<?php
//Globals
$API_KEY            = "8E6375533B878";

function parse_input($data) 
{
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}

function getUserIP() 
{
    // Get real visitor IP behind CloudFlare network
    if (isset($_SERVER["HTTP_CF_CONNECTING_IP"])) 
    {
        $_SERVER['REMOTE_ADDR'] = $_SERVER["HTTP_CF_CONNECTING_IP"];
        $_SERVER['HTTP_CLIENT_IP'] = $_SERVER["HTTP_CF_CONNECTING_IP"];
    }

    $client  = @$_SERVER['HTTP_CLIENT_IP'];
    $forward = @$_SERVER['HTTP_X_FORWARDED_FOR'];
    $remote  = $_SERVER['REMOTE_ADDR'];

    if(filter_var($client, FILTER_VALIDATE_IP))
    {
        $ip = $client;
    }
    elseif(filter_var($forward, FILTER_VALIDATE_IP))
    {
        $ip = $forward;
    }
    else
    {
        $ip = $remote;
    }

    return $ip;
}

function WriteToLog($Client_Auth_Success) 
{
    //Get Date And Time
    $CurrentDateTime = date('h:i a d/m/Y');

    //Open File
    $myfile = fopen(__DIR__."/client.log", "a+") or die("Unable to open file!");

    //Get Data Ready that is to be written into file
    $dataToWriteInFile = $CurrentDateTime;		                    //TimeStamp
    $dataToWriteInFile .= " - IP: '" . getUserIP();	                    //Remote IP
    $dataToWriteInFile .= "', Auth: '" . (int)$Client_Auth_Success . "'";   //Auth Status
    $dataToWriteInFile .= "\n";

    //Write To File
    fwrite($myfile, $dataToWriteInFile);

    //Save File
    fclose($myfile);
}

function handle_AUTH_POST($CORRECT_API_KEY) 
{
    //if GET Request recieved
    if ($_SERVER["REQUEST_METHOD"] == "POST") 
    {
        //Verify Client
        $Received_API_Key = parse_input($_POST["AK"]);
    
        if (strcmp($Received_API_Key, $CORRECT_API_KEY) == 0) 
        {
            return true;
        }
    }

    return false;
}

function send_AllowedList_to_Client()
{
    echo "1,2,3,4,5";
}

function send_Invalid_APIKEY_Msg_to_Client()
{
    echo "Invalid API Key!";
}

function main() 
{
    global $API_KEY;

    $Client_Authenticated = handle_AUTH_POST($API_KEY);

    WriteToLog($Client_Authenticated);

    if ($Client_Authenticated)
    {
        send_AllowedList_to_Client();
    }
    else
    {
        send_Invalid_APIKEY_Msg_to_Client();
    }
}

main();
?>