/*
 * Copyright 2021 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef skgpu_DrawPass_DEFINED
#define skgpu_DrawPass_DEFINED

#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"

#include <memory>

namespace skgpu {

class BoundsManager;
class CommandBuffer;
class DrawList;
class Recorder;
class TextureProxy;

/**
 * DrawPass is analogous to a subpass, storing the drawing operations in the order they are stored
 * in the eventual command buffer, as well as the surface proxy the operations are intended for.
 * DrawPasses are grouped into a RenderPassTask for execution within a single render pass if the
 * subpasses are compatible with each other.
 *
 * Unlike DrawList, DrawPasses are immutable and represent as closely as possible what will be
 * stored in the command buffer while being flexible as to how the pass is incorporated. Depending
 * on the backend, it may even be able to write accumulated vertex and uniform data directly to
 * mapped GPU memory, although that is the extent of the CPU->GPU work they perform before they are
 * executed by a RenderPassTask.
 */
class DrawPass {
public:
    ~DrawPass();

    // TODO: Replace SDC with the SDC's surface proxy view
    static std::unique_ptr<DrawPass> Make(Recorder*,
                                          std::unique_ptr<DrawList>,
                                          sk_sp<TextureProxy>,
                                          const BoundsManager* occlusionCuller);

    // Defined relative to the top-left corner of the surface the DrawPass renders to, and is
    // contained within its dimensions.
    const SkIRect&      bounds() const { return fBounds;       }
    const TextureProxy* target() const { return fTarget.get(); }

    bool requiresDstTexture() const { return false;            }
    bool requiresStencil()    const { return fRequiresStencil; }
    bool requiresMSAA()       const { return fRequiresMSAA;    }

    size_t vertexBufferSize()  const { return 0; }
    size_t uniformBufferSize() const { return 0; }

    // TODO: Real return types, but it seems useful for DrawPass to report these as sets so that
    // task execution can compile necessary programs and track resources within a render pass.
    // Maybe these won't need to be exposed and RenderPassTask can do it per command as needed when
    // it iterates over the DrawPass contents.
    void samplers() const {}
    void programs() const {}

    // Transform this DrawPass into commands issued to the CommandBuffer. Assumes that the buffer
    // has already begun a correctly configured render pass matching this pass's target.
    void execute(CommandBuffer* buffer) const;

private:
    class SortKey;

    DrawPass(sk_sp<TextureProxy> target,
             const SkIRect& bounds,
             bool requiresStencil,
             bool requiresMSAA);

    sk_sp<TextureProxy> fTarget;
    SkIRect             fBounds;

    bool fRequiresStencil;
    bool fRequiresMSAA;

    // TODO: actually implement this. Will own the results of sorting/culling/merging a DrawList,
    // however that is actually specified.
};

} // namespace skgpu

#endif // skgpu_DrawPass_DEFINED