#include "BlendStateMTL.h"

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namespace
{
    MTLColorWriteMask toMTLColorWriteMask(ColorWriteMask mask)
    {
        switch (mask) {
            case ColorWriteMask::NONE:
                return MTLColorWriteMaskNone;
            case ColorWriteMask::RED:
                return MTLColorWriteMaskRed;
            case ColorWriteMask::GREEN:
                return MTLColorWriteMaskGreen;
            case ColorWriteMask::BLUE:
                return MTLColorWriteMaskBlue;
            case ColorWriteMask::ALPHA:
                return MTLColorWriteMaskAlpha;
            case ColorWriteMask::ALL:
                return MTLColorWriteMaskAll;
        }
    }
    
    MTLBlendFactor toMTLBlendFactor(BlendFactor factor)
    {
        switch (factor) {
            case BlendFactor::ZERO:
                return MTLBlendFactorZero;
            case BlendFactor::ONE:
                return MTLBlendFactorOne;
            case BlendFactor::SRC_COLOR:
                return MTLBlendFactorSourceColor;
            case BlendFactor::ONE_MINUS_SRC_COLOR:
                return MTLBlendFactorOneMinusSourceColor;
            case BlendFactor::SRC_ALPHA:
                return MTLBlendFactorSourceAlpha;
            case BlendFactor::ONE_MINUS_SRC_ALPHA:
                return MTLBlendFactorOneMinusSourceAlpha;
            case BlendFactor::DST_COLOR:
                return MTLBlendFactorDestinationColor;
            case BlendFactor::ONE_MINUS_DST_COLOR:
                return MTLBlendFactorOneMinusDestinationColor;
            case BlendFactor::DST_ALPHA:
                return MTLBlendFactorDestinationAlpha;
            case BlendFactor::ONE_MINUS_DST_ALPHA:
                return MTLBlendFactorOneMinusDestinationAlpha;
            case BlendFactor::SRC_ALPHA_SATURATE:
                return MTLBlendFactorSourceAlphaSaturated;
            case BlendFactor::BLEND_CLOLOR:
                return MTLBlendFactorBlendColor;
        }
    }
    
    MTLBlendOperation toMTLBlendOperation(BlendOperation operation)
    {
        switch (operation) {
            case BlendOperation::ADD:
                return MTLBlendOperationAdd;
            case BlendOperation::SUBTRACT:
                return MTLBlendOperationSubtract;
            case BlendOperation::RESERVE_SUBTRACT:
                return MTLBlendOperationReverseSubtract;
        }
    }
}

BlendStateMTL::BlendStateMTL(const BlendDescriptor& descriptor)
{
    _blendDescriptorMTL.writeMask = toMTLColorWriteMask(descriptor.writeMask);
    _blendDescriptorMTL.blendEnabled = descriptor.blendEnabled;
    
    _blendDescriptorMTL.rgbBlendOperation = toMTLBlendOperation(descriptor.rgbBlendOperation);
    _blendDescriptorMTL.alphaBlendOperation = toMTLBlendOperation(descriptor.alphaBlendOperation);
    
    _blendDescriptorMTL.sourceRGBBlendFactor = toMTLBlendFactor(descriptor.sourceRGBBlendFactor);
    _blendDescriptorMTL.destinationRGBBlendFactor = toMTLBlendFactor(descriptor.destinationRGBBlendFactor);
    _blendDescriptorMTL.sourceAlphaBlendFactor = toMTLBlendFactor(descriptor.sourceAlphaBlendFactor);
    _blendDescriptorMTL.destinationAlphaBlendFactor = toMTLBlendFactor(descriptor.destinationAlphaBlendFactor);
}

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