/*
 * Copyright 2012 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/effects/SkMagnifierImageFilter.h"

#include "include/core/SkBitmap.h"
#include "include/private/SkColorData.h"
#include "include/private/SkTPin.h"
#include "src/core/SkImageFilter_Base.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSpecialImage.h"
#include "src/core/SkValidationUtils.h"
#include "src/core/SkWriteBuffer.h"

////////////////////////////////////////////////////////////////////////////////
#if SK_SUPPORT_GPU
#include "src/gpu/GrColorSpaceXform.h"
#include "src/gpu/effects/GrTextureEffect.h"
#include "src/gpu/effects/generated/GrMagnifierEffect.h"
#include "src/gpu/glsl/GrGLSLFragmentProcessor.h"
#include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
#include "src/gpu/glsl/GrGLSLProgramDataManager.h"
#include "src/gpu/glsl/GrGLSLUniformHandler.h"
#endif

namespace {

class SkMagnifierImageFilterImpl final : public SkImageFilter_Base {
public:
    SkMagnifierImageFilterImpl(const SkRect& srcRect, SkScalar inset, sk_sp<SkImageFilter> input,
                               const CropRect* cropRect)
            : INHERITED(&input, 1, cropRect)
            , fSrcRect(srcRect)
            , fInset(inset) {
        SkASSERT(srcRect.left() >= 0 && srcRect.top() >= 0 && inset >= 0);
    }

protected:
    void flatten(SkWriteBuffer&) const override;

    sk_sp<SkSpecialImage> onFilterImage(const Context&, SkIPoint* offset) const override;

private:
    friend void SkMagnifierImageFilter::RegisterFlattenables();
    SK_FLATTENABLE_HOOKS(SkMagnifierImageFilterImpl)

    SkRect   fSrcRect;
    SkScalar fInset;

    using INHERITED = SkImageFilter_Base;
};

} // end namespace

sk_sp<SkImageFilter> SkMagnifierImageFilter::Make(const SkRect& srcRect, SkScalar inset,
                                                  sk_sp<SkImageFilter> input,
                                                  const SkImageFilter::CropRect* cropRect) {
    if (!SkScalarIsFinite(inset) || !SkIsValidRect(srcRect)) {
        return nullptr;
    }
    if (inset < 0) {
        return nullptr;
    }
    // Negative numbers in src rect are not supported
    if (srcRect.fLeft < 0 || srcRect.fTop < 0) {
        return nullptr;
    }
    return sk_sp<SkImageFilter>(new SkMagnifierImageFilterImpl(srcRect, inset, std::move(input),
                                                               cropRect));
}

void SkMagnifierImageFilter::RegisterFlattenables() {
    SK_REGISTER_FLATTENABLE(SkMagnifierImageFilterImpl);
    // TODO (michaelludwig) - Remove after grace period for SKPs to stop using old name
    SkFlattenable::Register("SkMagnifierImageFilter", SkMagnifierImageFilterImpl::CreateProc);
}

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

sk_sp<SkFlattenable> SkMagnifierImageFilterImpl::CreateProc(SkReadBuffer& buffer) {
    SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 1);
    SkRect src;
    buffer.readRect(&src);
    return SkMagnifierImageFilter::Make(src, buffer.readScalar(), common.getInput(0),
                                        &common.cropRect());
}

void SkMagnifierImageFilterImpl::flatten(SkWriteBuffer& buffer) const {
    this->INHERITED::flatten(buffer);
    buffer.writeRect(fSrcRect);
    buffer.writeScalar(fInset);
}

sk_sp<SkSpecialImage> SkMagnifierImageFilterImpl::onFilterImage(const Context& ctx,
                                                                SkIPoint* offset) const {
    SkIPoint inputOffset = SkIPoint::Make(0, 0);
    sk_sp<SkSpecialImage> input(this->filterInput(0, ctx, &inputOffset));
    if (!input) {
        return nullptr;
    }

    const SkIRect inputBounds = SkIRect::MakeXYWH(inputOffset.x(), inputOffset.y(),
                                                  input->width(), input->height());

    SkIRect bounds;
    if (!this->applyCropRect(ctx, inputBounds, &bounds)) {
        return nullptr;
    }

    SkScalar invInset = fInset > 0 ? SkScalarInvert(fInset) : SK_Scalar1;

    SkScalar invXZoom = fSrcRect.width() / bounds.width();
    SkScalar invYZoom = fSrcRect.height() / bounds.height();


#if SK_SUPPORT_GPU
    if (ctx.gpuBacked()) {
        auto context = ctx.getContext();

        GrSurfaceProxyView inputView = input->view(context);
        SkASSERT(inputView.asTextureProxy());

        const auto isProtected = inputView.proxy()->isProtected();

        offset->fX = bounds.left();
        offset->fY = bounds.top();
        bounds.offset(-inputOffset);

        // Map bounds and srcRect into the proxy space. Due to the zoom effect,
        // it's not just an offset for fSrcRect.
        bounds.offset(input->subset().x(), input->subset().y());
        SkRect srcRect = fSrcRect.makeOffset((1.f - invXZoom) * input->subset().x(),
                                             (1.f - invYZoom) * input->subset().y());
        auto inputFP = GrTextureEffect::Make(std::move(inputView), kPremul_SkAlphaType);

        auto fp = GrMagnifierEffect::Make(std::move(inputFP),
                                          bounds,
                                          srcRect,
                                          invXZoom,
                                          invYZoom,
                                          bounds.width() * invInset,
                                          bounds.height() * invInset);
        fp = GrColorSpaceXformEffect::Make(std::move(fp),
                                           input->getColorSpace(), input->alphaType(),
                                           ctx.colorSpace(), kPremul_SkAlphaType);
        if (!fp) {
            return nullptr;
        }

        return DrawWithFP(context, std::move(fp), bounds, ctx.colorType(), ctx.colorSpace(),
                          isProtected);
    }
#endif

    SkBitmap inputBM;

    if (!input->getROPixels(&inputBM)) {
        return nullptr;
    }

    if ((inputBM.colorType() != kN32_SkColorType) ||
        (fSrcRect.width() >= inputBM.width()) || (fSrcRect.height() >= inputBM.height())) {
        return nullptr;
    }

    SkASSERT(inputBM.getPixels());
    if (!inputBM.getPixels() || inputBM.width() <= 0 || inputBM.height() <= 0) {
        return nullptr;
    }

    const SkImageInfo info = SkImageInfo::MakeN32Premul(bounds.width(), bounds.height());

    SkBitmap dst;
    if (!dst.tryAllocPixels(info)) {
        return nullptr;
    }

    SkColor* dptr = dst.getAddr32(0, 0);
    int dstWidth = dst.width(), dstHeight = dst.height();
    for (int y = 0; y < dstHeight; ++y) {
        for (int x = 0; x < dstWidth; ++x) {
            SkScalar x_dist = std::min(x, dstWidth - x - 1) * invInset;
            SkScalar y_dist = std::min(y, dstHeight - y - 1) * invInset;
            SkScalar weight = 0;

            static const SkScalar kScalar2 = SkScalar(2);

            // To create a smooth curve at the corners, we need to work on
            // a square twice the size of the inset.
            if (x_dist < kScalar2 && y_dist < kScalar2) {
                x_dist = kScalar2 - x_dist;
                y_dist = kScalar2 - y_dist;

                SkScalar dist = SkScalarSqrt(SkScalarSquare(x_dist) +
                                             SkScalarSquare(y_dist));
                dist = std::max(kScalar2 - dist, 0.0f);
                // SkTPin rather than std::max to handle potential NaN
                weight = SkTPin(SkScalarSquare(dist), 0.0f, SK_Scalar1);
            } else {
                SkScalar sqDist = std::min(SkScalarSquare(x_dist),
                                           SkScalarSquare(y_dist));
                // SkTPin rather than std::max to handle potential NaN
                weight = SkTPin(sqDist, 0.0f, SK_Scalar1);
            }

            SkScalar x_interp = weight * (fSrcRect.x() + x * invXZoom) + (1 - weight) * x;
            SkScalar y_interp = weight * (fSrcRect.y() + y * invYZoom) + (1 - weight) * y;

            int x_val = SkTPin(bounds.x() + SkScalarFloorToInt(x_interp), 0, inputBM.width() - 1);
            int y_val = SkTPin(bounds.y() + SkScalarFloorToInt(y_interp), 0, inputBM.height() - 1);

            *dptr = *inputBM.getAddr32(x_val, y_val);
            dptr++;
        }
    }

    offset->fX = bounds.left();
    offset->fY = bounds.top();
    return SkSpecialImage::MakeFromRaster(SkIRect::MakeWH(bounds.width(), bounds.height()),
                                          dst);
}