/*
 * Copyright 2022 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/gpu/graphite/PaintParams.h"

#include "include/core/SkColorSpace.h"
#include "include/core/SkShader.h"
#include "src/core/SkBlendModeBlender.h"
#include "src/core/SkBlenderBase.h"
#include "src/core/SkColorSpacePriv.h"
#include "src/effects/colorfilters/SkColorFilterBase.h"
#include "src/gpu/Blend.h"
#include "src/gpu/DitherUtils.h"
#include "src/gpu/graphite/KeyContext.h"
#include "src/gpu/graphite/KeyHelpers.h"
#include "src/gpu/graphite/Log.h"
#include "src/gpu/graphite/PaintParamsKey.h"
#include "src/gpu/graphite/PipelineData.h"
#include "src/gpu/graphite/RecorderPriv.h"
#include "src/gpu/graphite/Uniform.h"
#include "src/shaders/SkShaderBase.h"

namespace skgpu::graphite {

namespace {

// This should be kept in sync w/ SkPaintPriv::ShouldDither and PaintOption::shouldDither
bool should_dither(const PaintParams& p, SkColorType dstCT) {
    // The paint dither flag can veto.
    if (!p.dither()) {
        return false;
    }

    if (dstCT == kUnknown_SkColorType) {
        return false;
    }

    // We always dither 565 or 4444 when requested.
    if (dstCT == kRGB_565_SkColorType || dstCT == kARGB_4444_SkColorType) {
        return true;
    }

    // Otherwise, dither is only needed for non-const paints.
    return p.shader() && !as_SB(p.shader())->isConstant();
}

} // anonymous namespace

PaintParams::PaintParams(const SkPaint& paint,
                         sk_sp<SkBlender> primitiveBlender,
                         sk_sp<SkShader> clipShader,
                         DstReadRequirement dstReadReq,
                         bool skipColorXform)
        : fColor(paint.getColor4f())
        , fFinalBlender(paint.refBlender())
        , fShader(paint.refShader())
        , fColorFilter(paint.refColorFilter())
        , fPrimitiveBlender(std::move(primitiveBlender))
        , fClipShader(std::move(clipShader))
        , fDstReadReq(dstReadReq)
        , fSkipColorXform(skipColorXform)
        , fDither(paint.isDither()) {}

PaintParams::PaintParams(const PaintParams& other) = default;
PaintParams::~PaintParams() = default;
PaintParams& PaintParams::operator=(const PaintParams& other) = default;

std::optional<SkBlendMode> PaintParams::asFinalBlendMode() const {
    return fFinalBlender ? as_BB(fFinalBlender)->asBlendMode()
                         : SkBlendMode::kSrcOver;
}

sk_sp<SkBlender> PaintParams::refFinalBlender() const { return fFinalBlender; }

sk_sp<SkShader> PaintParams::refShader() const { return fShader; }

sk_sp<SkColorFilter> PaintParams::refColorFilter() const { return fColorFilter; }

sk_sp<SkBlender> PaintParams::refPrimitiveBlender() const { return fPrimitiveBlender; }

SkColor4f PaintParams::Color4fPrepForDst(SkColor4f srcColor, const SkColorInfo& dstColorInfo) {
    // xform from sRGB to the destination colorspace
    SkColorSpaceXformSteps steps(sk_srgb_singleton(),       kUnpremul_SkAlphaType,
                                 dstColorInfo.colorSpace(), kUnpremul_SkAlphaType);

    SkColor4f result = srcColor;
    steps.apply(result.vec());
    return result;
}

void Blend(const KeyContext& keyContext,
           PaintParamsKeyBuilder* keyBuilder,
           PipelineDataGatherer* gatherer,
           AddToKeyFn addBlendToKey,
           AddToKeyFn addSrcToKey,
           AddToKeyFn addDstToKey) {
    BlendShaderBlock::BeginBlock(keyContext, keyBuilder, gatherer);

        addSrcToKey();

        addDstToKey();

        addBlendToKey();

    keyBuilder->endBlock();  // BlendShaderBlock
}

void Compose(const KeyContext& keyContext,
             PaintParamsKeyBuilder* keyBuilder,
             PipelineDataGatherer* gatherer,
             AddToKeyFn addInnerToKey,
             AddToKeyFn addOuterToKey) {
    ComposeBlock::BeginBlock(keyContext, keyBuilder, gatherer);

        addInnerToKey();

        addOuterToKey();

    keyBuilder->endBlock();  // ComposeBlock
}

void AddKnownModeBlend(const KeyContext& keyContext,
                       PaintParamsKeyBuilder* builder,
                       PipelineDataGatherer* gatherer,
                       SkBlendMode bm) {
    SkASSERT(bm <= SkBlendMode::kLastCoeffMode);
    BuiltInCodeSnippetID id = static_cast<BuiltInCodeSnippetID>(kFixedFunctionBlendModeIDOffset +
                                                                static_cast<int>(bm));
    builder->addBlock(id);
}

void AddModeBlend(const KeyContext& keyContext,
                  PaintParamsKeyBuilder* builder,
                  PipelineDataGatherer* gatherer,
                  SkBlendMode bm) {
    SkSpan<const float> coeffs = skgpu::GetPorterDuffBlendConstants(bm);
    if (!coeffs.empty()) {
        CoeffBlenderBlock::AddBlock(keyContext, builder, gatherer, coeffs);
    } else {
        BlendModeBlenderBlock::AddBlock(keyContext, builder, gatherer, bm);
    }
}

void AddDstReadBlock(const KeyContext& keyContext,
                     PaintParamsKeyBuilder* builder,
                     PipelineDataGatherer* gatherer,
                     DstReadRequirement dstReadReq) {
    switch(dstReadReq) {
        case DstReadRequirement::kNone:
            SkASSERT(false);            // This should never be reached
            return;
        case DstReadRequirement::kTextureCopy:
            [[fallthrough]];
        case DstReadRequirement::kTextureSample:
            DstReadSampleBlock::AddBlock(keyContext, builder, gatherer, keyContext.dstTexture(),
                                         keyContext.dstOffset());
            break;
        case DstReadRequirement::kFramebufferFetch:
            builder->addBlock(BuiltInCodeSnippetID::kDstReadFetch);
            break;
    }
}

void AddDitherBlock(const KeyContext& keyContext,
                    PaintParamsKeyBuilder* builder,
                    PipelineDataGatherer* gatherer,
                    SkColorType ct) {
    static const SkBitmap gLUT = skgpu::MakeDitherLUT();

    sk_sp<TextureProxy> proxy = RecorderPriv::CreateCachedProxy(keyContext.recorder(), gLUT);
    if (keyContext.recorder() && !proxy) {
        SKGPU_LOG_W("Couldn't create dither shader's LUT");
        builder->addBlock(BuiltInCodeSnippetID::kPriorOutput);
        return;
    }

    DitherShaderBlock::DitherData data(skgpu::DitherRangeForConfig(ct), std::move(proxy));

    DitherShaderBlock::AddBlock(keyContext, builder, gatherer, data);
}

void PaintParams::addPaintColorToKey(const KeyContext& keyContext,
                                     PaintParamsKeyBuilder* keyBuilder,
                                     PipelineDataGatherer* gatherer) const {
    if (fShader) {
        AddToKey(keyContext, keyBuilder, gatherer, fShader.get());
    } else {
        RGBPaintColorBlock::AddBlock(keyContext, keyBuilder, gatherer);
    }
}

/**
 * Primitive blend blocks are used to blend either the paint color or the output of another shader
 * with a primitive color emitted by certain draw geometry calls (drawVertices, drawAtlas, etc.).
 * Dst: primitiveColor Src: Paint color/shader output
 */
void PaintParams::handlePrimitiveColor(const KeyContext& keyContext,
                                       PaintParamsKeyBuilder* keyBuilder,
                                       PipelineDataGatherer* gatherer) const {
    if (fPrimitiveBlender) {
        Blend(keyContext, keyBuilder, gatherer,
              /* addBlendToKey= */ [&] () -> void {
                  AddToKey(keyContext, keyBuilder, gatherer, fPrimitiveBlender.get());
              },
              /* addSrcToKey= */ [&]() -> void {
                  this->addPaintColorToKey(keyContext, keyBuilder, gatherer);
              },
              /* addDstToKey= */ [&]() -> void {
                  keyBuilder->addBlock(BuiltInCodeSnippetID::kPrimitiveColor);
              });
    } else {
        this->addPaintColorToKey(keyContext, keyBuilder, gatherer);
    }
}

// Apply the paint's alpha value.
void PaintParams::handlePaintAlpha(const KeyContext& keyContext,
                                   PaintParamsKeyBuilder* keyBuilder,
                                   PipelineDataGatherer* gatherer) const {

    if (!fShader && !fPrimitiveBlender) {
        // If there is no shader and no primitive blending the input to the colorFilter stage
        // is just the premultiplied paint color.
        SkPMColor4f paintColor = PaintParams::Color4fPrepForDst(fColor,
                                                                keyContext.dstColorInfo()).premul();
        SolidColorShaderBlock::AddBlock(keyContext, keyBuilder, gatherer, paintColor);
        return;
    }

    if (fColor.fA != 1.0f) {
        Blend(keyContext, keyBuilder, gatherer,
              /* addBlendToKey= */ [&] () -> void {
                  AddKnownModeBlend(keyContext, keyBuilder, gatherer, SkBlendMode::kSrcIn);
              },
              /* addSrcToKey= */ [&]() -> void {
                  this->handlePrimitiveColor(keyContext, keyBuilder, gatherer);
              },
              /* addDstToKey= */ [&]() -> void {
                  AlphaOnlyPaintColorBlock::AddBlock(keyContext, keyBuilder, gatherer);
              });
    } else {
        this->handlePrimitiveColor(keyContext, keyBuilder, gatherer);
    }
}

void PaintParams::handleColorFilter(const KeyContext& keyContext,
                                    PaintParamsKeyBuilder* builder,
                                    PipelineDataGatherer* gatherer) const {
    if (fColorFilter) {
        Compose(keyContext, builder, gatherer,
                /* addInnerToKey= */ [&]() -> void {
                    this->handlePaintAlpha(keyContext, builder, gatherer);
                },
                /* addOuterToKey= */ [&]() -> void {
                    AddToKey(keyContext, builder, gatherer, fColorFilter.get());
                });
    } else {
        this->handlePaintAlpha(keyContext, builder, gatherer);
    }
}

void PaintParams::handleDithering(const KeyContext& keyContext,
                                  PaintParamsKeyBuilder* builder,
                                  PipelineDataGatherer* gatherer) const {

#ifndef SK_IGNORE_GPU_DITHER
    SkColorType ct = keyContext.dstColorInfo().colorType();
    if (should_dither(*this, ct)) {
        Compose(keyContext, builder, gatherer,
                /* addInnerToKey= */ [&]() -> void {
                    this->handleColorFilter(keyContext, builder, gatherer);
                },
                /* addOuterToKey= */ [&]() -> void {
                    AddDitherBlock(keyContext, builder, gatherer, ct);
                });
    } else
#endif
    {
        this->handleColorFilter(keyContext, builder, gatherer);
    }
}

void PaintParams::handleDstRead(const KeyContext& keyContext,
                                PaintParamsKeyBuilder* builder,
                                PipelineDataGatherer* gatherer) const {
    if (fDstReadReq != DstReadRequirement::kNone) {
        Blend(keyContext, builder, gatherer,
              /* addBlendToKey= */ [&] () -> void {
                  if (fFinalBlender) {
                      AddToKey(keyContext, builder, gatherer, fFinalBlender.get());
                  } else {
                      AddKnownModeBlend(keyContext, builder, gatherer, SkBlendMode::kSrcOver);
                  }
              },
              /* addSrcToKey= */ [&]() -> void {
                  this->handleDithering(keyContext, builder, gatherer);
              },
              /* addDstToKey= */ [&]() -> void {
                  AddDstReadBlock(keyContext, builder, gatherer, fDstReadReq);
              });
    } else {
        this->handleDithering(keyContext, builder, gatherer);
    }
}

void PaintParams::toKey(const KeyContext& keyContext,
                        PaintParamsKeyBuilder* builder,
                        PipelineDataGatherer* gatherer) const {
    this->handleDstRead(keyContext, builder, gatherer);

    std::optional<SkBlendMode> finalBlendMode = this->asFinalBlendMode();
    if (fDstReadReq != DstReadRequirement::kNone) {
        // In this case the blend will have been handled by shader-based blending with the dstRead.
        finalBlendMode = SkBlendMode::kSrc;
    }

    if (fClipShader) {
        ClipShaderBlock::BeginBlock(keyContext, builder, gatherer);

            AddToKey(keyContext, builder, gatherer, fClipShader.get());

        builder->endBlock();
    }

    // Set the hardware blend mode.
    SkASSERT(finalBlendMode);
    BuiltInCodeSnippetID fixedFuncBlendModeID = static_cast<BuiltInCodeSnippetID>(
            kFixedFunctionBlendModeIDOffset + static_cast<int>(*finalBlendMode));

    builder->addBlock(fixedFuncBlendModeID);
}

} // namespace skgpu::graphite
