package webhooks

import (
	"errors"
	"fmt"
	"log"

	controller "github.com/nirmata/kube-policy/controller"
	kubeclient "github.com/nirmata/kube-policy/kubeclient"
	types "github.com/nirmata/kube-policy/pkg/apis/policy/v1alpha1"
	v1beta1 "k8s.io/api/admission/v1beta1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
)

// MutationWebhook is a data type that represents
// buisness logic for resource mutation
type MutationWebhook struct {
	kubeclient *kubeclient.KubeClient
	controller *controller.PolicyController
	logger     *log.Logger
}

// NewMutationWebhook is a method that returns new instance
// of MutationWebhook struct
func NewMutationWebhook(kubeclient *kubeclient.KubeClient, controller *controller.PolicyController, logger *log.Logger) (*MutationWebhook, error) {
	if kubeclient == nil || controller == nil || logger == nil {
		return nil, errors.New("Some parameters are not set")
	}
	return &MutationWebhook{kubeclient: kubeclient, controller: controller, logger: logger}, nil
}

// Mutate applies admission to request
func (mw *MutationWebhook) Mutate(request *v1beta1.AdmissionRequest) *v1beta1.AdmissionResponse {
	mw.logger.Printf("AdmissionReview for Kind=%v, Namespace=%v Name=%v UID=%v patchOperation=%v UserInfo=%v",
		request.Kind.Kind, request.Namespace, request.Name, request.UID, request.Operation, request.UserInfo)

	policies := mw.controller.GetPolicies()
	if len(policies) == 0 {
		return nil
	}

	var allPatches []PatchBytes
	for _, policy := range policies {
		mw.logger.Printf("Applying policy %s with %d rules", policy.ObjectMeta.Name, len(policy.Spec.Rules))

		policyPatches, err := mw.applyPolicyRules(request, policy)
		if err != nil {
			mw.controller.LogPolicyError(policy.Name, err.Error())

			errStr := fmt.Sprintf("Unable to apply policy %s: %v", policy.Name, err)
			mw.logger.Printf("Denying the request because of error: %s", errStr)
			return mw.denyResourceCreation(errStr)
		}

		if len(policyPatches) > 0 {
			meta := parseMetadataFromObject(request.Object.Raw)
			namespace := parseNamespaceFromMetadata(meta)
			name := parseNameFromMetadata(meta)
			mw.controller.LogPolicyInfo(policy.Name, fmt.Sprintf("Applied to %s %s/%s", request.Kind.Kind, namespace, name))

			allPatches = append(allPatches, policyPatches...)
		}
	}

	patchType := v1beta1.PatchTypeJSONPatch
	return &v1beta1.AdmissionResponse{
		Allowed:   true,
		Patch:     JoinPatches(allPatches),
		PatchType: &patchType,
	}
}

func getPolicyPatchingSets(policy types.Policy) PatchingSets {
	// failurePolicy property is the only available way for now to define behavior on patching error.
	// TODO: define new failurePolicy values specific for patching and other policy features.
	if policy.Spec.FailurePolicy != nil && *policy.Spec.FailurePolicy == "continueOnError" {
		return PatchingSetsContinueAlways
	}
	return PatchingSetsDefault
}

// Applies all policy rules to the created object and returns list of processed JSON patches.
// May return nil patches if it is not necessary to create patches for requested object.
// Returns error ONLY in case when creation of resource should be denied.
func (mw *MutationWebhook) applyPolicyRules(request *v1beta1.AdmissionRequest, policy types.Policy) ([]PatchBytes, error) {
	patchingSets := getPolicyPatchingSets(policy)
	var policyPatches []PatchBytes

	for ruleIdx, rule := range policy.Spec.Rules {
		err := rule.Validate()
		if err != nil {
			mw.logger.Printf("Invalid rule detected: #%d in policy %s", ruleIdx, policy.ObjectMeta.Name)
			continue
		}

		if !IsRuleApplicableToRequest(rule.Resource, request) {
			return nil, nil
		}

		err = mw.applyRuleGenerators(request, rule)
		if err != nil && patchingSets == PatchingSetsStopOnError {
			return nil, errors.New(fmt.Sprintf("Failed to apply generators from rule #%d: %s", ruleIdx, err))
		}

		rulePatchesProcessed, err := ProcessPatches(rule.Patches, request.Object.Raw, patchingSets)
		if err != nil {
			return nil, errors.New(fmt.Sprintf("Failed to process patches from rule #%d: %s", ruleIdx, err))
		}

		if rulePatchesProcessed != nil {
			policyPatches = append(policyPatches, rulePatchesProcessed...)
			mw.logger.Printf("Rule %d: prepared %d patches", ruleIdx, len(rulePatchesProcessed))
		} else {
			mw.logger.Print("Rule %d: no patches prepared")
		}
	}

	return policyPatches, nil
}

// Applies "configMapGenerator" and "secretGenerator" described in PolicyRule
func (mw *MutationWebhook) applyRuleGenerators(request *v1beta1.AdmissionRequest, rule types.PolicyRule) error {
	// configMapGenerator and secretGenerator can be applied only to namespaces
	if request.Kind.Kind == "Namespace" {
		meta := parseMetadataFromObject(request.Object.Raw)
		namespaceName := parseNameFromMetadata(meta)

		err := mw.applyConfigGenerator(rule.ConfigMapGenerator, namespaceName, "ConfigMap")
		if err == nil {
			err = mw.applyConfigGenerator(rule.SecretGenerator, namespaceName, "Secret")
		}
		return err
	}
	return nil
}

// Creates resourceKind (ConfigMap or Secret) with parameters specified in generator in cluster specified in request.
func (mw *MutationWebhook) applyConfigGenerator(generator *types.PolicyConfigGenerator, namespace string, configKind string) error {
	if generator == nil {
		return nil
	}

	err := generator.Validate()
	if err != nil {
		return errors.New(fmt.Sprintf("Generator for '%s' is invalid: %s", configKind, err))
	}

	switch configKind {
	case "ConfigMap":
		err = mw.kubeclient.GenerateConfigMap(*generator, namespace)
	case "Secret":
		err = mw.kubeclient.GenerateSecret(*generator, namespace)
	default:
		err = errors.New(fmt.Sprintf("Unsupported config Kind '%s'", configKind))
	}

	if err != nil {
		return errors.New(fmt.Sprintf("Unable to apply generator for %s '%s/%s' : %s", configKind, namespace, generator.Name, err))
	}

	return nil
}

// Forms AdmissionResponse with denial of resource creation and error message
func (mw *MutationWebhook) denyResourceCreation(errStr string) *v1beta1.AdmissionResponse {
	return &v1beta1.AdmissionResponse{
		Result: &metav1.Status{
			Message: errStr,
		},
		Allowed: false,
	}
}