<?php
namespace Advently\Door;

use Advently\Calendar\Schedule;
use Advently\Door\Contracts\CouponIssuer;
use Advently\Door\Contracts\Mailer;
use Advently\Door\Contracts\OpenRepo;

defined( 'ABSPATH' ) || exit;

/**
 * Opens a door: the one place that decides what a visitor receives.
 *
 * Order matters and is tested: the schedule is checked first (a locked door
 * reveals nothing, not even which identity it would need), then identity, then
 * an earlier open is reused so the same person never gets a second coupon for
 * the same door.
 *
 * The unlock mode always comes from the calendar config, never from the
 * request. Identity is resolved by the REST layer:
 *   subscriber: ?array{id:int, email:string} — from the signed cookie (email
 *               mode) or the logged-in user's subscriber row (login mode)
 *   user_email: ?string — the logged-in account's email (login mode)
 */
final class Opener {

	/** @var array */
	private $config;

	/** @var Schedule */
	private $schedule;

	/** @var OpenRepo */
	private $opens;

	/** @var CouponIssuer */
	private $issuer;

	/** @var Mailer */
	private $mailer;

	public function __construct( array $config, Schedule $schedule, OpenRepo $opens, CouponIssuer $issuer, Mailer $mailer ) {
		$this->config   = $config;
		$this->schedule = $schedule;
		$this->opens    = $opens;
		$this->issuer   = $issuer;
		$this->mailer   = $mailer;
	}

	/**
	 * @return array{ok:bool, status:int, reason:string, door?:array, coupon?:?array, coupon_withheld?:bool, repeat?:bool, emailed?:bool}
	 */
	public function open( int $n, array $identity, \DateTimeImmutable $now ): array {
		$decision = $this->schedule->decide( $n, $now, $this->config['missed'] );
		if ( ! $decision['allowed'] ) {
			return self::refuse( 'invalid' === $decision['reason'] ? 404 : 403, $decision['reason'] );
		}

		$mode       = $this->config['mode'];
		$subscriber = $identity['subscriber'] ?? null;
		$userEmail  = $identity['user_email'] ?? null;

		if ( 'email' === $mode && empty( $subscriber['id'] ) ) {
			return self::refuse( 403, 'need_email' );
		}
		if ( 'login' === $mode && ( empty( $subscriber['id'] ) || empty( $userEmail ) ) ) {
			return self::refuse( 403, 'need_login' );
		}

		$door       = $this->config['door_list'][ $n ];
		$hasCoupon  = 'content' !== $door['type'];
		$wantCoupon = $hasCoupon && $decision['coupon'];
		$result     = [
			'ok'              => true,
			'status'          => 200,
			'reason'          => $decision['reason'],
			'door'            => self::payload( $door, $n ),
			'coupon'          => null,
			'coupon_withheld' => $hasCoupon && ! $decision['coupon'],
			'repeat'          => false,
			'emailed'         => false,
		];

		if ( 'open' === $mode ) {
			$coupon           = $wantCoupon ? $this->issuer->shared( $door, $n ) : null;
			$result['coupon'] = $coupon;
			$this->opens->record( null, $n, $coupon ? $coupon['id'] : null );
			return $result;
		}

		$subscriberId = (int) $subscriber['id'];
		$existing     = $this->opens->find( $subscriberId, $n );
		if ( null !== $existing ) {
			return $this->repeat( $result, $existing );
		}

		$email  = 'login' === $mode ? $userEmail : $subscriber['email'];
		$coupon = $wantCoupon ? $this->issuer->issue( $door, $n, $email ) : null;

		if ( ! $this->opens->record( $subscriberId, $n, $coupon ? $coupon['id'] : null ) ) {
			// A parallel request opened this door first; its coupon is the real one.
			if ( $coupon ) {
				$this->issuer->discard( $coupon['id'] );
			}
			return $this->repeat( $result, $this->opens->find( $subscriberId, $n ) );
		}

		$result['coupon'] = $coupon;
		if ( $coupon && 'email' === $mode ) {
			$result['emailed'] = $this->mail( $email, $coupon, $n );
		}
		return $result;
	}

	private function repeat( array $result, ?array $existing ): array {
		$couponId         = $existing['coupon_id'] ?? null;
		$result['repeat'] = true;
		$result['coupon'] = $couponId ? $this->issuer->find( (int) $couponId ) : null;
		return $result;
	}

	/**
	 * A failed email must not cost the visitor a coupon they can already see.
	 */
	private function mail( string $email, array $coupon, int $n ): bool {
		try {
			$this->mailer->sendCoupon( $email, $coupon, $n );
			return true;
		} catch ( \Throwable $e ) {
			return false;
		}
	}

	private static function payload( array $door, int $n ): array {
		return [
			'number'  => $n,
			'type'    => $door['type'],
			'content' => 'coupon' === $door['type'] ? null : $door['content'],
		];
	}

	private static function refuse( int $status, string $reason ): array {
		return [
			'ok'     => false,
			'status' => $status,
			'reason' => $reason,
		];
	}
}