/*
Copyright 2014 The Kubernetes 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 server

import (
	"fmt"
	"mime"
	"net/http"
	"strings"
	"sync"
	"time"

	systemd "github.com/coreos/go-systemd/daemon"
	"github.com/emicklei/go-restful"
	"github.com/emicklei/go-restful/swagger"
	"github.com/golang/glog"

	"k8s.io/apimachinery/pkg/apimachinery"
	"k8s.io/apimachinery/pkg/apimachinery/registered"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	openapicommon "k8s.io/apimachinery/pkg/openapi"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/runtime/serializer"
	utilnet "k8s.io/apimachinery/pkg/util/net"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apiserver/pkg/admission"
	genericapi "k8s.io/apiserver/pkg/endpoints"
	apirequest "k8s.io/apiserver/pkg/endpoints/request"
	"k8s.io/apiserver/pkg/registry/rest"
	"k8s.io/apiserver/pkg/server/healthz"
	"k8s.io/apiserver/pkg/server/mux"
	genericmux "k8s.io/apiserver/pkg/server/mux"
	"k8s.io/apiserver/pkg/server/routes"
	restclient "k8s.io/client-go/rest"
)

// Info about an API group.
type APIGroupInfo struct {
	GroupMeta apimachinery.GroupMeta
	// Info about the resources in this group. Its a map from version to resource to the storage.
	VersionedResourcesStorageMap map[string]map[string]rest.Storage
	// OptionsExternalVersion controls the APIVersion used for common objects in the
	// schema like api.Status, api.DeleteOptions, and metav1.ListOptions. Other implementors may
	// define a version "v1beta1" but want to use the Kubernetes "v1" internal objects.
	// If nil, defaults to groupMeta.GroupVersion.
	// TODO: Remove this when https://github.com/kubernetes/kubernetes/issues/19018 is fixed.
	OptionsExternalVersion *schema.GroupVersion
	// MetaGroupVersion defaults to "meta.k8s.io/v1" and is the scheme group version used to decode
	// common API implementations like ListOptions. Future changes will allow this to vary by group
	// version (for when the inevitable meta/v2 group emerges).
	MetaGroupVersion *schema.GroupVersion

	// Scheme includes all of the types used by this group and how to convert between them (or
	// to convert objects from outside of this group that are accepted in this API).
	// TODO: replace with interfaces
	Scheme *runtime.Scheme
	// NegotiatedSerializer controls how this group encodes and decodes data
	NegotiatedSerializer runtime.NegotiatedSerializer
	// ParameterCodec performs conversions for query parameters passed to API calls
	ParameterCodec runtime.ParameterCodec

	// SubresourceGroupVersionKind contains the GroupVersionKind overrides for each subresource that is
	// accessible from this API group version. The GroupVersionKind is that of the external version of
	// the subresource. The key of this map should be the path of the subresource. The keys here should
	// match the keys in the Storage map above for subresources.
	SubresourceGroupVersionKind map[string]schema.GroupVersionKind
}

// GenericAPIServer contains state for a Kubernetes cluster api server.
type GenericAPIServer struct {
	// discoveryAddresses is used to build cluster IPs for discovery.
	discoveryAddresses DiscoveryAddresses

	// LoopbackClientConfig is a config for a privileged loopback connection to the API server
	LoopbackClientConfig *restclient.Config

	// minRequestTimeout is how short the request timeout can be.  This is used to build the RESTHandler
	minRequestTimeout time.Duration

	// legacyAPIGroupPrefixes is used to set up URL parsing for authorization and for validating requests
	// to InstallLegacyAPIGroup
	legacyAPIGroupPrefixes sets.String

	// admissionControl is used to build the RESTStorage that backs an API Group.
	admissionControl admission.Interface

	// requestContextMapper provides a way to get the context for a request.  It may be nil.
	requestContextMapper apirequest.RequestContextMapper

	// The registered APIs
	HandlerContainer *genericmux.APIContainer

	SecureServingInfo *SecureServingInfo

	// numerical ports, set after listening
	effectiveSecurePort int

	// ExternalAddress is the address (hostname or IP and port) that should be used in
	// external (public internet) URLs for this GenericAPIServer.
	ExternalAddress string

	// storage contains the RESTful endpoints exposed by this GenericAPIServer
	storage map[string]rest.Storage

	// Serializer controls how common API objects not in a group/version prefix are serialized for this server.
	// Individual APIGroups may define their own serializers.
	Serializer runtime.NegotiatedSerializer

	// "Outputs"
	Handler http.Handler
	// FallThroughHandler is the final HTTP handler in the chain.
	// It comes after all filters and the API handling
	FallThroughHandler *mux.PathRecorderMux

	// listedPathProvider is a lister which provides the set of paths to show at /
	listedPathProvider routes.ListedPathProvider

	// Map storing information about all groups to be exposed in discovery response.
	// The map is from name to the group.
	// The slice preserves group name insertion order.
	apiGroupsForDiscoveryLock sync.RWMutex
	apiGroupsForDiscovery     map[string]metav1.APIGroup
	apiGroupNamesForDiscovery []string

	// Enable swagger and/or OpenAPI if these configs are non-nil.
	swaggerConfig *swagger.Config
	openAPIConfig *openapicommon.Config

	// PostStartHooks are each called after the server has started listening, in a separate go func for each
	// with no guarantee of ordering between them.  The map key is a name used for error reporting.
	// It may kill the process with a panic if it wishes to by returning an error.
	postStartHookLock      sync.Mutex
	postStartHooks         map[string]postStartHookEntry
	postStartHooksCalled   bool
	disabledPostStartHooks sets.String

	// healthz checks
	healthzLock    sync.Mutex
	healthzChecks  []healthz.HealthzChecker
	healthzCreated bool
}

// DelegationTarget is an interface which allows for composition of API servers with top level handling that works
// as expected.
type DelegationTarget interface {
	// UnprotectedHandler returns a handler that is NOT protected by a normal chain
	UnprotectedHandler() http.Handler

	// RequestContextMapper returns the existing RequestContextMapper.  Because we cannot rewire all existing
	// uses of this function, this will be used in any delegating API server
	RequestContextMapper() apirequest.RequestContextMapper

	// PostStartHooks returns the post-start hooks that need to be combined
	PostStartHooks() map[string]postStartHookEntry

	// HealthzChecks returns the healthz checks that need to be combined
	HealthzChecks() []healthz.HealthzChecker

	// ListedPaths returns the paths for supporting an index
	ListedPaths() []string
}

func (s *GenericAPIServer) UnprotectedHandler() http.Handler {
	return s.HandlerContainer.ServeMux
}
func (s *GenericAPIServer) PostStartHooks() map[string]postStartHookEntry {
	return s.postStartHooks
}
func (s *GenericAPIServer) HealthzChecks() []healthz.HealthzChecker {
	return s.healthzChecks
}
func (s *GenericAPIServer) ListedPaths() []string {
	return s.listedPathProvider.ListedPaths()
}

var EmptyDelegate = emptyDelegate{
	requestContextMapper: apirequest.NewRequestContextMapper(),
}

type emptyDelegate struct {
	requestContextMapper apirequest.RequestContextMapper
}

func (s emptyDelegate) UnprotectedHandler() http.Handler {
	return http.NotFoundHandler()
}
func (s emptyDelegate) PostStartHooks() map[string]postStartHookEntry {
	return map[string]postStartHookEntry{}
}
func (s emptyDelegate) HealthzChecks() []healthz.HealthzChecker {
	return []healthz.HealthzChecker{}
}
func (s emptyDelegate) ListedPaths() []string {
	return []string{}
}
func (s emptyDelegate) RequestContextMapper() apirequest.RequestContextMapper {
	return s.requestContextMapper
}

func init() {
	// Send correct mime type for .svg files.
	// TODO: remove when https://github.com/golang/go/commit/21e47d831bafb59f22b1ea8098f709677ec8ce33
	// makes it into all of our supported go versions (only in v1.7.1 now).
	mime.AddExtensionType(".svg", "image/svg+xml")
}

// RequestContextMapper is exposed so that third party resource storage can be build in a different location.
// TODO refactor third party resource storage
func (s *GenericAPIServer) RequestContextMapper() apirequest.RequestContextMapper {
	return s.requestContextMapper
}

// MinRequestTimeout is exposed so that third party resource storage can be build in a different location.
// TODO refactor third party resource storage
func (s *GenericAPIServer) MinRequestTimeout() time.Duration {
	return s.minRequestTimeout
}

type preparedGenericAPIServer struct {
	*GenericAPIServer
}

// PrepareRun does post API installation setup steps.
func (s *GenericAPIServer) PrepareRun() preparedGenericAPIServer {
	if s.swaggerConfig != nil {
		routes.Swagger{Config: s.swaggerConfig}.Install(s.HandlerContainer)
	}
	if s.openAPIConfig != nil {
		routes.OpenAPI{
			Config: s.openAPIConfig,
		}.Install(s.HandlerContainer, s.FallThroughHandler)
	}

	s.installHealthz()

	return preparedGenericAPIServer{s}
}

// Run spawns the http servers (secure and insecure). It only returns if stopCh is closed
// or one of the ports cannot be listened on initially.
func (s preparedGenericAPIServer) Run(stopCh <-chan struct{}) error {
	err := s.NonBlockingRun(stopCh)
	if err != nil {
		return err
	}

	<-stopCh
	return nil
}

// NonBlockingRun spawns the http servers (secure and insecure). An error is
// returned if either of the ports cannot be listened on.
func (s preparedGenericAPIServer) NonBlockingRun(stopCh <-chan struct{}) error {
	// Use an internal stop channel to allow cleanup of the listeners on error.
	internalStopCh := make(chan struct{})

	if s.SecureServingInfo != nil && s.Handler != nil {
		if err := s.serveSecurely(internalStopCh); err != nil {
			close(internalStopCh)
			return err
		}
	}

	// Now that both listeners have bound successfully, it is the
	// responsibility of the caller to close the provided channel to
	// ensure cleanup.
	go func() {
		<-stopCh
		close(internalStopCh)
	}()

	s.RunPostStartHooks()

	if _, err := systemd.SdNotify(true, "READY=1\n"); err != nil {
		glog.Errorf("Unable to send systemd daemon successful start message: %v\n", err)
	}

	return nil
}

// EffectiveSecurePort returns the secure port we bound to.
func (s *GenericAPIServer) EffectiveSecurePort() int {
	return s.effectiveSecurePort
}

// installAPIResources is a private method for installing the REST storage backing each api groupversionresource
func (s *GenericAPIServer) installAPIResources(apiPrefix string, apiGroupInfo *APIGroupInfo) error {
	for _, groupVersion := range apiGroupInfo.GroupMeta.GroupVersions {
		if len(apiGroupInfo.VersionedResourcesStorageMap[groupVersion.Version]) == 0 {
			glog.Warningf("Skipping API %v because it has no resources.", groupVersion)
			continue
		}

		apiGroupVersion := s.getAPIGroupVersion(apiGroupInfo, groupVersion, apiPrefix)
		if apiGroupInfo.OptionsExternalVersion != nil {
			apiGroupVersion.OptionsExternalVersion = apiGroupInfo.OptionsExternalVersion
		}

		if err := apiGroupVersion.InstallREST(s.HandlerContainer.Container); err != nil {
			return fmt.Errorf("Unable to setup API %v: %v", apiGroupInfo, err)
		}
	}

	return nil
}

func (s *GenericAPIServer) InstallLegacyAPIGroup(apiPrefix string, apiGroupInfo *APIGroupInfo) error {
	if !s.legacyAPIGroupPrefixes.Has(apiPrefix) {
		return fmt.Errorf("%q is not in the allowed legacy API prefixes: %v", apiPrefix, s.legacyAPIGroupPrefixes.List())
	}
	if err := s.installAPIResources(apiPrefix, apiGroupInfo); err != nil {
		return err
	}

	// setup discovery
	apiVersions := []string{}
	for _, groupVersion := range apiGroupInfo.GroupMeta.GroupVersions {
		apiVersions = append(apiVersions, groupVersion.Version)
	}
	// Install the version handler.
	// Add a handler at /<apiPrefix> to enumerate the supported api versions.
	genericapi.AddApiWebService(s.Serializer, s.HandlerContainer.Container, apiPrefix, func(req *restful.Request) *metav1.APIVersions {
		clientIP := utilnet.GetClientIP(req.Request)

		apiVersionsForDiscovery := metav1.APIVersions{
			ServerAddressByClientCIDRs: s.discoveryAddresses.ServerAddressByClientCIDRs(clientIP),
			Versions:                   apiVersions,
		}
		return &apiVersionsForDiscovery
	})
	return nil
}

// Exposes the given api group in the API.
func (s *GenericAPIServer) InstallAPIGroup(apiGroupInfo *APIGroupInfo) error {
	// Do not register empty group or empty version.  Doing so claims /apis/ for the wrong entity to be returned.
	// Catching these here places the error  much closer to its origin
	if len(apiGroupInfo.GroupMeta.GroupVersion.Group) == 0 {
		return fmt.Errorf("cannot register handler with an empty group for %#v", *apiGroupInfo)
	}
	if len(apiGroupInfo.GroupMeta.GroupVersion.Version) == 0 {
		return fmt.Errorf("cannot register handler with an empty version for %#v", *apiGroupInfo)
	}

	if err := s.installAPIResources(APIGroupPrefix, apiGroupInfo); err != nil {
		return err
	}

	// setup discovery
	// Install the version handler.
	// Add a handler at /apis/<groupName> to enumerate all versions supported by this group.
	apiVersionsForDiscovery := []metav1.GroupVersionForDiscovery{}
	for _, groupVersion := range apiGroupInfo.GroupMeta.GroupVersions {
		// Check the config to make sure that we elide versions that don't have any resources
		if len(apiGroupInfo.VersionedResourcesStorageMap[groupVersion.Version]) == 0 {
			continue
		}
		apiVersionsForDiscovery = append(apiVersionsForDiscovery, metav1.GroupVersionForDiscovery{
			GroupVersion: groupVersion.String(),
			Version:      groupVersion.Version,
		})
	}
	preferedVersionForDiscovery := metav1.GroupVersionForDiscovery{
		GroupVersion: apiGroupInfo.GroupMeta.GroupVersion.String(),
		Version:      apiGroupInfo.GroupMeta.GroupVersion.Version,
	}
	apiGroup := metav1.APIGroup{
		Name:             apiGroupInfo.GroupMeta.GroupVersion.Group,
		Versions:         apiVersionsForDiscovery,
		PreferredVersion: preferedVersionForDiscovery,
	}

	s.AddAPIGroupForDiscovery(apiGroup)
	s.HandlerContainer.Add(genericapi.NewGroupWebService(s.Serializer, APIGroupPrefix+"/"+apiGroup.Name, apiGroup))

	return nil
}

// AddAPIGroupForDiscovery adds the specified group to the list served to discovery queries.
// Groups are listed in the order they are added.
func (s *GenericAPIServer) AddAPIGroupForDiscovery(apiGroup metav1.APIGroup) {
	s.apiGroupsForDiscoveryLock.Lock()
	defer s.apiGroupsForDiscoveryLock.Unlock()

	// Insert the group into the ordered list if it is not already present
	if _, exists := s.apiGroupsForDiscovery[apiGroup.Name]; !exists {
		s.apiGroupNamesForDiscovery = append(s.apiGroupNamesForDiscovery, apiGroup.Name)
	}

	s.apiGroupsForDiscovery[apiGroup.Name] = apiGroup
}

func (s *GenericAPIServer) RemoveAPIGroupForDiscovery(groupName string) {
	s.apiGroupsForDiscoveryLock.Lock()
	defer s.apiGroupsForDiscoveryLock.Unlock()

	// Remove the group from the ordered list
	// https://github.com/golang/go/wiki/SliceTricks#filtering-without-allocating
	newOrder := s.apiGroupNamesForDiscovery[:0]
	for _, orderedGroupName := range s.apiGroupNamesForDiscovery {
		if orderedGroupName != groupName {
			newOrder = append(newOrder, orderedGroupName)
		}
	}
	s.apiGroupNamesForDiscovery = newOrder

	delete(s.apiGroupsForDiscovery, groupName)
}

func (s *GenericAPIServer) getAPIGroupVersion(apiGroupInfo *APIGroupInfo, groupVersion schema.GroupVersion, apiPrefix string) *genericapi.APIGroupVersion {
	storage := make(map[string]rest.Storage)
	for k, v := range apiGroupInfo.VersionedResourcesStorageMap[groupVersion.Version] {
		storage[strings.ToLower(k)] = v
	}
	version := s.newAPIGroupVersion(apiGroupInfo, groupVersion)
	version.Root = apiPrefix
	version.Storage = storage
	return version
}

func (s *GenericAPIServer) newAPIGroupVersion(apiGroupInfo *APIGroupInfo, groupVersion schema.GroupVersion) *genericapi.APIGroupVersion {
	return &genericapi.APIGroupVersion{
		GroupVersion:     groupVersion,
		MetaGroupVersion: apiGroupInfo.MetaGroupVersion,

		ParameterCodec:  apiGroupInfo.ParameterCodec,
		Serializer:      apiGroupInfo.NegotiatedSerializer,
		Creater:         apiGroupInfo.Scheme,
		Convertor:       apiGroupInfo.Scheme,
		UnsafeConvertor: runtime.UnsafeObjectConvertor(apiGroupInfo.Scheme),
		Copier:          apiGroupInfo.Scheme,
		Defaulter:       apiGroupInfo.Scheme,
		Typer:           apiGroupInfo.Scheme,
		SubresourceGroupVersionKind: apiGroupInfo.SubresourceGroupVersionKind,
		Linker: apiGroupInfo.GroupMeta.SelfLinker,
		Mapper: apiGroupInfo.GroupMeta.RESTMapper,

		Admit:             s.admissionControl,
		Context:           s.RequestContextMapper(),
		MinRequestTimeout: s.minRequestTimeout,
	}
}

// DynamicApisDiscovery returns a webservice serving api group discovery.
// Note: during the server runtime apiGroupsForDiscovery might change.
func (s *GenericAPIServer) DynamicApisDiscovery() *restful.WebService {
	return genericapi.NewApisWebService(s.Serializer, APIGroupPrefix, func(req *restful.Request) []metav1.APIGroup {
		s.apiGroupsForDiscoveryLock.RLock()
		defer s.apiGroupsForDiscoveryLock.RUnlock()

		sortedGroups := []metav1.APIGroup{}

		// ranging over apiGroupNamesForDiscovery preserves the registration order
		for _, groupName := range s.apiGroupNamesForDiscovery {
			sortedGroups = append(sortedGroups, s.apiGroupsForDiscovery[groupName])
		}

		clientIP := utilnet.GetClientIP(req.Request)
		serverCIDR := s.discoveryAddresses.ServerAddressByClientCIDRs(clientIP)
		groups := make([]metav1.APIGroup, len(sortedGroups))
		for i := range sortedGroups {
			groups[i] = sortedGroups[i]
			groups[i].ServerAddressByClientCIDRs = serverCIDR
		}
		return groups
	})
}

// NewDefaultAPIGroupInfo returns an APIGroupInfo stubbed with "normal" values
// exposed for easier composition from other packages
func NewDefaultAPIGroupInfo(group string, registry *registered.APIRegistrationManager, scheme *runtime.Scheme, parameterCodec runtime.ParameterCodec, codecs serializer.CodecFactory) APIGroupInfo {
	groupMeta := registry.GroupOrDie(group)

	return APIGroupInfo{
		GroupMeta:                    *groupMeta,
		VersionedResourcesStorageMap: map[string]map[string]rest.Storage{},
		// TODO unhardcode this.  It was hardcoded before, but we need to re-evaluate
		OptionsExternalVersion: &schema.GroupVersion{Version: "v1"},
		Scheme:                 scheme,
		ParameterCodec:         parameterCodec,
		NegotiatedSerializer:   codecs,
	}
}
