// Copyright 2019 Istio 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 sidecar

import (
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/labels"

	"istio.io/api/networking/v1alpha3"

	"istio.io/istio/galley/pkg/config/analysis"
	"istio.io/istio/galley/pkg/config/analysis/msg"
	"istio.io/istio/pkg/config/resource"
	"istio.io/istio/pkg/config/schema/collection"
	"istio.io/istio/pkg/config/schema/collections"
)

// SelectorAnalyzer validates, per namespace, that:
// * sidecar resources that define a workload selector match at least one pod
// * there aren't multiple sidecar resources that select overlapping pods
type SelectorAnalyzer struct{}

var _ analysis.Analyzer = &SelectorAnalyzer{}

// Metadata implements Analyzer
func (a *SelectorAnalyzer) Metadata() analysis.Metadata {
	return analysis.Metadata{
		Name: "sidecar.SelectorAnalyzer",
		Description: "Validates that sidecars that define a workload selector " +
			"match at least one pod, and that there aren't multiple sidecar resources that select overlapping pods",
		Inputs: collection.Names{
			collections.IstioNetworkingV1Alpha3Sidecars.Name(),
			collections.K8SCoreV1Pods.Name(),
		},
	}
}

// Analyze implements Analyzer
func (a *SelectorAnalyzer) Analyze(c analysis.Context) {
	podsToSidecars := make(map[resource.FullName][]*resource.Instance)

	// This is using an unindexed approach for matching selectors.
	// Using an index for selectoes is problematic because selector != label
	// We can match a label to a selector, but we can't generate a selector from a label.
	c.ForEach(collections.IstioNetworkingV1Alpha3Sidecars.Name(), func(rs *resource.Instance) bool {
		s := rs.Message.(*v1alpha3.Sidecar)

		// For this analysis, ignore Sidecars with no workload selectors specified at all.
		if s.WorkloadSelector == nil || len(s.WorkloadSelector.Labels) == 0 {
			return true
		}

		sNs := rs.Metadata.FullName.Namespace
		sel := labels.SelectorFromSet(s.WorkloadSelector.Labels)

		foundPod := false
		c.ForEach(collections.K8SCoreV1Pods.Name(), func(rp *resource.Instance) bool {
			pod := rp.Message.(*v1.Pod)
			pNs := rp.Metadata.FullName.Namespace
			podLabels := labels.Set(pod.ObjectMeta.Labels)

			// Only attempt to match in the same namespace
			if pNs != sNs {
				return true
			}

			if sel.Matches(podLabels) {
				foundPod = true
				podsToSidecars[rp.Metadata.FullName] = append(podsToSidecars[rp.Metadata.FullName], rs)
			}

			return true
		})

		if !foundPod {
			c.Report(collections.IstioNetworkingV1Alpha3Sidecars.Name(), msg.NewReferencedResourceNotFound(rs, "selector", sel.String()))
		}

		return true
	})

	for p, sList := range podsToSidecars {
		if len(sList) == 1 {
			continue
		}

		sNames := getNames(sList)

		for _, rs := range sList {
			c.Report(collections.IstioNetworkingV1Alpha3Sidecars.Name(), msg.NewConflictingSidecarWorkloadSelectors(rs, sNames,
				p.Namespace.String(), p.Name.String()))
		}
	}
}
