<?php

/**
 * Reading, counting and checking booking dates
 *
 * @link       #
 * @since      1.0.0
 *
 * @package    Abfw
 * @subpackage Abfw/Booking
 */

namespace AdvancedBooking\Booking;

use AdvancedBooking\Settings;
use DateTimeImmutable;
use DateTimeZone;

/**
 * Turns what a customer picked into a length, and says whether it is allowed.
 *
 * @since      1.0.0
 * @package    Abfw
 * @subpackage Abfw/Booking
 */
class Dates {

	/**
	 * Most nights or days one stay can last, two years, even when a product sets no
	 * longest booking: a mistyped departure can never become a stay of centuries.
	 */
	const LONGEST = 730;

	/**
	 * Read a date coming from a form, keeping only a plain calendar day.
	 *
	 * @since 1.0.0
	 * @param string $raw Date as typed or posted.
	 * @return DateTimeImmutable|null
	 */
	public static function parse( $raw ) {
		$raw = trim( (string) $raw );

		if ( '' === $raw || ! preg_match( '/^\d{4}-\d{2}-\d{2}$/', $raw ) ) {
			return null;
		}

		$date = DateTimeImmutable::createFromFormat( '!Y-m-d', $raw, self::timezone() );

		return $date instanceof DateTimeImmutable ? $date : null;
	}

	/**
	 * Today, in the time zone of the shop.
	 *
	 * @since 1.0.0
	 * @return DateTimeImmutable
	 */
	public static function today() {
		return new DateTimeImmutable( 'today', self::timezone() );
	}

	/**
	 * How many days or nights a stay covers.
	 *
	 * Nights count the gaps between the days, so five days is four nights.
	 *
	 * @since 1.0.0
	 * @param DateTimeImmutable $start      First day.
	 * @param DateTimeImmutable $end        Last day.
	 * @param string            $mode       Either days or nights.
	 * @return int
	 */
	public static function units( DateTimeImmutable $start, DateTimeImmutable $end, $mode ) {
		$nights = (int) $start->diff( $end )->format( '%a' );

		return 'days' === $mode ? $nights + 1 : $nights;
	}

	/**
	 * Check a pair of dates against the rules of a product.
	 *
	 * @since 1.0.0
	 * @param string $raw_start    Start date as posted.
	 * @param string $raw_end      End date as posted, empty when one date is asked for.
	 * @param int    $product_id   Product being booked.
	 * @param int    $variation_id Variation being booked, when there is one.
	 * @return array|\WP_Error Booking data on success.
	 */
	public static function validate( $raw_start, $raw_end, $product_id, $variation_id = 0 ) {
		$mode     = Settings::get( 'mode', $product_id, $variation_id );
		$two      = 'two' === Settings::get( 'dates', $product_id, $variation_id );
		$duration = max( 1, (int) Settings::get( 'duration', $product_id, $variation_id ) );
		$start    = self::parse( $raw_start );

		if ( ! $start ) {
			return new \WP_Error( 'abfw_no_start', __( 'Please choose a date.', 'abogo-booking' ) );
		}

		$end = $two ? self::parse( $raw_end ) : self::end_of_single_date( $start, $mode );

		if ( ! $end ) {
			return new \WP_Error( 'abfw_no_end', __( 'Please choose an end date.', 'abogo-booking' ) );
		}

		if ( $end < $start ) {
			return new \WP_Error( 'abfw_reversed', __( 'The end date cannot come before the start date.', 'abogo-booking' ) );
		}

		$window = self::check_window( $start, $product_id, $variation_id );

		if ( is_wp_error( $window ) ) {
			return $window;
		}

		$units = self::units( $start, $end, $mode );

		if ( $units < 1 ) {
			return new \WP_Error( 'abfw_too_short', __( 'Please choose at least one night.', 'abogo-booking' ) );
		}

		$length = self::check_length( $units, $duration, $product_id, $variation_id );

		if ( is_wp_error( $length ) ) {
			return $length;
		}

		return array(
			'start' => $start->format( 'Y-m-d' ),
			'end'   => $end->format( 'Y-m-d' ),
			'units' => $units,
			'mode'  => $mode,
		);
	}

	/**
	 * Read dates the shop sets by hand: only dates that cannot exist, or a stay
	 * longer than any can be, are refused, never the product's own rules.
	 *
	 * @since 1.0.1
	 * @param string $raw_start    Start date as posted.
	 * @param string $raw_end      End date as posted, empty when one date is asked for.
	 * @param int    $product_id   Product booked.
	 * @param int    $variation_id Variation booked, when there is one.
	 * @return array|null Booking data, null when the dates cannot exist.
	 */
	public static function possible( $raw_start, $raw_end, $product_id, $variation_id = 0 ) {
		$mode  = Settings::get( 'mode', $product_id, $variation_id );
		$start = self::parse( $raw_start );

		if ( ! $start ) {
			return null;
		}

		$end = 'two' === Settings::get( 'dates', $product_id, $variation_id ) ? self::parse( $raw_end ) : self::end_of_single_date( $start, $mode );

		$units = $end ? self::units( $start, $end, $mode ) : 0;

		if ( ! $end || $end < $start || $units < 1 || $units > self::LONGEST ) {
			return null;
		}

		return array(
			'start' => $start->format( 'Y-m-d' ),
			'end'   => $end->format( 'Y-m-d' ),
			'units' => $units,
			'mode'  => $mode,
		);
	}

	/**
	 * Whether the start date falls inside the period open to booking.
	 *
	 * @since 1.0.0
	 * @param DateTimeImmutable $start        Chosen start.
	 * @param int               $product_id   Product being booked.
	 * @param int               $variation_id Variation being booked, when there is one.
	 * @return true|\WP_Error
	 */
	private static function check_window( DateTimeImmutable $start, $product_id, $variation_id = 0 ) {
		$first = (int) Settings::get( 'first', $product_id, $variation_id );
		$last  = (int) Settings::get( 'last', $product_id, $variation_id );
		$today = self::today();

		if ( $start < $today->modify( '+' . $first . ' days' ) ) {
			return new \WP_Error(
				'abfw_too_soon',
				sprintf(
					/* translators: %s: number of days. */
					_n( 'Bookings open %s day from today.', 'Bookings open %s days from today.', max( 1, $first ), 'abogo-booking' ),
					number_format_i18n( $first )
				)
			);
		}

		if ( $last > 0 && $start > $today->modify( '+' . $last . ' days' ) ) {
			return new \WP_Error( 'abfw_too_far', __( 'This date is too far ahead to be booked.', 'abogo-booking' ) );
		}

		return true;
	}

	/**
	 * Whether the length fits the block size, the allowed minimum and maximum, and
	 * the longest stay any product can take.
	 *
	 * @since 1.0.0
	 * @param int $units        Nights or days chosen.
	 * @param int $duration     Size of one block.
	 * @param int $product_id   Product being booked.
	 * @param int $variation_id Variation being booked, when there is one.
	 * @return true|\WP_Error
	 */
	private static function check_length( $units, $duration, $product_id, $variation_id = 0 ) {
		if ( $units > self::LONGEST ) {
			return new \WP_Error(
				'abfw_too_long',
				sprintf(
					/* translators: %s: number of blocks. */
					__( 'Please book no more than %s.', 'abogo-booking' ),
					number_format_i18n( self::LONGEST )
				)
			);
		}

		if ( $units % $duration !== 0 ) {
			return new \WP_Error(
				'abfw_bad_block',
				sprintf(
					/* translators: %s: number of days or nights. */
					__( 'Bookings are taken in blocks of %s.', 'abogo-booking' ),
					number_format_i18n( $duration )
				)
			);
		}

		$blocks = (int) ( $units / $duration );
		$min    = (int) Settings::get( 'min', $product_id, $variation_id );
		$max    = (int) Settings::get( 'max', $product_id, $variation_id );

		if ( $min > 0 && $blocks < $min ) {
			return new \WP_Error(
				'abfw_too_short_block',
				sprintf(
					/* translators: %s: number of blocks. */
					__( 'Please book at least %s.', 'abogo-booking' ),
					number_format_i18n( $min * $duration )
				)
			);
		}

		if ( $max > 0 && $blocks > $max ) {
			return new \WP_Error(
				'abfw_too_long',
				sprintf(
					/* translators: %s: number of blocks. */
					__( 'Please book no more than %s.', 'abogo-booking' ),
					number_format_i18n( $max * $duration )
				)
			);
		}

		return true;
	}

	/**
	 * Where a booking of a single date ends: a night runs into the next day.
	 *
	 * @since 1.0.1
	 * @param DateTimeImmutable $start Chosen date.
	 * @param string            $mode  Either days or nights.
	 * @return DateTimeImmutable
	 */
	private static function end_of_single_date( DateTimeImmutable $start, $mode ) {
		return $start->modify( 'nights' === $mode ? '+1 day' : '+0 day' );
	}

	/**
	 * Time zone of the shop, so a date never shifts by one day.
	 *
	 * @since 1.0.0
	 * @return DateTimeZone
	 */
	private static function timezone() {
		return function_exists( 'wp_timezone' ) ? wp_timezone() : new DateTimeZone( 'UTC' );
	}
}