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

#include "experimental/ngatoy/Cmds.h"
#include "experimental/ngatoy/Fake.h"
#include "experimental/ngatoy/SortKey.h"

#include "include/core/SkBitmap.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkColor.h"
#include "include/core/SkPaint.h"
#include "include/effects/SkGradientShader.h"

//------------------------------------------------------------------------------------------------
RectCmd::RectCmd(ID id,
                 uint32_t paintersOrder,
                 SkIRect r,
                 const FakePaint& p,
                 sk_sp<FakeMCBlob> state)
    : Cmd(id)
    , fPaintersOrder(paintersOrder)
    , fRect(r)
    , fPaint(p)
    , fMCState(std::move(state)) {
}

SortKey RectCmd::getKey() {
    return SortKey(fPaint.isTransparent(), fMCState->id(), fPaintersOrder, fPaint.toID());
}

static void apply_diff(FakeCanvas* c, const FakeMCBlob& desired, const FakeMCBlob* prior) {
    int prefix = desired.determineSharedPrefix(prior);

    if (prior) {
        for (int j = prefix; j < prior->count(); ++j) {
            c->restore();
        }
    }

    for (int j = prefix; j < desired.count(); ++j) {
        desired[j].apply(c);
    }
}

void RectCmd::execute(FakeCanvas* c) const {
    apply_diff(c, *fMCState, c->snapState().get());

    c->drawRect(fID, fRect, fPaint);
}

static void apply_diff(SkCanvas* c, const FakeMCBlob& desired, const FakeMCBlob* prior) {
    int prefix = desired.determineSharedPrefix(prior);

    if (prior) {
        for (int j = prefix; j < prior->count(); ++j) {
            c->restore();
        }
    }

    for (int j = prefix; j < desired.count(); ++j) {
        desired[j].apply(c);
    }
}

void RectCmd::execute(SkCanvas* c, const FakeMCBlob* priorState) const {

    SkColor4f colors[2] = {
        SkColor4f::FromColor(fPaint.c0()),
        SkColor4f::FromColor(fPaint.c1())
    };

    SkPaint p;
    if (fPaint.toID() == kSolidMat) {
        p.setColor(fPaint.c0());
    } else if (fPaint.toID() == kLinearMat) {
        SkPoint pts[] = { { 0.0f, 0.0f, }, { 256.0f, 256.0f } };
        p.setShader(SkGradientShader::MakeLinear(pts, colors, nullptr, nullptr, 2,
                                                 SkTileMode::kClamp));
    } else {
        SkASSERT(fPaint.toID() == kRadialMat);
        auto shader = SkGradientShader::MakeRadial(SkPoint::Make(128.0f, 128.0f),
                                                   128.0f,
                                                   colors,
                                                   nullptr,
                                                   nullptr,
                                                   2,
                                                   SkTileMode::kRepeat);
        p.setShader(std::move(shader));
    }

    apply_diff(c, *fMCState, priorState);

    c->drawRect(SkRect::Make(fRect), p);
}

static bool is_opaque(SkColor c) {
    return 0xFF == SkColorGetA(c);
}

void RectCmd::rasterize(uint32_t zBuffer[256][256], SkBitmap* dstBM) const {

    unsigned int z = fPaintersOrder;

    for (int y = fRect.fTop; y < fRect.fBottom; ++y) {
        for (int x = fRect.fLeft; x < fRect.fRight; ++x) {
            if (fMCState->clipped(x, y)) {
                continue;
            }

            if (z > zBuffer[x][y]) {
                zBuffer[x][y] = z;

                SkColor c = fPaint.evalColor(x, y);

                if (is_opaque(c)) {
                    *dstBM->getAddr32(x, y) = c;
                } else {
                    SkColor4f bot = SkColor4f::FromColor(*dstBM->getAddr32(x, y));
                    SkColor4f top = SkColor4f::FromColor(c);
                    SkColor4f result = {
                        top.fA * top.fR + (1.0f - top.fA) * bot.fR,
                        top.fA * top.fG + (1.0f - top.fA) * bot.fG,
                        top.fA * top.fB + (1.0f - top.fA) * bot.fB,
                                 top.fA + (1.0f - top.fA) * bot.fA
                    };
                    *dstBM->getAddr32(x, y) = result.toSkColor();
                }
            }
        }
    }
}