// Copyright 2016 The Kubernetes Authors.
// Copyright 2020 Authors of Cilium
//
// 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 v1

import (
	"fmt"

	"github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/labels"
	"github.com/cilium/cilium/pkg/k8s/slim/k8s/apis/selection"
)

// LabelSelectorAsSelector converts the LabelSelector api type into a struct that implements
// labels.Selector
// Note: This function should be kept in sync with the selector methods in pkg/labels/selector.go
func LabelSelectorAsSelector(ps *LabelSelector) (labels.Selector, error) {
	if ps == nil {
		return labels.Nothing(), nil
	}
	if len(ps.MatchLabels)+len(ps.MatchExpressions) == 0 {
		return labels.Everything(), nil
	}
	selector := labels.NewSelector()
	for k, v := range ps.MatchLabels {
		r, err := labels.NewRequirement(k, selection.Equals, []string{v})
		if err != nil {
			return nil, err
		}
		selector = selector.Add(*r)
	}
	for _, expr := range ps.MatchExpressions {
		var op selection.Operator
		switch expr.Operator {
		case LabelSelectorOpIn:
			op = selection.In
		case LabelSelectorOpNotIn:
			op = selection.NotIn
		case LabelSelectorOpExists:
			op = selection.Exists
		case LabelSelectorOpDoesNotExist:
			op = selection.DoesNotExist
		default:
			return nil, fmt.Errorf("%q is not a valid pod selector operator", expr.Operator)
		}
		r, err := labels.NewRequirement(expr.Key, op, append([]string(nil), expr.Values...))
		if err != nil {
			return nil, err
		}
		selector = selector.Add(*r)
	}
	return selector, nil
}

// LabelSelectorAsMap converts the LabelSelector api type into a map of strings, ie. the
// original structure of a label selector. Operators that cannot be converted into plain
// labels (Exists, DoesNotExist, NotIn, and In with more than one value) will result in
// an error.
func LabelSelectorAsMap(ps *LabelSelector) (map[string]string, error) {
	if ps == nil {
		return nil, nil
	}
	selector := map[string]string{}
	for k, v := range ps.MatchLabels {
		selector[k] = v
	}
	for _, expr := range ps.MatchExpressions {
		switch expr.Operator {
		case LabelSelectorOpIn:
			if len(expr.Values) != 1 {
				return selector, fmt.Errorf("operator %q without a single value cannot be converted into the old label selector format", expr.Operator)
			}
			// Should we do anything in case this will override a previous key-value pair?
			selector[expr.Key] = expr.Values[0]
		case LabelSelectorOpNotIn, LabelSelectorOpExists, LabelSelectorOpDoesNotExist:
			return selector, fmt.Errorf("operator %q cannot be converted into the old label selector format", expr.Operator)
		default:
			return selector, fmt.Errorf("%q is not a valid selector operator", expr.Operator)
		}
	}
	return selector, nil
}

// ParseToLabelSelector parses a string representing a selector into a LabelSelector object.
// Note: This function should be kept in sync with the parser in pkg/labels/selector.go
func ParseToLabelSelector(selector string) (*LabelSelector, error) {
	reqs, err := labels.ParseToRequirements(selector)
	if err != nil {
		return nil, fmt.Errorf("couldn't parse the selector string \"%s\": %v", selector, err)
	}

	labelSelector := &LabelSelector{
		MatchLabels:      map[string]string{},
		MatchExpressions: []LabelSelectorRequirement{},
	}
	for _, req := range reqs {
		var op LabelSelectorOperator
		switch req.Operator() {
		case selection.Equals, selection.DoubleEquals:
			vals := req.Values()
			if vals.Len() != 1 {
				return nil, fmt.Errorf("equals operator must have exactly one value")
			}
			val, ok := vals.PopAny()
			if !ok {
				return nil, fmt.Errorf("equals operator has exactly one value but it cannot be retrieved")
			}
			labelSelector.MatchLabels[req.Key()] = val
			continue
		case selection.In:
			op = LabelSelectorOpIn
		case selection.NotIn:
			op = LabelSelectorOpNotIn
		case selection.Exists:
			op = LabelSelectorOpExists
		case selection.DoesNotExist:
			op = LabelSelectorOpDoesNotExist
		case selection.GreaterThan, selection.LessThan:
			// Adding a separate case for these operators to indicate that this is deliberate
			return nil, fmt.Errorf("%q isn't supported in label selectors", req.Operator())
		default:
			return nil, fmt.Errorf("%q is not a valid label selector operator", req.Operator())
		}
		labelSelector.MatchExpressions = append(labelSelector.MatchExpressions, LabelSelectorRequirement{
			Key:      req.Key(),
			Operator: op,
			Values:   req.Values().List(),
		})
	}
	return labelSelector, nil
}

// SetAsLabelSelector converts the labels.Set object into a LabelSelector api object.
func SetAsLabelSelector(ls labels.Set) *LabelSelector {
	if ls == nil {
		return nil
	}

	selector := &LabelSelector{
		MatchLabels: make(map[string]string),
	}
	for label, value := range ls {
		selector.MatchLabels[label] = value
	}

	return selector
}

// FormatLabelSelector convert labelSelector into plain string
func FormatLabelSelector(labelSelector *LabelSelector) string {
	selector, err := LabelSelectorAsSelector(labelSelector)
	if err != nil {
		return "<error>"
	}

	l := selector.String()
	if len(l) == 0 {
		l = "<none>"
	}
	return l
}
