import { __ } from '@wordpress/i18n';
import { currentLocale } from './locale';
import {
	JUST_NOW_SECONDS,
	MILLISECONDS_PER_SECOND,
	SECONDS_PER_DAY,
	SECONDS_PER_HOUR,
	SECONDS_PER_MINUTE,
} from './timeUnits';

function secondsSince( isoTime: string, now: number ): number {
	const elapsedMilliseconds = now - Date.parse( isoTime );

	return Math.max(
		0,
		Math.round( elapsedMilliseconds / MILLISECONDS_PER_SECOND )
	);
}

function relativeText( seconds: number ): string {
	const relativeFormat = new Intl.RelativeTimeFormat( currentLocale(), {
		numeric: 'always',
	} );

	if ( seconds < SECONDS_PER_HOUR ) {
		const minutes = Math.max(
			1,
			Math.round( seconds / SECONDS_PER_MINUTE )
		);

		return relativeFormat.format( -minutes, 'minute' );
	}

	if ( seconds < SECONDS_PER_DAY ) {
		return relativeFormat.format(
			-Math.round( seconds / SECONDS_PER_HOUR ),
			'hour'
		);
	}

	return relativeFormat.format(
		-Math.round( seconds / SECONDS_PER_DAY ),
		'day'
	);
}

export function timeAgo( isoTime: string | null, now: number ): string {
	if ( isoTime === null || isoTime === '' ) {
		return __( 'never', 'aiplaz-link-checkup' );
	}

	const seconds = secondsSince( isoTime, now );

	if ( seconds < JUST_NOW_SECONDS ) {
		return __( 'just now', 'aiplaz-link-checkup' );
	}

	return relativeText( seconds );
}

export function timeAgoSentence( isoTime: string | null, now: number ): string {
	const text = timeAgo( isoTime, now );
	const firstLetter = text.charAt( 0 ).toLocaleUpperCase( currentLocale() );

	return firstLetter + text.slice( 1 );
}

export function dayAndMonth( isoTime: string | null ): string {
	if ( isoTime === null || isoTime === '' ) {
		return '';
	}

	return new Intl.DateTimeFormat( currentLocale(), {
		day: 'numeric',
		month: 'long',
	} ).format( new Date( isoTime ) );
}