<?php
/**
 * Signed context for native Booking Form AJAX requests.
 *
 * @package Booking Calendar
 */

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

/**
 * Return the current signed Booking Form context contract version.
 *
 * Version 2 adds a server-authored workflow identity. Rejecting older tokens
 * prevents indefinitely cached pre-fix Appointment or Resource Selector forms
 * from being replayed as unsigned Classic bookings.
 *
 * @return int Current context contract version.
 */
function wpbc_classic_booking_context_get_version() {
	return 2;
}

/**
 * Resolve an actionable visitor message for a Booking Form context failure.
 *
 * The frontend message registry makes these notices translatable and editable
 * with the other Form Messages. The local defaults keep this security boundary
 * usable in isolated tests and integrations that load the context API before
 * the central message registry.
 *
 * @param string $message_key Stable frontend message key.
 * @param mixed  $resource_id Booking Resource ID associated with the form.
 *
 * @return string Plain-text visitor message, or an empty string for an unsupported key.
 */
function wpbc_classic_booking_context_get_visitor_message( $message_key, $resource_id = 0 ) {
	$resource_id = absint( $resource_id );
	$fallbacks   = array(
		/* translators: Keep the {resource_id} placeholder unchanged. */
		'message_booking_form_context_required' => __( 'This booking form is not connected to a valid calendar for Booking Resource ID {resource_id}. This can happen when the same Booking Resource is used more than once on the page, including in hidden content, or when the page cache is outdated. Reload the page and try again. If the problem continues, ask the site administrator to remove duplicate forms for this Booking Resource and clear the page cache.', 'booking' ),
		/* translators: Keep the {resource_id} placeholder unchanged. */
		'message_booking_form_context_expired'  => __( 'This booking form was generated by an older or cached version of the page for Booking Resource ID {resource_id}. Reload the page and try again. If the problem continues, ask the site administrator to clear the page cache and remove any duplicate calendar or form for this Booking Resource.', 'booking' ),
	);

	if ( ! isset( $fallbacks[ $message_key ] ) ) {
		return '';
	}

	$replacements = array( '{resource_id}' => (string) $resource_id );
	if ( function_exists( 'wpbc_frontend_messages__get' ) ) {
		$resolved_message = wpbc_frontend_messages__get( $message_key, $replacements, $resource_id );
		if ( '' !== $resolved_message ) {
			return $resolved_message;
		}
	}

	return strtr( $fallbacks[ $message_key ], $replacements );
}

/**
 * Normalize one YYYY-MM-DD value and reject impossible calendar dates.
 *
 * @param mixed $date_value Candidate date value.
 *
 * @return string Valid normalized date or an empty string.
 */
function wpbc_classic_booking_context_normalize_date( $date_value ) {
	$date_value = sanitize_text_field( (string) $date_value );
	if ( ! preg_match( '/^\d{4}-\d{2}-\d{2}$/', $date_value ) ) {
		return '';
	}

	$date_object = DateTimeImmutable::createFromFormat( '!Y-m-d', $date_value, wp_timezone() );
	if ( false === $date_object || $date_object->format( 'Y-m-d' ) !== $date_value ) {
		return '';
	}

	return $date_value;
}

/**
 * Determine whether a Classic shortcode range intentionally starts in the past.
 *
 * The historical Booking Calendar contract treats a past calendar_dates_start
 * value as site-author permission to submit dates from that visible range.
 *
 * @param mixed  $calendar_dates_start Inclusive shortcode start date.
 * @param string $today_ymd            Optional YYYY-MM-DD comparison date for deterministic callers and tests.
 *
 * @return bool True when the valid range start is earlier than today.
 */
function wpbc_classic_booking_context_should_allow_past( $calendar_dates_start, $today_ymd = '' ) {
	$calendar_dates_start = wpbc_classic_booking_context_normalize_date( $calendar_dates_start );
	$today_ymd            = wpbc_classic_booking_context_normalize_date( $today_ymd );

	if ( '' === $today_ymd ) {
		$today_ymd = current_time( 'Y-m-d' );
	}

	return '' !== $calendar_dates_start && $calendar_dates_start < $today_ymd;
}

/**
 * Normalize the legacy default Booking Form representation.
 *
 * The standard form does not render a booking_form_type hidden field, so its
 * frontend submission uses an empty string even though the shortcode resolver
 * represents the same form as "standard".
 *
 * @param mixed $custom_form Candidate Booking Form slug.
 *
 * @return string Sanitized Booking Form slug, using "standard" for an omitted value.
 */
function wpbc_classic_booking_context_normalize_form( $custom_form ) {
	$custom_form = sanitize_text_field( (string) $custom_form );

	return '' === $custom_form ? 'standard' : $custom_form;
}

/**
 * Normalize additional aggregate Booking Resource IDs for signed contexts.
 *
 * The legacy shortcode renderer represents an aggregate form as the primary
 * Resource followed by its additional Resources. Calendar runtime state
 * intentionally stores only the additional Resources because the primary is
 * already carried separately as resource_id. Removing that separately bound
 * primary gives both established shapes one canonical representation while
 * preserving an exact-set security comparison for every additional Resource.
 *
 * @param array|string|int $aggregate_resource_ids Candidate Resource IDs.
 * @param mixed            $primary_resource_id    Separately bound primary Resource ID.
 *
 * @return int[] Sorted unique positive IDs excluding the primary Resource.
 */
function wpbc_classic_booking_context_normalize_aggregate_resource_ids( $aggregate_resource_ids, $primary_resource_id = 0 ) {
	$aggregate_resource_ids  = is_array( $aggregate_resource_ids ) ? $aggregate_resource_ids : array( $aggregate_resource_ids );
	$primary_resource_id     = absint( $primary_resource_id );
	$normalized_resource_ids = array();

	foreach ( $aggregate_resource_ids as $aggregate_resource_id ) {
		if ( ! is_int( $aggregate_resource_id ) && ! is_float( $aggregate_resource_id ) && ! is_string( $aggregate_resource_id ) ) {
			continue;
		}

		$resource_id_parts = preg_split( '/[;,\s]+/', (string) $aggregate_resource_id, -1, PREG_SPLIT_NO_EMPTY );
		foreach ( (array) $resource_id_parts as $resource_id_part ) {
			$resource_id = absint( $resource_id_part );
			if ( ! $resource_id || $resource_id === $primary_resource_id ) {
				continue;
			}

			$normalized_resource_ids[ $resource_id ] = $resource_id;
		}
	}

	$normalized_resource_ids = array_values( $normalized_resource_ids );
	sort( $normalized_resource_ids, SORT_NUMERIC );

	return $normalized_resource_ids;
}

/**
 * Normalize the native Booking Form context before it is signed or consumed.
 *
 * @param mixed $context Raw context values.
 *
 * @return array<string,mixed> Stable context contract.
 */
function wpbc_classic_booking_context_normalize( $context ) {
	$context = is_array( $context ) ? $context : array();
	$context = wp_parse_args(
		$context,
		array(
			'context_version'        => 0,
			'booking_workflow'       => 'classic',
			'resource_id'            => 0,
			'calendar_dates_start'   => '',
			'calendar_dates_end'     => '',
			'custom_form'            => 'standard',
			'aggregate_resource_ids' => array(),
			'allow_past'             => false,
		)
	);
	$calendar_dates_start   = wpbc_classic_booking_context_normalize_date( $context['calendar_dates_start'] );
	$resource_id            = absint( $context['resource_id'] );
	$aggregate_resource_ids = wpbc_classic_booking_context_normalize_aggregate_resource_ids( $context['aggregate_resource_ids'], $resource_id );
	$booking_workflow        = sanitize_key( (string) $context['booking_workflow'] );
	if ( ! in_array( $booking_workflow, array( 'classic', 'appointment', 'resource_selector' ), true ) ) {
		$booking_workflow = 'classic';
	}

	// Derive permission from the site-authored date boundary; never trust a caller-supplied allow_past flag.
	return array(
		'context_version'        => absint( $context['context_version'] ),
		'booking_workflow'       => $booking_workflow,
		'resource_id'            => $resource_id,
		'calendar_dates_start'   => $calendar_dates_start,
		'calendar_dates_end'     => wpbc_classic_booking_context_normalize_date( $context['calendar_dates_end'] ),
		'custom_form'            => wpbc_classic_booking_context_normalize_form( $context['custom_form'] ),
		'aggregate_resource_ids' => $aggregate_resource_ids,
		'allow_past'             => wpbc_classic_booking_context_should_allow_past( $calendar_dates_start ),
	);
}

/**
 * Base64-url encode a context value without padding.
 *
 * @param string $context_value Value to encode.
 *
 * @return string URL-safe encoded value.
 */
function wpbc_classic_booking_context_base64url_encode( $context_value ) {
	return rtrim( strtr( base64_encode( (string) $context_value ), '+/', '-_' ), '=' ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode
}

/**
 * Decode one strict base64-url context value.
 *
 * @param string $encoded_value Encoded value.
 *
 * @return string|false Decoded value or false when malformed.
 */
function wpbc_classic_booking_context_base64url_decode( $encoded_value ) {
	$encoded_value = strtr( (string) $encoded_value, '-_', '+/' );
	$padding       = strlen( $encoded_value ) % 4;
	if ( $padding ) {
		$encoded_value .= str_repeat( '=', 4 - $padding );
	}

	return base64_decode( $encoded_value, true ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode
}

/**
 * Sign a normalized native Booking Form context for cache-safe AJAX round trips.
 *
 * The HMAC has no time component, so cached front-end pages remain usable until
 * WordPress authentication salts change. No secret or raw signature key is
 * exposed to the browser.
 *
 * @param mixed $context Raw or normalized context.
 *
	 * @return string Signed opaque token, or an empty string for invalid context.
 */
function wpbc_classic_booking_context_encode( $context ) {
	$context = is_array( $context ) ? $context : array();
	$context['context_version'] = wpbc_classic_booking_context_get_version();
	$context = wpbc_classic_booking_context_normalize( $context );
	if (
		0 === $context['resource_id']
		|| ( ( '' === $context['calendar_dates_start'] ) !== ( '' === $context['calendar_dates_end'] ) )
		|| (
			'' !== $context['calendar_dates_start']
			&& $context['calendar_dates_start'] > $context['calendar_dates_end']
		)
	) {
		return '';
	}

	$payload   = wpbc_classic_booking_context_base64url_encode( wp_json_encode( $context ) );
	$signature = hash_hmac( 'sha256', $payload, wp_salt( 'auth' ), true );

	return $payload . '.' . wpbc_classic_booking_context_base64url_encode( $signature );
}

/**
 * Verify and decode a signed native Booking Form context token.
 *
 * @param string $context_token Signed token received through AJAX.
 *
 * @return array<string,mixed>|WP_Error Normalized context or a safe validation error.
 */
function wpbc_classic_booking_context_decode( $context_token ) {
	$token_parts = explode( '.', (string) $context_token, 2 );
	if ( 2 !== count( $token_parts ) ) {
		return new WP_Error( 'classic_booking_context_invalid', __( 'The booking form context could not be verified. Please reload the page and try again.', 'booking' ) );
	}

	$expected_signature = hash_hmac( 'sha256', $token_parts[0], wp_salt( 'auth' ), true );
	$actual_signature   = wpbc_classic_booking_context_base64url_decode( $token_parts[1] );
	if ( false === $actual_signature || ! hash_equals( $expected_signature, $actual_signature ) ) {
		return new WP_Error( 'classic_booking_context_invalid', __( 'The booking form context could not be verified. Please reload the page and try again.', 'booking' ) );
	}

	$context_json = wpbc_classic_booking_context_base64url_decode( $token_parts[0] );
	$context      = false !== $context_json ? json_decode( $context_json, true ) : null;
	if ( ! is_array( $context ) ) {
		return new WP_Error( 'classic_booking_context_invalid', __( 'The booking form context could not be verified. Please reload the page and try again.', 'booking' ) );
	}

	$context = wpbc_classic_booking_context_normalize( $context );
	if ( wpbc_classic_booking_context_get_version() !== $context['context_version'] ) {
		return new WP_Error(
			'classic_booking_context_expired',
			wpbc_classic_booking_context_get_visitor_message( 'message_booking_form_context_expired', $context['resource_id'] )
		);
	}
	if (
		0 === $context['resource_id']
		|| ( ( '' === $context['calendar_dates_start'] ) !== ( '' === $context['calendar_dates_end'] ) )
		|| (
			'' !== $context['calendar_dates_start']
			&& $context['calendar_dates_start'] > $context['calendar_dates_end']
		)
	) {
		return new WP_Error( 'classic_booking_context_invalid', __( 'The booking form context could not be verified. Please reload the page and try again.', 'booking' ) );
	}

	return $context;
}

/**
 * Validate a Booking Form AJAX request against its signed server-rendered boundaries.
 *
 * @param string       $context_token         Signed Booking Form context token.
 * @param mixed        $resource_id           Submitted primary Booking Resource ID.
 * @param array|string $submitted_dates       Submitted YYYY-MM-DD dates.
 * @param string       $custom_form           Submitted Booking Form identifier.
 * @param array|string $aggregate_resource_ids Submitted aggregate Booking Resource IDs.
 *
 * @return array<string,mixed>|WP_Error Verified context or a validation error.
 */
function wpbc_classic_booking_context_validate_submission( $context_token, $resource_id, $submitted_dates, $custom_form = 'standard', $aggregate_resource_ids = array() ) {
	$context = wpbc_classic_booking_context_decode( $context_token );
	if ( is_wp_error( $context ) ) {
		return $context;
	}

	if ( absint( $resource_id ) !== $context['resource_id'] ) {
		return new WP_Error( 'classic_booking_context_resource_mismatch', __( 'The selected booking resource does not match this booking form. Please reload the page and try again.', 'booking' ) );
	}

	$custom_form = wpbc_classic_booking_context_normalize_form( $custom_form );
	if ( $custom_form !== $context['custom_form'] ) {
		return new WP_Error( 'classic_booking_context_form_mismatch', __( 'The selected Booking Form does not match this calendar. Please reload the page and try again.', 'booking' ) );
	}

	$aggregate_resource_ids = wpbc_classic_booking_context_normalize_aggregate_resource_ids( $aggregate_resource_ids, $context['resource_id'] );
	if ( $aggregate_resource_ids !== $context['aggregate_resource_ids'] ) {
		$troubleshooting_url       = 'https://wpbookingcalendar.com/faq/troubleshooting-the-booking-resources-do-not-match-this-calendar/';
		$aggregate_mismatch_message = esc_html__( 'The booking resources do not match this calendar. Please reload the page and try again.', 'booking' );
		$aggregate_mismatch_message .= sprintf(
			'<br><a href="%1$s" target="_blank" rel="noopener noreferrer">%2$s</a>',
			esc_url( $troubleshooting_url ),
			esc_html__( 'Open the troubleshooting guide.', 'booking' )
		);

		return new WP_Error( 'classic_booking_context_aggregate_mismatch', $aggregate_mismatch_message );
	}

	if ( is_string( $submitted_dates ) ) {
		$submitted_dates = preg_split( '/\s*,\s*/', $submitted_dates, -1, PREG_SPLIT_NO_EMPTY );
	}
	$submitted_dates = array_values( (array) $submitted_dates );
	if ( empty( $submitted_dates ) ) {
		return new WP_Error( 'classic_booking_context_date_invalid', __( 'The selected booking date is invalid. Please select the date again.', 'booking' ) );
	}

	foreach ( $submitted_dates as $submitted_date ) {
		$submitted_date = wpbc_classic_booking_context_normalize_date( $submitted_date );
		if ( '' === $submitted_date ) {
			return new WP_Error( 'classic_booking_context_date_invalid', __( 'The selected booking date is invalid. Please select the date again.', 'booking' ) );
		}
		if (
			'' !== $context['calendar_dates_start']
			&& ( $submitted_date < $context['calendar_dates_start'] || $submitted_date > $context['calendar_dates_end'] )
		) {
			return new WP_Error( 'classic_booking_context_date_outside_range', __( 'The selected booking date is outside this calendar range. Please select another date.', 'booking' ) );
		}
	}

	return $context;
}