/*
 * 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/core/SkCanvas.h"
#include "include/core/SkFlattenable.h"
#include "include/core/SkImageFilter.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRect.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/core/SkTypes.h"
#include "include/effects/SkImageFilters.h"
#include "src/core/SkImageFilter_Base.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSpecialImage.h"
#include "src/core/SkSpecialSurface.h"

#include <memory>

namespace {

class SkMergeImageFilter final : public SkImageFilter_Base {
public:
    SkMergeImageFilter(sk_sp<SkImageFilter>* const filters, int count,
                       const SkRect* cropRect)
            : INHERITED(filters, count, cropRect) {
        SkASSERT(count >= 0);
    }

protected:
    sk_sp<SkSpecialImage> onFilterImage(const Context&, SkIPoint* offset) const override;
    MatrixCapability onGetCTMCapability() const override { return MatrixCapability::kComplex; }

private:
    friend void ::SkRegisterMergeImageFilterFlattenable();
    SK_FLATTENABLE_HOOKS(SkMergeImageFilter)

    using INHERITED = SkImageFilter_Base;
};

} // end namespace
sk_sp<SkImageFilter> SkImageFilters::Merge(sk_sp<SkImageFilter>* const filters, int count,
                                           const CropRect& cropRect) {
    return sk_sp<SkImageFilter>(new SkMergeImageFilter(filters, count, cropRect));
}

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

sk_sp<SkFlattenable> SkMergeImageFilter::CreateProc(SkReadBuffer& buffer) {
    Common common;
    if (!common.unflatten(buffer, -1) || !buffer.isValid()) {
        return nullptr;
    }
    return SkImageFilters::Merge(common.inputs(), common.inputCount(), common.cropRect());
}

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

sk_sp<SkSpecialImage> SkMergeImageFilter::onFilterImage(const Context& ctx,
                                                        SkIPoint* offset) const {
    int inputCount = this->countInputs();
    if (inputCount < 1) {
        return nullptr;
    }

    SkIRect bounds;
    bounds.setEmpty();

    std::unique_ptr<sk_sp<SkSpecialImage>[]> inputs(new sk_sp<SkSpecialImage>[inputCount]);
    std::unique_ptr<SkIPoint[]> offsets(new SkIPoint[inputCount]);

    // Filter all of the inputs.
    for (int i = 0; i < inputCount; ++i) {
        offsets[i] = { 0, 0 };
        inputs[i] = this->filterInput(i, ctx, &offsets[i]);
        if (!inputs[i]) {
            continue;
        }
        const SkIRect inputBounds = SkIRect::MakeXYWH(offsets[i].fX, offsets[i].fY,
                                                      inputs[i]->width(), inputs[i]->height());
        bounds.join(inputBounds);
    }
    if (bounds.isEmpty()) {
        return nullptr;
    }

    // Apply the crop rect to the union of the inputs' bounds.
    // Note that the crop rect can only reduce the bounds, since this
    // filter does not affect transparent black.
    bool embiggen = false;
    this->getCropRect().applyTo(bounds, ctx.ctm(), embiggen, &bounds);
    if (!bounds.intersect(ctx.clipBounds())) {
        return nullptr;
    }

    const int x0 = bounds.left();
    const int y0 = bounds.top();

    sk_sp<SkSpecialSurface> surf(ctx.makeSurface(bounds.size()));
    if (!surf) {
        return nullptr;
    }

    SkCanvas* canvas = surf->getCanvas();
    SkASSERT(canvas);

    canvas->clear(0x0);

    // Composite all of the filter inputs.
    for (int i = 0; i < inputCount; ++i) {
        if (!inputs[i]) {
            continue;
        }

        inputs[i]->draw(canvas,
                        SkIntToScalar(offsets[i].x()) - x0, SkIntToScalar(offsets[i].y()) - y0);
    }

    offset->fX = bounds.left();
    offset->fY = bounds.top();
    return surf->makeImageSnapshot();
}