<?php
/**
 * Cache of the Kordiam status list.
 *
 * @package Kordiam
 */

declare( strict_types=1 );

namespace Kordiam\Import;

use Kordiam\Contracts\StatusSource;
use Kordiam\Export\ApiClient;
use Kordiam\Support\Options;

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

/**
 * Holds the statuses Kordiam has for this site's platform.
 *
 * Pushed lists and fetched lists both go through prepare().
 */
final class StatusRegistry {

	/**
	 * Option holding the statuses that trigger an export.
	 *
	 * @var string
	 */
	public const ACTIVE_OPTION = 'active_statuses';

	/**
	 * Option holding the statuses that are switched off or do not trigger an export.
	 *
	 * @var string
	 */
	public const DEACTIVATED_OPTION = 'deactivated_statuses';

	/**
	 * Where to fetch the list from.
	 *
	 * @var StatusSource
	 */
	private StatusSource $source;

	/**
	 * Reconciler removing mappings for deleted statuses.
	 *
	 * @var DeletedItemsReconciler
	 */
	private DeletedItemsReconciler $reconciler;

	/**
	 * Constructing the registry.
	 *
	 * @param StatusSource|null           $source     Where to fetch from, or null for a default client.
	 * @param DeletedItemsReconciler|null $reconciler Reconciler to use, or null for a default one.
	 */
	public function __construct( ?StatusSource $source = null, ?DeletedItemsReconciler $reconciler = null ) {
		$this->source     = $source ?? new ApiClient();
		$this->reconciler = $reconciler ?? new DeletedItemsReconciler();
	}

	/**
	 * Checking whether the site holds any statuses.
	 *
	 * @return bool Whether anything is cached.
	 */
	public static function is_populated(): bool {
		return array() !== Options::get_array( self::ACTIVE_OPTION )
			|| array() !== Options::get_array( self::DEACTIVATED_OPTION );
	}

	/**
	 * Fetching the list afresh and caching it.
	 *
	 * @return bool Whether a new list was stored.
	 */
	public function refresh(): bool {
		return RefreshOutcome::UPDATED === $this->refresh_outcome();
	}

	/**
	 * Fetching the list afresh, caching it, and saying how that went.
	 *
	 * @return string One of the RefreshOutcome constants.
	 */
	public function refresh_outcome(): string {
		$platform_id = Options::get_int( PublicationResolver::PLATFORM_OPTION );

		if ( $platform_id <= 0 ) {
			// The resource is addressed per platform.
			return RefreshOutcome::FAILED;
		}

		$response = $this->source->fetch_statuses( $platform_id );

		if ( null === $response ) {
			return RefreshOutcome::FAILED;
		}

		$active      = array();
		$deactivated = array();

		// A fetch is one list with an "active" flag; a push carries two lists.
		foreach ( $response as $status ) {
			if ( ! is_array( $status ) || ! isset( $status['id'] ) ) {
				continue;
			}

			if ( array_key_exists( 'active', $status ) && false === $status['active'] ) {
				$deactivated[] = $status;
			} else {
				$active[] = $status;
			}
		}

		if ( array() === $active && array() === $deactivated ) {
			$this->forget_deleted( array() );

			Options::delete( self::ACTIVE_OPTION );
			Options::delete( self::DEACTIVATED_OPTION );

			return RefreshOutcome::EMPTY;
		}

		list( $active, $deactivated ) = $this->prepare( $active, $deactivated );

		// Write both, even if empty: a fetch is the whole list.
		Options::set( self::ACTIVE_OPTION, $active );
		Options::set( self::DEACTIVATED_OPTION, $deactivated );

		return RefreshOutcome::UPDATED;
	}

	/**
	 * Making an incoming list ready to store.
	 *
	 * Must run before storing: deleted statuses are found by comparing with the stored list.
	 *
	 * @param array<int, array<string, mixed>> $active      Active statuses.
	 * @param array<int, array<string, mixed>> $deactivated Deactivated statuses.
	 *
	 * @return array{0: array<int, array<string, mixed>>, 1: array<int, array<string, mixed>>} The adjusted lists.
	 */
	public function prepare( array $active, array $deactivated ): array {
		list( $active, $deactivated ) = self::apply_export_triggers( $active, $deactivated );

		$this->forget_deleted( array_merge( $active, $deactivated ) );

		return array( $active, $deactivated );
	}

	/**
	 * Moving statuses that no longer trigger an export into the deactivated list.
	 *
	 * @param array<int, array<string, mixed>> $active      Active statuses.
	 * @param array<int, array<string, mixed>> $deactivated Deactivated statuses.
	 *
	 * @return array{0: array<int, array<string, mixed>>, 1: array<int, array<string, mixed>>} The adjusted lists.
	 */
	private static function apply_export_triggers( array $active, array $deactivated ): array {
		$still_active = array();

		foreach ( $active as $status ) {
			if ( array_key_exists( 'triggersExport', $status ) && false === $status['triggersExport'] ) {
				array_unshift( $deactivated, $status );

				continue;
			}

			$still_active[] = $status;
		}

		return array( $still_active, $deactivated );
	}

	/**
	 * Removing mappings for statuses Kordiam no longer has.
	 *
	 * @param array<int, array<string, mixed>> $incoming Every status in the incoming list.
	 */
	private function forget_deleted( array $incoming ): void {
		$stored = Options::get_array( self::ACTIVE_OPTION );

		if ( array() === $stored ) {
			return;
		}

		$this->reconciler->reconcile(
			$stored,
			$incoming,
			array_keys( StatusMapper::selectable_statuses() ),
			DeletedItemsReconciler::TYPE_STATUS
		);
	}
}