/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "GrConfigConversionEffect.h"
#include "GrContext.h"
#include "GrDrawContext.h"
#include "GrInvariantOutput.h"
#include "GrSimpleTextureEffect.h"
#include "SkMatrix.h"
#include "glsl/GrGLSLFragmentProcessor.h"
#include "glsl/GrGLSLFragmentShaderBuilder.h"

class GrGLConfigConversionEffect : public GrGLSLFragmentProcessor {
public:
    void emitCode(EmitArgs& args) override {
        const GrConfigConversionEffect& cce = args.fFp.cast<GrConfigConversionEffect>();
        const GrSwizzle& swizzle = cce.swizzle();
        GrConfigConversionEffect::PMConversion pmConversion = cce.pmConversion();

        // Using highp for GLES here in order to avoid some precision issues on specific GPUs.
        GrGLSLShaderVar tmpVar("tmpColor", kVec4f_GrSLType, 0, kHigh_GrSLPrecision);
        SkString tmpDecl;
        tmpVar.appendDecl(args.fGLSLCaps, &tmpDecl);

        GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;

        fragBuilder->codeAppendf("%s;", tmpDecl.c_str());

        fragBuilder->codeAppendf("%s = ", tmpVar.c_str());
        fragBuilder->appendTextureLookup(args.fTexSamplers[0], args.fCoords[0].c_str(),
                                       args.fCoords[0].getType());
        fragBuilder->codeAppend(";");

        if (GrConfigConversionEffect::kNone_PMConversion == pmConversion) {
            SkASSERT(GrSwizzle::RGBA() != swizzle);
            fragBuilder->codeAppendf("%s = %s.%s;", args.fOutputColor, tmpVar.c_str(),
                                     swizzle.c_str());
        } else {
            switch (pmConversion) {
                case GrConfigConversionEffect::kMulByAlpha_RoundUp_PMConversion:
                    fragBuilder->codeAppendf(
                        "%s = vec4(ceil(%s.rgb * %s.a * 255.0) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str());
                    break;
                case GrConfigConversionEffect::kMulByAlpha_RoundDown_PMConversion:
                    // Add a compensation(0.001) here to avoid the side effect of the floor operation.
                    // In Intel GPUs, the integer value converted from floor(%s.r * 255.0) / 255.0
                    // is less than the integer value converted from  %s.r by 1 when the %s.r is
                    // converted from the integer value 2^n, such as 1, 2, 4, 8, etc.
                    fragBuilder->codeAppendf(
                        "%s = vec4(floor(%s.rgb * %s.a * 255.0 + 0.001) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str());

                    break;
                case GrConfigConversionEffect::kDivByAlpha_RoundUp_PMConversion:
                    fragBuilder->codeAppendf(
                        "%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(ceil(%s.rgb / %s.a * 255.0) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(),
                        tmpVar.c_str());
                    break;
                case GrConfigConversionEffect::kDivByAlpha_RoundDown_PMConversion:
                    fragBuilder->codeAppendf(
                        "%s = %s.a <= 0.0 ? vec4(0,0,0,0) : vec4(floor(%s.rgb / %s.a * 255.0) / 255.0, %s.a);",
                        tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(), tmpVar.c_str(),
                        tmpVar.c_str());
                    break;
                default:
                    SkFAIL("Unknown conversion op.");
                    break;
            }
            fragBuilder->codeAppendf("%s = %s.%s;", args.fOutputColor, tmpVar.c_str(),
                                     swizzle.c_str());
        }
        SkString modulate;
        GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
        fragBuilder->codeAppend(modulate.c_str());
    }

    static inline void GenKey(const GrProcessor& processor, const GrGLSLCaps&,
                              GrProcessorKeyBuilder* b) {
        const GrConfigConversionEffect& cce = processor.cast<GrConfigConversionEffect>();
        uint32_t key = (cce.swizzle().asKey()) | (cce.pmConversion() << 16);
        b->add32(key);
    }

private:
    typedef GrGLSLFragmentProcessor INHERITED;

};

///////////////////////////////////////////////////////////////////////////////

GrConfigConversionEffect::GrConfigConversionEffect(GrTexture* texture,
                                                   const GrSwizzle& swizzle,
                                                   PMConversion pmConversion,
                                                   const SkMatrix& matrix)
    : INHERITED(texture, nullptr, matrix)
    , fSwizzle(swizzle)
    , fPMConversion(pmConversion) {
    this->initClassID<GrConfigConversionEffect>();
    // We expect to get here with non-BGRA/RGBA only if we're doing not doing a premul/unpremul
    // conversion.
    SkASSERT((kRGBA_8888_GrPixelConfig == texture->config() ||
              kBGRA_8888_GrPixelConfig == texture->config()) ||
              kNone_PMConversion == pmConversion);
    // Why did we pollute our texture cache instead of using a GrSingleTextureEffect?
    SkASSERT(swizzle != GrSwizzle::RGBA() || kNone_PMConversion != pmConversion);
}

bool GrConfigConversionEffect::onIsEqual(const GrFragmentProcessor& s) const {
    const GrConfigConversionEffect& other = s.cast<GrConfigConversionEffect>();
    return other.fSwizzle == fSwizzle &&
           other.fPMConversion == fPMConversion;
}

void GrConfigConversionEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
    this->updateInvariantOutputForModulation(inout);
}

///////////////////////////////////////////////////////////////////////////////

GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrConfigConversionEffect);

sk_sp<GrFragmentProcessor> GrConfigConversionEffect::TestCreate(GrProcessorTestData* d) {
    PMConversion pmConv = static_cast<PMConversion>(d->fRandom->nextULessThan(kPMConversionCnt));
    GrSwizzle swizzle;
    do {
        swizzle = GrSwizzle::CreateRandom(d->fRandom);
    } while (pmConv == kNone_PMConversion && swizzle == GrSwizzle::RGBA());
    return sk_sp<GrFragmentProcessor>(
        new GrConfigConversionEffect(d->fTextures[GrProcessorUnitTest::kSkiaPMTextureIdx],
                                     swizzle, pmConv, GrTest::TestMatrix(d->fRandom)));
}

///////////////////////////////////////////////////////////////////////////////

void GrConfigConversionEffect::onGetGLSLProcessorKey(const GrGLSLCaps& caps,
                                                     GrProcessorKeyBuilder* b) const {
    GrGLConfigConversionEffect::GenKey(*this, caps, b);
}

GrGLSLFragmentProcessor* GrConfigConversionEffect::onCreateGLSLInstance() const {
    return new GrGLConfigConversionEffect();
}


void GrConfigConversionEffect::TestForPreservingPMConversions(GrContext* context,
                                                              PMConversion* pmToUPMRule,
                                                              PMConversion* upmToPMRule) {
    *pmToUPMRule = kNone_PMConversion;
    *upmToPMRule = kNone_PMConversion;
    static constexpr int kSize = 256;
    static constexpr GrPixelConfig kConfig = kRGBA_8888_GrPixelConfig;
    SkAutoTMalloc<uint32_t> data(kSize * kSize * 3);
    uint32_t* srcData = data.get();
    uint32_t* firstRead = data.get() + kSize * kSize;
    uint32_t* secondRead = data.get() + 2 * kSize * kSize;

    // Fill with every possible premultiplied A, color channel value. There will be 256-y duplicate
    // values in row y. We set r,g, and b to the same value since they are handled identically.
    for (int y = 0; y < kSize; ++y) {
        for (int x = 0; x < kSize; ++x) {
            uint8_t* color = reinterpret_cast<uint8_t*>(&srcData[kSize*y + x]);
            color[3] = y;
            color[2] = SkTMin(x, y);
            color[1] = SkTMin(x, y);
            color[0] = SkTMin(x, y);
        }
    }

    sk_sp<GrDrawContext> readDC(context->newDrawContext(SkBackingFit::kExact, kSize, kSize,
                                                        kConfig));
    sk_sp<GrDrawContext> tempDC(context->newDrawContext(SkBackingFit::kExact, kSize, kSize,
                                                        kConfig));
    if (!readDC || !tempDC) {
        return;
    }
    GrSurfaceDesc desc;
    desc.fWidth = kSize;
    desc.fHeight = kSize;
    desc.fConfig = kConfig;
    SkAutoTUnref<GrTexture> dataTex(context->textureProvider()->createTexture(
        desc, SkBudgeted::kYes, data, 0));
    if (!dataTex.get()) {
        return;
    }

    static const PMConversion kConversionRules[][2] = {
        {kDivByAlpha_RoundDown_PMConversion, kMulByAlpha_RoundUp_PMConversion},
        {kDivByAlpha_RoundUp_PMConversion, kMulByAlpha_RoundDown_PMConversion},
    };

    bool failed = true;

    for (size_t i = 0; i < SK_ARRAY_COUNT(kConversionRules) && failed; ++i) {
        *pmToUPMRule = kConversionRules[i][0];
        *upmToPMRule = kConversionRules[i][1];

        static const SkRect kDstRect = SkRect::MakeIWH(kSize, kSize);
        static const SkRect kSrcRect = SkRect::MakeIWH(1, 1);
        // We do a PM->UPM draw from dataTex to readTex and read the data. Then we do a UPM->PM draw
        // from readTex to tempTex followed by a PM->UPM draw to readTex and finally read the data.
        // We then verify that two reads produced the same values.

        GrPaint paint1;
        GrPaint paint2;
        GrPaint paint3;
        sk_sp<GrFragmentProcessor> pmToUPM1(new GrConfigConversionEffect(
                dataTex, GrSwizzle::RGBA(), *pmToUPMRule, SkMatrix::I()));
        sk_sp<GrFragmentProcessor> upmToPM(new GrConfigConversionEffect(
                readDC->asTexture().get(), GrSwizzle::RGBA(), *upmToPMRule, SkMatrix::I()));
        sk_sp<GrFragmentProcessor> pmToUPM2(new GrConfigConversionEffect(
                tempDC->asTexture().get(), GrSwizzle::RGBA(), *pmToUPMRule, SkMatrix::I()));

        paint1.addColorFragmentProcessor(std::move(pmToUPM1));
        paint1.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);

        readDC->fillRectToRect(GrNoClip(), paint1, SkMatrix::I(), kDstRect, kSrcRect);

        readDC->asTexture()->readPixels(0, 0, kSize, kSize, kConfig, firstRead);

        paint2.addColorFragmentProcessor(std::move(upmToPM));
        paint2.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);

        tempDC->fillRectToRect(GrNoClip(), paint2, SkMatrix::I(), kDstRect, kSrcRect);

        paint3.addColorFragmentProcessor(std::move(pmToUPM2));
        paint3.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);

        readDC->fillRectToRect(GrNoClip(), paint3, SkMatrix::I(), kDstRect, kSrcRect);

        readDC->asTexture()->readPixels(0, 0, kSize, kSize, kConfig, secondRead);

        failed = false;
        for (int y = 0; y < kSize && !failed; ++y) {
            for (int x = 0; x <= y; ++x) {
                if (firstRead[kSize * y + x] != secondRead[kSize * y + x]) {
                    failed = true;
                    break;
                }
            }
        }
    }
    if (failed) {
        *pmToUPMRule = kNone_PMConversion;
        *upmToPMRule = kNone_PMConversion;
    }
}

sk_sp<GrFragmentProcessor> GrConfigConversionEffect::Make(GrTexture* texture,
                                                          const GrSwizzle& swizzle,
                                                          PMConversion pmConversion,
                                                          const SkMatrix& matrix) {
    if (swizzle == GrSwizzle::RGBA() && kNone_PMConversion == pmConversion) {
        // If we returned a GrConfigConversionEffect that was equivalent to a GrSimpleTextureEffect
        // then we may pollute our texture cache with redundant shaders. So in the case that no
        // conversions were requested we instead return a GrSimpleTextureEffect.
        return GrSimpleTextureEffect::Make(texture, nullptr, matrix);
    } else {
        if (kRGBA_8888_GrPixelConfig != texture->config() &&
            kBGRA_8888_GrPixelConfig != texture->config() &&
            kNone_PMConversion != pmConversion) {
            // The PM conversions assume colors are 0..255
            return nullptr;
        }
        return sk_sp<GrFragmentProcessor>(
            new GrConfigConversionEffect(texture, swizzle, pmConversion, matrix));
    }
}