<?php
/**
 * Date/time helpers for UTC storage and local display.
 *
 * @package Abientot
 */

namespace Abientot\Support;

use Abientot\Admin\Settings;
use DateTimeImmutable;
use DateTimeZone;
use Exception;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

final class DateTimeHelper {
	private const DATE_FORMATS = array(
		'wordpress'      => '',
		'ymd-dashes'     => 'Y-m-d',
		'mdy-dashes'     => 'm-d-Y',
		'dmy-dashes'     => 'd-m-Y',
		'dmy-short-year' => 'd-m-y',
		'mdy-slashes'    => 'm/d/Y',
		'dmy-slashes'    => 'd/m/Y',
		'month-day-year' => 'F j, Y',
		'day-month-year' => 'j F Y',
	);

	private const TIME_FORMATS = array(
		'wordpress' => '',
		'time-24'   => 'H:i',
		'time-12'   => 'g:i a',
	);

	/**
	 * Returns the configured business timezone.
	 */
	public static function business_timezone(): DateTimeZone {
		$settings = get_option( 'abientot_settings', array() );
		$timezone = is_array( $settings ) && ! empty( $settings['business_timezone'] )
			? (string) $settings['business_timezone']
			: wp_timezone_string();

		try {
			return new DateTimeZone( $timezone );
		} catch ( Exception $exception ) {
			return wp_timezone();
		}
	}

	/**
	 * Returns a UTC timezone instance.
	 */
	public static function utc_timezone(): DateTimeZone {
		return new DateTimeZone( 'UTC' );
	}

	/**
	 * Allowed date display formats.
	 *
	 * @return array<string,string>
	 */
	public static function date_format_choices(): array {
		return self::DATE_FORMATS;
	}

	/**
	 * Allowed time display formats.
	 *
	 * @return array<string,string>
	 */
	public static function time_format_choices(): array {
		return self::TIME_FORMATS;
	}

	/**
	 * Whether an Abientot language override differs from the site language.
	 * WordPress's date and time format options then belong to another language.
	 */
	private static function language_override_active(): bool {
		$locale = Settings::configured_locale();

		return '' !== $locale && get_locale() !== $locale;
	}

	/**
	 * WordPress's date format, or the plugin language's own default under an override.
	 */
	public static function wordpress_date_format(): string {
		if ( self::language_override_active() ) {
			/* translators: Default date format for this language, as PHP date() characters (https://www.php.net/manual/datetime.format.php). Escape literal letters with a backslash. */
			return _x( 'F j, Y', 'default date format', 'abientot' );
		}

		return (string) get_option( 'date_format', 'Y-m-d' );
	}

	/**
	 * WordPress's time format, or the plugin language's own default under an override.
	 */
	public static function wordpress_time_format(): string {
		if ( self::language_override_active() ) {
			/* translators: Default time format for this language, as PHP date() characters (https://www.php.net/manual/datetime.format.php). Escape literal letters with a backslash. */
			return _x( 'g:i a', 'default time format', 'abientot' );
		}

		return (string) get_option( 'time_format', 'H:i' );
	}

	/**
	 * Weekday with full date, e.g. headings.
	 */
	public static function full_date_format(): string {
		/* translators: Weekday and full date format for headings, as PHP date() characters (https://www.php.net/manual/datetime.format.php). Escape literal letters with a backslash. */
		return _x( 'l, j F Y', 'full date format', 'abientot' );
	}

	/**
	 * Month and year, e.g. calendar month titles.
	 */
	public static function month_year_format(): string {
		/* translators: Month and year format for calendar titles, as PHP date() characters (https://www.php.net/manual/datetime.format.php). Escape literal letters with a backslash. */
		return _x( 'F Y', 'month and year format', 'abientot' );
	}

	/**
	 * Returns the configured human-readable date format.
	 */
	public static function date_display_format(): string {
		$settings = get_option( 'abientot_settings', array() );
		$value    = is_array( $settings ) && isset( $settings['date_display_format'] ) ? (string) $settings['date_display_format'] : 'wordpress';

		if ( ! array_key_exists( $value, self::DATE_FORMATS ) || 'wordpress' === $value ) {
			return self::wordpress_date_format();
		}

		return self::DATE_FORMATS[ $value ];
	}

	/**
	 * Returns the configured human-readable time format.
	 */
	public static function time_display_format(): string {
		$settings = get_option( 'abientot_settings', array() );
		$value    = is_array( $settings ) && isset( $settings['time_display_format'] ) ? (string) $settings['time_display_format'] : 'wordpress';

		if ( ! array_key_exists( $value, self::TIME_FORMATS ) || 'wordpress' === $value ) {
			return self::wordpress_time_format();
		}

		return self::TIME_FORMATS[ $value ];
	}

	/**
	 * Returns the configured human-readable datetime format.
	 */
	public static function datetime_display_format(): string {
		return trim( self::date_display_format() . ' ' . self::time_display_format() );
	}

	/**
	 * Formats a UTC SQL datetime for display in a given local timezone.
	 */
	public static function format_utc_datetime( string $utc_datetime, ?string $timezone = null, string $format = '' ): string {
		$format = '' !== $format ? $format : self::datetime_display_format();

		try {
			$date = new DateTimeImmutable( $utc_datetime, self::utc_timezone() );
			return Locale::date( $format, $date->getTimestamp(), self::timezone_from_string( $timezone ) );
		} catch ( Exception $exception ) {
			return get_date_from_gmt( $utc_datetime, $format );
		}
	}

	/**
	 * Formats a local SQL datetime for display.
	 */
	public static function format_local_datetime( string $local_datetime, ?string $timezone = null, string $format = '' ): string {
		$format = '' !== $format ? $format : self::datetime_display_format();

		try {
			$timezone_object = self::timezone_from_string( $timezone );
			$date            = new DateTimeImmutable( $local_datetime, $timezone_object );
			return Locale::date( $format, $date->getTimestamp(), $timezone_object );
		} catch ( Exception $exception ) {
			return $local_datetime;
		}
	}

	/**
	 * Formats a local SQL datetime as a display time.
	 */
	public static function format_local_time( string $local_datetime, ?string $timezone = null ): string {
		return self::format_local_datetime( $local_datetime, $timezone, self::time_display_format() );
	}

	private static function timezone_from_string( ?string $timezone ): DateTimeZone {
		try {
			return new DateTimeZone( $timezone ?: self::business_timezone()->getName() );
		} catch ( Exception $exception ) {
			return self::business_timezone();
		}
	}

	/**
	 * Returns the current UTC SQL datetime.
	 */
	public static function now_utc_sql(): string {
		return gmdate( 'Y-m-d H:i:s' );
	}

	/**
	 * Converts a local SQL datetime into UTC SQL datetime.
	 */
	public static function local_to_utc_sql( string $local_datetime, ?DateTimeZone $timezone = null ): string {
		$timezone = $timezone ?: self::business_timezone();
		$date     = new DateTimeImmutable( $local_datetime, $timezone );

		return $date->setTimezone( self::utc_timezone() )->format( 'Y-m-d H:i:s' );
	}

	/**
	 * Converts a UTC SQL datetime into local SQL datetime.
	 */
	public static function utc_to_local_sql( string $utc_datetime, ?DateTimeZone $timezone = null ): string {
		$timezone = $timezone ?: self::business_timezone();
		$date     = new DateTimeImmutable( $utc_datetime, self::utc_timezone() );

		return $date->setTimezone( $timezone )->format( 'Y-m-d H:i:s' );
	}
}