<?php
/**
 * UserModel - Handles user authentication and management
 */
class UserModel {
    private mysqli $conn;
    private static array $userCache = []; // ['key' => ['data' => ..., 'expires' => timestamp]]
    private static int $cacheTTL = 300; // 5 minutes

    public function __construct(mysqli $conn) {
        $this->conn = $conn;
    }

    /**
     * Get cached user data if not expired
     */
    private static function getCached(string $key): ?array {
        if (isset(self::$userCache[$key])) {
            $cached = self::$userCache[$key];
            if ($cached['expires'] > time()) {
                return $cached['data'];
            }
            // Expired - remove from cache
            unset(self::$userCache[$key]);
        }
        return null;
    }

    /**
     * Store user data in cache with expiration
     */
    private static function setCached(string $key, array $data): void {
        self::$userCache[$key] = [
            'data' => $data,
            'expires' => time() + self::$cacheTTL
        ];
    }

    /**
     * Invalidate specific user cache entry
     */
    public static function invalidateCache(?int $userId = null, ?string $username = null): void {
        if ($userId !== null) {
            unset(self::$userCache["user_id_$userId"]);
        }
        if ($username !== null) {
            unset(self::$userCache["user_$username"]);
        }
    }

    /**
     * Sync user from Authelia headers (create or update)
     *
     * @param string $username Username from Remote-User header
     * @param string $displayName Display name from Remote-Name header
     * @param string $email Email from Remote-Email header
     * @param string $groups Comma-separated groups from Remote-Groups header
     * @return array User data array
     */
    public function syncUserFromAuthelia(string $username, string $displayName = '', string $email = '', string $groups = ''): array {
        // Check cache first
        $cacheKey = "user_$username";
        $cached = self::getCached($cacheKey);
        if ($cached !== null) {
            return $cached;
        }

        // Determine if user is admin based on groups
        $isAdmin = $this->checkAdminStatus($groups);

        // Try to find existing user
        $stmt = $this->conn->prepare("SELECT * FROM users WHERE username = ?");
        $stmt->bind_param("s", $username);
        $stmt->execute();
        $result = $stmt->get_result();

        if ($result->num_rows > 0) {
            // Update existing user
            $user = $result->fetch_assoc();

            $updateStmt = $this->conn->prepare(
                "UPDATE users SET display_name = ?, email = ?, groups = ?, is_admin = ?, last_login = NOW() WHERE username = ?"
            );
            $updateStmt->bind_param("sssis", $displayName, $email, $groups, $isAdmin, $username);
            $updateStmt->execute();
            $updateStmt->close();

            // Refresh user data
            $user['display_name'] = $displayName;
            $user['email'] = $email;
            $user['groups'] = $groups;
            $user['is_admin'] = $isAdmin;
        } else {
            // Create new user
            $insertStmt = $this->conn->prepare(
                "INSERT INTO users (username, display_name, email, groups, is_admin, last_login) VALUES (?, ?, ?, ?, ?, NOW())"
            );
            $insertStmt->bind_param("ssssi", $username, $displayName, $email, $groups, $isAdmin);
            $insertStmt->execute();

            $userId = $this->conn->insert_id;
            $insertStmt->close();

            // Get the newly created user
            $stmt = $this->conn->prepare("SELECT * FROM users WHERE user_id = ?");
            $stmt->bind_param("i", $userId);
            $stmt->execute();
            $result = $stmt->get_result();
            $user = $result->fetch_assoc();
        }

        $stmt->close();

        // Cache user with TTL
        self::setCached($cacheKey, $user);

        return $user;
    }

    /**
     * Get system user (for hwmonDaemon)
     *
     * @return array|null System user data or null if not found
     */
    public function getSystemUser(): ?array {
        // Check cache first
        $cached = self::getCached('system');
        if ($cached !== null) {
            return $cached;
        }

        $stmt = $this->conn->prepare("SELECT * FROM users WHERE username = 'system'");
        $stmt->execute();
        $result = $stmt->get_result();

        if ($result->num_rows > 0) {
            $user = $result->fetch_assoc();
            self::setCached('system', $user);
            $stmt->close();
            return $user;
        }

        $stmt->close();
        return null;
    }

    /**
     * Get user by ID
     *
     * @param int $userId User ID
     * @return array|null User data or null if not found
     */
    public function getUserById(int $userId): ?array {
        // Check cache first
        $cacheKey = "user_id_$userId";
        $cached = self::getCached($cacheKey);
        if ($cached !== null) {
            return $cached;
        }

        $stmt = $this->conn->prepare("SELECT * FROM users WHERE user_id = ?");
        $stmt->bind_param("i", $userId);
        $stmt->execute();
        $result = $stmt->get_result();

        if ($result->num_rows > 0) {
            $user = $result->fetch_assoc();
            self::setCached($cacheKey, $user);
            $stmt->close();
            return $user;
        }

        $stmt->close();
        return null;
    }

    /**
     * Get user by username
     *
     * @param string $username Username
     * @return array|null User data or null if not found
     */
    public function getUserByUsername(string $username): ?array {
        // Check cache first
        $cacheKey = "user_$username";
        $cached = self::getCached($cacheKey);
        if ($cached !== null) {
            return $cached;
        }

        $stmt = $this->conn->prepare("SELECT * FROM users WHERE username = ?");
        $stmt->bind_param("s", $username);
        $stmt->execute();
        $result = $stmt->get_result();

        if ($result->num_rows > 0) {
            $user = $result->fetch_assoc();
            self::setCached($cacheKey, $user);
            $stmt->close();
            return $user;
        }

        $stmt->close();
        return null;
    }

    /**
     * Check if user has admin privileges based on groups
     *
     * @param string $groups Comma-separated group names
     * @return bool True if user is in admin group
     */
    private function checkAdminStatus(string $groups): bool {
        if (empty($groups)) {
            return false;
        }

        // Split groups by comma and check for 'admin' group
        $groupArray = array_map('trim', explode(',', strtolower($groups)));
        return in_array('admin', $groupArray);
    }

    /**
     * Check if user is admin
     *
     * @param array $user User data array
     * @return bool True if user is admin
     */
    public function isAdmin(array $user): bool {
        return isset($user['is_admin']) && $user['is_admin'] == 1;
    }

    /**
     * Check if user has required group membership
     *
     * @param array $user User data array
     * @param array $requiredGroups Array of required group names
     * @return bool True if user is in at least one required group
     */
    public function hasGroupAccess(array $user, array $requiredGroups = ['admin', 'employee']): bool {
        if (empty($user['groups'])) {
            return false;
        }

        $userGroups = array_map('trim', explode(',', strtolower($user['groups'])));
        $requiredGroups = array_map('strtolower', $requiredGroups);

        return !empty(array_intersect($userGroups, $requiredGroups));
    }

    /**
     * Get all users (for admin panel)
     *
     * @return array Array of user records
     */
    public function getAllUsers(): array {
        $stmt = $this->conn->prepare("SELECT * FROM users ORDER BY created_at DESC");
        $stmt->execute();
        $result = $stmt->get_result();

        $users = [];
        while ($row = $result->fetch_assoc()) {
            $users[] = $row;
        }

        $stmt->close();
        return $users;
    }

    /**
     * Get all distinct groups from all users
     * Used for visibility group selection UI
     *
     * @return array Array of unique group names
     */
    public function getAllGroups(): array {
        $stmt = $this->conn->prepare("SELECT DISTINCT groups FROM users WHERE groups IS NOT NULL AND groups != ''");
        $stmt->execute();
        $result = $stmt->get_result();

        $allGroups = [];
        while ($row = $result->fetch_assoc()) {
            $userGroups = array_filter(array_map('trim', explode(',', $row['groups'])));
            $allGroups = array_merge($allGroups, $userGroups);
        }

        $stmt->close();

        // Return unique groups sorted alphabetically
        $uniqueGroups = array_unique($allGroups);
        sort($uniqueGroups);
        return $uniqueGroups;
    }
}