ...strings[locale],
      },
      i18n: new I18nFormatter(locale),
      reportJson: null,
    });

    return {
      formatter: Globals.i18n,
      strings: Globals.strings as typeof UIStrings & typeof ReportUIStrings,
    };
  }, [locale, lhrStrings]);

  return (
    <I18nContext.Provider value={i18n}>
      {children}
    </I18nContext.Provider>
  );
};

export {
  useI18n,
  useLocalizedStrings,
  useStringFormatter,
  I18nProvider,
};