package main

import (
	"crypto/tls"
	"errors"
	fmtlog "log"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"reflect"
	"runtime"
	"strings"
	"syscall"
	"time"

	log "github.com/Sirupsen/logrus"
	"github.com/codegangsta/negroni"
	"github.com/emilevauge/traefik/middlewares"
	"github.com/emilevauge/traefik/provider"
	"github.com/emilevauge/traefik/types"
	"github.com/gorilla/mux"
	"github.com/mailgun/manners"
	"github.com/mailgun/oxy/cbreaker"
	"github.com/mailgun/oxy/forward"
	"github.com/mailgun/oxy/roundrobin"
	"github.com/thoas/stats"
	"gopkg.in/alecthomas/kingpin.v2"
	"sync"
)

var (
	globalConfigFile      = kingpin.Arg("conf", "Main configration file.").Default("traefik.toml").String()
	version               = kingpin.Flag("version", "Get Version.").Short('v').Bool()
	currentConfigurations = make(configs)
	metrics               = stats.New()
	oxyLogger             = &OxyLogger{}
)

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())
	kingpin.Version(Version + " built on the " + BuildDate)
	kingpin.Parse()
	fmtlog.SetFlags(fmtlog.Lshortfile | fmtlog.LstdFlags)
	var srv *manners.GracefulServer
	var configurationRouter *mux.Router
	var configurationChan = make(chan types.ConfigMessage, 10)
	defer close(configurationChan)
	var configurationChanValidated = make(chan types.ConfigMessage, 10)
	defer close(configurationChanValidated)
	var sigs = make(chan os.Signal, 1)
	defer close(sigs)
	var stopChan = make(chan bool)
	defer close(stopChan)
	var providers = []provider.Provider{}
	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
	var serverLock sync.Mutex

	// load global configuration
	globalConfiguration := LoadFileConfig(*globalConfigFile)

	loggerMiddleware := middlewares.NewLogger(globalConfiguration.AccessLogsFile)
	defer loggerMiddleware.Close()

	// logging
	level, err := log.ParseLevel(strings.ToLower(globalConfiguration.LogLevel))
	if err != nil {
		log.Fatal("Error getting level", err)
	}
	log.SetLevel(level)

	if len(globalConfiguration.TraefikLogsFile) > 0 {
		fi, err := os.OpenFile(globalConfiguration.TraefikLogsFile, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
		defer fi.Close()
		if err != nil {
			log.Fatal("Error opening file", err)
		} else {
			log.SetOutput(fi)
			log.SetFormatter(&log.TextFormatter{DisableColors: true, FullTimestamp: true, DisableSorting: true})
		}
	} else {
		log.SetFormatter(&log.TextFormatter{FullTimestamp: true, DisableSorting: true})
	}
	log.Debugf("Global configuration loaded %+v", globalConfiguration)
	configurationRouter = LoadDefaultConfig(globalConfiguration)

	// listen new configurations from providers
	go func() {
		lastReceivedConfiguration := time.Unix(0, 0)
		lastConfigs := make(map[string]*types.ConfigMessage)
		for {
			configMsg := <-configurationChan
			log.Infof("Configuration receveived from provider %s: %#v", configMsg.ProviderName, configMsg.Configuration)
			lastConfigs[configMsg.ProviderName] = &configMsg
			if time.Now().After(lastReceivedConfiguration.Add(time.Duration(globalConfiguration.ProvidersThrottleDuration))) {
				log.Infof("Last %s config received more than %s, OK", configMsg.ProviderName, globalConfiguration.ProvidersThrottleDuration)
				// last config received more than n s ago
				configurationChanValidated <- configMsg
			} else {
				log.Infof("Last %s config received less than %s, waiting...", configMsg.ProviderName, globalConfiguration.ProvidersThrottleDuration)
				go func() {
					<-time.After(globalConfiguration.ProvidersThrottleDuration)
					if time.Now().After(lastReceivedConfiguration.Add(time.Duration(globalConfiguration.ProvidersThrottleDuration))) {
						log.Infof("Waited for %s config, OK", configMsg.ProviderName)
						configurationChanValidated <- *lastConfigs[configMsg.ProviderName]
					}
				}()
			}
			lastReceivedConfiguration = time.Now()
		}
	}()
	go func() {
		for {
			configMsg := <-configurationChanValidated
			if configMsg.Configuration == nil {
				log.Info("Skipping empty Configuration")
			} else if reflect.DeepEqual(currentConfigurations[configMsg.ProviderName], configMsg.Configuration) {
				log.Info("Skipping same configuration")
			} 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

				newConfigurationRouter, err := LoadConfig(newConfigurations, globalConfiguration)
				if err == nil {
					serverLock.Lock()
					currentConfigurations = newConfigurations
					configurationRouter = newConfigurationRouter
					oldServer := srv
					newsrv, err := prepareServer(configurationRouter, globalConfiguration, oldServer, loggerMiddleware, metrics)
					if err != nil {
						log.Fatal("Error preparing server: ", err)
					}
					go startServer(newsrv, globalConfiguration)
					srv = newsrv
					time.Sleep(1 * time.Second)
					if oldServer != nil {
						log.Info("Stopping old server")
						oldServer.Close()
					}
					serverLock.Unlock()
				} else {
					log.Error("Error loading new configuration, aborted ", err)
				}
			}
		}
	}()

	// configure providers
	if globalConfiguration.Docker != nil {
		providers = append(providers, globalConfiguration.Docker)
	}
	if globalConfiguration.Marathon != nil {
		providers = append(providers, globalConfiguration.Marathon)
	}
	if globalConfiguration.File != nil {
		if len(globalConfiguration.File.Filename) == 0 {
			// no filename, setting to global config file
			globalConfiguration.File.Filename = *globalConfigFile
		}
		providers = append(providers, globalConfiguration.File)
	}
	if globalConfiguration.Web != nil {
		providers = append(providers, globalConfiguration.Web)
	}
	if globalConfiguration.Consul != nil {
		providers = append(providers, globalConfiguration.Consul)
	}
	if globalConfiguration.Etcd != nil {
		providers = append(providers, globalConfiguration.Etcd)
	}
	if globalConfiguration.Zookeeper != nil {
		providers = append(providers, globalConfiguration.Zookeeper)
	}
	if globalConfiguration.Boltdb != nil {
		providers = append(providers, globalConfiguration.Boltdb)
	}

	// start providers
	for _, provider := range providers {
		log.Infof("Starting provider %v %+v", reflect.TypeOf(provider), provider)
		currentProvider := provider
		go func() {
			err := currentProvider.Provide(configurationChan)
			if err != nil {
				log.Errorf("Error starting provider %s", err)
			}
		}()
	}

	go func() {
		sig := <-sigs
		log.Infof("I have to go... %+v", sig)
		log.Info("Stopping server")
		srv.Close()
		stopChan <- true
	}()

	//negroni.Use(middlewares.NewCircuitBreaker(oxyLogger))
	//negroni.Use(middlewares.NewRoutes(configurationRouter))

	var er error
	serverLock.Lock()
	srv, er = prepareServer(configurationRouter, globalConfiguration, nil, loggerMiddleware, metrics)
	if er != nil {
		log.Fatal("Error preparing server: ", er)
	}
	go startServer(srv, globalConfiguration)
	//TODO change that!
	time.Sleep(100 * time.Millisecond)
	serverLock.Unlock()

	<-stopChan
	log.Info("Shutting down")
}

// creates a TLS config that allows terminating HTTPS for multiple domains using SNI
func createTLSConfig(certs []Certificate) (*tls.Config, error) {
	if len(certs) == 0 {
		return nil, nil
	}

	config := &tls.Config{}
	if config.NextProtos == nil {
		config.NextProtos = []string{"http/1.1"}
	}

	var err error
	config.Certificates = make([]tls.Certificate, len(certs))
	for i, v := range certs {
		config.Certificates[i], err = tls.LoadX509KeyPair(v.CertFile, v.KeyFile)
		if err != nil {
			return nil, err
		}
	}
	// BuildNameToCertificate parses the CommonName and SubjectAlternateName fields
	// in each certificate and populates the config.NameToCertificate map.
	config.BuildNameToCertificate()
	return config, nil
}

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

func prepareServer(router *mux.Router, globalConfiguration *GlobalConfiguration, oldServer *manners.GracefulServer, middlewares ...negroni.Handler) (*manners.GracefulServer, error) {
	log.Info("Preparing server")
	// middlewares
	var negroni = negroni.New()
	for _, middleware := range middlewares {
		negroni.Use(middleware)
	}
	negroni.UseHandler(router)
	tlsConfig, err := createTLSConfig(globalConfiguration.Certificates)
	if err != nil {
		log.Fatalf("Error creating TLS config %s", err)
		return nil, err
	}

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

// LoadConfig returns a new gorrilla.mux Route from the specified global configuration and the dynamic
// provider configurations.
func LoadConfig(configurations configs, globalConfiguration *GlobalConfiguration) (*mux.Router, error) {
	router := mux.NewRouter()
	router.NotFoundHandler = http.HandlerFunc(notFoundHandler)
	backends := map[string]http.Handler{}
	for _, configuration := range configurations {
		for frontendName, frontend := range configuration.Frontends {
			log.Debugf("Creating frontend %s", frontendName)
			fwd, _ := forward.New(forward.Logger(oxyLogger), forward.PassHostHeader(frontend.PassHostHeader))
			newRoute := router.NewRoute().Name(frontendName)
			for routeName, route := range frontend.Routes {
				log.Debugf("Creating route %s %s:%s", routeName, route.Rule, route.Value)
				newRouteReflect, err := invoke(newRoute, route.Rule, route.Value)
				if err != nil {
					return nil, err
				}
				newRoute = newRouteReflect[0].Interface().(*mux.Route)
			}
			if backends[frontend.Backend] == nil {
				log.Debugf("Creating backend %s", frontend.Backend)
				var lb http.Handler
				rr, _ := roundrobin.New(fwd)
				if configuration.Backends[frontend.Backend] == nil {
					return nil, errors.New("Backend not found: " + 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.Infof("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
						}
						log.Infof("Creating server %s %s", serverName, url.String())
						rebalancer.UpsertServer(url, roundrobin.Weight(server.Weight))
					}
				case types.Wrr:
					log.Infof("Creating load-balancer wrr")
					lb = middlewares.NewWebsocketUpgrader(rr)
					for serverName, server := range configuration.Backends[frontend.Backend].Servers {
						url, err := url.Parse(server.URL)
						if err != nil {
							return nil, err
						}
						log.Infof("Creating server %s %s", serverName, url.String())
						rr.UpsertServer(url, roundrobin.Weight(server.Weight))
					}
				}
				var negroni = negroni.New()
				if configuration.Backends[frontend.Backend].CircuitBreaker != nil {
					log.Infof("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.Infof("Reusing backend %s", frontend.Backend)
			}
			//		stream.New(backends[frontend.Backend], stream.Retry("IsNetworkError() && Attempts() <= " + strconv.Itoa(globalConfiguration.Replay)), stream.Logger(oxyLogger))

			newRoute.Handler(backends[frontend.Backend])
			err := newRoute.GetError()
			if err != nil {
				log.Errorf("Error building route: %s", err)
			}
		}
	}
	return router, nil
}

// Invoke calls the specified method with the specified arguments on the specified interface.
// It uses the go(lang) reflect package.
func invoke(any interface{}, name string, args ...interface{}) ([]reflect.Value, error) {
	inputs := make([]reflect.Value, len(args))
	for i := range args {
		inputs[i] = reflect.ValueOf(args[i])
	}
	method := reflect.ValueOf(any).MethodByName(name)
	if method.IsValid() {
		return method.Call(inputs), nil
	}
	return nil, errors.New("Method not found: " + name)
}