package validatingadmissionpolicy

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/kyverno/kyverno/pkg/clients/dclient"
	engineapi "github.com/kyverno/kyverno/pkg/engine/api"
	celutils "github.com/kyverno/kyverno/pkg/utils/cel"
	datautils "github.com/kyverno/kyverno/pkg/utils/data"
	kubeutils "github.com/kyverno/kyverno/pkg/utils/kube"
	"golang.org/x/text/cases"
	"golang.org/x/text/language"
	admissionregistrationv1 "k8s.io/api/admissionregistration/v1"
	admissionregistrationv1beta1 "k8s.io/api/admissionregistration/v1beta1"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apiserver/pkg/admission"
	"k8s.io/apiserver/pkg/admission/plugin/cel"
	"k8s.io/apiserver/pkg/admission/plugin/policy/generic"
	"k8s.io/apiserver/pkg/admission/plugin/policy/matching"
	"k8s.io/apiserver/pkg/admission/plugin/policy/validating"
	"k8s.io/apiserver/pkg/admission/plugin/webhook/matchconditions"
	celconfig "k8s.io/apiserver/pkg/apis/cel"
)

func GetKinds(policy admissionregistrationv1beta1.ValidatingAdmissionPolicy) []string {
	var kindList []string

	matchResources := policy.Spec.MatchConstraints
	for _, rule := range matchResources.ResourceRules {
		group := rule.APIGroups[0]
		version := rule.APIVersions[0]
		for _, resource := range rule.Resources {
			isSubresource := kubeutils.IsSubresource(resource)
			if isSubresource {
				parts := strings.Split(resource, "/")

				kind := cases.Title(language.English, cases.NoLower).String(parts[0])
				kind, _ = strings.CutSuffix(kind, "s")
				subresource := parts[1]

				if group == "" {
					kindList = append(kindList, strings.Join([]string{version, kind, subresource}, "/"))
				} else {
					kindList = append(kindList, strings.Join([]string{group, version, kind, subresource}, "/"))
				}
			} else {
				resource = cases.Title(language.English, cases.NoLower).String(resource)
				resource, _ = strings.CutSuffix(resource, "s")
				kind := resource

				if group == "" {
					kindList = append(kindList, strings.Join([]string{version, kind}, "/"))
				} else {
					kindList = append(kindList, strings.Join([]string{group, version, kind}, "/"))
				}
			}
		}
	}

	return kindList
}

func Validate(
	policyData PolicyData,
	resource unstructured.Unstructured,
	namespaceSelectorMap map[string]map[string]string,
	client dclient.Interface,
) (engineapi.EngineResponse, error) {
	resPath := fmt.Sprintf("%s/%s/%s", resource.GetNamespace(), resource.GetKind(), resource.GetName())
	policy := policyData.definition
	bindings := policyData.bindings
	engineResponse := engineapi.NewEngineResponse(resource, engineapi.NewValidatingAdmissionPolicy(policy), nil)

	gvk := resource.GroupVersionKind()
	gvr := schema.GroupVersionResource{
		Group:    gvk.Group,
		Version:  gvk.Version,
		Resource: strings.ToLower(gvk.Kind) + "s",
	}

	var namespace *corev1.Namespace
	namespaceName := resource.GetNamespace()
	// Special case, the namespace object has the namespace of itself.
	// unset it if the incoming object is a namespace
	if gvk.Kind == "Namespace" && gvk.Version == "v1" && gvk.Group == "" {
		namespaceName = ""
	}

	if namespaceName != "" {
		namespace = &corev1.Namespace{
			ObjectMeta: metav1.ObjectMeta{
				Name:   namespaceName,
				Labels: namespaceSelectorMap[namespaceName],
			},
		}
	}

	a := admission.NewAttributesRecord(resource.DeepCopyObject(), nil, resource.GroupVersionKind(), resource.GetNamespace(), resource.GetName(), gvr, "", admission.Create, nil, false, nil)

	if len(bindings) == 0 {
		isMatch, err := matches(a, namespaceSelectorMap, *policy.Spec.MatchConstraints)
		if err != nil {
			return engineResponse, err
		}
		if !isMatch {
			return engineResponse, nil
		}
		logger.V(3).Info("validate resource %s against policy %s", resPath, policy.GetName())
		return validateResource(policy, nil, resource, *namespace, a)
	}

	if client != nil {
		nsLister := NewCustomNamespaceLister(client)
		matcher := generic.NewPolicyMatcher(matching.NewMatcher(nsLister, client.GetKubeClient()))

		// convert policy from v1beta1 to v1
		v1policy := ConvertValidatingAdmissionPolicy(policy)

		// construct admission attributes
		gvr, err := client.Discovery().GetGVRFromGVK(gvk)
		if err != nil {
			return engineResponse, err
		}
		a = admission.NewAttributesRecord(resource.DeepCopyObject(), nil, gvk, resource.GetNamespace(), resource.GetName(), gvr, "", admission.Create, nil, false, nil)

		// check if policy matches the incoming resource
		o := admission.NewObjectInterfacesFromScheme(runtime.NewScheme())
		isMatch, _, _, err := matcher.DefinitionMatches(a, o, validating.NewValidatingAdmissionPolicyAccessor(&v1policy))
		if err != nil {
			return engineResponse, err
		}
		if !isMatch {
			return engineResponse, nil
		}

		if namespaceName != "" {
			namespace, err = client.GetKubeClient().CoreV1().Namespaces().Get(context.TODO(), namespaceName, metav1.GetOptions{})
			if err != nil {
				return engineResponse, err
			}
		}

		for i, binding := range bindings {
			// convert policy binding from v1alpha1 to v1
			v1binding := ConvertValidatingAdmissionPolicyBinding(binding)
			isMatch, err := matcher.BindingMatches(a, o, validating.NewValidatingAdmissionPolicyBindingAccessor(&v1binding))
			if err != nil {
				return engineResponse, err
			}
			if !isMatch {
				continue
			}

			logger.V(3).Info("validate resource %s against policy %s with binding %s", resPath, policy.GetName(), binding.GetName())
			return validateResource(policy, &bindings[i], resource, *namespace, a)
		}
	} else {
		for i, binding := range bindings {
			isMatch, err := matches(a, namespaceSelectorMap, *binding.Spec.MatchResources)
			if err != nil {
				return engineResponse, err
			}
			if !isMatch {
				continue
			}
			logger.V(3).Info("validate resource %s against policy %s with binding %s", resPath, policy.GetName(), binding.GetName())
			return validateResource(policy, &bindings[i], resource, *namespace, a)
		}
	}

	return engineResponse, nil
}

func validateResource(
	policy admissionregistrationv1beta1.ValidatingAdmissionPolicy,
	binding *admissionregistrationv1beta1.ValidatingAdmissionPolicyBinding,
	resource unstructured.Unstructured,
	namespace corev1.Namespace,
	a admission.Attributes,
) (engineapi.EngineResponse, error) {
	startTime := time.Now()

	engineResponse := engineapi.NewEngineResponse(resource, engineapi.NewValidatingAdmissionPolicy(policy), nil)
	policyResp := engineapi.NewPolicyResponse()
	var ruleResp *engineapi.RuleResponse

	// compile CEL expressions
	matchConditions := ConvertMatchConditionsV1(policy.Spec.MatchConditions)
	compiler, err := celutils.NewCompiler(policy.Spec.Validations, policy.Spec.AuditAnnotations, matchConditions, policy.Spec.Variables)
	if err != nil {
		return engineResponse, err
	}
	hasParam := policy.Spec.ParamKind != nil
	optionalVars := cel.OptionalVariableDeclarations{HasParams: hasParam, HasAuthorizer: false}
	compiler.CompileVariables(optionalVars)

	var failPolicy admissionregistrationv1.FailurePolicyType
	if policy.Spec.FailurePolicy == nil {
		failPolicy = admissionregistrationv1.Fail
	} else {
		failPolicy = admissionregistrationv1.FailurePolicyType(*policy.Spec.FailurePolicy)
	}

	var matchPolicy admissionregistrationv1beta1.MatchPolicyType
	if policy.Spec.MatchConstraints.MatchPolicy == nil {
		matchPolicy = admissionregistrationv1beta1.Equivalent
	} else {
		matchPolicy = *policy.Spec.MatchConstraints.MatchPolicy
	}

	newMatcher := matchconditions.NewMatcher(compiler.CompileMatchExpressions(optionalVars), &failPolicy, "", string(matchPolicy), "")
	validator := validating.NewValidator(
		compiler.CompileValidateExpressions(optionalVars),
		newMatcher,
		compiler.CompileAuditAnnotationsExpressions(optionalVars),
		compiler.CompileMessageExpressions(optionalVars),
		&failPolicy,
	)
	versionedAttr, _ := admission.NewVersionedAttributes(a, a.GetKind(), nil)
	validateResult := validator.Validate(context.TODO(), a.GetResource(), versionedAttr, nil, &namespace, celconfig.RuntimeCELCostBudget, nil)

	// no validations are returned if match conditions aren't met
	if datautils.DeepEqual(validateResult, validating.ValidateResult{}) {
		ruleResp = engineapi.RuleSkip(policy.GetName(), engineapi.Validation, "match conditions aren't met", nil)
	} else {
		isPass := true
		for _, policyDecision := range validateResult.Decisions {
			if policyDecision.Evaluation == validating.EvalError {
				isPass = false
				ruleResp = engineapi.RuleError(policy.GetName(), engineapi.Validation, policyDecision.Message, nil, nil)
				break
			} else if policyDecision.Action == validating.ActionDeny {
				isPass = false
				ruleResp = engineapi.RuleFail(policy.GetName(), engineapi.Validation, policyDecision.Message, nil)
				break
			}
		}

		if isPass {
			ruleResp = engineapi.RulePass(policy.GetName(), engineapi.Validation, "", nil)
		}
	}

	if binding != nil {
		ruleResp = ruleResp.WithBinding(binding)
	}
	policyResp.Add(engineapi.NewExecutionStats(startTime, time.Now()), *ruleResp)
	engineResponse = engineResponse.WithPolicyResponse(policyResp)

	return engineResponse, nil
}