<?php
/**
 * Mapping of Kordiam custom fields onto WordPress post fields.
 *
 * @package Kordiam
 */

declare( strict_types=1 );

namespace Kordiam\Import;

use Kordiam\Support\MetaValue;
use Kordiam\Support\Options;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Writes Kordiam custom field values into the post fields they are mapped to.
 *
 * Handles story- and publication-scoped fields. A selection arrives as an option ID and
 * is resolved to its label through the cached field definitions.
 */
final class CustomFieldSync {

	/**
	 * Scope for fields defined on the story.
	 *
	 * @var string
	 */
	public const SCOPE_STORY = 'story';

	/**
	 * Scope for fields defined on the publication.
	 *
	 * @var string
	 */
	public const SCOPE_PUBLICATION = 'publication';

	/**
	 * Kordiam field type for free text.
	 *
	 * @var int
	 */
	private const TYPE_TEXT = 1;

	/**
	 * Kordiam field type for single selection.
	 *
	 * @var int
	 */
	private const TYPE_SINGLE_SELECTION = 2;

	/**
	 * Blocking instantiation: this class is a namespaced function group.
	 */
	private function __construct() {
	}

	/**
	 * Applying a set of custom fields to the post data being assembled.
	 *
	 * @param array<string, mixed>             $post_data     Post data being assembled.
	 * @param array<int, array<string, mixed>> $custom_fields Custom fields from Kordiam.
	 * @param string                           $scope         SCOPE_STORY or SCOPE_PUBLICATION.
	 *
	 * @return array<string, mixed>|null Updated post data, or null to skip the story.
	 */
	public static function apply( array $post_data, array $custom_fields, string $scope = self::SCOPE_STORY ): ?array {
		foreach ( $custom_fields as $custom_field ) {
			$field_id = self::field_id( $custom_field );

			if ( 0 === $field_id ) {
				continue;
			}

			$option_key = self::option_key( $field_id, $scope );

			if ( Options::is_do_not_import( $option_key ) ) {
				return null;
			}

			$target = Options::get_string( $option_key );

			if ( '' === $target || Options::is_no_sync( $option_key ) ) {
				continue;
			}

			$value = self::value_for( $custom_field, $scope );

			if ( null === $value ) {
				continue;
			}

			$post_data = self::write( $post_data, $target, $value );
		}

		return $post_data;
	}

	/**
	 * Reading a custom field's Kordiam ID.
	 *
	 * @param array<string, mixed> $custom_field Custom field data.
	 *
	 * @return int Field ID, or 0 when absent.
	 */
	public static function field_id( array $custom_field ): int {
		$field_id = $custom_field['customFieldId'] ?? null;

		return is_numeric( $field_id ) ? (int) $field_id : 0;
	}

	/**
	 * Building the option key holding a field's mapping.
	 *
	 * @param int    $field_id Kordiam field ID.
	 * @param string $scope    SCOPE_STORY or SCOPE_PUBLICATION.
	 *
	 * @return string Unprefixed option key.
	 */
	public static function option_key( int $field_id, string $scope = self::SCOPE_STORY ): string {
		$prefix = self::SCOPE_PUBLICATION === $scope ? 'publication_custom_field_import_' : 'custom_field_import_';

		return $prefix . $field_id;
	}

	/**
	 * Building the option key holding a scope's field definitions.
	 *
	 * @param string $scope SCOPE_STORY or SCOPE_PUBLICATION.
	 *
	 * @return string Unprefixed option key.
	 */
	public static function definitions_option_key( string $scope = self::SCOPE_STORY ): string {
		return self::SCOPE_PUBLICATION === $scope ? 'publication_custom_fields_list' : 'custom_fields_list';
	}

	/**
	 * Resolving the value a custom field contributes.
	 *
	 * @param array<string, mixed> $custom_field Custom field data.
	 * @param string               $scope        SCOPE_STORY or SCOPE_PUBLICATION.
	 *
	 * @return string|null The value, or null when it cannot be resolved.
	 */
	private static function value_for( array $custom_field, string $scope ): ?string {
		$type = isset( $custom_field['type'] ) && is_numeric( $custom_field['type'] )
			? (int) $custom_field['type']
			: 0;

		if ( self::TYPE_TEXT === $type ) {
			$value = $custom_field['value'] ?? null;

			return is_scalar( $value ) && '' !== trim( (string) $value ) ? (string) $value : null;
		}

		if ( self::TYPE_SINGLE_SELECTION === $type ) {
			return self::selected_option_label( $custom_field, $scope );
		}

		return null;
	}

	/**
	 * Resolving a selection to the label of the option chosen.
	 *
	 * @param array<string, mixed> $custom_field Custom field data.
	 * @param string               $scope        SCOPE_STORY or SCOPE_PUBLICATION.
	 *
	 * @return string|null The label, or null when it cannot be resolved.
	 */
	private static function selected_option_label( array $custom_field, string $scope ): ?string {
		$selected = $custom_field['selectedOption'][0] ?? null;

		if ( ! is_numeric( $selected ) ) {
			return null;
		}

		$selected_id = (int) $selected;
		$field_id    = self::field_id( $custom_field );

		foreach ( self::definitions( $scope ) as $definition ) {
			if ( ! isset( $definition['id'] ) || ! is_numeric( $definition['id'] ) ) {
				continue;
			}

			if ( (int) $definition['id'] !== $field_id ) {
				continue;
			}

			$options = $definition['options'] ?? null;

			if ( ! is_array( $options ) ) {
				return null;
			}

			foreach ( $options as $option ) {
				if ( ! is_array( $option ) || ! isset( $option['id'] ) || ! is_numeric( $option['id'] ) ) {
					continue;
				}

				if ( (int) $option['id'] === $selected_id && isset( $option['name'] ) && is_scalar( $option['name'] ) ) {
					return (string) $option['name'];
				}
			}

			return null;
		}

		return null;
	}

	/**
	 * Reading the cached field definitions for a scope.
	 *
	 * @param string $scope SCOPE_STORY or SCOPE_PUBLICATION.
	 *
	 * @return array<int, array<string, mixed>> Definitions.
	 */
	private static function definitions( string $scope ): array {
		return CustomFieldRegistry::cached( $scope );
	}

	/**
	 * Writing a resolved value into post data (title, URL alias, or meta).
	 *
	 * @param array<string, mixed> $post_data Post data being assembled.
	 * @param string               $target    Mapping target.
	 * @param string               $value     Value to write.
	 *
	 * @return array<string, mixed> Updated post data.
	 */
	private static function write( array $post_data, string $target, string $value ): array {
		if ( 'title' === $target ) {
			$post_data['post_title'] = $value;

			return $post_data;
		}

		if ( 'url_alias' === $target ) {
			$sanitised = sanitize_title( $value );

			if ( '' !== $sanitised ) {
				$post_data['post_name'] = $sanitised;
			}

			return $post_data;
		}

		if ( ! isset( $post_data['meta_input'] ) || ! is_array( $post_data['meta_input'] ) ) {
			$post_data['meta_input'] = array();
		}

		// Unlike post_title and post_name, meta_input is not sanitised by WordPress.
		$post_data['meta_input'][ $target ] = MetaValue::sanitise( $value );

		return $post_data;
	}
}