/*
Copyright 2016 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 (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"io"
	"net"
	"net/http"
	goruntime "runtime"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/emicklei/go-restful-swagger12"
	"github.com/go-openapi/spec"
	"github.com/pborman/uuid"

	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/serializer"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/version"
	"k8s.io/apiserver/pkg/admission"
	"k8s.io/apiserver/pkg/audit"
	auditpolicy "k8s.io/apiserver/pkg/audit/policy"
	"k8s.io/apiserver/pkg/authentication/authenticator"
	"k8s.io/apiserver/pkg/authentication/authenticatorfactory"
	authenticatorunion "k8s.io/apiserver/pkg/authentication/request/union"
	"k8s.io/apiserver/pkg/authentication/user"
	"k8s.io/apiserver/pkg/authorization/authorizer"
	"k8s.io/apiserver/pkg/authorization/authorizerfactory"
	authorizerunion "k8s.io/apiserver/pkg/authorization/union"
	"k8s.io/apiserver/pkg/endpoints/discovery"
	genericapifilters "k8s.io/apiserver/pkg/endpoints/filters"
	apiopenapi "k8s.io/apiserver/pkg/endpoints/openapi"
	apirequest "k8s.io/apiserver/pkg/endpoints/request"
	"k8s.io/apiserver/pkg/features"
	genericregistry "k8s.io/apiserver/pkg/registry/generic"
	genericfilters "k8s.io/apiserver/pkg/server/filters"
	"k8s.io/apiserver/pkg/server/healthz"
	"k8s.io/apiserver/pkg/server/routes"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	"k8s.io/client-go/informers"
	restclient "k8s.io/client-go/rest"
	certutil "k8s.io/client-go/util/cert"
	openapicommon "k8s.io/kube-openapi/pkg/common"

	_ "k8s.io/apiserver/pkg/apis/apiserver/install"
)

const (
	// DefaultLegacyAPIPrefix is where the the legacy APIs will be located.
	DefaultLegacyAPIPrefix = "/api"

	// APIGroupPrefix is where non-legacy API group will be located.
	APIGroupPrefix = "/apis"
)

// Config is a structure used to configure a GenericAPIServer.
// Its members are sorted roughly in order of importance for composers.
type Config struct {
	// SecureServingInfo is required to serve https
	SecureServingInfo *SecureServingInfo

	// LoopbackClientConfig is a config for a privileged loopback connection to the API server
	// This is required for proper functioning of the PostStartHooks on a GenericAPIServer
	LoopbackClientConfig *restclient.Config
	// Authenticator determines which subject is making the request
	Authenticator authenticator.Request
	// Authorizer determines whether the subject is allowed to make the request based only
	// on the RequestURI
	Authorizer authorizer.Authorizer
	// AdmissionControl performs deep inspection of a given request (including content)
	// to set values and determine whether its allowed
	AdmissionControl      admission.Interface
	CorsAllowedOriginList []string

	EnableSwaggerUI bool
	EnableIndex     bool
	EnableProfiling bool
	EnableDiscovery bool
	// Requires generic profiling enabled
	EnableContentionProfiling bool
	EnableMetrics             bool

	DisabledPostStartHooks sets.String

	// Version will enable the /version endpoint if non-nil
	Version *version.Info
	// LegacyAuditWriter is the destination for audit logs. If nil, they will not be written.
	LegacyAuditWriter io.Writer
	// AuditBackend is where audit events are sent to.
	AuditBackend audit.Backend
	// AuditPolicyChecker makes the decision of whether and how to audit log a request.
	AuditPolicyChecker auditpolicy.Checker
	// SupportsBasicAuth indicates that's at least one Authenticator supports basic auth
	// If this is true, a basic auth challenge is returned on authentication failure
	// TODO(roberthbailey): Remove once the server no longer supports http basic auth.
	SupportsBasicAuth bool
	// ExternalAddress is the host name to use for external (public internet) facing URLs (e.g. Swagger)
	// Will default to a value based on secure serving info and available ipv4 IPs.
	ExternalAddress string

	// SharedInformerFactory provides shared informers for resources
	SharedInformerFactory informers.SharedInformerFactory
	//===========================================================================
	// Fields you probably don't care about changing
	//===========================================================================

	// BuildHandlerChainFunc allows you to build custom handler chains by decorating the apiHandler.
	BuildHandlerChainFunc func(apiHandler http.Handler, c *Config) (secure http.Handler)
	// DiscoveryAddresses is used to build the IPs pass to discovery. If nil, the ExternalAddress is
	// always reported
	DiscoveryAddresses discovery.Addresses
	// The default set of healthz checks. There might be more added via AddHealthzChecks dynamically.
	HealthzChecks []healthz.HealthzChecker
	// LegacyAPIGroupPrefixes is used to set up URL parsing for authorization and for validating requests
	// to InstallLegacyAPIGroup. New API servers don't generally have legacy groups at all.
	LegacyAPIGroupPrefixes sets.String
	// RequestContextMapper maps requests to contexts. Exported so downstream consumers can provider their own mappers
	// TODO confirm that anyone downstream actually uses this and doesn't just need an accessor
	RequestContextMapper apirequest.RequestContextMapper
	// Serializer is required and provides the interface for serializing and converting objects to and from the wire
	// The default (api.Codecs) usually works fine.
	Serializer runtime.NegotiatedSerializer
	// OpenAPIConfig will be used in generating OpenAPI spec. This is nil by default. Use DefaultOpenAPIConfig for "working" defaults.
	OpenAPIConfig *openapicommon.Config
	// SwaggerConfig will be used in generating Swagger spec. This is nil by default. Use DefaultSwaggerConfig for "working" defaults.
	SwaggerConfig *swagger.Config

	// RESTOptionsGetter is used to construct RESTStorage types via the generic registry.
	RESTOptionsGetter genericregistry.RESTOptionsGetter

	// If specified, requests will be allocated a random timeout between this value, and twice this value.
	// Note that it is up to the request handlers to ignore or honor this timeout. In seconds.
	MinRequestTimeout int
	// MaxRequestsInFlight is the maximum number of parallel non-long-running requests. Every further
	// request has to wait. Applies only to non-mutating requests.
	MaxRequestsInFlight int
	// MaxMutatingRequestsInFlight is the maximum number of parallel mutating requests. Every further
	// request has to wait.
	MaxMutatingRequestsInFlight int
	// Predicate which is true for paths of long-running http requests
	LongRunningFunc apirequest.LongRunningRequestCheck

	// EnableAPIResponseCompression indicates whether API Responses should support compression
	// if the client requests it via Accept-Encoding
	EnableAPIResponseCompression bool

	//===========================================================================
	// values below here are targets for removal
	//===========================================================================

	// The port on PublicAddress where a read-write server will be installed.
	// Defaults to 6443 if not set.
	ReadWritePort int
	// PublicAddress is the IP address where members of the cluster (kubelet,
	// kube-proxy, services, etc.) can reach the GenericAPIServer.
	// If nil or 0.0.0.0, the host's default interface will be used.
	PublicAddress net.IP
}

type SecureServingInfo struct {
	// BindAddress is the ip:port to serve on
	BindAddress string
	// BindNetwork is the type of network to bind to - defaults to "tcp", accepts "tcp",
	// "tcp4", and "tcp6".
	BindNetwork string

	// Cert is the main server cert which is used if SNI does not match. Cert must be non-nil and is
	// allowed to be in SNICerts.
	Cert *tls.Certificate

	// CACert is an optional certificate authority used for the loopback connection of the Admission controllers.
	// If this is nil, the certificate authority is extracted from Cert or a matching SNI certificate.
	CACert *tls.Certificate

	// SNICerts are the TLS certificates by name used for SNI.
	SNICerts map[string]*tls.Certificate

	// ClientCA is the certificate bundle for all the signers that you'll recognize for incoming client certificates
	ClientCA *x509.CertPool

	// MinTLSVersion optionally overrides the minimum TLS version supported.
	// Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants).
	MinTLSVersion uint16

	// CipherSuites optionally overrides the list of allowed cipher suites for the server.
	// Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants).
	CipherSuites []uint16
}

// NewConfig returns a Config struct with the default values
func NewConfig(codecs serializer.CodecFactory) *Config {
	return &Config{
		Serializer:                   codecs,
		ReadWritePort:                443,
		RequestContextMapper:         apirequest.NewRequestContextMapper(),
		BuildHandlerChainFunc:        DefaultBuildHandlerChain,
		LegacyAPIGroupPrefixes:       sets.NewString(DefaultLegacyAPIPrefix),
		DisabledPostStartHooks:       sets.NewString(),
		HealthzChecks:                []healthz.HealthzChecker{healthz.PingHealthz},
		EnableIndex:                  true,
		EnableDiscovery:              true,
		EnableProfiling:              true,
		MaxRequestsInFlight:          400,
		MaxMutatingRequestsInFlight:  200,
		MinRequestTimeout:            1800,
		EnableAPIResponseCompression: utilfeature.DefaultFeatureGate.Enabled(features.APIResponseCompression),

		// Default to treating watch as a long-running operation
		// Generic API servers have no inherent long-running subresources
		LongRunningFunc: genericfilters.BasicLongRunningRequestCheck(sets.NewString("watch"), sets.NewString()),
	}
}

func DefaultOpenAPIConfig(getDefinitions openapicommon.GetOpenAPIDefinitions, scheme *runtime.Scheme) *openapicommon.Config {
	defNamer := apiopenapi.NewDefinitionNamer(scheme)
	return &openapicommon.Config{
		ProtocolList:   []string{"https"},
		IgnorePrefixes: []string{"/swaggerapi"},
		Info: &spec.Info{
			InfoProps: spec.InfoProps{
				Title: "Generic API Server",
			},
		},
		DefaultResponse: &spec.Response{
			ResponseProps: spec.ResponseProps{
				Description: "Default Response.",
			},
		},
		GetOperationIDAndTags: apiopenapi.GetOperationIDAndTags,
		GetDefinitionName:     defNamer.GetDefinitionName,
		GetDefinitions:        getDefinitions,
	}
}

// DefaultSwaggerConfig returns a default configuration without WebServiceURL and
// WebServices set.
func DefaultSwaggerConfig() *swagger.Config {
	return &swagger.Config{
		ApiPath:         "/swaggerapi",
		SwaggerPath:     "/swaggerui/",
		SwaggerFilePath: "/swagger-ui/",
		SchemaFormatHandler: func(typeName string) string {
			switch typeName {
			case "metav1.Time", "*metav1.Time":
				return "date-time"
			}
			return ""
		},
	}
}

func (c *Config) ApplyClientCert(clientCAFile string) (*Config, error) {
	if c.SecureServingInfo != nil {
		if len(clientCAFile) > 0 {
			clientCAs, err := certutil.CertsFromFile(clientCAFile)
			if err != nil {
				return nil, fmt.Errorf("unable to load client CA file: %v", err)
			}
			if c.SecureServingInfo.ClientCA == nil {
				c.SecureServingInfo.ClientCA = x509.NewCertPool()
			}
			for _, cert := range clientCAs {
				c.SecureServingInfo.ClientCA.AddCert(cert)
			}
		}
	}

	return c, nil
}

type completedConfig struct {
	*Config
}

// Complete fills in any fields not set that are required to have valid data and can be derived
// from other fields. If you're going to `ApplyOptions`, do that first. It's mutating the receiver.
func (c *Config) Complete() completedConfig {
	if len(c.ExternalAddress) == 0 && c.PublicAddress != nil {
		hostAndPort := c.PublicAddress.String()
		if c.ReadWritePort != 0 {
			hostAndPort = net.JoinHostPort(hostAndPort, strconv.Itoa(c.ReadWritePort))
		}
		c.ExternalAddress = hostAndPort
	}
	if c.OpenAPIConfig != nil && c.OpenAPIConfig.SecurityDefinitions != nil {
		// Setup OpenAPI security: all APIs will have the same authentication for now.
		c.OpenAPIConfig.DefaultSecurity = []map[string][]string{}
		keys := []string{}
		for k := range *c.OpenAPIConfig.SecurityDefinitions {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			c.OpenAPIConfig.DefaultSecurity = append(c.OpenAPIConfig.DefaultSecurity, map[string][]string{k: {}})
		}
		if c.OpenAPIConfig.CommonResponses == nil {
			c.OpenAPIConfig.CommonResponses = map[int]spec.Response{}
		}
		if _, exists := c.OpenAPIConfig.CommonResponses[http.StatusUnauthorized]; !exists {
			c.OpenAPIConfig.CommonResponses[http.StatusUnauthorized] = spec.Response{
				ResponseProps: spec.ResponseProps{
					Description: "Unauthorized",
				},
			}
		}

		if c.OpenAPIConfig.Info == nil {
			c.OpenAPIConfig.Info = &spec.Info{}
		}
		if c.OpenAPIConfig.Info.Version == "" {
			if c.Version != nil {
				c.OpenAPIConfig.Info.Version = strings.Split(c.Version.String(), "-")[0]
			} else {
				c.OpenAPIConfig.Info.Version = "unversioned"
			}
		}
	}
	if c.SwaggerConfig != nil && len(c.SwaggerConfig.WebServicesUrl) == 0 {
		if c.SecureServingInfo != nil {
			c.SwaggerConfig.WebServicesUrl = "https://" + c.ExternalAddress
		} else {
			c.SwaggerConfig.WebServicesUrl = "http://" + c.ExternalAddress
		}
	}
	if c.DiscoveryAddresses == nil {
		c.DiscoveryAddresses = discovery.DefaultAddresses{DefaultAddress: c.ExternalAddress}
	}

	// If the loopbackclientconfig is specified AND it has a token for use against the API server
	// wrap the authenticator and authorizer in loopback authentication logic
	if c.Authenticator != nil && c.Authorizer != nil && c.LoopbackClientConfig != nil && len(c.LoopbackClientConfig.BearerToken) > 0 {
		privilegedLoopbackToken := c.LoopbackClientConfig.BearerToken
		var uid = uuid.NewRandom().String()
		tokens := make(map[string]*user.DefaultInfo)
		tokens[privilegedLoopbackToken] = &user.DefaultInfo{
			Name:   user.APIServerUser,
			UID:    uid,
			Groups: []string{user.SystemPrivilegedGroup},
		}

		tokenAuthenticator := authenticatorfactory.NewFromTokens(tokens)
		c.Authenticator = authenticatorunion.New(tokenAuthenticator, c.Authenticator)

		tokenAuthorizer := authorizerfactory.NewPrivilegedGroups(user.SystemPrivilegedGroup)
		c.Authorizer = authorizerunion.New(tokenAuthorizer, c.Authorizer)
	}

	return completedConfig{c}
}

// SkipComplete provides a way to construct a server instance without config completion.
func (c *Config) SkipComplete() completedConfig {
	return completedConfig{c}
}

// New creates a new server which logically combines the handling chain with the passed server.
// name is used to differentiate for logging. The handler chain in particular can be difficult as it starts delgating.
func (c completedConfig) New(name string, delegationTarget DelegationTarget) (*GenericAPIServer, error) {
	// The delegationTarget and the config must agree on the RequestContextMapper

	if c.Serializer == nil {
		return nil, fmt.Errorf("Genericapiserver.New() called with config.Serializer == nil")
	}
	if c.LoopbackClientConfig == nil {
		return nil, fmt.Errorf("Genericapiserver.New() called with config.LoopbackClientConfig == nil")
	}

	handlerChainBuilder := func(handler http.Handler) http.Handler {
		return c.BuildHandlerChainFunc(handler, c.Config)
	}
	apiServerHandler := NewAPIServerHandler(name, c.RequestContextMapper, c.Serializer, handlerChainBuilder, delegationTarget.UnprotectedHandler())

	s := &GenericAPIServer{
		discoveryAddresses:     c.DiscoveryAddresses,
		LoopbackClientConfig:   c.LoopbackClientConfig,
		legacyAPIGroupPrefixes: c.LegacyAPIGroupPrefixes,
		admissionControl:       c.AdmissionControl,
		requestContextMapper:   c.RequestContextMapper,
		Serializer:             c.Serializer,
		AuditBackend:           c.AuditBackend,

		minRequestTimeout: time.Duration(c.MinRequestTimeout) * time.Second,

		SecureServingInfo: c.SecureServingInfo,
		ExternalAddress:   c.ExternalAddress,

		Handler: apiServerHandler,

		listedPathProvider: apiServerHandler,

		swaggerConfig: c.SwaggerConfig,
		openAPIConfig: c.OpenAPIConfig,

		postStartHooks:         map[string]postStartHookEntry{},
		disabledPostStartHooks: c.DisabledPostStartHooks,

		healthzChecks: c.HealthzChecks,

		DiscoveryGroupManager: discovery.NewRootAPIsHandler(c.DiscoveryAddresses, c.Serializer, c.RequestContextMapper),

		enableAPIResponseCompression: c.EnableAPIResponseCompression,
	}

	for k, v := range delegationTarget.PostStartHooks() {
		s.postStartHooks[k] = v
	}

	genericApiServerHookName := "generic-apiserver-start-informers"
	if c.SharedInformerFactory != nil && !s.isHookRegistered(genericApiServerHookName) {
		err := s.AddPostStartHook(genericApiServerHookName, func(context PostStartHookContext) error {
			c.SharedInformerFactory.Start(context.StopCh)
			return nil
		})
		if err != nil {
			return nil, err
		}
	}
	for _, delegateCheck := range delegationTarget.HealthzChecks() {
		skip := false
		for _, existingCheck := range c.HealthzChecks {
			if existingCheck.Name() == delegateCheck.Name() {
				skip = true
				break
			}
		}
		if skip {
			continue
		}

		s.healthzChecks = append(s.healthzChecks, delegateCheck)
	}

	s.listedPathProvider = routes.ListedPathProviders{s.listedPathProvider, delegationTarget}

	installAPI(s, c.Config)

	// use the UnprotectedHandler from the delegation target to ensure that we don't attempt to double authenticator, authorize,
	// or some other part of the filter chain in delegation cases.
	if delegationTarget.UnprotectedHandler() == nil && c.EnableIndex {
		s.Handler.NonGoRestfulMux.NotFoundHandler(routes.IndexLister{
			StatusCode:   http.StatusNotFound,
			PathProvider: s.listedPathProvider,
		})
	}

	return s, nil
}

func DefaultBuildHandlerChain(apiHandler http.Handler, c *Config) http.Handler {
	handler := genericapifilters.WithAuthorization(apiHandler, c.RequestContextMapper, c.Authorizer, c.Serializer)
	handler = genericfilters.WithMaxInFlightLimit(handler, c.MaxRequestsInFlight, c.MaxMutatingRequestsInFlight, c.RequestContextMapper, c.LongRunningFunc)
	handler = genericapifilters.WithImpersonation(handler, c.RequestContextMapper, c.Authorizer, c.Serializer)
	if utilfeature.DefaultFeatureGate.Enabled(features.AdvancedAuditing) {
		handler = genericapifilters.WithAudit(handler, c.RequestContextMapper, c.AuditBackend, c.AuditPolicyChecker, c.LongRunningFunc)
	} else {
		handler = genericapifilters.WithLegacyAudit(handler, c.RequestContextMapper, c.LegacyAuditWriter)
	}
	handler = genericapifilters.WithAuthentication(handler, c.RequestContextMapper, c.Authenticator, genericapifilters.Unauthorized(c.RequestContextMapper, c.Serializer, c.SupportsBasicAuth))
	handler = genericfilters.WithCORS(handler, c.CorsAllowedOriginList, nil, nil, nil, "true")
	handler = genericfilters.WithTimeoutForNonLongRunningRequests(handler, c.RequestContextMapper, c.LongRunningFunc)
	handler = genericapifilters.WithRequestInfo(handler, NewRequestInfoResolver(c), c.RequestContextMapper)
	handler = apirequest.WithRequestContext(handler, c.RequestContextMapper)
	handler = genericfilters.WithPanicRecovery(handler)
	return handler
}

func installAPI(s *GenericAPIServer, c *Config) {
	if c.EnableIndex {
		routes.Index{}.Install(s.listedPathProvider, s.Handler.NonGoRestfulMux)
	}
	if c.SwaggerConfig != nil && c.EnableSwaggerUI {
		routes.SwaggerUI{}.Install(s.Handler.NonGoRestfulMux)
	}
	if c.EnableProfiling {
		routes.Profiling{}.Install(s.Handler.NonGoRestfulMux)
		if c.EnableContentionProfiling {
			goruntime.SetBlockProfileRate(1)
		}
	}
	if c.EnableMetrics {
		if c.EnableProfiling {
			routes.MetricsWithReset{}.Install(s.Handler.NonGoRestfulMux)
		} else {
			routes.DefaultMetrics{}.Install(s.Handler.NonGoRestfulMux)
		}
	}
	routes.Version{Version: c.Version}.Install(s.Handler.GoRestfulContainer)

	if c.EnableDiscovery {
		s.Handler.GoRestfulContainer.Add(s.DiscoveryGroupManager.WebService())
	}
}

func NewRequestInfoResolver(c *Config) *apirequest.RequestInfoFactory {
	apiPrefixes := sets.NewString(strings.Trim(APIGroupPrefix, "/")) // all possible API prefixes
	legacyAPIPrefixes := sets.String{}                               // APIPrefixes that won't have groups (legacy)
	for legacyAPIPrefix := range c.LegacyAPIGroupPrefixes {
		apiPrefixes.Insert(strings.Trim(legacyAPIPrefix, "/"))
		legacyAPIPrefixes.Insert(strings.Trim(legacyAPIPrefix, "/"))
	}

	return &apirequest.RequestInfoFactory{
		APIPrefixes:          apiPrefixes,
		GrouplessAPIPrefixes: legacyAPIPrefixes,
	}
}
