io/fileview: add adapter support and JsonAdapter

src/io/jsonadapter.hpp

@@ -0,0 +1,116 @@
+#pragma once
+
+#include <qjsondocument.h>
+#include <qjsonobject.h>
+#include <qjsonvalue.h>
+#include <qjsvalue.h>
+#include <qlist.h>
+#include <qobjectdefs.h>
+#include <qqmlintegration.h>
+#include <qqmlparserstatus.h>
+#include <qstringview.h>
+#include <qtmetamacros.h>
+
+#include "fileview.hpp"
+
+namespace qs::io {
+
+/// See @@JsonAdapter.
+class JsonObject: public QObject {
+	Q_OBJECT;
+	QML_ELEMENT;
+};
+
+///! FileView adapter for accessing JSON files.
+/// JsonAdapter is a @@FileView adapter that exposes a JSON file as a set of QML
+/// properties that can be read and written to.
+///
+/// Each property defined in a JsonAdapter corresponds to a key in the JSON file.
+/// Supported property types are:
+/// - Primitves (`int`, `bool`, `string`, `real`)
+/// - Sub-object adapters (@@JsonObject$)
+/// - JSON objects and arrays, as a `var` type
+/// - Lists of any of the above (`list<string>` etc)
+///
+/// When the @@FileView$'s data is loaded, properties of a JsonAdapter or
+/// sub-object adapter (@@JsonObject$) are updated if their values have changed.
+///
+/// When properties of a JsonAdapter or sub-object adapter are changed from QML,
+/// @@FileView.adapterUpdated(s) is emitted, which may be used to save the file's new
+/// state (see @@FileView.writeAdapter()$).
+///
+/// ### Example
+/// ```qml
+/// @@FileView {
+///   path: "/path/to/file"
+///
+///   // when changes are made on disk, reload the file's content
+///   watchChanges: true
+///   onFileChanged: reload()
+///
+///   // when changes are made to properties in the adapter, save them
+///   onAdapterUpdated: writeAdapter()
+///
+///   JsonAdapter {
+///     property string myStringProperty: "default value"
+///     onMyStringPropertyChanged: {
+///       console.log("myStringProperty was changed via qml or on disk")
+///     }
+///
+///     property list<string> stringList: [ "default", "value" ]
+///
+///     property JsonObject subObject: JsonObject {
+///       property string subObjectProperty: "default value"
+///       onSubObjectPropertyChanged: console.log("same as above")
+///     }
+///
+///     // works the same way as subObject
+///     property var inlineJson: { "a": "b" }
+///   }
+/// }
+/// ```
+///
+/// The above snippet produces the JSON document below:
+/// ```json
+/// {
+///    "myStringProperty": "default value",
+///    "stringList": [
+///      "default",
+///      "value"
+///    ],
+///    "subObject": {
+///      "subObjectProperty": "default value"
+///    },
+///    "inlineJson": {
+///      "a": "b"
+///    }
+/// }
+/// ```
+class JsonAdapter
+    : public FileViewAdapter
+    , public QQmlParserStatus {
+	Q_OBJECT;
+	QML_ELEMENT;
+
+public:
+	void classBegin() override {}
+	void componentComplete() override;
+
+	void deserializeAdapter(const QByteArray& data) override;
+	[[nodiscard]] QByteArray serializeAdapter() override;
+
+private slots:
+	void onPropertyChanged();
+
+private:
+	void connectNotifiers();
+	void connectNotifiersRec(int notifySlot, QObject* obj, const QMetaObject* base);
+	void deserializeRec(const QJsonObject& json, QObject* obj, const QMetaObject* base);
+	[[nodiscard]] QJsonObject serializeRec(const QObject* obj, const QMetaObject* base) const;
+
+	bool changesBlocked = false;
+	QList<JsonObject*> createdObjects;
+	QList<JsonObject*> oldCreatedObjects;
+};
+
+} // namespace qs::io