<?php
include('db.php');

function sendResponse($message, $type = "1") {
    if($type == "1") {
        $_SESSION['success_msg'] = $message;
    }
    else {
        $_SESSION['error_msg'] = $message;
    }
    echo "<script>window.location.href='bulk-assign-subject.php';</script>";
    exit;
}

if (!isset($_SESSION['userData'])) {
    sendResponse("Session expired. Please log in again.", "0"); exit;
}

if (!isset($_POST['students']) || !isset($_POST['subjects'])) {
    sendResponse("Please select at least one student and one subject.", "0"); exit;
}

$students = $_POST['students'];
$subjects = $_POST['subjects'];

$assigning = isset($_POST['btnSubmit']);
$removing = isset($_POST['btnRemove']);

if (!$assigning && !$removing) {
    sendResponse("Invalid action.", "0"); exit;
}

$successCount = 0;
$failCount = 0;
//echo"<pre>"; print_r($_POST); exit;
foreach ($students as $studentID) {
    foreach ($subjects as $subjectID) {
        $studentID = $studentID;
        $subjectID = $subjectID;
        if ($assigning) {
            $check = mysqli_query($con, "SELECT * FROM Bridge_SubjectStudentWise_Table WHERE Student_ID = '$studentID' AND Subject_ID = '$subjectID'");
            if (mysqli_num_rows($check) == 0) {
                $insert = mysqli_query($con, "INSERT INTO Bridge_SubjectStudentWise_Table (Student_ID, Subject_ID) VALUES ('$studentID', '$subjectID')");
                if ($insert) {
                    $successCount++;
                } else {
                    $failCount++;
                }
            }
        }

        if ($removing) {
            $delete = mysqli_query($con, "DELETE FROM Bridge_SubjectStudentWise_Table WHERE Student_ID = '$studentID' AND Subject_ID = '$subjectID'");
            if ($delete) {
                $successCount++;
            } else {
                $failCount++;
            }
        }
    }
}

$actionText = $assigning ? 'assigned' : 'removed';
sendResponse("Subjects $actionText successfully for $successCount pair(s). Failed: $failCount.", "1");
?>