package main

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

	gosundheit "github.com/AppsFlyer/go-sundheit"
	"github.com/AppsFlyer/go-sundheit/checks"
	gosundheithttp "github.com/AppsFlyer/go-sundheit/http"
	"github.com/ghodss/yaml"
	grpcprometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
	"github.com/oklog/run"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/sirupsen/logrus"
	"github.com/spf13/cobra"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/reflection"

	"github.com/dexidp/dex/api/v2"
	"github.com/dexidp/dex/pkg/log"
	"github.com/dexidp/dex/server"
	"github.com/dexidp/dex/storage"
)

type serveOptions struct {
	// Config file path
	config string

	// Flags
	webHTTPAddr   string
	webHTTPSAddr  string
	telemetryAddr string
	grpcAddr      string
}

func commandServe() *cobra.Command {
	options := serveOptions{}

	cmd := &cobra.Command{
		Use:     "serve [flags] [config file]",
		Short:   "Launch Dex",
		Example: "dex serve config.yaml",
		Args:    cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			cmd.SilenceUsage = true
			cmd.SilenceErrors = true

			options.config = args[0]

			return runServe(options)
		},
	}

	flags := cmd.Flags()

	flags.StringVar(&options.webHTTPAddr, "web-http-addr", "", "Web HTTP address")
	flags.StringVar(&options.webHTTPSAddr, "web-https-addr", "", "Web HTTPS address")
	flags.StringVar(&options.telemetryAddr, "telemetry-addr", "", "Telemetry address")
	flags.StringVar(&options.grpcAddr, "grpc-addr", "", "gRPC API address")

	return cmd
}

func runServe(options serveOptions) error {
	configFile := options.config
	configData, err := ioutil.ReadFile(configFile)
	if err != nil {
		return fmt.Errorf("failed to read config file %s: %v", configFile, err)
	}

	var c Config
	if err := yaml.Unmarshal(configData, &c); err != nil {
		return fmt.Errorf("error parse config file %s: %v", configFile, err)
	}

	applyConfigOverrides(options, &c)

	logger, err := newLogger(c.Logger.Level, c.Logger.Format)
	if err != nil {
		return fmt.Errorf("invalid config: %v", err)
	}
	if c.Logger.Level != "" {
		logger.Infof("config using log level: %s", c.Logger.Level)
	}
	if err := c.Validate(); err != nil {
		return err
	}

	logger.Infof("config issuer: %s", c.Issuer)

	prometheusRegistry := prometheus.NewRegistry()
	err = prometheusRegistry.Register(prometheus.NewGoCollector())
	if err != nil {
		return fmt.Errorf("failed to register Go runtime metrics: %v", err)
	}

	err = prometheusRegistry.Register(prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{}))
	if err != nil {
		return fmt.Errorf("failed to register process metrics: %v", err)
	}

	grpcMetrics := grpcprometheus.NewServerMetrics()
	err = prometheusRegistry.Register(grpcMetrics)
	if err != nil {
		return fmt.Errorf("failed to register gRPC server metrics: %v", err)
	}

	var grpcOptions []grpc.ServerOption

	allowedTLSCiphers := []uint16{
		tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
		tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
		tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
		tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
		tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
		tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
		tls.TLS_RSA_WITH_AES_128_GCM_SHA256,
		tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
	}

	if c.GRPC.TLSCert != "" {
		// Parse certificates from certificate file and key file for server.
		cert, err := tls.LoadX509KeyPair(c.GRPC.TLSCert, c.GRPC.TLSKey)
		if err != nil {
			return fmt.Errorf("invalid config: error parsing gRPC certificate file: %v", err)
		}

		tlsConfig := tls.Config{
			Certificates:             []tls.Certificate{cert},
			MinVersion:               tls.VersionTLS12,
			CipherSuites:             allowedTLSCiphers,
			PreferServerCipherSuites: true,
		}

		if c.GRPC.TLSClientCA != "" {
			// Parse certificates from client CA file to a new CertPool.
			cPool := x509.NewCertPool()
			clientCert, err := ioutil.ReadFile(c.GRPC.TLSClientCA)
			if err != nil {
				return fmt.Errorf("invalid config: reading from client CA file: %v", err)
			}
			if !cPool.AppendCertsFromPEM(clientCert) {
				return errors.New("invalid config: failed to parse client CA")
			}

			tlsConfig.ClientAuth = tls.RequireAndVerifyClientCert
			tlsConfig.ClientCAs = cPool

			// Only add metrics if client auth is enabled
			grpcOptions = append(grpcOptions,
				grpc.StreamInterceptor(grpcMetrics.StreamServerInterceptor()),
				grpc.UnaryInterceptor(grpcMetrics.UnaryServerInterceptor()),
			)
		}

		grpcOptions = append(grpcOptions, grpc.Creds(credentials.NewTLS(&tlsConfig)))
	}

	s, err := c.Storage.Config.Open(logger)
	if err != nil {
		return fmt.Errorf("failed to initialize storage: %v", err)
	}
	defer s.Close()

	logger.Infof("config storage: %s", c.Storage.Type)

	if len(c.StaticClients) > 0 {
		for i, client := range c.StaticClients {
			if client.Name == "" {
				return fmt.Errorf("invalid config: Name field is required for a client")
			}
			if client.ID == "" && client.IDEnv == "" {
				return fmt.Errorf("invalid config: ID or IDEnv field is required for a client")
			}
			if client.IDEnv != "" {
				if client.ID != "" {
					return fmt.Errorf("invalid config: ID and IDEnv fields are exclusive for client %q", client.ID)
				}
				c.StaticClients[i].ID = os.Getenv(client.IDEnv)
			}
			if client.Secret == "" && client.SecretEnv == "" && !client.Public {
				return fmt.Errorf("invalid config: Secret or SecretEnv field is required for client %q", client.ID)
			}
			if client.SecretEnv != "" {
				if client.Secret != "" {
					return fmt.Errorf("invalid config: Secret and SecretEnv fields are exclusive for client %q", client.ID)
				}
				c.StaticClients[i].Secret = os.Getenv(client.SecretEnv)
			}
			logger.Infof("config static client: %s", client.Name)
		}
		s = storage.WithStaticClients(s, c.StaticClients)
	}
	if len(c.StaticPasswords) > 0 {
		passwords := make([]storage.Password, len(c.StaticPasswords))
		for i, p := range c.StaticPasswords {
			passwords[i] = storage.Password(p)
		}
		s = storage.WithStaticPasswords(s, passwords, logger)
	}

	storageConnectors := make([]storage.Connector, len(c.StaticConnectors))
	for i, c := range c.StaticConnectors {
		if c.ID == "" || c.Name == "" || c.Type == "" {
			return fmt.Errorf("invalid config: ID, Type and Name fields are required for a connector")
		}
		if c.Config == nil {
			return fmt.Errorf("invalid config: no config field for connector %q", c.ID)
		}
		logger.Infof("config connector: %s", c.ID)

		// convert to a storage connector object
		conn, err := ToStorageConnector(c)
		if err != nil {
			return fmt.Errorf("failed to initialize storage connectors: %v", err)
		}
		storageConnectors[i] = conn
	}

	if c.EnablePasswordDB {
		storageConnectors = append(storageConnectors, storage.Connector{
			ID:   server.LocalConnector,
			Name: "Email",
			Type: server.LocalConnector,
		})
		logger.Infof("config connector: local passwords enabled")
	}

	s = storage.WithStaticConnectors(s, storageConnectors)

	if len(c.OAuth2.ResponseTypes) > 0 {
		logger.Infof("config response types accepted: %s", c.OAuth2.ResponseTypes)
	}
	if c.OAuth2.SkipApprovalScreen {
		logger.Infof("config skipping approval screen")
	}
	if c.OAuth2.PasswordConnector != "" {
		logger.Infof("config using password grant connector: %s", c.OAuth2.PasswordConnector)
	}
	if len(c.Web.AllowedOrigins) > 0 {
		logger.Infof("config allowed origins: %s", c.Web.AllowedOrigins)
	}

	// explicitly convert to UTC.
	now := func() time.Time { return time.Now().UTC() }

	healthChecker := gosundheit.New()

	serverConfig := server.Config{
		SupportedResponseTypes: c.OAuth2.ResponseTypes,
		SkipApprovalScreen:     c.OAuth2.SkipApprovalScreen,
		AlwaysShowLoginScreen:  c.OAuth2.AlwaysShowLoginScreen,
		PasswordConnector:      c.OAuth2.PasswordConnector,
		AllowedOrigins:         c.Web.AllowedOrigins,
		Issuer:                 c.Issuer,
		Storage:                s,
		Web:                    c.Frontend,
		Logger:                 logger,
		Now:                    now,
		PrometheusRegistry:     prometheusRegistry,
		HealthChecker:          healthChecker,
	}
	if c.Expiry.SigningKeys != "" {
		signingKeys, err := time.ParseDuration(c.Expiry.SigningKeys)
		if err != nil {
			return fmt.Errorf("invalid config value %q for signing keys expiry: %v", c.Expiry.SigningKeys, err)
		}
		logger.Infof("config signing keys expire after: %v", signingKeys)
		serverConfig.RotateKeysAfter = signingKeys
	}
	if c.Expiry.IDTokens != "" {
		idTokens, err := time.ParseDuration(c.Expiry.IDTokens)
		if err != nil {
			return fmt.Errorf("invalid config value %q for id token expiry: %v", c.Expiry.IDTokens, err)
		}
		logger.Infof("config id tokens valid for: %v", idTokens)
		serverConfig.IDTokensValidFor = idTokens
	}
	if c.Expiry.AuthRequests != "" {
		authRequests, err := time.ParseDuration(c.Expiry.AuthRequests)
		if err != nil {
			return fmt.Errorf("invalid config value %q for auth request expiry: %v", c.Expiry.AuthRequests, err)
		}
		logger.Infof("config auth requests valid for: %v", authRequests)
		serverConfig.AuthRequestsValidFor = authRequests
	}
	if c.Expiry.DeviceRequests != "" {
		deviceRequests, err := time.ParseDuration(c.Expiry.DeviceRequests)
		if err != nil {
			return fmt.Errorf("invalid config value %q for device request expiry: %v", c.Expiry.AuthRequests, err)
		}
		logger.Infof("config device requests valid for: %v", deviceRequests)
		serverConfig.DeviceRequestsValidFor = deviceRequests
	}
	serv, err := server.NewServer(context.Background(), serverConfig)
	if err != nil {
		return fmt.Errorf("failed to initialize server: %v", err)
	}

	telemetryRouter := http.NewServeMux()
	telemetryRouter.Handle("/metrics", promhttp.HandlerFor(prometheusRegistry, promhttp.HandlerOpts{}))

	// Configure health checker
	{
		handler := gosundheithttp.HandleHealthJSON(healthChecker)
		telemetryRouter.Handle("/healthz", handler)

		// Kubernetes style health checks
		telemetryRouter.HandleFunc("/healthz/live", func(w http.ResponseWriter, _ *http.Request) {
			_, _ = w.Write([]byte("ok"))
		})
		telemetryRouter.Handle("/healthz/ready", handler)
	}

	healthChecker.RegisterCheck(&gosundheit.Config{
		Check: &checks.CustomCheck{
			CheckName: "storage",
			CheckFunc: storage.NewCustomHealthCheckFunc(serverConfig.Storage, serverConfig.Now),
		},
		ExecutionPeriod:  15 * time.Second,
		InitiallyPassing: true,
	})

	var group run.Group

	// Set up telemetry server
	if c.Telemetry.HTTP != "" {
		const name = "telemetry"

		logger.Infof("listening (%s) on %s", name, c.Telemetry.HTTP)

		l, err := net.Listen("tcp", c.Telemetry.HTTP)
		if err != nil {
			return fmt.Errorf("listening (%s) on %s: %v", name, c.Telemetry.HTTP, err)
		}

		server := &http.Server{
			Handler: telemetryRouter,
		}
		defer server.Close()

		group.Add(func() error {
			return server.Serve(l)
		}, func(err error) {
			ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
			defer cancel()

			logger.Debugf("starting graceful shutdown (%s)", name)
			if err := server.Shutdown(ctx); err != nil {
				logger.Errorf("graceful shutdown (%s): %v", name, err)
			}
		})
	}

	// Set up http server
	if c.Web.HTTP != "" {
		const name = "http"

		logger.Infof("listening (%s) on %s", name, c.Web.HTTP)

		l, err := net.Listen("tcp", c.Web.HTTP)
		if err != nil {
			return fmt.Errorf("listening (%s) on %s: %v", name, c.Web.HTTP, err)
		}

		server := &http.Server{
			Handler: serv,
		}
		defer server.Close()

		group.Add(func() error {
			return server.Serve(l)
		}, func(err error) {
			ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
			defer cancel()

			logger.Debugf("starting graceful shutdown (%s)", name)
			if err := server.Shutdown(ctx); err != nil {
				logger.Errorf("graceful shutdown (%s): %v", name, err)
			}
		})
	}

	// Set up https server
	if c.Web.HTTPS != "" {
		const name = "https"

		logger.Infof("listening (%s) on %s", name, c.Web.HTTPS)

		l, err := net.Listen("tcp", c.Web.HTTPS)
		if err != nil {
			return fmt.Errorf("listening (%s) on %s: %v", name, c.Web.HTTPS, err)
		}

		server := &http.Server{
			Handler: serv,
			TLSConfig: &tls.Config{
				CipherSuites:             allowedTLSCiphers,
				PreferServerCipherSuites: true,
				MinVersion:               tls.VersionTLS12,
			},
		}
		defer server.Close()

		group.Add(func() error {
			return server.ServeTLS(l, c.Web.TLSCert, c.Web.TLSKey)
		}, func(err error) {
			ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
			defer cancel()

			logger.Debugf("starting graceful shutdown (%s)", name)
			if err := server.Shutdown(ctx); err != nil {
				logger.Errorf("graceful shutdown (%s): %v", name, err)
			}
		})
	}

	// Set up grpc server
	if c.GRPC.Addr != "" {
		logger.Infof("listening (grpc) on %s", c.GRPC.Addr)

		grpcListener, err := net.Listen("tcp", c.GRPC.Addr)
		if err != nil {
			return fmt.Errorf("listening (grcp) on %s: %w", c.GRPC.Addr, err)
		}

		grpcSrv := grpc.NewServer(grpcOptions...)
		api.RegisterDexServer(grpcSrv, server.NewAPI(serverConfig.Storage, logger))

		grpcMetrics.InitializeMetrics(grpcSrv)
		if c.GRPC.Reflection {
			logger.Info("enabling reflection in grpc service")
			reflection.Register(grpcSrv)
		}

		group.Add(func() error {
			return grpcSrv.Serve(grpcListener)
		}, func(err error) {
			logger.Debugf("starting graceful shutdown (grpc)")
			grpcSrv.GracefulStop()
		})
	}

	group.Add(run.SignalHandler(context.Background(), os.Interrupt, syscall.SIGTERM))
	if err := group.Run(); err != nil {
		if _, ok := err.(run.SignalError); !ok {
			return fmt.Errorf("run groups: %w", err)
		}
		logger.Infof("%v, shutdown now", err)
	}
	return nil
}

var (
	logLevels  = []string{"debug", "info", "error"}
	logFormats = []string{"json", "text"}
)

type utcFormatter struct {
	f logrus.Formatter
}

func (f *utcFormatter) Format(e *logrus.Entry) ([]byte, error) {
	e.Time = e.Time.UTC()
	return f.f.Format(e)
}

func newLogger(level string, format string) (log.Logger, error) {
	var logLevel logrus.Level
	switch strings.ToLower(level) {
	case "debug":
		logLevel = logrus.DebugLevel
	case "", "info":
		logLevel = logrus.InfoLevel
	case "error":
		logLevel = logrus.ErrorLevel
	default:
		return nil, fmt.Errorf("log level is not one of the supported values (%s): %s", strings.Join(logLevels, ", "), level)
	}

	var formatter utcFormatter
	switch strings.ToLower(format) {
	case "", "text":
		formatter.f = &logrus.TextFormatter{DisableColors: true}
	case "json":
		formatter.f = &logrus.JSONFormatter{}
	default:
		return nil, fmt.Errorf("log format is not one of the supported values (%s): %s", strings.Join(logFormats, ", "), format)
	}

	return &logrus.Logger{
		Out:       os.Stderr,
		Formatter: &formatter,
		Level:     logLevel,
	}, nil
}

func applyConfigOverrides(options serveOptions, config *Config) {
	if options.webHTTPAddr != "" {
		config.Web.HTTP = options.webHTTPAddr
	}

	if options.webHTTPSAddr != "" {
		config.Web.HTTPS = options.webHTTPSAddr
	}

	if options.telemetryAddr != "" {
		config.Telemetry.HTTP = options.telemetryAddr
	}

	if options.grpcAddr != "" {
		config.GRPC.Addr = options.grpcAddr
	}
}
