<?php

namespace ABeCe\Booking\Support;

use DateTimeImmutable;
use DateTimeInterface;
use DateTimeZone;

/** Scheduling uses local wall times; stored instants and comparisons use UTC timestamps. */
final class Time {
	/** Midnight may be skipped by DST; the first real instant still belongs to this local date. */
	public static function day( string $date ): ?DateTimeImmutable {
		$result = new DateTimeImmutable( $date . ' 00:00:00', wp_timezone() );
		return $result->format( 'Y-m-d' ) === $date ? $result : null;
	}

	public static function nextDay( string $date ): ?DateTimeImmutable {
		$next = ( new DateTimeImmutable( $date, new DateTimeZone( 'UTC' ) ) )->modify( '+1 day' )->format( 'Y-m-d' );
		return new DateTimeImmutable( $next . ' 00:00:00', wp_timezone() );
	}

	public static function local( string $date, string $clock ): ?DateTimeImmutable {
		$value = $date . ' ' . ( 5 === strlen( $clock ) ? $clock . ':00' : $clock );
		$result = DateTimeImmutable::createFromFormat( '!Y-m-d H:i:s', $value, wp_timezone() );
		return $result && $result->format( 'Y-m-d H:i:s' ) === $value ? $result : null;
	}

	public static function timestamp( int $timestamp ): DateTimeImmutable {
		return ( new DateTimeImmutable( '@' . $timestamp ) )->setTimezone( wp_timezone() );
	}

	public static function iso( int $timestamp ): string { return self::timestamp( $timestamp )->format( DATE_ATOM ); }
	public static function sql( DateTimeInterface $instant ): string { return DateTimeImmutable::createFromInterface( $instant )->setTimezone( new DateTimeZone( 'UTC' ) )->format( 'Y-m-d H:i:s' ); }
	public static function fromSql( string $instant ): int { return ( new DateTimeImmutable( $instant, new DateTimeZone( 'UTC' ) ) )->getTimestamp(); }
}