<?php
/**
 * The Dashboard's "Scheduled elements" card.
 *
 * @package Yangra\Conditional
 */

namespace Yangra\Conditional\Admin;

use Yangra\Conditional\Rest\ScheduledElementsController;
use Yangra\Conditional\Scheduling\ScheduledElements;

defined( 'ABSPATH' ) || exit;

/**
 * Counts the schedules that are on by status (active, upcoming, ended), and
 * lists the active and upcoming ones: active first, then by the time of their
 * next change. Ended ones are only counted, with a link to the full list.
 *
 * Only for users who manage schedules (`manage_options`).
 */
class ScheduledElementsCard {

	/**
	 * Items listed on the card itself.
	 */
	const CARD_ITEMS = 10;

	/**
	 * Items per page of the full list.
	 */
	const PER_PAGE = 20;

	/**
	 * Scheduled elements.
	 *
	 * @var ScheduledElements
	 */
	private $schedules;

	/**
	 * REST controller, which formats schedules for the screen.
	 *
	 * @var ScheduledElementsController
	 */
	private $controller;

	/**
	 * Constructor.
	 *
	 * @param ScheduledElements           $schedules  Scheduled elements.
	 * @param ScheduledElementsController $controller REST controller, for formatting.
	 */
	public function __construct( ScheduledElements $schedules, ScheduledElementsController $controller ) {
		$this->schedules  = $schedules;
		$this->controller = $controller;
	}

	/**
	 * Whether the current user can see the card.
	 *
	 * @return bool
	 */
	public function can_view(): bool {
		return current_user_can( ScheduledElementsController::CAPABILITY );
	}

	/**
	 * The card's data: counts by status, one page of active and upcoming
	 * schedules, and the screen's address.
	 *
	 * @param int      $page     Page number, from 1.
	 * @param int      $per_page Items per page.
	 * @param int|null $now      UTC timestamp; now by default.
	 * @return array{counts: array{active: int, upcoming: int, ended: int}, total: int, page: int, pages: int, items: array<int, array<string, mixed>>, screenUrl: string}
	 */
	public function data( int $page = 1, int $per_page = self::CARD_ITEMS, ?int $now = null ): array {
		$now    = $now ?? time();
		$counts = array(
			ScheduledElements::ACTIVE   => 0,
			ScheduledElements::UPCOMING => 0,
			ScheduledElements::ENDED    => 0,
		);
		$listed = array();
		foreach ( $this->schedules->all() as $schedule ) {
			if ( ! $schedule['enabled'] ) {
				continue;
			}
			$status = ScheduledElements::status( $schedule, $now );
			++$counts[ $status ];
			if ( ScheduledElements::ENDED !== $status ) {
				$listed[] = $schedule + array( '_status' => $status );
			}
		}

		usort( $listed, array( $this, 'compare' ) );

		$per_page = max( 1, $per_page );
		$pages    = (int) max( 1, ceil( count( $listed ) / $per_page ) );
		$page     = min( max( 1, $page ), $pages );
		$items    = array();
		foreach ( array_slice( $listed, ( $page - 1 ) * $per_page, $per_page ) as $schedule ) {
			unset( $schedule['_status'] );
			$items[] = $this->controller->prepare( $schedule );
		}

		return array(
			'counts'    => $counts,
			'total'     => count( $listed ),
			'page'      => $page,
			'pages'     => $pages,
			'items'     => $items,
			'screenUrl' => admin_url( 'admin.php?page=' . ScheduledElementsPage::SLUG ),
		);
	}

	/**
	 * Active schedules first (soonest to end first, never-ending last), then
	 * upcoming ones (soonest to start first).
	 *
	 * @param array<string, mixed> $a Schedule with `_status`.
	 * @param array<string, mixed> $b Schedule with `_status`.
	 * @return int
	 */
	private function compare( array $a, array $b ): int {
		return array( $this->rank( $a ), $this->next_change( $a ) ) <=> array( $this->rank( $b ), $this->next_change( $b ) );
	}

	/**
	 * 0 for active, 1 for upcoming.
	 *
	 * @param array<string, mixed> $schedule Schedule with `_status`.
	 * @return int
	 */
	private function rank( array $schedule ): int {
		return ScheduledElements::ACTIVE === $schedule['_status'] ? 0 : 1;
	}

	/**
	 * When the schedule next changes: its hide time while active, its show
	 * time while upcoming. No end sorts last.
	 *
	 * @param array<string, mixed> $schedule Schedule with `_status`.
	 * @return int
	 */
	private function next_change( array $schedule ): int {
		$time = ScheduledElements::ACTIVE === $schedule['_status'] ? $schedule['hide_at'] : $schedule['show_at'];

		return null === $time ? PHP_INT_MAX : (int) $time;
	}
}