iOS: Extract basic devicectl output processing

Put creating the JSON document and error parsing into a separate
function.

Change-Id: I257f82249a07220467c33220c6b8e4650266b8d9
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/ios/devicectlutils.cpp

@@ -0,0 +1,47 @@
+// Copyright (C) 2024 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#include "devicectlutils.h"
+
+#include "iostr.h"
+
+#include <QJsonDocument>
+
+Utils::expected_str<QJsonValue> Ios::Internal::parseDevicectlResult(const QByteArray &rawOutput)
+{
+    // there can be crap (progress info) at front and/or end
+    const int firstCurly = rawOutput.indexOf('{');
+    const int start = std::max(firstCurly, 0);
+    const int lastCurly = rawOutput.lastIndexOf('}');
+    const int end = lastCurly >= 0 ? lastCurly : rawOutput.size() - 1;
+    QJsonParseError parseError;
+    auto jsonOutput = QJsonDocument::fromJson(rawOutput.sliced(start, end - start + 1), &parseError);
+    if (jsonOutput.isNull()) {
+        // parse error
+        return Utils::make_unexpected(
+            Tr::tr("Failed to parse devicectl output: %1.").arg(parseError.errorString()));
+    }
+    const QJsonValue errorValue = jsonOutput["error"];
+    if (!errorValue.isUndefined()) {
+        // error
+        QString error
+            = Tr::tr("Operation failed: %1.")
+                  .arg(errorValue["userInfo"]["NSLocalizedDescription"]["string"].toString());
+        const QJsonValue userInfo
+            = errorValue["userInfo"]["NSUnderlyingError"]["error"]["userInfo"];
+        const QList<QJsonValue> moreInfo{userInfo["NSLocalizedDescription"]["string"],
+                                         userInfo["NSLocalizedFailureReason"]["string"],
+                                         userInfo["NSLocalizedRecoverySuggestion"]["string"]};
+        for (const QJsonValue &v : moreInfo) {
+            if (!v.isUndefined())
+                error += "\n" + v.toString();
+        }
+        return Utils::make_unexpected(error);
+    }
+    const QJsonValue resultValue = jsonOutput["result"];
+    if (resultValue.isUndefined()) {
+        return Utils::make_unexpected(
+            Tr::tr("Failed to parse devicectl output: 'result' is missing"));
+    }
+    return resultValue;
+}