/*
Copyright
*/
package main

import (
	"crypto/tls"
	"encoding/json"
	"errors"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"reflect"
	"regexp"
	"sort"
	"strconv"
	"syscall"
	"time"

	log "github.com/Sirupsen/logrus"
	"github.com/codegangsta/negroni"
	"github.com/containous/oxy/cbreaker"
	"github.com/containous/oxy/connlimit"
	"github.com/containous/oxy/forward"
	"github.com/containous/oxy/roundrobin"
	"github.com/containous/oxy/stream"
	"github.com/containous/oxy/utils"
	"github.com/containous/traefik/middlewares"
	"github.com/containous/traefik/provider"
	"github.com/containous/traefik/safe"
	"github.com/containous/traefik/types"
	"github.com/gorilla/mux"
	"github.com/mailgun/manners"
	"github.com/streamrail/concurrent-map"
)

var oxyLogger = &OxyLogger{}

// Server is the reverse-proxy/load-balancer engine
type Server struct {
	serverEntryPoints          serverEntryPoints
	configurationChan          chan types.ConfigMessage
	configurationValidatedChan chan types.ConfigMessage
	signals                    chan os.Signal
	stopChan                   chan bool
	providers                  []provider.Provider
	currentConfigurations      safe.Safe
	globalConfiguration        GlobalConfiguration
	loggerMiddleware           *middlewares.Logger
	routinesPool               safe.Pool
}

type serverEntryPoints map[string]*serverEntryPoint

type serverEntryPoint struct {
	httpServer *manners.GracefulServer
	httpRouter *middlewares.HandlerSwitcher
}

type serverRoute struct {
	route         *mux.Route
	stripPrefixes []string
}

// NewServer returns an initialized Server.
func NewServer(globalConfiguration GlobalConfiguration) *Server {
	server := new(Server)

	server.serverEntryPoints = make(map[string]*serverEntryPoint)
	server.configurationChan = make(chan types.ConfigMessage, 10)
	server.configurationValidatedChan = make(chan types.ConfigMessage, 10)
	server.signals = make(chan os.Signal, 1)
	server.stopChan = make(chan bool, 1)
	server.providers = []provider.Provider{}
	signal.Notify(server.signals, syscall.SIGINT, syscall.SIGTERM)
	currentConfigurations := make(configs)
	server.currentConfigurations.Set(currentConfigurations)
	server.globalConfiguration = globalConfiguration
	server.loggerMiddleware = middlewares.NewLogger(globalConfiguration.AccessLogsFile)

	return server
}

// Start starts the server and blocks until server is shutted down.
func (server *Server) Start() {
	server.startHTTPServers()
	server.routinesPool.Go(func(stop chan bool) {
		server.listenProviders(stop)
	})
	server.routinesPool.Go(func(stop chan bool) {
		server.listenConfigurations(stop)
	})
	server.configureProviders()
	server.startProviders()
	go server.listenSignals()
	<-server.stopChan
}

// Stop stops the server
func (server *Server) Stop() {
	for _, serverEntryPoint := range server.serverEntryPoints {
		serverEntryPoint.httpServer.BlockingClose()
	}
	server.stopChan <- true
}

// Close destroys the server
func (server *Server) Close() {
	server.routinesPool.Stop()
	close(server.configurationChan)
	close(server.configurationValidatedChan)
	close(server.signals)
	close(server.stopChan)
	server.loggerMiddleware.Close()
}

func (server *Server) startHTTPServers() {
	server.serverEntryPoints = server.buildEntryPoints(server.globalConfiguration)
	for newServerEntryPointName, newServerEntryPoint := range server.serverEntryPoints {
		newsrv, err := server.prepareServer(newServerEntryPointName, newServerEntryPoint.httpRouter, server.globalConfiguration.EntryPoints[newServerEntryPointName], nil, server.loggerMiddleware, metrics)
		if err != nil {
			log.Fatal("Error preparing server: ", err)
		}
		serverEntryPoint := server.serverEntryPoints[newServerEntryPointName]
		serverEntryPoint.httpServer = newsrv
		go server.startServer(serverEntryPoint.httpServer, server.globalConfiguration)
	}
}

func (server *Server) listenProviders(stop chan bool) {
	lastReceivedConfiguration := safe.New(time.Unix(0, 0))
	lastConfigs := cmap.New()
	for {
		select {
		case <-stop:
			return
		case configMsg, ok := <-server.configurationChan:
			if !ok {
				return
			}
			jsonConf, _ := json.Marshal(configMsg.Configuration)
			log.Debugf("Configuration received from provider %s: %s", configMsg.ProviderName, string(jsonConf))
			lastConfigs.Set(configMsg.ProviderName, &configMsg)
			lastReceivedConfigurationValue := lastReceivedConfiguration.Get().(time.Time)
			if time.Now().After(lastReceivedConfigurationValue.Add(time.Duration(server.globalConfiguration.ProvidersThrottleDuration))) {
				log.Debugf("Last %s config received more than %s, OK", configMsg.ProviderName, server.globalConfiguration.ProvidersThrottleDuration)
				// last config received more than n s ago
				server.configurationValidatedChan <- configMsg
			} else {
				log.Debugf("Last %s config received less than %s, waiting...", configMsg.ProviderName, server.globalConfiguration.ProvidersThrottleDuration)
				server.routinesPool.Go(func(stop chan bool) {
					select {
					case <-stop:
						return
					case <-time.After(server.globalConfiguration.ProvidersThrottleDuration):
						lastReceivedConfigurationValue := lastReceivedConfiguration.Get().(time.Time)
						if time.Now().After(lastReceivedConfigurationValue.Add(time.Duration(server.globalConfiguration.ProvidersThrottleDuration))) {
							log.Debugf("Waited for %s config, OK", configMsg.ProviderName)
							if lastConfig, ok := lastConfigs.Get(configMsg.ProviderName); ok {
								server.configurationValidatedChan <- *lastConfig.(*types.ConfigMessage)
							}
						}
					}
				})
			}
			lastReceivedConfiguration.Set(time.Now())
		}
	}
}

func (server *Server) listenConfigurations(stop chan bool) {
	for {
		select {
		case <-stop:
			return
		case configMsg, ok := <-server.configurationValidatedChan:
			if !ok {
				return
			}
			currentConfigurations := server.currentConfigurations.Get().(configs)
			if configMsg.Configuration == nil {
				log.Infof("Skipping empty Configuration for provider %s", configMsg.ProviderName)
			} else if reflect.DeepEqual(currentConfigurations[configMsg.ProviderName], configMsg.Configuration) {
				log.Infof("Skipping same configuration for provider %s", configMsg.ProviderName)
			} else {
				// Copy configurations to new map so we don't change current if LoadConfig fails
				newConfigurations := make(configs)
				for k, v := range currentConfigurations {
					newConfigurations[k] = v
				}
				newConfigurations[configMsg.ProviderName] = configMsg.Configuration

				newServerEntryPoints, err := server.loadConfig(newConfigurations, server.globalConfiguration)
				if err == nil {
					for newServerEntryPointName, newServerEntryPoint := range newServerEntryPoints {
						server.serverEntryPoints[newServerEntryPointName].httpRouter.UpdateHandler(newServerEntryPoint.httpRouter.GetHandler())
						log.Infof("Server configuration reloaded on %s", server.serverEntryPoints[newServerEntryPointName].httpServer.Addr)
					}
					server.currentConfigurations.Set(newConfigurations)
				} else {
					log.Error("Error loading new configuration, aborted ", err)
				}
			}
		}
	}
}

func (server *Server) configureProviders() {
	// configure providers
	if server.globalConfiguration.Docker != nil {
		server.providers = append(server.providers, server.globalConfiguration.Docker)
	}
	if server.globalConfiguration.Marathon != nil {
		server.providers = append(server.providers, server.globalConfiguration.Marathon)
	}
	if server.globalConfiguration.File != nil {
		server.providers = append(server.providers, server.globalConfiguration.File)
	}
	if server.globalConfiguration.Web != nil {
		server.globalConfiguration.Web.server = server
		server.providers = append(server.providers, server.globalConfiguration.Web)
	}
	if server.globalConfiguration.Consul != nil {
		server.providers = append(server.providers, server.globalConfiguration.Consul)
	}
	if server.globalConfiguration.ConsulCatalog != nil {
		server.providers = append(server.providers, server.globalConfiguration.ConsulCatalog)
	}
	if server.globalConfiguration.Etcd != nil {
		server.providers = append(server.providers, server.globalConfiguration.Etcd)
	}
	if server.globalConfiguration.Zookeeper != nil {
		server.providers = append(server.providers, server.globalConfiguration.Zookeeper)
	}
	if server.globalConfiguration.Boltdb != nil {
		server.providers = append(server.providers, server.globalConfiguration.Boltdb)
	}
	if server.globalConfiguration.Kubernetes != nil {
		server.providers = append(server.providers, server.globalConfiguration.Kubernetes)
	}
}

func (server *Server) startProviders() {
	// start providers
	for _, provider := range server.providers {
		jsonConf, _ := json.Marshal(provider)
		log.Infof("Starting provider %v %s", reflect.TypeOf(provider), jsonConf)
		currentProvider := provider
		safe.Go(func() {
			err := currentProvider.Provide(server.configurationChan, &server.routinesPool)
			if err != nil {
				log.Errorf("Error starting provider %s", err)
			}
		})
	}
}

func (server *Server) listenSignals() {
	sig := <-server.signals
	log.Infof("I have to go... %+v", sig)
	log.Info("Stopping server")
	server.Stop()
}

// creates a TLS config that allows terminating HTTPS for multiple domains using SNI
func (server *Server) createTLSConfig(entryPointName string, tlsOption *TLS, router *middlewares.HandlerSwitcher) (*tls.Config, error) {
	if tlsOption == nil {
		return nil, nil
	}

	config := &tls.Config{}
	config.Certificates = []tls.Certificate{}
	for _, v := range tlsOption.Certificates {
		cert, err := tls.LoadX509KeyPair(v.CertFile, v.KeyFile)
		if err != nil {
			return nil, err
		}
		config.Certificates = append(config.Certificates, cert)
	}

	if server.globalConfiguration.ACME != nil {
		if _, ok := server.serverEntryPoints[server.globalConfiguration.ACME.EntryPoint]; ok {
			if entryPointName == server.globalConfiguration.ACME.EntryPoint {
				checkOnDemandDomain := func(domain string) bool {
					if router.GetHandler().Match(&http.Request{URL: &url.URL{}, Host: domain}, &mux.RouteMatch{}) {
						return true
					}
					return false
				}
				err := server.globalConfiguration.ACME.CreateConfig(config, checkOnDemandDomain)
				if err != nil {
					return nil, err
				}
			}
		} else {
			return nil, errors.New("Unknown entrypoint " + server.globalConfiguration.ACME.EntryPoint + " for ACME configuration")
		}
	}
	if len(config.Certificates) == 0 {
		return nil, errors.New("No certificates found for TLS entrypoint " + entryPointName)
	}
	// BuildNameToCertificate parses the CommonName and SubjectAlternateName fields
	// in each certificate and populates the config.NameToCertificate map.
	config.BuildNameToCertificate()
	return config, nil
}

func (server *Server) startServer(srv *manners.GracefulServer, globalConfiguration GlobalConfiguration) {
	log.Infof("Starting server on %s", srv.Addr)
	if srv.TLSConfig != nil {
		if err := srv.ListenAndServeTLSWithConfig(srv.TLSConfig); err != nil {
			log.Fatal("Error creating server: ", err)
		}
	} else {
		if err := srv.ListenAndServe(); err != nil {
			log.Fatal("Error creating server: ", err)
		}
	}
	log.Info("Server stopped")
}

func (server *Server) prepareServer(entryPointName string, router *middlewares.HandlerSwitcher, entryPoint *EntryPoint, oldServer *manners.GracefulServer, middlewares ...negroni.Handler) (*manners.GracefulServer, error) {
	log.Infof("Preparing server %s %+v", entryPointName, entryPoint)
	// middlewares
	var negroni = negroni.New()
	for _, middleware := range middlewares {
		negroni.Use(middleware)
	}
	negroni.UseHandler(router)
	tlsConfig, err := server.createTLSConfig(entryPointName, entryPoint.TLS, router)
	if err != nil {
		log.Fatalf("Error creating TLS config %s", err)
		return nil, err
	}

	if oldServer == nil {
		return manners.NewWithServer(
			&http.Server{
				Addr:      entryPoint.Address,
				Handler:   negroni,
				TLSConfig: tlsConfig,
			}), nil
	}
	gracefulServer, err := oldServer.HijackListener(&http.Server{
		Addr:      entryPoint.Address,
		Handler:   negroni,
		TLSConfig: tlsConfig,
	}, tlsConfig)
	if err != nil {
		log.Fatalf("Error hijacking server %s", err)
		return nil, err
	}
	return gracefulServer, nil
}

func (server *Server) buildEntryPoints(globalConfiguration GlobalConfiguration) map[string]*serverEntryPoint {
	serverEntryPoints := make(map[string]*serverEntryPoint)
	for entryPointName := range globalConfiguration.EntryPoints {
		router := server.buildDefaultHTTPRouter()
		serverEntryPoints[entryPointName] = &serverEntryPoint{
			httpRouter: middlewares.NewHandlerSwitcher(router),
		}
	}
	return serverEntryPoints
}

// LoadConfig returns a new gorilla.mux Route from the specified global configuration and the dynamic
// provider configurations.
func (server *Server) loadConfig(configurations configs, globalConfiguration GlobalConfiguration) (map[string]*serverEntryPoint, error) {
	serverEntryPoints := server.buildEntryPoints(globalConfiguration)
	redirectHandlers := make(map[string]http.Handler)

	backends := map[string]http.Handler{}
	backend2FrontendMap := map[string]string{}
	for _, configuration := range configurations {
		frontendNames := sortedFrontendNamesForConfig(configuration)
		for _, frontendName := range frontendNames {
			frontend := configuration.Frontends[frontendName]

			log.Debugf("Creating frontend %s", frontendName)
			fwd, _ := forward.New(forward.Logger(oxyLogger), forward.PassHostHeader(frontend.PassHostHeader))
			saveBackend := middlewares.NewSaveBackend(fwd)
			// default endpoints if not defined in frontends
			if len(frontend.EntryPoints) == 0 {
				frontend.EntryPoints = globalConfiguration.DefaultEntryPoints
			}
			if len(frontend.EntryPoints) == 0 {
				log.Errorf("No entrypoint defined for frontend %s, defaultEntryPoints:%s. Skipping it", frontendName, globalConfiguration.DefaultEntryPoints)
				continue
			}
			for _, entryPointName := range frontend.EntryPoints {
				log.Debugf("Wiring frontend %s to entryPoint %s", frontendName, entryPointName)
				if _, ok := serverEntryPoints[entryPointName]; !ok {
					return nil, errors.New("Undefined entrypoint: " + entryPointName)
				}
				newServerRoute := &serverRoute{route: serverEntryPoints[entryPointName].httpRouter.GetHandler().NewRoute().Name(frontendName)}
				for routeName, route := range frontend.Routes {
					err := getRoute(newServerRoute, &route)
					if err != nil {
						return nil, err
					}
					log.Debugf("Creating route %s %s", routeName, route.Rule)
				}
				entryPoint := globalConfiguration.EntryPoints[entryPointName]
				if entryPoint.Redirect != nil {
					if redirectHandlers[entryPointName] != nil {
						newServerRoute.route.Handler(redirectHandlers[entryPointName])
					} else if handler, err := server.loadEntryPointConfig(entryPointName, entryPoint); err != nil {
						return nil, err
					} else {
						newServerRoute.route.Handler(handler)
						redirectHandlers[entryPointName] = handler
					}
				} else {
					if backends[frontend.Backend] == nil {
						log.Debugf("Creating backend %s", frontend.Backend)
						var lb http.Handler
						rr, _ := roundrobin.New(saveBackend)
						if configuration.Backends[frontend.Backend] == nil {
							return nil, errors.New("Undefined backend: " + frontend.Backend)
						}
						lbMethod, err := types.NewLoadBalancerMethod(configuration.Backends[frontend.Backend].LoadBalancer)
						if err != nil {
							configuration.Backends[frontend.Backend].LoadBalancer = &types.LoadBalancer{Method: "wrr"}
						}
						switch lbMethod {
						case types.Drr:
							log.Debugf("Creating load-balancer drr")
							rebalancer, _ := roundrobin.NewRebalancer(rr, roundrobin.RebalancerLogger(oxyLogger))
							lb = rebalancer
							for serverName, server := range configuration.Backends[frontend.Backend].Servers {
								url, err := url.Parse(server.URL)
								if err != nil {
									return nil, err
								}
								backend2FrontendMap[url.String()] = frontendName
								log.Debugf("Creating server %s at %s with weight %d", serverName, url.String(), server.Weight)
								if err := rebalancer.UpsertServer(url, roundrobin.Weight(server.Weight)); err != nil {
									return nil, err
								}
							}
						case types.Wrr:
							log.Debugf("Creating load-balancer wrr")
							lb = rr
							for serverName, server := range configuration.Backends[frontend.Backend].Servers {
								url, err := url.Parse(server.URL)
								if err != nil {
									return nil, err
								}
								backend2FrontendMap[url.String()] = frontendName
								log.Debugf("Creating server %s at %s with weight %d", serverName, url.String(), server.Weight)
								if err := rr.UpsertServer(url, roundrobin.Weight(server.Weight)); err != nil {
									return nil, err
								}
							}
						}
						maxConns := configuration.Backends[frontend.Backend].MaxConn
						if maxConns != nil && maxConns.Amount != 0 {
							extractFunc, err := utils.NewExtractor(maxConns.ExtractorFunc)
							if err != nil {
								return nil, err
							}
							log.Debugf("Creating loadd-balancer connlimit")
							lb, err = connlimit.New(lb, extractFunc, maxConns.Amount, connlimit.Logger(oxyLogger))
							if err != nil {
								return nil, err
							}
						}
						// retry ?
						if globalConfiguration.Retry != nil {
							retries := len(configuration.Backends[frontend.Backend].Servers)
							if globalConfiguration.Retry.Attempts > 0 {
								retries = globalConfiguration.Retry.Attempts
							}
							maxMem := int64(2 * 1024 * 1024)
							if globalConfiguration.Retry.MaxMem > 0 {
								maxMem = globalConfiguration.Retry.MaxMem
							}
							lb, err = stream.New(lb,
								stream.Logger(oxyLogger),
								stream.Retry("IsNetworkError() && Attempts() < "+strconv.Itoa(retries)),
								stream.MemRequestBodyBytes(maxMem),
								stream.MaxRequestBodyBytes(maxMem),
								stream.MemResponseBodyBytes(maxMem),
								stream.MaxResponseBodyBytes(maxMem))
							log.Debugf("Creating retries max attempts %d", retries)
							if err != nil {
								return nil, err
							}
						}

						var negroni = negroni.New()
						if configuration.Backends[frontend.Backend].CircuitBreaker != nil {
							log.Debugf("Creating circuit breaker %s", configuration.Backends[frontend.Backend].CircuitBreaker.Expression)
							negroni.Use(middlewares.NewCircuitBreaker(lb, configuration.Backends[frontend.Backend].CircuitBreaker.Expression, cbreaker.Logger(oxyLogger)))
						} else {
							negroni.UseHandler(lb)
						}
						backends[frontend.Backend] = negroni
					} else {
						log.Debugf("Reusing backend %s", frontend.Backend)
					}
					server.wireFrontendBackend(newServerRoute, backends[frontend.Backend])
				}
				err := newServerRoute.route.GetError()
				if err != nil {
					log.Errorf("Error building route: %s", err)
				}
			}
		}
	}
	middlewares.SetBackend2FrontendMap(&backend2FrontendMap)
	return serverEntryPoints, nil
}

func (server *Server) wireFrontendBackend(serverRoute *serverRoute, handler http.Handler) {
	// strip prefix
	if len(serverRoute.stripPrefixes) > 0 {
		serverRoute.route.Handler(&middlewares.StripPrefix{
			Prefixes: serverRoute.stripPrefixes,
			Handler:  handler,
		})
	} else {
		serverRoute.route.Handler(handler)
	}
}

func (server *Server) loadEntryPointConfig(entryPointName string, entryPoint *EntryPoint) (http.Handler, error) {
	regex := entryPoint.Redirect.Regex
	replacement := entryPoint.Redirect.Replacement
	if len(entryPoint.Redirect.EntryPoint) > 0 {
		regex = "^(?:https?:\\/\\/)?([\\da-z\\.-]+)(?::\\d+)?(.*)$"
		if server.globalConfiguration.EntryPoints[entryPoint.Redirect.EntryPoint] == nil {
			return nil, errors.New("Unknown entrypoint " + entryPoint.Redirect.EntryPoint)
		}
		protocol := "http"
		if server.globalConfiguration.EntryPoints[entryPoint.Redirect.EntryPoint].TLS != nil {
			protocol = "https"
		}
		r, _ := regexp.Compile("(:\\d+)")
		match := r.FindStringSubmatch(server.globalConfiguration.EntryPoints[entryPoint.Redirect.EntryPoint].Address)
		if len(match) == 0 {
			return nil, errors.New("Bad Address format: " + server.globalConfiguration.EntryPoints[entryPoint.Redirect.EntryPoint].Address)
		}
		replacement = protocol + "://$1" + match[0] + "$2"
	}
	rewrite, err := middlewares.NewRewrite(regex, replacement, true)
	if err != nil {
		return nil, err
	}
	log.Debugf("Creating entryPoint redirect %s -> %s : %s -> %s", entryPointName, entryPoint.Redirect.EntryPoint, regex, replacement)
	negroni := negroni.New()
	negroni.Use(rewrite)
	return negroni, nil
}

func (server *Server) buildDefaultHTTPRouter() *mux.Router {
	router := mux.NewRouter()
	router.NotFoundHandler = http.HandlerFunc(notFoundHandler)
	router.StrictSlash(true)
	return router
}

func getRoute(serverRoute *serverRoute, route *types.Route) error {
	// ⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠
	// TODO: backwards compatibility with DEPRECATED rule.Value
	if len(route.Value) > 0 {
		route.Rule += ":" + route.Value
		log.Warnf("Value %s is DEPRECATED (will be removed in v1.0.0), please refer to the new frontend notation: https://github.com/containous/traefik/blob/master/docs/index.md#-frontends", route.Value)
	}
	// ⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠⚠

	rules := Rules{route: serverRoute}
	newRoute, err := rules.Parse(route.Rule)
	if err != nil {
		return err
	}
	serverRoute.route = newRoute
	return nil
}

func sortedFrontendNamesForConfig(configuration *types.Configuration) []string {
	keys := []string{}
	for key := range configuration.Frontends {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	return keys
}