<?php
declare(strict_types=1);

require_once __DIR__ . '/db/config.php';

const TETRIS_ROOM_CODE_LENGTH = 6;
const TETRIS_ROOM_TTL_HOURS = 24;

function multiplayerEnsureSchema(): void
{
    static $ready = false;
    if ($ready) {
        return;
    }

    db()->exec(
        "CREATE TABLE IF NOT EXISTS tetris_rooms (
            id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
            room_code VARCHAR(6) NOT NULL,
            host_name VARCHAR(24) NOT NULL,
            guest_name VARCHAR(24) DEFAULT NULL,
            status ENUM('waiting', 'ready', 'closed') NOT NULL DEFAULT 'waiting',
            created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
            updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            expires_at TIMESTAMP NULL DEFAULT NULL,
            UNIQUE KEY uniq_room_code (room_code),
            KEY idx_status (status),
            KEY idx_expires_at (expires_at),
            KEY idx_updated_at (updated_at)
        ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci"
    );

    $ready = true;
}

function multiplayerSanitizePlayerName(string $value): string
{
    $value = trim($value);
    if ($value === '') {
        throw new InvalidArgumentException('Enter your nickname first.');
    }

    if (!preg_match('/^[\p{L}\p{N} _.-]+$/u', $value)) {
        throw new InvalidArgumentException('Nickname can use letters, numbers, spaces, dots, dashes, and underscores only.');
    }

    $length = function_exists('mb_strlen') ? mb_strlen($value) : strlen($value);
    if ($length > 24) {
        throw new InvalidArgumentException('Nickname must be 24 characters or fewer.');
    }

    return $value;
}

function multiplayerNormalizeRoomCode(string $value): string
{
    $value = strtoupper(preg_replace('/[^A-Z0-9]+/', '', $value) ?? '');
    if ($value === '') {
        throw new InvalidArgumentException('Enter a room code.');
    }
    if (strlen($value) !== TETRIS_ROOM_CODE_LENGTH) {
        throw new InvalidArgumentException('Room code must be exactly 6 characters.');
    }
    return $value;
}

function multiplayerFormatRoom(array $room): array
{
    $createdAt = strtotime((string) ($room['created_at'] ?? ''));
    $updatedAt = strtotime((string) ($room['updated_at'] ?? ''));
    $expiresAt = strtotime((string) ($room['expires_at'] ?? ''));
    $guestName = isset($room['guest_name']) ? trim((string) $room['guest_name']) : '';
    $status = (string) ($room['status'] ?? 'waiting');
    $playerCount = $guestName !== '' ? 2 : 1;

    return [
        'id' => (int) ($room['id'] ?? 0),
        'room_code' => (string) ($room['room_code'] ?? ''),
        'host_name' => (string) ($room['host_name'] ?? ''),
        'guest_name' => $guestName !== '' ? $guestName : null,
        'status' => $status,
        'player_count' => $playerCount,
        'is_ready' => $status === 'ready' && $playerCount >= 2,
        'created_at_iso' => $createdAt ? gmdate(DATE_ATOM, $createdAt) : null,
        'updated_at_iso' => $updatedAt ? gmdate(DATE_ATOM, $updatedAt) : null,
        'expires_at_iso' => $expiresAt ? gmdate(DATE_ATOM, $expiresAt) : null,
    ];
}

function multiplayerFetchRoomByCode(string $roomCode): ?array
{
    multiplayerEnsureSchema();
    $roomCode = multiplayerNormalizeRoomCode($roomCode);

    $stmt = db()->prepare(
        'SELECT id, room_code, host_name, guest_name, status, created_at, updated_at, expires_at
         FROM tetris_rooms
         WHERE room_code = :room_code
           AND (expires_at IS NULL OR expires_at >= UTC_TIMESTAMP())
         LIMIT 1'
    );
    $stmt->bindValue(':room_code', $roomCode, PDO::PARAM_STR);
    $stmt->execute();
    $room = $stmt->fetch();

    return $room ? multiplayerFormatRoom($room) : null;
}

function multiplayerGenerateRoomCode(): string
{
    $alphabet = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789';
    $maxIndex = strlen($alphabet) - 1;
    $roomCode = '';

    for ($i = 0; $i < TETRIS_ROOM_CODE_LENGTH; $i += 1) {
        $roomCode .= $alphabet[random_int(0, $maxIndex)];
    }

    return $roomCode;
}

function multiplayerCreateRoom(string $hostName): array
{
    multiplayerEnsureSchema();
    $hostName = multiplayerSanitizePlayerName($hostName);

    $expiresAt = gmdate('Y-m-d H:i:s', time() + (TETRIS_ROOM_TTL_HOURS * 3600));

    for ($attempt = 0; $attempt < 12; $attempt += 1) {
        $roomCode = multiplayerGenerateRoomCode();
        try {
            $stmt = db()->prepare(
                'INSERT INTO tetris_rooms (room_code, host_name, status, expires_at)
                 VALUES (:room_code, :host_name, :status, :expires_at)'
            );
            $stmt->bindValue(':room_code', $roomCode, PDO::PARAM_STR);
            $stmt->bindValue(':host_name', $hostName, PDO::PARAM_STR);
            $stmt->bindValue(':status', 'waiting', PDO::PARAM_STR);
            $stmt->bindValue(':expires_at', $expiresAt, PDO::PARAM_STR);
            $stmt->execute();

            $room = multiplayerFetchRoomByCode($roomCode);
            if ($room) {
                return $room;
            }
        } catch (PDOException $e) {
            if ((string) $e->getCode() !== '23000') {
                throw $e;
            }
        }
    }

    throw new RuntimeException('Unable to create a room right now. Please try again.');
}

function multiplayerJoinRoom(string $roomCode, string $guestName): array
{
    multiplayerEnsureSchema();
    $roomCode = multiplayerNormalizeRoomCode($roomCode);
    $guestName = multiplayerSanitizePlayerName($guestName);

    $pdo = db();
    $pdo->beginTransaction();

    try {
        $stmt = $pdo->prepare(
            'SELECT id, room_code, host_name, guest_name, status, created_at, updated_at, expires_at
             FROM tetris_rooms
             WHERE room_code = :room_code
               AND (expires_at IS NULL OR expires_at >= UTC_TIMESTAMP())
             LIMIT 1
             FOR UPDATE'
        );
        $stmt->bindValue(':room_code', $roomCode, PDO::PARAM_STR);
        $stmt->execute();
        $room = $stmt->fetch();

        if (!$room) {
            throw new InvalidArgumentException('Room not found or already expired.');
        }

        $existingGuest = trim((string) ($room['guest_name'] ?? ''));
        if ($existingGuest !== '' && strcasecmp($existingGuest, $guestName) !== 0) {
            throw new InvalidArgumentException('This room already has two players.');
        }

        if ($existingGuest === '') {
            $expiresAt = gmdate('Y-m-d H:i:s', time() + (TETRIS_ROOM_TTL_HOURS * 3600));
            $update = $pdo->prepare(
                'UPDATE tetris_rooms
                 SET guest_name = :guest_name,
                     status = :status,
                     expires_at = :expires_at
                 WHERE id = :id'
            );
            $update->bindValue(':guest_name', $guestName, PDO::PARAM_STR);
            $update->bindValue(':status', 'ready', PDO::PARAM_STR);
            $update->bindValue(':expires_at', $expiresAt, PDO::PARAM_STR);
            $update->bindValue(':id', (int) $room['id'], PDO::PARAM_INT);
            $update->execute();
        }

        $pdo->commit();
    } catch (Throwable $e) {
        if ($pdo->inTransaction()) {
            $pdo->rollBack();
        }
        throw $e;
    }

    $freshRoom = multiplayerFetchRoomByCode($roomCode);
    if (!$freshRoom) {
        throw new RuntimeException('Room state could not be loaded.');
    }

    return $freshRoom;
}