package openapi

import (
	"encoding/json"
	"errors"
	"fmt"

	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"

	runtimeSchema "k8s.io/apimachinery/pkg/runtime/schema"

	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"

	"gopkg.in/yaml.v2"

	"github.com/googleapis/gnostic/compiler"

	openapi_v2 "github.com/googleapis/gnostic/OpenAPIv2"
	log "sigs.k8s.io/controller-runtime/pkg/log"

	"github.com/nirmata/kyverno/pkg/constant"
	client "github.com/nirmata/kyverno/pkg/dclient"
	"k8s.io/apimachinery/pkg/util/wait"
)

type crdSync struct {
	client     *client.Client
	controller *Controller
}

// crdDefinitionPrior represents CRD's version prior to 1.16
var crdDefinitionPrior struct {
	Spec struct {
		Names struct {
			Kind string `json:"kind"`
		} `json:"names"`
		Validation struct {
			OpenAPIV3Schema interface{} `json:"openAPIV3Schema"`
		} `json:"validation"`
	} `json:"spec"`
}

// crdDefinitionNew represents CRD in version 1.16+
var crdDefinitionNew struct {
	Spec struct {
		Names struct {
			Kind string `json:"kind"`
		} `json:"names"`
		Versions []struct {
			Schema struct {
				OpenAPIV3Schema interface{} `json:"openAPIV3Schema"`
			} `json:"schema"`
			Storage bool `json:"storage"`
		} `json:"versions"`
	} `json:"spec"`
}

var crdVersion struct {
}

func NewCRDSync(client *client.Client, controller *Controller) *crdSync {
	if controller == nil {
		panic(fmt.Errorf("nil controller sent into crd sync"))
	}

	return &crdSync{
		controller: controller,
		client:     client,
	}
}

func (c *crdSync) Run(workers int, stopCh <-chan struct{}) {
	newDoc, err := c.client.DiscoveryClient.OpenAPISchema()
	if err != nil {
		log.Log.Error(err, "cannot get openapi schema")
	}

	err = c.controller.useOpenApiDocument(newDoc)
	if err != nil {
		log.Log.Error(err, "Could not set custom OpenApi document")
	}

	// Sync CRD before kyverno starts
	c.sync()

	for i := 0; i < workers; i++ {
		go wait.Until(c.sync, constant.CRDControllerResync, stopCh)
	}
}

func (c *crdSync) sync() {
	crds, err := c.client.GetDynamicInterface().Resource(runtimeSchema.GroupVersionResource{
		Group:    "apiextensions.k8s.io",
		Version:  "v1beta1",
		Resource: "customresourcedefinitions",
	}).List(v1.ListOptions{})
	if err != nil {
		log.Log.Error(err, "could not fetch crd's from server")
		return
	}

	c.controller.mutex.Lock()
	defer c.controller.mutex.Unlock()

	c.controller.deleteCRDFromPreviousSync()

	for _, crd := range crds.Items {
		c.controller.parseCRD(crd)
	}
}

func (o *Controller) deleteCRDFromPreviousSync() {
	for _, crd := range o.crdList {
		delete(o.kindToDefinitionName, crd)
		delete(o.definitions, crd)
	}

	o.crdList = []string{}
}

func (o *Controller) parseCRD(crd unstructured.Unstructured) {
	var err error

	crdRaw, _ := json.Marshal(crd.Object)
	_ = json.Unmarshal(crdRaw, &crdDefinitionPrior)

	openV3schema := crdDefinitionPrior.Spec.Validation.OpenAPIV3Schema
	crdName := crdDefinitionPrior.Spec.Names.Kind

	if openV3schema == nil {
		_ = json.Unmarshal(crdRaw, &crdDefinitionNew)
		for _, crdVersion := range crdDefinitionNew.Spec.Versions {
			if crdVersion.Storage {
				openV3schema = crdVersion.Schema.OpenAPIV3Schema
				crdName = crdDefinitionNew.Spec.Names.Kind
				break
			}
		}
	}

	schemaRaw, _ := json.Marshal(openV3schema)
	if len(schemaRaw) < 1 {
		log.Log.V(3).Info("could not parse crd schema", "name", crdName)
		return
	}

	schemaRaw, err = addingDefaultFieldsToSchema(schemaRaw)
	if err != nil {
		log.Log.Error(err, "could not parse crd schema", "name", crdName)
		return
	}

	var schema yaml.MapSlice
	_ = yaml.Unmarshal(schemaRaw, &schema)

	parsedSchema, err := openapi_v2.NewSchema(schema, compiler.NewContext("schema", nil))
	if err != nil {
		log.Log.Error(err, "could not parse crd schema", "name", crdName)
		return
	}

	o.crdList = append(o.crdList, crdName)

	o.kindToDefinitionName[crdName] = crdName
	o.definitions[crdName] = parsedSchema
}

// addingDefaultFieldsToSchema will add any default missing fields like apiVersion, metadata
func addingDefaultFieldsToSchema(schemaRaw []byte) ([]byte, error) {
	var schema struct {
		Properties map[string]interface{} `json:"properties"`
	}
	_ = json.Unmarshal(schemaRaw, &schema)

	if len(schema.Properties) < 1 {
		return nil, errors.New("crd schema has no properties")
	}

	if schema.Properties["apiVersion"] == nil {
		apiVersionDefRaw := `{"description":"APIVersion defines the versioned schema of this representation of an object. Servers should convert recognized schemas to the latest internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources","type":"string"}`
		apiVersionDef := make(map[string]interface{})
		_ = json.Unmarshal([]byte(apiVersionDefRaw), &apiVersionDef)
		schema.Properties["apiVersion"] = apiVersionDef
	}

	if schema.Properties["metadata"] == nil {
		metadataDefRaw := `{"$ref":"#/definitions/io.k8s.apimachinery.pkg.apis.meta.v1.ObjectMeta","description":"Standard object's metadata. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata"}`
		metadataDef := make(map[string]interface{})
		_ = json.Unmarshal([]byte(metadataDefRaw), &metadataDef)
		schema.Properties["metadata"] = metadataDef
	}

	schemaWithDefaultFields, _ := json.Marshal(schema)

	return schemaWithDefaultFields, nil
}