/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Creates an openGL frame buffer.

    @tags{OpenGL}
*/
class JUCE_API  OpenGLFrameBuffer
{
public:
    /** Creates an uninitialised buffer.
        To actually allocate the buffer, use initialise().
    */
    OpenGLFrameBuffer();

    /** Destructor. */
    ~OpenGLFrameBuffer();

    //==============================================================================
    /** Tries to allocates a buffer of the given size.
        Note that a valid openGL context must be selected when you call this method,
        or it will fail.
    */
    bool initialise (OpenGLContext& context, int width, int height);

    /** Tries to allocates a buffer containing a copy of a given image.
        Note that a valid openGL context must be selected when you call this method,
        or it will fail.
    */
    bool initialise (OpenGLContext& context, const Image& content);

    /** Tries to allocate a copy of another framebuffer.
    */
    bool initialise (OpenGLFrameBuffer& other);

    /** Releases the buffer, if one has been allocated.
        Any saved state that was created with saveAndRelease() will also be freed by this call.
    */
    void release();

    /** If the framebuffer is active, this will save a stashed copy of its contents in main memory,
        and will release the GL buffer.
        After saving, the original state can be restored again by calling reloadSavedCopy().
    */
    void saveAndRelease();

    /** Restores the framebuffer content that was previously saved using saveAndRelease().
        After saving to main memory, the original state can be restored by calling restoreToGPUMemory().
    */
    bool reloadSavedCopy (OpenGLContext& context);

    //==============================================================================
    /** Returns true if a valid buffer has been allocated. */
    bool isValid() const noexcept                       { return pimpl != nullptr; }

    /** Returns the width of the buffer. */
    int getWidth() const noexcept;

    /** Returns the height of the buffer. */
    int getHeight() const noexcept;

    /** Returns the texture ID number for using this buffer as a texture. */
    GLuint getTextureID() const noexcept;

    //==============================================================================
    /** Selects this buffer as the current OpenGL rendering target. */
    bool makeCurrentRenderingTarget();

    /** Deselects this buffer as the current OpenGL rendering target. */
    void releaseAsRenderingTarget();

    /** Returns the ID of this framebuffer, or 0 if it isn't initialised. */
    GLuint getFrameBufferID() const noexcept;

    /** Returns the current frame buffer ID for the current context. */
    static GLuint getCurrentFrameBufferTarget() noexcept;

    /** Clears the framebuffer with the specified colour. */
    void clear (Colour colour);

    /** Selects the framebuffer as the current target, and clears it to transparent. */
    void makeCurrentAndClear();

    /** Reads an area of pixels from the framebuffer into a 32-bit ARGB pixel array.
        The lineStride is measured as a number of pixels, not bytes - pass a stride
        of 0 to indicate a packed array.
    */
    bool readPixels (PixelARGB* targetData, const Rectangle<int>& sourceArea);

    /** Writes an area of pixels into the framebuffer from a specified pixel array.
        The lineStride is measured as a number of pixels, not bytes - pass a stride
        of 0 to indicate a packed array.
    */
    bool writePixels (const PixelARGB* srcData, const Rectangle<int>& targetArea);

private:
    class Pimpl;
    std::unique_ptr<Pimpl> pimpl;

    class SavedState;
    std::unique_ptr<SavedState> savedState;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (OpenGLFrameBuffer)
};

} // namespace juce