/*
Copyright 2020 The Kubernetes 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.
*/

// This code is directly lifted from the Kubernetes codebase in order to avoid relying on the k8s.io/kubernetes package.
// For reference:
// https://github.com/kubernetes/kubernetes/blob/release-1.23/pkg/apis/core/helper/helpers.go#L365-L397

package lifted

import (
	"fmt"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/selection"
)

// +lifted:source=https://github.com/kubernetes/kubernetes/blob/release-1.23/pkg/apis/core/helper/helpers.go#L365-L397

// NodeSelectorRequirementsAsSelector converts the []NodeSelectorRequirement core type into a struct that implements
// labels.Selector.
func NodeSelectorRequirementsAsSelector(nsm []corev1.NodeSelectorRequirement) (labels.Selector, error) {
	if len(nsm) == 0 {
		return labels.Nothing(), nil
	}
	selector := labels.NewSelector()
	for _, expr := range nsm {
		var op selection.Operator
		switch expr.Operator {
		case corev1.NodeSelectorOpIn:
			op = selection.In
		case corev1.NodeSelectorOpNotIn:
			op = selection.NotIn
		case corev1.NodeSelectorOpExists:
			op = selection.Exists
		case corev1.NodeSelectorOpDoesNotExist:
			op = selection.DoesNotExist
		case corev1.NodeSelectorOpGt:
			op = selection.GreaterThan
		case corev1.NodeSelectorOpLt:
			op = selection.LessThan
		default:
			return nil, fmt.Errorf("%q is not a valid node selector operator", expr.Operator)
		}
		r, err := labels.NewRequirement(expr.Key, op, expr.Values)
		if err != nil {
			return nil, err
		}
		selector = selector.Add(*r)
	}
	return selector, nil
}