<?php

use Random\RandomException;

/**
 * Checks if the current session represents a logged-in user.
 *
 * @global array $routerConfig Global configuration array containing permission thresholds.
 * @return bool Returns true if the user is logged in and meets the minimum privilege level; otherwise, false.
 */
function isLoggedIn(): bool
{
    global $routerConfig;
    return $_SESSION["ID"] > 0 && !empty($_SESSION["email"]) && $_SESSION["privilege_level"] >= $routerConfig["permissions"]["logged_in_default"];
}
/**
 * Checks if the logged-in user is verified.
 *
 * @global array $routerConfig Global configuration array containing permission thresholds.
 * @return bool Returns true if the user is logged in and verified; otherwise, false.
 */
function isVerified(): bool
{
    global $routerConfig;
    return isLoggedIn() && $_SESSION["privilege_level"] >= $routerConfig["permissions"]["verified"];
}

/**
 * Checks if the logged-in user is trustworthy.
 *
 * @global array $routerConfig Global configuration array containing permission thresholds.
 * @return bool Returns true if the user is logged in and considered trustworthy; otherwise, false.
 */
function isTrustWorthy(): bool
{
    global $routerConfig;
    return isLoggedIn() && $_SESSION["privilege_level"] >= $routerConfig["permissions"]["trustworthy"];
}
/**
 * Checks if the logged-in user is a moderator.
 *
 * @global array $routerConfig Global configuration array containing permission thresholds.
 * @return bool Returns true if the user is logged in and a moderator; otherwise, false.
 */
function isModerator(): bool
{
    global $routerConfig;
    return isLoggedIn() && $_SESSION["privilege_level"] >= $routerConfig["permissions"]["moderator"];
}
/**
 * Checks if the logged-in user is a user admin.
 *
 * @global array $routerConfig Global configuration array containing permission thresholds.
 * @return bool Returns true if the user is logged in and a user admin; otherwise, false.
 */
function isUserAdmin(): bool
{
    global $routerConfig;
    return isLoggedIn() && $_SESSION["privilege_level"] >= $routerConfig["permissions"]["user_admin"];
}
/**
 * Checks if the logged-in user is an admin.
 *
 * @global array $routerConfig Global configuration array containing permission thresholds.
 * @return bool Returns true if the user is logged in and an admin; otherwise, false.
 */
function isAdmin(): bool
{
    global $routerConfig;
    return isLoggedIn() && $_SESSION["privilege_level"] >= $routerConfig["permissions"]["admin"];
}

/**
 * Generates a secure token for account activation or other purposes using cryptographic methods.
 *
 * @return string|null Returns a hexadecimal token or null in case of an error.
 */
function generateActivationToken(): ?string
{
    try {
        return bin2hex(random_bytes(16));
    } catch (RandomException) {
        return null;
    }
}
/**
 * Checks if an email address is available for registration.
 *
 * @param string $email The email address to check.
 * @return bool Returns true if the email is not already registered; otherwise, false.
 *@global mysqli $mysqli Global mysqli object for database access.
 */
function isEmailAvailable(string $email): bool
{
    global $mysqli;
    $stmt = $mysqli->prepare("SELECT COUNT(*) FROM Users WHERE Email = ?");
    $stmt->bind_param("s", $email);
    $stmt->execute();
    $count = -1;
    $stmt->bind_result($count);
    $stmt->fetch();
    $stmt->close();

    return $count === 0;
}
/**
 * Sets default session data typically used for a logged-out user(includes users that have just visited the page).
 *
 * @global array $routerConfig Global configuration array used for setting initial privilege levels.
 * @return void
 */
function setDefaultSessionData(): void
{
    global $routerConfig;
    $_SESSION["ID"] = 0;
    $_SESSION["first_name"] = "";
    $_SESSION["last_name"] = "";
    $_SESSION["nickname"] = "";
    $_SESSION["email"] = "";
    $_SESSION["privilege_level"] = $routerConfig["permissions"]["logged_out"];
}
/**
 * Verifies if the provided password matches the stored hash for the user.
 *
 * @param int $userID The user ID whose password is to be verified.
 * @param string $password The password to verify.
 * @return bool Returns true if the password matches the stored hash; otherwise, false.
 *@global mysqli $mysqli Global mysqli object for database access.
 */
function verifyPassword(int $userID, string $password): bool
{
    global $mysqli;
    $stmt = $mysqli->prepare("SELECT PasswordHash FROM Users WHERE ID = ?");
    $stmt->bind_param("i", $userID);
    $stmt->execute();
    $password_hash = "";
    $stmt->bind_result($password_hash);
    $stmt->fetch();
    $stmt->close();

    return !empty($password_hash) && !empty($password) && password_verify($password, $password_hash);
}
/**
 * Updates session data from the database for the logged-in user.
 *
 * @global mysqli $mysqli Global mysqli object for database access.
 * @return void
 */
function UpdateSession(): void
{
    global $mysqli;
    $stmt = $mysqli->prepare("SELECT FirstName, LastName, Nickname, Email, PrivilegeLevel, LastLoginAt, LoginCount, ClassID, FavoriteColor FROM Users WHERE ID = ? AND isActivated = 1");
    $stmt->bind_param("i", $_SESSION["ID"]);
    $stmt->execute();

    $first_name = "";
    $last_name = "";
    $nickname = "";
    $email = "";
    $privilege_level = 0;
    $class_id = 0;
    $favorite_color = 0;
    $lastLoginAt = null;
    $loginCount = 0;
    $stmt->bind_result($first_name, $last_name, $nickname, $email, $privilege_level, $lastLoginAt, $loginCount, $class_id, $favorite_color);
    $stmt->fetch();
    $stmt->close();
    $_SESSION["first_name"] = $first_name;
    $_SESSION["last_name"] = $last_name;
    $_SESSION["nickname"] = $nickname;
    $_SESSION["email"] = $email;
    $_SESSION["privilege_level"] = $privilege_level;
    $_SESSION["lastLoginAt"] = $lastLoginAt;
    $_SESSION["loginCount"] = $loginCount;
    $_SESSION["class_id"] = $class_id;
    $_SESSION["favorite_color"] = $favorite_color;

}
/**
 * Attempts to log in a user with the given credentials.
 *
 * @param string $email The user's email address.
 * @param string $password The user's password.
 * @global mysqli $mysqli Global database connection object.
 * @return array An array containing the status of the login attempt ('Success' or 'Fail').
 */
function doLogin(string $email, string $password): array
{
    global $mysqli;
    $found = false;
    if (!empty($email) && !empty($password)) {
        $stmt = $mysqli->prepare("SELECT ID, PasswordHash FROM Users WHERE Email = ? AND isActivated = 1");
        $stmt->bind_param("s", $email);
        $stmt->execute();

        $uid = 0;

        $password_hash = "";
        $stmt->bind_result($uid, $password_hash);
        $stmt->fetch();
        $stmt->close();

        if (password_verify($password, $password_hash)) {
            $found = true;

            $_SESSION["ID"] = $uid;
            UpdateSession();
            // Update LastLoginAt and LoginCount
            $updateLoginStmt = $mysqli->prepare("UPDATE Users SET LastLoginAt = NOW(), LoginCount = LoginCount + 1 WHERE ID = ?");
            $updateLoginStmt->bind_param("i", $uid);
            $updateLoginStmt->execute();
            $updateLoginStmt->close();
        }
    }
    return $found ? ["Status" => "Success"] : ["Status" => "Fail"];
}
/**
 * Logs out the current user by resetting session data.
 * Fails when the user wasn't logged in
 *
 * @return array An array with the logout status ('Success' if logged out, 'Fail' otherwise).
 */
function doLogout(): array
{
    if(isLoggedIn()){
        setDefaultSessionData();
        return ["Status" => "Success"];
    } else {
        return ["Status" => "Fail"];
    }
}
/**
 * Registers a new user with provided personal details and activation token.
 *
 * @param string $firstname The user's first name.
 * @param string $lastname The user's last name.
 * @param string $email The user's email.
 * @param string $password The user's password.
 * @param string $activation_token The activation token to verify the registration.
 * @global mysqli $mysqli Global database connection object.
 * @global array $routerConfig Global configuration settings.
 * @return array An array with the registration status ('Success' or 'Fail').
 */
function doRegister(string $firstname, string $lastname, string $email, string $password, string $activation_token): array
{
    global $mysqli, $routerConfig;
    $status = ["Status" => "Fail"];

    if (!empty($activation_token) && !empty($email) && !empty($password) && !empty($firstname) && !empty($lastname) && isEmailAvailable($email)) {
        $passwordHash = password_hash($password, PASSWORD_DEFAULT);

        $stmt = $mysqli->prepare("UPDATE Users SET FirstName=?, LastName=?, Email=?, PasswordHash=?, PrivilegeLevel=?, isActivated=1, ActivationToken='', RegisteredAt=NOW() WHERE ActivationToken = ?");
        $privilege_level = $routerConfig["permissions"]["logged_in_default"];

        /** @noinspection SpellCheckingInspection */
        $stmt->bind_param("ssssis", $firstname, $lastname, $email, $passwordHash, $privilege_level, $activation_token);

        $stmt->execute();

        if ($stmt->affected_rows > 0) {
            $status["Status"] = "Success";
        }

        $stmt->close();
    }

    return $status;
}

/**
 * Changes the user's password after verifying the old password.
 *
 * @param string $oldPassword The current password for verification.
 * @param string $newPassword The new password to be set.
 * @return array An array indicating whether the password change was successful ('Success' or 'Fail').
 *@global mysqli $mysqli Global database connection object.
 */
function changePassword(string $oldPassword, string $newPassword): array
{
    global $mysqli;
    $status = ["Status" => "Fail"];
    $userID = $_SESSION["ID"];
    if(!empty($oldPassword) && !empty($newPassword) && isLoggedIn() && verifyPassword($userID, $oldPassword)){
        $passwordHash = password_hash($newPassword, PASSWORD_DEFAULT);
        $stmt = $mysqli->prepare("UPDATE Users SET PasswordHash = ? WHERE ID = ?");
        $stmt->bind_param("si", $passwordHash, $userID);
        $stmt->execute();
        if ($stmt->affected_rows > 0) {
            $status["Status"] = "Success";
        }
        $stmt->close();
    }
    return $status;
}


/**
 * Updates user profile information in the database.
 *
 * @param string $firstName The new first name.
 * @param string $lastName The new last name.
 * @param string $nickname The new nickname.
 * @return array Status of the profile update ('Success' or 'Fail').
 *@global mysqli $mysqli Global database connection object.
 */
function updateUserProfile(string $firstName, string $lastName, string $nickname): array
{
    global $mysqli;
    $status = ["Status" => "Fail"];

    if (isLoggedIn() && !empty($firstName) && !empty($lastName) && !empty($nickname)) {

        $stmt = $mysqli->prepare("UPDATE Users SET FirstName = ?, LastName = ?, Nickname = ? WHERE ID = ?");
        /** @noinspection SpellCheckingInspection */
        $stmt->bind_param("ssssi", $firstName, $lastName, $nickname, $_SESSION["ID"]);
        $stmt->execute();

        if ($stmt->affected_rows > 0) {
            $status["Status"] = "Success";
        }
        else {
            $status["Status"] = "$firstName $lastName $nickname";
        }

        $stmt->close();
    }

    return $status;
}

/**
 * Updates the email address of the logged-in user after validation.
 *
 * @param string $email The new email address to update.
 * @return array Status of the email update ('Success' or 'Fail').
 *@global mysqli $mysqli Global database connection object.
 */
function updateUserEmail(string $email): array
{
    global $mysqli;
    $status = ["Status" => "Fail"];
    /** @noinspection SpellCheckingInspection */
    $validmail = false;

    if (isLoggedIn() && !empty($email)) {
        $userID = $_SESSION["ID"];

        $stmt_email_check = $mysqli->prepare("SELECT Email FROM Users WHERE ID = ?");
        $stmt_email_check->bind_param("i", $userID);
        $old_email = "";
        $stmt_email_check->bind_result($old_email);
        $stmt_email_check->execute();
        $stmt_email_check->fetch();
        $stmt_email_check->close();

        if ($email != $old_email) {
            if (isEmailAvailable($email)) {
                /** @noinspection SpellCheckingInspection */
                $validmail = true;
            }
        } else {
            /** @noinspection SpellCheckingInspection */
            $validmail = true;
        }

        if ($validmail) {
            $stmt = $mysqli->prepare("UPDATE Users SET Email = ? WHERE ID = ?");
            $stmt->bind_param("si", $email, $userID);
            $stmt->execute();

            if ($stmt->affected_rows > 0) {
                $status["Status"] = "Success";
            }

            $stmt->close();
        }
    }

    return $status;
}
/**
 * Retrieves and updates the current session with user information from the database.
 *
 * @return array Contains user information and status if the user is logged in.
 */
function getUserInfo(): array
{
    $output = ["Status" => "Fail"];
    if(isLoggedIn()) {
        global $mysqli;
        $userID = $_SESSION["ID"];
        $stmt = $mysqli->prepare("SELECT FirstName, LastName, Nickname, Email FROM Users WHERE ID = ?");
        $stmt->bind_param("i", $userID);
        $stmt->execute();

        $firstName = "";
        $lastName = "";
        $nickname = "";
        $email = "";

        $stmt->bind_result($firstName, $lastName, $nickname, $email);
        $stmt->fetch();
        $stmt->close();
        UpdateSession();
        $output["Status"] = "Success";

        $output["UserInfo"] = [
            "ID" => $userID,
            "FirstName" => $firstName,
            "LastName" => $lastName,
            "Nickname" => $nickname,
            "Email" => $email
        ];

    }
    return $output;
}

/**
 * Generates a specified number of activation codes for user registration and adds them to the database.
 *
 * @param int $count Number of activation codes to generate.
 * @return array An array containing the generated codes and status ('Success' or 'Fail').
 *@global mysqli $mysqli Global database connection object.
 */
function addActivationCodes(int $count): array
{
    global $mysqli;
    $activationCodes = [];

    $output = ["Status" => "Fail"]; // Default Status is "Fail"

    if ($count > 0 && isUserAdmin() && isLoggedIn()) {
        $stmt = $mysqli->prepare("INSERT INTO Users (ActivationToken, CreatedAt, CreatedBy) VALUES (?, NOW(), ?)");

        for ($i = 0; $i < $count; $i++) {
            $activationCode = generateActivationToken();
            $stmt->bind_param("si", $activationCode, $_SESSION["ID"]);
            $stmt->execute();

            if ($stmt->affected_rows > 0) {
                $activationCodes[] = [
                    "Code" => $activationCode,
                    "CreatedAt" => date("Y-m-d H:i:s"),
                    "CreatedBy" => $_SESSION["ID"]
                ];
                $output["Status"] = "Success";
                $output["ActivationCodes"] = $activationCodes;
            }
        }

        $stmt->close();
    }

    return $output;
}
/**
 * Lists all registered users, available only to user admins.
 *
 * @global mysqli $mysqli Global database connection object.
 * @return array An array containing user data and status.
 */
function listUsers(): array
{
    global $mysqli;
    $output = ["Status" => "Fail"]; // Default Status is "Fail"

    if (isUserAdmin()) {
        $users = [];
        $result = $mysqli->query("SELECT ID, FirstName, LastName, Nickname, Email, PrivilegeLevel, CreatedAt, RegisteredAt, LastLoginAt, LoginCount, CreatedBy FROM Users WHERE isActivated = 1");

        // Check if the query executed Successfully
        if ($result) {
            while ($row = $result->fetch_assoc()) {
                $users[] = $row;
            }
            $output["Status"] = "Success";
            $output["Users"] = $users;
        }
    }

    return $output;
}
/**
 * Lists activation codes available for assigning to new users, available only for user admins.
 *
 * @global mysqli $mysqli Global database connection object.
 * @return array An array containing activation codes and status.
 */
function listActivationCodes(): array
{
    global $mysqli;
    $output = ["Status" => "Fail"]; // Default Status is "Fail"

    if (isUserAdmin()) {
        $activationCodes = [];

        // Use placeholders in the query
        $query = "SELECT ActivationToken, CreatedAt, CreatedBy FROM Users WHERE isActivated = 0";
        $stmt = $mysqli->prepare($query);

        if ($stmt) {
            // Bind the result variables
            $activationToken = "";
            $createdAt = "";
            $createdBy = "";
            $stmt->bind_result($activationToken, $createdAt, $createdBy);

            // Execute the prepared statement
            $stmt->execute();

            // Fetch the results into the bound variables
            while ($stmt->fetch()) {
                $activationCodes[] = [
                    'ActivationToken' => $activationToken,
                    'CreatedAt' => $createdAt,
                    'CreatedBy' => $createdBy
                ];
            }

            // Check if any results were fetched
            if (!empty($activationCodes)) {
                $output["Status"] = "Success";
                $output["ActivationCodes"] = $activationCodes;
            }

            // Close the statement
            $stmt->close();
        }
    }
    return $output;
}

/**
 * Deletes a user by their ID, available only to user admins.
 *
 * @param int $userID The ID of the user to delete.
 * @return array Status of the delete operation ('Success' or 'Fail').
 *@global mysqli $mysqli Global database connection object.
 */
function deleteUser(int $userID): array
{
    global $mysqli;
    $status = ["Status" => "Fail"];
    if (!empty($userID) && isUserAdmin()) {
        $stmt = $mysqli->prepare("DELETE FROM Users WHERE ID = ?");
        $stmt->bind_param("i", $userID);
        $stmt->execute();
        if ($stmt->affected_rows > 0) {
            $status["Status"] = "Success";
        }
        $stmt->close();
    }
    return $status;
}
/**
 * Deletes an activation code, available only to user admins.
 *
 * @param string $activationCode The activation code to delete.
 * @return array Status of the delete operation ('Success' or 'Fail').
 *@global mysqli $mysqli Global database connection object.
 */
function deleteActivationCode(string $activationCode): array
{
    global $mysqli;
    $status = ["Status" => "Fail"];
    if (!empty($activationCode) && isUserAdmin()) {
        $stmt = $mysqli->prepare("DELETE FROM Users WHERE ActivationToken = ?");
        $stmt->bind_param("s", $activationCode);
        $stmt->execute();
        if ($stmt->affected_rows > 0) {
            $status["Status"] = "Success";
        }
        $stmt->close();
    }
    return $status;
}