#pragma once

#include <mbgl/map/change.hpp>

#include <memory>

namespace mbgl {

namespace gl {
class Context;
} // namespace gl

class BackendScope;

class Backend {
public:
    Backend();
    virtual ~Backend();

    // Returns the backend's context which manages OpenGL state.
    gl::Context& getContext();

    // Called when the map needs to be rendered; the backend should call Map::render() at some point
    // in the near future. (Not called for Map::renderStill() mode.)
    virtual void invalidate() = 0;

    // Notifies a watcher of map x/y/scale/rotation changes.
    virtual void notifyMapChange(MapChange change);

protected:
    // Called when the backend's GL context needs to be made active or inactive. These are called,
    // as a matched pair, in four situations:
    //
    //   1. When releasing GL resources during Map destruction
    //   2. When calling a CustomLayerInitializeFunction, during Map::addLayer
    //   3. When calling a CustomLayerDeinitializeFunction, during Map::removeLayer
    //   4. When rendering for Map::renderStill
    //
    // They are *not* called for Map::render; it is assumed that the correct context is already
    // activated prior to calling Map::render.
    virtual void activate() = 0;
    virtual void deactivate() = 0;

private:
    const std::unique_ptr<gl::Context> context;

    friend class BackendScope;
};

class BackendScope {
public:
    BackendScope(Backend& backend_) : backend(backend_) {
        backend.activate();
    }

    ~BackendScope() {
        backend.deactivate();
    }

private:
    Backend& backend;
};

} // namespace mbgl