// Copyright 2022 The Ebitengine Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package graphicsdriver

type Blend struct {
	BlendFactorSourceRGB        BlendFactor
	BlendFactorSourceAlpha      BlendFactor
	BlendFactorDestinationRGB   BlendFactor
	BlendFactorDestinationAlpha BlendFactor
	BlendOperationRGB           BlendOperation
	BlendOperationAlpha         BlendOperation
}

type BlendFactor byte

const (
	BlendFactorZero BlendFactor = iota
	BlendFactorOne
	BlendFactorSourceAlpha
	BlendFactorDestinationAlpha
	BlendFactorOneMinusSourceAlpha
	BlendFactorOneMinusDestinationAlpha
	BlendFactorDestinationRGB
)

type BlendOperation byte

const (
	BlendOperationAdd BlendOperation = iota
	BlendOperationSubtract
	BlendOperationReverseSubtract
)

var BlendSourceOver = Blend{
	BlendFactorSourceRGB:        BlendFactorOne,
	BlendFactorSourceAlpha:      BlendFactorOne,
	BlendFactorDestinationRGB:   BlendFactorOneMinusSourceAlpha,
	BlendFactorDestinationAlpha: BlendFactorOneMinusSourceAlpha,
	BlendOperationRGB:           BlendOperationAdd,
	BlendOperationAlpha:         BlendOperationAdd,
}

var BlendClear = Blend{
	BlendFactorSourceRGB:        BlendFactorZero,
	BlendFactorSourceAlpha:      BlendFactorZero,
	BlendFactorDestinationRGB:   BlendFactorZero,
	BlendFactorDestinationAlpha: BlendFactorZero,
	BlendOperationRGB:           BlendOperationAdd,
	BlendOperationAlpha:         BlendOperationAdd,
}

var BlendCopy = Blend{
	BlendFactorSourceRGB:        BlendFactorOne,
	BlendFactorSourceAlpha:      BlendFactorOne,
	BlendFactorDestinationRGB:   BlendFactorZero,
	BlendFactorDestinationAlpha: BlendFactorZero,
	BlendOperationRGB:           BlendOperationAdd,
	BlendOperationAlpha:         BlendOperationAdd,
}