<?php
/**
 * Matching a Kordiam assignee to a WordPress user.
 *
 * @package Kordiam
 */

declare( strict_types=1 );

namespace Kordiam\Import;

use Kordiam\Support\MetaKeys;

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

/**
 * Finds the WordPress user a story's assignee corresponds to.
 *
 * Kordiam sends the assignee's email address in the task's assignee.name field.
 */
final class AuthorResolver {

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

	/**
	 * Reading the assignee address off a task.
	 *
	 * @param array<string, mixed> $task Task data.
	 *
	 * @return string The address, or an empty string when the task carries none.
	 */
	public static function assignee_email( array $task ): string {
		$name = $task['assignee']['name'] ?? null;

		if ( ! is_scalar( $name ) ) {
			return '';
		}

		$candidate = trim( (string) $name );

		return false === is_email( $candidate ) ? '' : $candidate;
	}

	/**
	 * Reading the Kordiam assignee ID off a task.
	 *
	 * @param array<string, mixed> $task Task data.
	 *
	 * @return int Assignee ID, or 0 when absent.
	 */
	public static function assignee_id( array $task ): int {
		$id = $task['assignee']['id'] ?? null;

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

	/**
	 * Finding the WordPress user for a task's assignee.
	 *
	 * @param array<string, mixed> $task Task data.
	 *
	 * @return int User ID, or 0 when nobody on this site matches.
	 */
	public static function user_id_for_task( array $task ): int {
		$email = self::assignee_email( $task );

		if ( '' === $email ) {
			return 0;
		}

		$user = get_user_by( 'email', $email );

		if ( ! is_object( $user ) || ! isset( $user->ID ) || ! is_numeric( $user->ID ) ) {
			return 0;
		}

		return (int) $user->ID;
	}

	/**
	 * Finding the first task whose assignee exists on this site.
	 *
	 * @param array<int, array<string, mixed>> $tasks Story tasks.
	 *
	 * @return array{user_id: int, assignee_id: int}|null The match, or null when none of the assignees is known here.
	 */
	public static function first_known_assignee( array $tasks ): ?array {
		foreach ( $tasks as $task ) {
			$user_id = self::user_id_for_task( $task );

			if ( $user_id > 0 ) {
				return array(
					'user_id'     => $user_id,
					'assignee_id' => self::assignee_id( $task ),
				);
			}
		}

		return null;
	}

	/**
	 * Setting a post's author and remembering the Kordiam ID behind it (used by export).
	 *
	 * @param array<string, mixed> $post_data   Post data being assembled.
	 * @param int                  $user_id     WordPress user ID.
	 * @param int                  $assignee_id Kordiam assignee ID.
	 *
	 * @return array<string, mixed> Post data with the author set.
	 */
	public static function assign( array $post_data, int $user_id, int $assignee_id ): array {
		if ( $user_id <= 0 ) {
			return $post_data;
		}

		$post_data['post_author'] = $user_id;

		if ( $assignee_id > 0 ) {
			self::remember_kordiam_id( $user_id, $assignee_id );
		}

		return $post_data;
	}

	/**
	 * Reading the Kordiam assignee ID stored against a user.
	 *
	 * @param int $user_id WordPress user ID.
	 *
	 * @return int Assignee ID, or 0 when none is stored.
	 */
	public static function kordiam_id_for_user( int $user_id ): int {
		$stored = self::read_user_meta( $user_id, MetaKeys::AUTHOR_ID );

		if ( is_numeric( $stored ) ) {
			return (int) $stored;
		}

		$legacy = self::read_user_meta( $user_id, MetaKeys::legacy_user_meta()[ MetaKeys::AUTHOR_ID ] );

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

	/**
	 * Storing the Kordiam assignee ID against a user.
	 *
	 * @param int $user_id     WordPress user ID.
	 * @param int $assignee_id Kordiam assignee ID.
	 */
	private static function remember_kordiam_id( int $user_id, int $assignee_id ): void {
		// VIP uses its own attribute store; the constant alone does not guarantee the helper.
		if ( defined( 'WPCOM_IS_VIP_ENV' ) && WPCOM_IS_VIP_ENV && function_exists( 'update_user_attribute' ) ) {
			update_user_attribute( $user_id, MetaKeys::AUTHOR_ID, (string) $assignee_id );

			return;
		}

		update_user_meta( $user_id, MetaKeys::AUTHOR_ID, $assignee_id );
	}

	/**
	 * Reading a user meta value, honouring the VIP attribute store.
	 *
	 * @param int    $user_id  WordPress user ID.
	 * @param string $meta_key Meta key.
	 *
	 * @return mixed Stored value.
	 */
	private static function read_user_meta( int $user_id, string $meta_key ) {
		if ( defined( 'WPCOM_IS_VIP_ENV' ) && WPCOM_IS_VIP_ENV && function_exists( 'get_user_attribute' ) ) {
			return get_user_attribute( $user_id, $meta_key );
		}

		return get_user_meta( $user_id, $meta_key, true );
	}
}