<?php
/**
 * writeNewRelation.php - Speichert eine neue Relation
 * 
 * Parameter (POST):
 * - IDAnchor: ID des Ausgangseintrags
 * - IDEntry: ID des Zieleintrags
 * - Relationtype: Art der Relation (BT, NT, RT, USE, UF)
 */

header('Content-Type: application/json; charset=utf-8');

include "db_connection.php";

$conn = mysqli_connect(HOST, USER, PASSWORD, DATABASE);
if (mysqli_connect_errno()) {
    echo json_encode(['success' => false, 'error' => 'Datenbankverbindung fehlgeschlagen']);
    exit();
}

mysqli_set_charset($conn, "utf8");

// Parameter aus JavaScript (AnchorID, relationType, relationID)
$idAnchor = isset($_POST['AnchorID']) ? intval($_POST['AnchorID']) : 0;
if ($idAnchor === 0) {
    $idAnchor = isset($_POST['IDAnchor']) ? intval($_POST['IDAnchor']) : 0;
}

$idEntry = isset($_POST['relationID']) ? intval($_POST['relationID']) : 0;
if ($idEntry === 0) {
    $idEntry = isset($_POST['IDEntry']) ? intval($_POST['IDEntry']) : 0;
}

$relationtype = isset($_POST['relationType']) ? trim($_POST['relationType']) : '';
if (empty($relationtype)) {
    $relationtype = isset($_POST['Relationtype']) ? trim($_POST['Relationtype']) : '';
}

if ($idAnchor === 0 || $idEntry === 0) {
    echo json_encode(['success' => false, 'error' => 'IDAnchor und IDEntry müssen angegeben werden']);
    exit();
}

if (empty($relationtype)) {
    echo json_encode(['success' => false, 'error' => 'Relationtype muss angegeben werden']);
    exit();
}

// Erlaubte Relationstypen
$allowedTypes = ['BT', 'NT', 'RT', 'USE', 'UF'];
if (!in_array($relationtype, $allowedTypes)) {
    echo json_encode(['success' => false, 'error' => 'Ungültiger Relationstyp']);
    exit();
}

// Prüfen ob Relation bereits existiert
$checkSql = "SELECT ID FROM Linking WHERE IDAnchor = $idAnchor AND IDEntry = $idEntry AND Relationtype = '" . mysqli_real_escape_string($conn, $relationtype) . "'";
$checkResult = mysqli_query($conn, $checkSql);

if ($checkResult && mysqli_num_rows($checkResult) > 0) {
    echo json_encode(['success' => false, 'error' => 'Diese Relation existiert bereits']);
    mysqli_close($conn);
    exit();
}

// Relation einfügen
$insertSql = "INSERT INTO Linking (IDAnchor, IDEntry, Relationtype) VALUES ($idAnchor, $idEntry, '" . mysqli_real_escape_string($conn, $relationtype) . "')";

if (mysqli_query($conn, $insertSql)) {
    $newId = mysqli_insert_id($conn);
    
    // Reziproke Relation erstellen (BT <-> NT, RT <-> RT)
    $reciprocalType = null;
    switch ($relationtype) {
        case 'BT':
            $reciprocalType = 'NT';
            break;
        case 'NT':
            $reciprocalType = 'BT';
            break;
        case 'RT':
            $reciprocalType = 'RT';
            break;
        case 'USE':
            $reciprocalType = 'UF';
            break;
        case 'UF':
            $reciprocalType = 'USE';
            break;
    }
    
    if ($reciprocalType) {
        // Prüfen ob reziproke Relation schon existiert
        $checkRecSql = "SELECT ID FROM Linking WHERE IDAnchor = $idEntry AND IDEntry = $idAnchor AND Relationtype = '$reciprocalType'";
        $checkRecResult = mysqli_query($conn, $checkRecSql);
        
        if (!$checkRecResult || mysqli_num_rows($checkRecResult) === 0) {
            $insertRecSql = "INSERT INTO Linking (IDAnchor, IDEntry, Relationtype) VALUES ($idEntry, $idAnchor, '$reciprocalType')";
            mysqli_query($conn, $insertRecSql);
        }
    }
    
    echo json_encode([
        'success' => true, 
        'message' => 'Relation erfolgreich erstellt',
        'id' => $newId
    ]);
} else {
    echo json_encode(['success' => false, 'error' => 'Fehler beim Speichern: ' . mysqli_error($conn)]);
}

mysqli_close($conn);
?>