package engine

type sequenceItemProjectionIndex struct {
	outputByInput map[int]int
	inputByOutput map[int]int
}

func newSequenceItemProjectionIndex(projections []sequenceItemProjection) sequenceItemProjectionIndex {
	index := sequenceItemProjectionIndex{
		outputByInput: make(map[int]int, len(projections)),
		inputByOutput: make(map[int]int, len(projections)),
	}
	for _, projection := range projections {
		if projection.inputIndex >= 0 && projection.outputIndex >= 0 {
			index.outputByInput[projection.inputIndex] = projection.outputIndex
			index.inputByOutput[projection.outputIndex] = projection.inputIndex
		}
	}
	return index
}

func (index sequenceItemProjectionIndex) outputForInput(inputIndex int) (int, bool) {
	output, found := index.outputByInput[inputIndex]
	return output, found
}

func (index sequenceItemProjectionIndex) inputForOutput(outputIndex int) (int, bool) {
	input, found := index.inputByOutput[outputIndex]
	return input, found
}