prepare for selectable backends

backend.h

@@ -0,0 +1,70 @@
+#pragma once
+
+#include <QObject>
+#include <QHash>
+#include <QString>
+#include <cstdint>
+#include <stdexcept>
+#include <string>
+#include <QUrl>
+
+class AiBackend: public QObject
+{
+	Q_OBJECT
+public:
+
+	class backend_error: public std::runtime_error
+	{
+	public:
+		backend_error(std::string err): runtime_error(err){}
+	};
+
+	class Request
+	{
+	protected:
+		inline static uint32_t idCounter = 0;
+		QString text;
+		uint32_t id;
+		void* userPtr;
+
+	public:
+		Request() = default;
+		Request(const QString& text, void* userPtr = nullptr);
+		const QString& getText() const;
+		uint32_t getId() const;
+		bool operator==(const Request& in);
+		void* getUserPtr() const;
+	};
+
+	class Response: public Request
+	{
+	private:
+		bool finished;
+
+	public:
+		Response() = default;
+		Response(QString text, uint32_t id, bool finished, void* userPtr = nullptr);
+		bool isFinished() const;
+		void setUserPtr(void* ptr);
+	};
+
+protected:
+	QHash<uint32_t, Request> m_requests;
+
+	void feedResponse(Response response);
+	bool isValidId(uint32_t id);
+	virtual void generateImpl(const Request& request) = 0;
+
+public:
+
+	virtual bool ready() = 0;
+	void generate(const Request& request);
+	virtual void abort(uint64_t id){(void)id;}
+	virtual void open(const QUrl& url){(void)url;};
+	Q_SIGNAL void gotResponse(Response response);
+
+	virtual ~AiBackend() = default;
+};
+
+Q_DECLARE_METATYPE(AiBackend::Response);
+Q_DECLARE_METATYPE(AiBackend::Request);