<?php
/**
 * deleteRelation.php - Löscht eine Relation
 * 
 * Parameter (POST):
 * - IDAnchor: ID des Ausgangseintrags
 * - LinkingID: ID der Relation in der Linking-Tabelle
 */

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");

$idAnchor = isset($_POST['IDAnchor']) ? intval($_POST['IDAnchor']) : 0;
$linkingId = isset($_POST['LinkingID']) ? intval($_POST['LinkingID']) : 0;

if ($linkingId === 0) {
    echo json_encode(['success' => false, 'error' => 'LinkingID muss angegeben werden']);
    exit();
}

// Zuerst Relation lesen für reziproke Löschung
$getSql = "SELECT IDAnchor, IDEntry, Relationtype FROM Linking WHERE ID = $linkingId";
$getResult = mysqli_query($conn, $getSql);

if (!$getResult || mysqli_num_rows($getResult) === 0) {
    echo json_encode(['success' => false, 'error' => 'Relation nicht gefunden']);
    mysqli_close($conn);
    exit();
}

$relation = mysqli_fetch_assoc($getResult);
$targetId = $relation['IDEntry'];
$relationType = $relation['Relationtype'];

// Reziproke Relation bestimmen
$reciprocalType = null;
switch ($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;
}

// Relation löschen
$deleteSql = "DELETE FROM Linking WHERE ID = $linkingId";

if (mysqli_query($conn, $deleteSql)) {
    $affectedRows = mysqli_affected_rows($conn);
    
    // Reziproke Relation ebenfalls löschen
    if ($reciprocalType) {
        $deleteRecSql = "DELETE FROM Linking WHERE IDAnchor = $targetId AND IDEntry = " . $relation['IDAnchor'] . " AND Relationtype = '$reciprocalType'";
        mysqli_query($conn, $deleteRecSql);
    }
    
    echo json_encode([
        'success' => true, 
        'message' => 'Relation erfolgreich gelöscht',
        'affected' => $affectedRows
    ]);
} else {
    echo json_encode(['success' => false, 'error' => 'Fehler beim Löschen: ' . mysqli_error($conn)]);
}

mysqli_close($conn);
?>