package registry

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"rsc.io/letsencrypt"

	"github.com/Shopify/logrus-bugsnag"
	logstash "github.com/bshuster-repo/logrus-logstash-hook"
	"github.com/bugsnag/bugsnag-go"
	"github.com/docker/distribution/configuration"
	dcontext "github.com/docker/distribution/context"
	"github.com/docker/distribution/health"
	"github.com/docker/distribution/registry/handlers"
	"github.com/docker/distribution/registry/listener"
	"github.com/docker/distribution/uuid"
	"github.com/docker/distribution/version"
	"github.com/docker/go-metrics"
	gorhandlers "github.com/gorilla/handlers"
	log "github.com/sirupsen/logrus"
	"github.com/spf13/cobra"
	"github.com/yvasiyarov/gorelic"
)

// this channel gets notified when process receives signal. It is global to ease unit testing
var quit = make(chan os.Signal, 1)

// ServeCmd is a cobra command for running the registry.
var ServeCmd = &cobra.Command{
	Use:   "serve <config>",
	Short: "`serve` stores and distributes Docker images",
	Long:  "`serve` stores and distributes Docker images.",
	Run: func(cmd *cobra.Command, args []string) {

		// setup context
		ctx := dcontext.WithVersion(dcontext.Background(), version.Version)

		config, err := resolveConfiguration(args)
		if err != nil {
			fmt.Fprintf(os.Stderr, "configuration error: %v\n", err)
			cmd.Usage()
			os.Exit(1)
		}

		if config.HTTP.Debug.Addr != "" {
			go func(addr string) {
				log.Infof("debug server listening %v", addr)
				if err := http.ListenAndServe(addr, nil); err != nil {
					log.Fatalf("error listening on debug interface: %v", err)
				}
			}(config.HTTP.Debug.Addr)
		}

		registry, err := NewRegistry(ctx, config)
		if err != nil {
			log.Fatalln(err)
		}

		if config.HTTP.Debug.Prometheus.Enabled {
			path := config.HTTP.Debug.Prometheus.Path
			if path == "" {
				path = "/metrics"
			}
			log.Info("providing prometheus metrics on ", path)
			http.Handle(path, metrics.Handler())
		}

		if err = registry.ListenAndServe(); err != nil {
			log.Fatalln(err)
		}
	},
}

// A Registry represents a complete instance of the registry.
// TODO(aaronl): It might make sense for Registry to become an interface.
type Registry struct {
	config *configuration.Configuration
	app    *handlers.App
	server *http.Server
}

// NewRegistry creates a new registry from a context and configuration struct.
func NewRegistry(ctx context.Context, config *configuration.Configuration) (*Registry, error) {
	var err error
	ctx, err = configureLogging(ctx, config)
	if err != nil {
		return nil, fmt.Errorf("error configuring logger: %v", err)
	}

	configureBugsnag(config)

	// inject a logger into the uuid library. warns us if there is a problem
	// with uuid generation under low entropy.
	uuid.Loggerf = dcontext.GetLogger(ctx).Warnf

	app := handlers.NewApp(ctx, config)
	// TODO(aaronl): The global scope of the health checks means NewRegistry
	// can only be called once per process.
	app.RegisterHealthChecks()
	handler := configureReporting(app)
	handler = alive("/", handler)
	handler = health.Handler(handler)
	handler = panicHandler(handler)
	if !config.Log.AccessLog.Disabled {
		handler = gorhandlers.CombinedLoggingHandler(os.Stdout, handler)
	}

	server := &http.Server{
		Handler: handler,
	}

	return &Registry{
		app:    app,
		config: config,
		server: server,
	}, nil
}

// ListenAndServe runs the registry's HTTP server.
func (registry *Registry) ListenAndServe() error {
	config := registry.config

	ln, err := listener.NewListener(config.HTTP.Net, config.HTTP.Addr)
	if err != nil {
		return err
	}

	if config.HTTP.TLS.Certificate != "" || config.HTTP.TLS.LetsEncrypt.CacheFile != "" {
		var tlsMinVersion uint16
		if config.HTTP.TLS.MinimumTLS == "" {
			tlsMinVersion = tls.VersionTLS10
		} else {
			switch config.HTTP.TLS.MinimumTLS {
			case "tls1.0":
				tlsMinVersion = tls.VersionTLS10
			case "tls1.1":
				tlsMinVersion = tls.VersionTLS11
			case "tls1.2":
				tlsMinVersion = tls.VersionTLS12
			default:
				return fmt.Errorf("unknown minimum TLS level '%s' specified for http.tls.minimumtls", config.HTTP.TLS.MinimumTLS)
			}
			dcontext.GetLogger(registry.app).Infof("restricting TLS to %s or higher", config.HTTP.TLS.MinimumTLS)
		}
		tlsConf := &tls.Config{
			ClientAuth:               tls.NoClientCert,
			NextProtos:               nextProtos(config),
			MinVersion:               tlsMinVersion,
			PreferServerCipherSuites: true,
			CipherSuites: []uint16{
				tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
				tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
				tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
				tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
				tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
				tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
			},
		}

		if config.HTTP.TLS.LetsEncrypt.CacheFile != "" {
			if config.HTTP.TLS.Certificate != "" {
				return fmt.Errorf("cannot specify both certificate and Let's Encrypt")
			}
			var m letsencrypt.Manager
			if err := m.CacheFile(config.HTTP.TLS.LetsEncrypt.CacheFile); err != nil {
				return err
			}
			if !m.Registered() {
				if err := m.Register(config.HTTP.TLS.LetsEncrypt.Email, nil); err != nil {
					return err
				}
			}
			if len(config.HTTP.TLS.LetsEncrypt.Hosts) > 0 {
				m.SetHosts(config.HTTP.TLS.LetsEncrypt.Hosts)
			}
			tlsConf.GetCertificate = m.GetCertificate
		} else {
			tlsConf.Certificates = make([]tls.Certificate, 1)
			tlsConf.Certificates[0], err = tls.LoadX509KeyPair(config.HTTP.TLS.Certificate, config.HTTP.TLS.Key)
			if err != nil {
				return err
			}
		}

		if len(config.HTTP.TLS.ClientCAs) != 0 {
			pool := x509.NewCertPool()

			for _, ca := range config.HTTP.TLS.ClientCAs {
				caPem, err := ioutil.ReadFile(ca)
				if err != nil {
					return err
				}

				if ok := pool.AppendCertsFromPEM(caPem); !ok {
					return fmt.Errorf("could not add CA to pool")
				}
			}

			for _, subj := range pool.Subjects() {
				dcontext.GetLogger(registry.app).Debugf("CA Subject: %s", string(subj))
			}

			tlsConf.ClientAuth = tls.RequireAndVerifyClientCert
			tlsConf.ClientCAs = pool
		}

		ln = tls.NewListener(ln, tlsConf)
		dcontext.GetLogger(registry.app).Infof("listening on %v, tls", ln.Addr())
	} else {
		dcontext.GetLogger(registry.app).Infof("listening on %v", ln.Addr())
	}

	if config.HTTP.DrainTimeout == 0 {
		return registry.server.Serve(ln)
	}

	// setup channel to get notified on SIGTERM signal
	signal.Notify(quit, syscall.SIGTERM)
	serveErr := make(chan error)

	// Start serving in goroutine and listen for stop signal in main thread
	go func() {
		serveErr <- registry.server.Serve(ln)
	}()

	select {
	case err := <-serveErr:
		return err
	case <-quit:
		dcontext.GetLogger(registry.app).Info("stopping server gracefully. Draining connections for ", config.HTTP.DrainTimeout)
		// shutdown the server with a grace period of configured timeout
		c, cancel := context.WithTimeout(context.Background(), config.HTTP.DrainTimeout)
		defer cancel()
		return registry.server.Shutdown(c)
	}
}

func configureReporting(app *handlers.App) http.Handler {
	var handler http.Handler = app

	if app.Config.Reporting.Bugsnag.APIKey != "" {
		handler = bugsnag.Handler(handler)
	}

	if app.Config.Reporting.NewRelic.LicenseKey != "" {
		agent := gorelic.NewAgent()
		agent.NewrelicLicense = app.Config.Reporting.NewRelic.LicenseKey
		if app.Config.Reporting.NewRelic.Name != "" {
			agent.NewrelicName = app.Config.Reporting.NewRelic.Name
		}
		agent.CollectHTTPStat = true
		agent.Verbose = app.Config.Reporting.NewRelic.Verbose
		agent.Run()

		handler = agent.WrapHTTPHandler(handler)
	}

	return handler
}

// configureLogging prepares the context with a logger using the
// configuration.
func configureLogging(ctx context.Context, config *configuration.Configuration) (context.Context, error) {
	log.SetLevel(logLevel(config.Log.Level))

	formatter := config.Log.Formatter
	if formatter == "" {
		formatter = "text" // default formatter
	}

	switch formatter {
	case "json":
		log.SetFormatter(&log.JSONFormatter{
			TimestampFormat: time.RFC3339Nano,
		})
	case "text":
		log.SetFormatter(&log.TextFormatter{
			TimestampFormat: time.RFC3339Nano,
		})
	case "logstash":
		log.SetFormatter(&logstash.LogstashFormatter{
			TimestampFormat: time.RFC3339Nano,
		})
	default:
		// just let the library use default on empty string.
		if config.Log.Formatter != "" {
			return ctx, fmt.Errorf("unsupported logging formatter: %q", config.Log.Formatter)
		}
	}

	if config.Log.Formatter != "" {
		log.Debugf("using %q logging formatter", config.Log.Formatter)
	}

	if len(config.Log.Fields) > 0 {
		// build up the static fields, if present.
		var fields []interface{}
		for k := range config.Log.Fields {
			fields = append(fields, k)
		}

		ctx = dcontext.WithValues(ctx, config.Log.Fields)
		ctx = dcontext.WithLogger(ctx, dcontext.GetLogger(ctx, fields...))
	}

	return ctx, nil
}

func logLevel(level configuration.Loglevel) log.Level {
	l, err := log.ParseLevel(string(level))
	if err != nil {
		l = log.InfoLevel
		log.Warnf("error parsing level %q: %v, using %q	", level, err, l)
	}

	return l
}

// configureBugsnag configures bugsnag reporting, if enabled
func configureBugsnag(config *configuration.Configuration) {
	if config.Reporting.Bugsnag.APIKey == "" {
		return
	}

	bugsnagConfig := bugsnag.Configuration{
		APIKey: config.Reporting.Bugsnag.APIKey,
	}
	if config.Reporting.Bugsnag.ReleaseStage != "" {
		bugsnagConfig.ReleaseStage = config.Reporting.Bugsnag.ReleaseStage
	}
	if config.Reporting.Bugsnag.Endpoint != "" {
		bugsnagConfig.Endpoint = config.Reporting.Bugsnag.Endpoint
	}
	bugsnag.Configure(bugsnagConfig)

	// configure logrus bugsnag hook
	hook, err := logrus_bugsnag.NewBugsnagHook()
	if err != nil {
		log.Fatalln(err)
	}

	log.AddHook(hook)
}

// panicHandler add an HTTP handler to web app. The handler recover the happening
// panic. logrus.Panic transmits panic message to pre-config log hooks, which is
// defined in config.yml.
func panicHandler(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if err := recover(); err != nil {
				log.Panic(fmt.Sprintf("%v", err))
			}
		}()
		handler.ServeHTTP(w, r)
	})
}

// alive simply wraps the handler with a route that always returns an http 200
// response when the path is matched. If the path is not matched, the request
// is passed to the provided handler. There is no guarantee of anything but
// that the server is up. Wrap with other handlers (such as health.Handler)
// for greater affect.
func alive(path string, handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == path {
			w.Header().Set("Cache-Control", "no-cache")
			w.WriteHeader(http.StatusOK)
			return
		}

		handler.ServeHTTP(w, r)
	})
}

func resolveConfiguration(args []string) (*configuration.Configuration, error) {
	var configurationPath string

	if len(args) > 0 {
		configurationPath = args[0]
	} else if os.Getenv("REGISTRY_CONFIGURATION_PATH") != "" {
		configurationPath = os.Getenv("REGISTRY_CONFIGURATION_PATH")
	}

	if configurationPath == "" {
		return nil, fmt.Errorf("configuration path unspecified")
	}

	fp, err := os.Open(configurationPath)
	if err != nil {
		return nil, err
	}

	defer fp.Close()

	config, err := configuration.Parse(fp)
	if err != nil {
		return nil, fmt.Errorf("error parsing %s: %v", configurationPath, err)
	}

	return config, nil
}

func nextProtos(config *configuration.Configuration) []string {
	switch config.HTTP.HTTP2.Disabled {
	case true:
		return []string{"http/1.1"}
	default:
		return []string{"h2", "http/1.1"}
	}
}
