package backends

import (
	"fmt"
	"strings"

	"github.com/iegomez/mosquitto-go-auth/hashing"
	"github.com/pkg/errors"
	log "github.com/sirupsen/logrus"
)

type Backend interface {
	GetUser(username, password, clientid string) (bool, error)
	GetSuperuser(username string) (bool, error)
	CheckAcl(username, topic, clientId string, acc int32) (bool, error)
	GetName() string
	Halt()
}

type Backends struct {
	backends map[string]Backend

	aclCheckers       []string
	userCheckers      []string
	superuserCheckers []string

	checkPrefix bool
	stripPrefix bool
	prefixes    map[string]string

	disableSuperuser bool
}

const (
	// backends
	postgresBackend = "postgres"
	jwtBackend      = "jwt"
	redisBackend    = "redis"
	httpBackend     = "http"
	filesBackend    = "files"
	mysqlBackend    = "mysql"
	sqliteBackend   = "sqlite"
	mongoBackend    = "mongo"
	pluginBackend   = "plugin"
	grpcBackend     = "grpc"
	jsBackend       = "js"

	// checks
	aclCheck       = "acl"
	userCheck      = "user"
	superuserCheck = "superuser"

	// other constants
	defaultUserAgent = "mosquitto"
)

// AllowedBackendsOptsPrefix serves as a check for allowed backends and a map from backend to expected opts prefix.
var allowedBackendsOptsPrefix = map[string]string{
	postgresBackend: "pg",
	jwtBackend:      "jwt",
	redisBackend:    "redis",
	httpBackend:     "http",
	filesBackend:    "files",
	mysqlBackend:    "mysql",
	sqliteBackend:   "sqlite",
	mongoBackend:    "mongo",
	pluginBackend:   "plugin",
	grpcBackend:     "grpc",
	jsBackend:       "js",
}

// Initialize sets general options, tries to build the backends and register their checkers.
func Initialize(authOpts map[string]string, logLevel log.Level, version string) (*Backends, error) {

	b := &Backends{
		backends:          make(map[string]Backend),
		aclCheckers:       make([]string, 0),
		userCheckers:      make([]string, 0),
		superuserCheckers: make([]string, 0),
		prefixes:          make(map[string]string),
	}

	//Disable superusers for all backends if option is set.
	if authOpts["disable_superuser"] == "true" {
		b.disableSuperuser = true

	}

	backendsOpt, ok := authOpts["backends"]
	if !ok || backendsOpt == "" {
		return nil, fmt.Errorf("missing or blank option backends")
	}

	backends := strings.Split(strings.Replace(backendsOpt, " ", "", -1), ",")
	if len(backends) < 1 {
		return nil, fmt.Errorf("missing or blank option backends")
	}

	for _, backend := range backends {
		if _, ok := allowedBackendsOptsPrefix[backend]; !ok {
			return nil, fmt.Errorf("unknown backend %s", backend)
		}
	}

	err := b.addBackends(authOpts, logLevel, backends, version)
	if err != nil {
		return nil, err
	}

	err = b.setCheckers(authOpts)
	if err != nil {
		return nil, err
	}

	b.setPrefixes(authOpts, backends)

	return b, nil
}

func (b *Backends) addBackends(authOpts map[string]string, logLevel log.Level, backends []string, version string) error {
	for _, bename := range backends {
		var beIface Backend
		var err error

		hasher := hashing.NewHasher(authOpts, allowedBackendsOptsPrefix[bename])
		switch bename {
		case postgresBackend:
			beIface, err = NewPostgres(authOpts, logLevel, hasher)
			if err != nil {
				log.Fatalf("backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("backend registered: %s", beIface.GetName())
				b.backends[postgresBackend] = beIface.(Postgres)
			}
		case jwtBackend:
			beIface, err = NewJWT(authOpts, logLevel, hasher, version)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[jwtBackend] = beIface.(*JWT)
			}
		case filesBackend:
			beIface, err = NewFiles(authOpts, logLevel, hasher)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[filesBackend] = beIface.(*Files)
			}
		case redisBackend:
			beIface, err = NewRedis(authOpts, logLevel, hasher)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[redisBackend] = beIface.(Redis)
			}
		case mysqlBackend:
			beIface, err = NewMysql(authOpts, logLevel, hasher)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[mysqlBackend] = beIface.(Mysql)
			}
		case httpBackend:
			beIface, err = NewHTTP(authOpts, logLevel, version)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[httpBackend] = beIface.(HTTP)
			}
		case sqliteBackend:
			beIface, err = NewSqlite(authOpts, logLevel, hasher)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[sqliteBackend] = beIface.(Sqlite)
			}
		case mongoBackend:
			beIface, err = NewMongo(authOpts, logLevel, hasher)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[mongoBackend] = beIface.(Mongo)
			}
		case grpcBackend:
			beIface, err = NewGRPC(authOpts, logLevel)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[grpcBackend] = beIface.(*GRPC)
			}
		case jsBackend:
			beIface, err = NewJavascript(authOpts, logLevel)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[jsBackend] = beIface.(*Javascript)
			}
		case pluginBackend:
			beIface, err = NewCustomPlugin(authOpts, logLevel)
			if err != nil {
				log.Fatalf("Backend register error: couldn't initialize %s backend with error %s.", bename, err)
			} else {
				log.Infof("Backend registered: %s", beIface.GetName())
				b.backends[pluginBackend] = beIface.(*CustomPlugin)
			}
		default:
			return fmt.Errorf("unkown backend %s", bename)
		}
	}

	return nil
}

func (b *Backends) setCheckers(authOpts map[string]string) error {
	// We'll register which plugins will perform checks for user, superuser and acls.
	// At least one backend must be registered for user and acl checks.
	// When option auth_opt_backend_register is missing for the backend, we register all checks.
	for name := range b.backends {
		opt := fmt.Sprintf("%s_register", allowedBackendsOptsPrefix[name])
		options, ok := authOpts[opt]

		if ok {
			checkers := strings.Split(strings.Replace(options, " ", "", -1), ",")
			for _, check := range checkers {
				switch check {
				case aclCheck:
					b.aclCheckers = append(b.aclCheckers, name)
					log.Infof("registered acl checker: %s", name)
				case userCheck:
					b.userCheckers = append(b.userCheckers, name)
					log.Infof("registered user checker: %s", name)
				case superuserCheck:
					if !b.disableSuperuser {
						b.superuserCheckers = append(b.superuserCheckers, name)
						log.Infof("registered superuser checker: %s", name)
					}
				default:
					return fmt.Errorf("unsupported check %s found for backend %s", check, name)
				}
			}
		} else {
			b.aclCheckers = append(b.aclCheckers, name)
			log.Infof("registered acl checker: %s", name)
			b.userCheckers = append(b.userCheckers, name)
			log.Infof("registered user checker: %s", name)

			if !b.disableSuperuser {
				b.superuserCheckers = append(b.superuserCheckers, name)
				log.Infof("registered superuser checker: %s", name)
			}
		}
	}

	if len(b.userCheckers) == 0 && len(b.aclCheckers) == 0 {
		return errors.New("no backends registered")
	}

	return nil
}

// setPrefixes sets options for prefixes handling.
func (b *Backends) setPrefixes(authOpts map[string]string, backends []string) {
	checkPrefix, ok := authOpts["check_prefix"]

	if !ok || strings.Replace(checkPrefix, " ", "", -1) != "true" {
		b.checkPrefix = false
		b.stripPrefix = false

		return
	}

	prefixesStr, ok := authOpts["prefixes"]

	if !ok {
		log.Warn("Error: prefixes enabled but no options given, defaulting to prefixes disabled.")
		b.checkPrefix = false
		b.stripPrefix = false

		return
	}

	prefixes := strings.Split(strings.Replace(prefixesStr, " ", "", -1), ",")

	if len(prefixes) != len(backends) {
		log.Errorf("Error: got %d backends and %d prefixes, defaulting to prefixes disabled.", len(backends), len(prefixes))
		b.checkPrefix = false
		b.stripPrefix = false

		return
	}

	if authOpts["strip_prefix"] == "true" {
		b.stripPrefix = true
	}

	for i, backend := range backends {
		b.prefixes[prefixes[i]] = backend
	}

	log.Infof("prefixes enabled for backends %s with prefixes %s.", authOpts["backends"], authOpts["prefixes"])
	b.checkPrefix = true
}

// checkPrefix checks if a username contains a valid prefix. If so, returns ok and the suitable backend name; else, !ok and empty string.
func (b *Backends) lookupPrefix(username string) (bool, string) {
	if strings.Index(username, "_") > 0 {
		userPrefix := username[0:strings.Index(username, "_")]
		if prefix, ok := b.prefixes[userPrefix]; ok {
			log.Debugf("Found prefix for user %s, using backend %s.", username, prefix)
			return true, prefix
		}
	}
	return false, ""
}

// getPrefixForBackend retrieves the user provided prefix for a given backend.
func (b *Backends) getPrefixForBackend(backend string) string {
	for k, v := range b.prefixes {
		if v == backend {
			return k
		}
	}
	return ""
}

func checkRegistered(bename string, checkers []string) bool {
	for _, b := range checkers {
		if b == bename {
			return true
		}
	}

	return false
}

// AuthUnpwdCheck checks user authentication.
func (b *Backends) AuthUnpwdCheck(username, password, clientid string) (bool, error) {
	var authenticated bool
	var err error

	// If prefixes are enabled, check if username has a valid prefix and use the correct backend if so.
	if !b.checkPrefix {
		return b.checkAuth(username, password, clientid)
	}

	validPrefix, bename := b.lookupPrefix(username)

	if !validPrefix {
		return b.checkAuth(username, password, clientid)
	}

	if !checkRegistered(bename, b.userCheckers) {
		return false, fmt.Errorf("backend %s not registered to check users", bename)
	}

	// If the backend is JWT and the token was prefixed, then strip the token.
	// If the token was passed without a prefix it will be handled in the common case.
	// Also strip the prefix if the strip_prefix option was set.
	if bename == jwtBackend || b.stripPrefix {
		prefix := b.getPrefixForBackend(bename)
		username = strings.TrimPrefix(username, prefix+"_")
	}
	var backend = b.backends[bename]

	authenticated, err = backend.GetUser(username, password, clientid)
	if authenticated && err == nil {
		log.Debugf("user %s authenticated with backend %s", username, backend.GetName())
	}

	return authenticated, err
}

func (b *Backends) checkAuth(username, password, clientid string) (bool, error) {
	var err error
	authenticated := false

	for _, bename := range b.userCheckers {
		var backend = b.backends[bename]

		log.Debugf("checking user %s with backend %s", username, backend.GetName())

		if ok, getUserErr := backend.GetUser(username, password, clientid); ok && getUserErr == nil {
			authenticated = true
			log.Debugf("user %s authenticated with backend %s", username, backend.GetName())
			break
		} else if getUserErr != nil && err == nil {
			err = getUserErr
		}
	}

	// If authenticated is true, it means at least one backend didn't fail and
	// accepted the user. If so, honor the backend and clear the error.
	if authenticated {
		err = nil
	}

	return authenticated, err
}

// AuthAclCheck checks user/topic/acc authorization.
func (b *Backends) AuthAclCheck(clientid, username, topic string, acc int) (bool, error) {
	var aclCheck bool
	var err error

	// If prefixes are enabled, check if username has a valid prefix and use the correct backend if so.
	// Else, check all backends.
	if !b.checkPrefix {
		return b.checkAcl(username, topic, clientid, acc)
	}

	validPrefix, bename := b.lookupPrefix(username)

	if !validPrefix {
		return b.checkAcl(username, topic, clientid, acc)
	}

	// If the backend is JWT and the token was prefixed, then strip the token.
	// If the token was passed without a prefix then let it be handled in the common case.
	// Also strip the prefix if the strip_prefix option was set.
	if bename == jwtBackend || b.stripPrefix {
		prefix := b.getPrefixForBackend(bename)
		username = strings.TrimPrefix(username, prefix+"_")
	}
	var backend = b.backends[bename]

	// Short circuit checks when superusers are disabled.
	if !b.disableSuperuser && checkRegistered(bename, b.superuserCheckers) {
		log.Debugf("Superuser check with backend %s", backend.GetName())

		aclCheck, err = backend.GetSuperuser(username)

		if aclCheck && err == nil {
			log.Debugf("superuser %s acl authenticated with backend %s", username, backend.GetName())
		}
	}
	// If not superuser, check acl.
	if !aclCheck {
		if !checkRegistered(bename, b.aclCheckers) {
			return false, fmt.Errorf("backend %s not registered to check acls", bename)
		}

		log.Debugf("Acl check with backend %s", backend.GetName())
		if ok, checkACLErr := backend.CheckAcl(username, topic, clientid, int32(acc)); ok && checkACLErr == nil {
			aclCheck = true
			log.Debugf("user %s acl authenticated with backend %s", username, backend.GetName())
		} else if checkACLErr != nil && err == nil {
			err = checkACLErr
		}
	}

	log.Debugf("Acl is %t for user %s", aclCheck, username)
	return aclCheck, err
}

func (b *Backends) checkAcl(username, topic, clientid string, acc int) (bool, error) {
	// Check superusers first
	var err error
	aclCheck := false
	if !b.disableSuperuser {
		for _, bename := range b.superuserCheckers {
			var backend = b.backends[bename]

			log.Debugf("Superuser check with backend %s", backend.GetName())
			if ok, getSuperuserErr := backend.GetSuperuser(username); ok && getSuperuserErr == nil {
				log.Debugf("superuser %s acl authenticated with backend %s", username, backend.GetName())
				aclCheck = true
				break
			} else if getSuperuserErr != nil && err == nil {
				err = getSuperuserErr
			}
		}
	}

	if !aclCheck {
		for _, bename := range b.aclCheckers {
			var backend = b.backends[bename]

			log.Debugf("Acl check with backend %s", backend.GetName())
			if ok, checkACLErr := backend.CheckAcl(username, topic, clientid, int32(acc)); ok && checkACLErr == nil {
				log.Debugf("user %s acl authenticated with backend %s", username, backend.GetName())
				aclCheck = true
				break
			} else if checkACLErr != nil && err == nil {
				err = checkACLErr
			}
		}
	}

	// If aclCheck is true, it means at least one backend didn't fail and
	// accepted the access. In this case trust this backend and clear the error.
	if aclCheck {
		err = nil
	}

	return aclCheck, err
}

func (b *Backends) Halt() {
	// Halt every registered backend.
	for _, v := range b.backends {
		v.Halt()
	}
}