utils.go

package onion

// MergeLayersData is an helper function to merge more layers in one.
// Following slice order, a previous layer key is overriden by an equal key in
// next layer.
func mergeLayersData(layers ...map[string]interface{}) map[string]interface{} {
	if len(layers) == 0 {
		return map[string]interface{}{}
	}

	mergedLayer := layers[len(layers)-1]
	layers = layers[:len(layers)-1]

	for i := len(layers) - 1; i >= 0; i-- {
		mergedLayer = mergeKeys(mergedLayer, layers[i])
	}

	return mergedLayer
}

// mergeKeys recursively merge right into left, never replacing any key that already exists in left
func mergeKeys(left, right map[string]interface{}) map[string]interface{} {
	if left == nil {
		return right
	}

	for key, rightVal := range right {

		if _, present := left[key]; !present {
			left[key] = rightVal
			continue
		}

		leftMap, isLeftValAMap := left[key].(map[string]interface{})
		rightMap, isRightValAMap := rightVal.(map[string]interface{})
		if isLeftValAMap && isRightValAMap {
			left[key] = mergeKeys(leftMap, rightMap)
		}
	}

	return left
}