package policy

import (
	"encoding/json"
	"fmt"
	"reflect"
	"strings"
	"time"

	jsonpatch "github.com/evanphx/json-patch"
	"github.com/golang/glog"
	kyverno "github.com/nirmata/kyverno/pkg/api/kyverno/v1"
	"github.com/nirmata/kyverno/pkg/engine"
	"github.com/nirmata/kyverno/pkg/engine/context"
	"github.com/nirmata/kyverno/pkg/engine/response"
	"github.com/nirmata/kyverno/pkg/utils"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
)

// applyPolicy applies policy on a resource
//TODO: generation rules
func applyPolicy(policy kyverno.ClusterPolicy, resource unstructured.Unstructured) (responses []response.EngineResponse) {
	startTime := time.Now()

	glog.V(4).Infof("Started apply policy %s on resource %s/%s/%s (%v)", policy.Name, resource.GetKind(), resource.GetNamespace(), resource.GetName(), startTime)
	defer func() {
		glog.V(4).Infof("Finished applying %s on resource %s/%s/%s (%v)", policy.Name, resource.GetKind(), resource.GetNamespace(), resource.GetName(), time.Since(startTime))
	}()

	var engineResponses []response.EngineResponse
	var engineResponse response.EngineResponse
	var err error
	// build context
	ctx := context.NewContext()
	ctx.AddResource(transformResource(resource))

	//MUTATION
	engineResponse, err = mutation(policy, resource, ctx)
	engineResponses = append(engineResponses, engineResponse)
	if err != nil {
		glog.Errorf("unable to process mutation rules: %v", err)
	}

	//VALIDATION
	engineResponse = engine.Validate(engine.PolicyContext{Policy: policy, Context: ctx, NewResource: resource})
	engineResponses = append(engineResponses, engineResponse)

	//TODO: GENERATION
	return engineResponses
}
func mutation(policy kyverno.ClusterPolicy, resource unstructured.Unstructured, ctx context.EvalInterface) (response.EngineResponse, error) {

	engineResponse := engine.Mutate(engine.PolicyContext{Policy: policy, NewResource: resource, Context: ctx})
	if !engineResponse.IsSuccesful() {
		glog.V(4).Infof("mutation had errors reporting them")
		return engineResponse, nil
	}
	// Verify if the JSON pathes returned by the Mutate are already applied to the resource
	if reflect.DeepEqual(resource, engineResponse.PatchedResource) {
		// resources matches
		glog.V(4).Infof("resource %s/%s/%s satisfies policy %s", engineResponse.PolicyResponse.Resource.Kind, engineResponse.PolicyResponse.Resource.Namespace, engineResponse.PolicyResponse.Resource.Name, engineResponse.PolicyResponse.Policy)
		return engineResponse, nil
	}
	return getFailedOverallRuleInfo(resource, engineResponse)
}

// getFailedOverallRuleInfo gets detailed info for over-all mutation failure
func getFailedOverallRuleInfo(resource unstructured.Unstructured, engineResponse response.EngineResponse) (response.EngineResponse, error) {
	rawResource, err := resource.MarshalJSON()
	if err != nil {
		glog.V(4).Infof("unable to marshal resource: %v\n", err)
		return response.EngineResponse{}, err
	}

	// resource does not match so there was a mutation rule violated
	for index, rule := range engineResponse.PolicyResponse.Rules {
		glog.V(4).Infof("veriying if policy %s rule %s was applied before to resource %s/%s/%s", engineResponse.PolicyResponse.Policy, rule.Name, engineResponse.PolicyResponse.Resource.Kind, engineResponse.PolicyResponse.Resource.Namespace, engineResponse.PolicyResponse.Resource.Name)
		if len(rule.Patches) == 0 {
			continue
		}
		patch, err := jsonpatch.DecodePatch(utils.JoinPatches(rule.Patches))
		if err != nil {
			glog.V(4).Infof("unable to decode patch %s: %v", rule.Patches, err)
			return response.EngineResponse{}, err
		}

		// apply the patches returned by mutate to the original resource
		patchedResource, err := patch.Apply(rawResource)
		if err != nil {
			glog.V(4).Infof("unable to apply patch %s: %v", rule.Patches, err)
			return response.EngineResponse{}, err
		}
		if !jsonpatch.Equal(patchedResource, rawResource) {
			glog.V(4).Infof("policy %s rule %s condition not satisfied by existing resource", engineResponse.PolicyResponse.Policy, rule.Name)
			engineResponse.PolicyResponse.Rules[index].Success = false
			engineResponse.PolicyResponse.Rules[index].Message = fmt.Sprintf("mutation json patches not found at resource path %s", extractPatchPath(rule.Patches))
		}
	}
	return engineResponse, nil
}

type jsonPatch struct {
	Op    string      `json:"op"`
	Path  string      `json:"path"`
	Value interface{} `json:"value"`
}

func extractPatchPath(patches [][]byte) string {
	var resultPath []string
	// extract the patch path and value
	for _, patch := range patches {
		glog.V(4).Infof("expected json patch not found in resource: %s", string(patch))
		var data jsonPatch
		if err := json.Unmarshal(patch, &data); err != nil {
			glog.V(4).Infof("Failed to decode the generated patch %v: Error %v", string(patch), err)
			continue
		}
		resultPath = append(resultPath, data.Path)
	}
	return strings.Join(resultPath, ";")
}