// SPDX-License-Identifier: Apache-2.0
package main

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strconv"
	"time"

	kitprometheus "github.com/go-kit/kit/metrics/prometheus"
	"github.com/go-redis/redis/v8"
	"github.com/mainflux/mainflux"
	authapi "github.com/mainflux/mainflux/auth/api/grpc"
	"github.com/mainflux/mainflux/certs"
	"github.com/mainflux/mainflux/certs/api"
	vault "github.com/mainflux/mainflux/certs/pki"
	"github.com/mainflux/mainflux/certs/postgres"
	"github.com/mainflux/mainflux/logger"
	"github.com/opentracing/opentracing-go"
	stdprometheus "github.com/prometheus/client_golang/prometheus"
	"golang.org/x/sync/errgroup"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"

	"github.com/jmoiron/sqlx"
	mflog "github.com/mainflux/mainflux/logger"
	"github.com/mainflux/mainflux/pkg/errors"
	mfsdk "github.com/mainflux/mainflux/pkg/sdk/go"
	jconfig "github.com/uber/jaeger-client-go/config"
)

const (
	stopWaitTime = 5 * time.Second

	defLogLevel      = "error"
	defDBHost        = "localhost"
	defDBPort        = "5432"
	defDBUser        = "mainflux"
	defDBPass        = "mainflux"
	defDB            = "certs"
	defDBSSLMode     = "disable"
	defDBSSLCert     = ""
	defDBSSLKey      = ""
	defDBSSLRootCert = ""
	defClientTLS     = "false"
	defCACerts       = ""
	defPort          = "8204"
	defServerCert    = ""
	defServerKey     = ""
	defCertsURL      = "http://localhost"
	defThingsURL     = "http://things:8182"
	defJaegerURL     = ""
	defAuthURL       = "localhost:8181"
	defAuthTimeout   = "1s"

	defSignCAPath     = "ca.crt"
	defSignCAKeyPath  = "ca.key"
	defSignHoursValid = "2048h"
	defSignRSABits    = ""

	defVaultHost       = ""
	defVaultRole       = "mainflux"
	defVaultToken      = ""
	defVaultPKIIntPath = "pki_int"

	envPort           = "MF_CERTS_HTTP_PORT"
	envLogLevel       = "MF_CERTS_LOG_LEVEL"
	envDBHost         = "MF_CERTS_DB_HOST"
	envDBPort         = "MF_CERTS_DB_PORT"
	envDBUser         = "MF_CERTS_DB_USER"
	envDBPass         = "MF_CERTS_DB_PASS"
	envDB             = "MF_CERTS_DB"
	envDBSSLMode      = "MF_CERTS_DB_SSL_MODE"
	envDBSSLCert      = "MF_CERTS_DB_SSL_CERT"
	envDBSSLKey       = "MF_CERTS_DB_SSL_KEY"
	envDBSSLRootCert  = "MF_CERTS_DB_SSL_ROOT_CERT"
	envClientTLS      = "MF_CERTS_CLIENT_TLS"
	envCACerts        = "MF_CERTS_CA_CERTS"
	envServerCert     = "MF_CERTS_SERVER_CERT"
	envServerKey      = "MF_CERTS_SERVER_KEY"
	envCertsURL       = "MF_SDK_CERTS_URL"
	envJaegerURL      = "MF_JAEGER_URL"
	envAuthURL        = "MF_AUTH_GRPC_URL"
	envAuthTimeout    = "MF_AUTH_GRPC_TIMEOUT"
	envThingsURL      = "MF_THINGS_URL"
	envSignCAPath     = "MF_CERTS_SIGN_CA_PATH"
	envSignCAKey      = "MF_CERTS_SIGN_CA_KEY_PATH"
	envSignHoursValid = "MF_CERTS_SIGN_HOURS_VALID"
	envSignRSABits    = "MF_CERTS_SIGN_RSA_BITS"

	envVaultHost       = "MF_CERTS_VAULT_HOST"
	envVaultPKIIntPath = "MF_VAULT_PKI_INT_PATH"
	envVaultRole       = "MF_VAULT_CA_ROLE_NAME"
	envVaultToken      = "MF_VAULT_TOKEN"
)

var (
	errFailedCertLoading     = errors.New("failed to load certificate")
	errFailedCertDecode      = errors.New("failed to decode certificate")
	errCACertificateNotExist = errors.New("CA certificate does not exist")
	errCAKeyNotExist         = errors.New("CA certificate key does not exist")
)

type config struct {
	logLevel    string
	dbConfig    postgres.Config
	clientTLS   bool
	caCerts     string
	httpPort    string
	serverCert  string
	serverKey   string
	certsURL    string
	thingsURL   string
	jaegerURL   string
	authURL     string
	authTimeout time.Duration
	// Sign and issue certificates without 3rd party PKI
	signCAPath     string
	signCAKeyPath  string
	signRSABits    int
	signHoursValid string
	// 3rd party PKI API access settings
	pkiPath  string
	pkiToken string
	pkiHost  string
	pkiRole  string
}

func main() {
	cfg := loadConfig()
	ctx, cancel := context.WithCancel(context.Background())
	g, ctx := errgroup.WithContext(ctx)

	logger, err := mflog.New(os.Stdout, cfg.logLevel)
	if err != nil {
		log.Fatalf(err.Error())
	}

	tlsCert, caCert, err := loadCertificates(cfg)
	if err != nil {
		logger.Error("Failed to load CA certificates for issuing client certs")
	}

	if cfg.pkiHost == "" {
		log.Fatalf("No host specified for PKI engine")
	}

	pkiClient, err := vault.NewVaultClient(cfg.pkiToken, cfg.pkiHost, cfg.pkiPath, cfg.pkiRole)
	if err != nil {
		log.Fatalf("Failed to configure client for PKI engine")
	}

	db := connectToDB(cfg.dbConfig, logger)
	defer db.Close()

	authTracer, authCloser := initJaeger("auth", cfg.jaegerURL, logger)
	defer authCloser.Close()

	authConn := connectToAuth(cfg, logger)
	defer authConn.Close()

	auth := authapi.NewClient(authTracer, authConn, cfg.authTimeout)

	svc := newService(auth, db, logger, nil, tlsCert, caCert, cfg, pkiClient)

	g.Go(func() error {
		return startHTTPServer(ctx, svc, cfg, logger)
	})

	g.Go(func() error {
		if sig := errors.SignalHandler(ctx); sig != nil {
			cancel()
			logger.Info(fmt.Sprintf("Certs service shutdown by signal: %s", sig))
		}
		return nil
	})

	if err := g.Wait(); err != nil {
		logger.Error(fmt.Sprintf("Certs service terminated: %s", err))
	}
}

func loadConfig() config {
	tls, err := strconv.ParseBool(mainflux.Env(envClientTLS, defClientTLS))
	if err != nil {
		tls = false
	}
	dbConfig := postgres.Config{
		Host:        mainflux.Env(envDBHost, defDBHost),
		Port:        mainflux.Env(envDBPort, defDBPort),
		User:        mainflux.Env(envDBUser, defDBUser),
		Pass:        mainflux.Env(envDBPass, defDBPass),
		Name:        mainflux.Env(envDB, defDB),
		SSLMode:     mainflux.Env(envDBSSLMode, defDBSSLMode),
		SSLCert:     mainflux.Env(envDBSSLCert, defDBSSLCert),
		SSLKey:      mainflux.Env(envDBSSLKey, defDBSSLKey),
		SSLRootCert: mainflux.Env(envDBSSLRootCert, defDBSSLRootCert),
	}

	authTimeout, err := time.ParseDuration(mainflux.Env(envAuthTimeout, defAuthTimeout))
	if err != nil {
		log.Fatalf("Invalid %s value: %s", envAuthTimeout, err.Error())
	}

	signRSABits, err := strconv.Atoi(mainflux.Env(envSignRSABits, defSignRSABits))
	if err != nil {
		log.Fatalf("Invalid %s value: %s", envSignRSABits, err.Error())
	}

	return config{
		logLevel:    mainflux.Env(envLogLevel, defLogLevel),
		dbConfig:    dbConfig,
		clientTLS:   tls,
		caCerts:     mainflux.Env(envCACerts, defCACerts),
		httpPort:    mainflux.Env(envPort, defPort),
		serverCert:  mainflux.Env(envServerCert, defServerCert),
		serverKey:   mainflux.Env(envServerKey, defServerKey),
		certsURL:    mainflux.Env(envCertsURL, defCertsURL),
		thingsURL:   mainflux.Env(envThingsURL, defThingsURL),
		jaegerURL:   mainflux.Env(envJaegerURL, defJaegerURL),
		authURL:     mainflux.Env(envAuthURL, defAuthURL),
		authTimeout: authTimeout,

		signCAKeyPath:  mainflux.Env(envSignCAKey, defSignCAKeyPath),
		signCAPath:     mainflux.Env(envSignCAPath, defSignCAPath),
		signHoursValid: mainflux.Env(envSignHoursValid, defSignHoursValid),
		signRSABits:    signRSABits,

		pkiToken: mainflux.Env(envVaultToken, defVaultToken),
		pkiPath:  mainflux.Env(envVaultPKIIntPath, defVaultPKIIntPath),
		pkiRole:  mainflux.Env(envVaultRole, defVaultRole),
		pkiHost:  mainflux.Env(envVaultHost, defVaultHost),
	}

}

func connectToDB(dbConfig postgres.Config, logger logger.Logger) *sqlx.DB {
	db, err := postgres.Connect(dbConfig)
	if err != nil {
		logger.Error(fmt.Sprintf("Failed to connect to postgres: %s", err))
		os.Exit(1)
	}
	return db
}

func connectToAuth(cfg config, logger logger.Logger) *grpc.ClientConn {
	var opts []grpc.DialOption
	if cfg.clientTLS {
		if cfg.caCerts != "" {
			tpc, err := credentials.NewClientTLSFromFile(cfg.caCerts, "")
			if err != nil {
				logger.Error(fmt.Sprintf("Failed to create tls credentials: %s", err))
				os.Exit(1)
			}
			opts = append(opts, grpc.WithTransportCredentials(tpc))
		}
	} else {
		opts = append(opts, grpc.WithInsecure())
		logger.Info("gRPC communication is not encrypted")
	}

	conn, err := grpc.Dial(cfg.authURL, opts...)
	if err != nil {
		logger.Error(fmt.Sprintf("Failed to connect to auth service: %s", err))
		os.Exit(1)
	}

	return conn
}

func initJaeger(svcName, url string, logger logger.Logger) (opentracing.Tracer, io.Closer) {
	if url == "" {
		return opentracing.NoopTracer{}, ioutil.NopCloser(nil)
	}

	tracer, closer, err := jconfig.Configuration{
		ServiceName: svcName,
		Sampler: &jconfig.SamplerConfig{
			Type:  "const",
			Param: 1,
		},
		Reporter: &jconfig.ReporterConfig{
			LocalAgentHostPort: url,
			LogSpans:           true,
		},
	}.NewTracer()
	if err != nil {
		logger.Error(fmt.Sprintf("Failed to init Jaeger client: %s", err))
		os.Exit(1)
	}

	return tracer, closer
}

func newService(auth mainflux.AuthServiceClient, db *sqlx.DB, logger mflog.Logger, esClient *redis.Client, tlsCert tls.Certificate, x509Cert *x509.Certificate, cfg config, pkiAgent vault.Agent) certs.Service {
	certsRepo := postgres.NewRepository(db, logger)

	certsConfig := certs.Config{
		LogLevel:       cfg.logLevel,
		ClientTLS:      cfg.clientTLS,
		CaCerts:        cfg.caCerts,
		HTTPPort:       cfg.httpPort,
		ServerCert:     cfg.serverCert,
		ServerKey:      cfg.serverKey,
		CertsURL:       cfg.certsURL,
		JaegerURL:      cfg.jaegerURL,
		AuthURL:        cfg.authURL,
		AuthTimeout:    cfg.authTimeout,
		SignTLSCert:    tlsCert,
		SignX509Cert:   x509Cert,
		SignHoursValid: cfg.signHoursValid,
		SignRSABits:    cfg.signRSABits,
		PKIToken:       cfg.pkiToken,
		PKIHost:        cfg.pkiHost,
		PKIPath:        cfg.pkiPath,
		PKIRole:        cfg.pkiRole,
	}

	config := mfsdk.Config{
		CertsURL:  cfg.certsURL,
		ThingsURL: cfg.thingsURL,
	}

	sdk := mfsdk.NewSDK(config)

	svc := certs.New(auth, certsRepo, sdk, certsConfig, pkiAgent)
	svc = api.NewLoggingMiddleware(svc, logger)
	svc = api.MetricsMiddleware(
		svc,
		kitprometheus.NewCounterFrom(stdprometheus.CounterOpts{
			Namespace: "certs",
			Subsystem: "api",
			Name:      "request_count",
			Help:      "Number of requests received.",
		}, []string{"method"}),
		kitprometheus.NewSummaryFrom(stdprometheus.SummaryOpts{
			Namespace: "certs",
			Subsystem: "api",
			Name:      "request_latency_microseconds",
			Help:      "Total duration of requests in microseconds.",
		}, []string{"method"}),
	)
	return svc
}

func startHTTPServer(ctx context.Context, svc certs.Service, cfg config, logger mflog.Logger) error {
	p := fmt.Sprintf(":%s", cfg.httpPort)
	errCh := make(chan error)
	server := &http.Server{Addr: p, Handler: api.MakeHandler(svc, logger)}
	switch {
	case cfg.serverCert != "" || cfg.serverKey != "":
		logger.Info(fmt.Sprintf("Certs service started using https on port %s with cert %s key %s", cfg.httpPort, cfg.serverCert, cfg.serverKey))
		go func() {
			errCh <- server.ListenAndServeTLS(cfg.serverCert, cfg.serverKey)
		}()

	default:
		logger.Info(fmt.Sprintf("Certs service started using http on port %s", cfg.httpPort))
		go func() {
			errCh <- http.ListenAndServe(p, api.MakeHandler(svc, logger))
		}()
	}
	select {
	case <-ctx.Done():
		ctxShutdown, cancelShutdown := context.WithTimeout(context.Background(), stopWaitTime)
		defer cancelShutdown()
		if err := server.Shutdown(ctxShutdown); err != nil {
			logger.Error(fmt.Sprintf("Certs service error occurred during shutdown at %s: %s", p, err))
			return fmt.Errorf("certs service  error occurred during shutdown at %s: %w", p, err)
		}
		logger.Info(fmt.Sprintf("Certs service  shutdown of http at %s", p))
		return nil
	case err := <-errCh:
		return err
	}
}

func loadCertificates(conf config) (tls.Certificate, *x509.Certificate, error) {
	var tlsCert tls.Certificate
	var caCert *x509.Certificate

	if conf.signCAPath == "" || conf.signCAKeyPath == "" {
		return tlsCert, caCert, nil
	}

	if _, err := os.Stat(conf.signCAPath); os.IsNotExist(err) {
		return tlsCert, caCert, errCACertificateNotExist
	}

	if _, err := os.Stat(conf.signCAKeyPath); os.IsNotExist(err) {
		return tlsCert, caCert, errCAKeyNotExist
	}

	tlsCert, err := tls.LoadX509KeyPair(conf.signCAPath, conf.signCAKeyPath)
	if err != nil {
		return tlsCert, caCert, errors.Wrap(errFailedCertLoading, err)
	}

	b, err := ioutil.ReadFile(conf.signCAPath)
	if err != nil {
		return tlsCert, caCert, errors.Wrap(errFailedCertLoading, err)
	}

	block, _ := pem.Decode(b)
	if block == nil {
		log.Fatalf("No PEM data found, failed to decode CA")
	}

	caCert, err = x509.ParseCertificate(block.Bytes)
	if err != nil {
		return tlsCert, caCert, errors.Wrap(errFailedCertDecode, err)
	}

	return tlsCert, caCert, nil
}