package auth

import (
	"context"
	"crypto/rsa"
	"crypto/tls"
	"crypto/x509"
	"embed"
	"encoding/json"
	"fmt"
	"html/template"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"

	"github.com/Masterminds/sprig"
	"github.com/cortezaproject/corteza-server/auth/external"
	"github.com/cortezaproject/corteza-server/auth/handlers"
	"github.com/cortezaproject/corteza-server/auth/oauth2"
	"github.com/cortezaproject/corteza-server/auth/request"
	"github.com/cortezaproject/corteza-server/auth/saml"
	"github.com/cortezaproject/corteza-server/auth/settings"
	"github.com/cortezaproject/corteza-server/pkg/actionlog"
	"github.com/cortezaproject/corteza-server/pkg/auth"
	"github.com/cortezaproject/corteza-server/pkg/locale"
	"github.com/cortezaproject/corteza-server/pkg/options"
	"github.com/cortezaproject/corteza-server/pkg/version"
	"github.com/cortezaproject/corteza-server/store"
	systemService "github.com/cortezaproject/corteza-server/system/service"
	"github.com/cortezaproject/corteza-server/system/types"
	"github.com/go-chi/chi/v5"
	oauth2def "github.com/go-oauth2/oauth2/v4"
	"go.uber.org/zap"
	"golang.org/x/text/language"
)

type (
	service struct {
		handlers *handlers.AuthHandlers
		log      *zap.Logger
		opt      options.AuthOpt
		settings *settings.Settings
		store    store.Storer
	}
)

//go:embed assets/public
var PublicAssets embed.FS

// New initializes Auth service that orchestrates session manager, oauth2 manager and http request handlers
func New(ctx context.Context, log *zap.Logger, oa2m oauth2def.Manager, s store.Storer, opt options.AuthOpt, defClient *types.AuthClient) (svc *service, err error) {
	var (
		tpls templateExecutor
	)

	log = log.Named("auth")
	ctx = actionlog.RequestOriginToContext(ctx, actionlog.RequestOrigin_Auth)

	svc = &service{
		opt:      opt,
		log:      log,
		store:    s,
		settings: &settings.Settings{ /* all disabled by default. */ },
	}

	if !opt.LogEnabled {
		log = zap.NewNop()
	}

	sesManager := request.NewSessionManager(s, opt, log)

	oauth2Server := oauth2.NewServer(oa2m)

	// Called after oauth2 authorization request is validated
	// We'll try to get valid user out of the session or redirect user to login page
	oauth2Server.SetUserAuthorizationHandler(oauth2.NewUserAuthorizer(
		sesManager,
		handlers.GetLinks().Login,
		handlers.GetLinks().OAuth2AuthorizeClient,
	))

	oauth2Server.SetClientAuthorizedHandler(func(id string, grant oauth2def.GrantType) (allowed bool, err error) {
		// this is a bit silly and a bad design of the oauth2 server lib
		// why do we need to keep on load the client??
		var (
			client *types.AuthClient
		)

		if client, err = clientLookup(ctx, s, id); err != nil {
			return false, fmt.Errorf("could not authorize client: %w", err)
		}

		// each client only has 1 valid grant type (+ refresh_token)!
		if client.ValidGrant != grant.String() && oauth2def.Refreshing != grant {
			return false, fmt.Errorf("client does not support %s flow", grant)
		}

		return true, nil
	})

	oauth2Server.SetClientScopeHandler(func(tgr *oauth2def.TokenGenerateRequest) (allowed bool, err error) {
		// this is a bit silly and a bad design of the oauth2 server lib
		// why do we need to keep on load the client??
		var (
			client *types.AuthClient
		)

		if client, err = clientLookup(ctx, s, tgr.ClientID); err != nil {
			return false, fmt.Errorf("could not authorize client: %w", err)
		}

		// ensure all requested scopes are allowed on a client
		if !auth.CheckScope(client.Scope, strings.Split(tgr.Scope, " ")...) {
			return false, fmt.Errorf("client does not allow use of '%s' scope", client.Scope)
		}

		return true, nil
	})

	oauth2Server.SetExtensionFieldsHandler(func(ti oauth2def.TokenInfo) (fieldsValue map[string]interface{}) {
		fieldsValue = make(map[string]interface{})
		handlers.SubSplit(ti, fieldsValue)
		fieldsValue["refresh_token_expires_in"] = int(ti.GetRefreshExpiresIn() / time.Second)
		if err = userProfile(ctx, s, ti, fieldsValue); err != nil {
			log.Error("failed to add profile data", zap.Error(err))
		}

		return
	})

	var (
		tplLoader templateLoader

		tplBase = template.New("").
			Funcs(sprig.FuncMap()).
			Funcs(template.FuncMap{
				"version":   func() string { return version.Version },
				"buildtime": func() string { return version.BuildTime },
				"links":     handlers.GetLinks,

				// temp, will be replaced
				"language": func() string { return language.Tag{}.String() },
				"tr":       func(key string, pp ...string) string { return key },
			})

		useEmbedded = len(opt.AssetsPath) == 0
	)

	if useEmbedded {
		tplLoader = EmbeddedTemplates
		log.Info("using embedded templates")
	} else {
		tplLoader = func(t *template.Template) (tpl *template.Template, err error) {
			if tpl, err = t.Clone(); err != nil {
				return nil, fmt.Errorf("cannot clone templates: %w", err)
			} else {
				return tpl.ParseGlob(opt.AssetsPath + "/templates/*.tpl")
			}
		}
		log.Info(
			"loading templates from filesystem",
			zap.String("AUTH_ASSETS_PATH", svc.opt.AssetsPath),
		)
	}

	if !useEmbedded && opt.DevelopmentMode {
		log.Info(
			"initializing reloadable templates",
			zap.Bool("AUTH_DEVELOPMENT_MODE", opt.DevelopmentMode),
		)
		tpls = NewReloadableTemplates(tplBase, tplLoader)
	} else {
		log.Info(
			"initializing templates without reloading",
			zap.Bool("AUTH_DEVELOPMENT_MODE", opt.DevelopmentMode),
		)
		tpls, err = NewStaticTemplates(tplBase, tplLoader)
		if err != nil {
			return nil, fmt.Errorf("cannot load templates: %w", err)
		}
	}

	svc.handlers = &handlers.AuthHandlers{
		Locale:         locale.Global(),
		Log:            log,
		Templates:      tpls,
		SessionManager: sesManager,
		OAuth2:         oauth2Server,
		AuthService:    systemService.DefaultAuth,
		UserService:    systemService.DefaultUser,
		ClientService:  &clientService{s},
		TokenService:   &tokenService{s},
		DefaultClient:  defClient,
		Opt:            svc.opt,
		Settings:       svc.settings,
	}

	external.Init(sesManager.Store())

	svc.log.Info(
		"auth server ready",
		zap.String("AUTH_BASE_URL", svc.opt.BaseURL),
		zap.String("AUTH_EXTERNAL_REDIRECT_URL", svc.opt.ExternalRedirectURL),
	)

	return
}

// LoadSamlService takes care of certificate preloading, fetching of the
// IDP metadata once the auth settings are loaded and registers the
// SAML middleware
func (svc *service) LoadSamlService(ctx context.Context, s *settings.Settings) (*saml.SamlSPService, error) {
	var (
		log     = svc.log.Named("saml")
		links   = handlers.GetLinks()
		keyPair tls.Certificate
		err     error
	)

	if keyPair, err = tls.X509KeyPair([]byte(s.Saml.Cert), []byte(s.Saml.Key)); err != nil {
		return nil, err
	}

	if keyPair.Leaf, err = x509.ParseCertificate(keyPair.Certificate[0]); err != nil {
		return nil, err
	}

	idpUrl, err := url.Parse(s.Saml.IDP.URL)
	if err != nil {
		return nil, err
	}

	// idp metadata needs to be loaded before
	// the internal samlsp package
	md, err := saml.FetchIDPMetadata(ctx, *idpUrl)
	if err != nil {
		return nil, err
	}

	ru, err := url.Parse(svc.opt.BaseURL)
	if err != nil {
		return nil, err
	}

	rootURL := &url.URL{
		Scheme: ru.Scheme,
		User:   ru.User,
		Host:   ru.Host,
	}

	return saml.NewSamlSPService(log, saml.SamlSPArgs{
		Enabled: s.Saml.Enabled,

		AcsURL:  links.SamlCallback,
		MetaURL: links.SamlMetadata,
		SloURL:  links.SamlLogout,

		IdpURL: *idpUrl,
		Host:   *rootURL,

		Certificate: keyPair.Leaf,
		PrivateKey:  keyPair.PrivateKey.(*rsa.PrivateKey),
		IdpMeta:     md,

		SignRequests:    s.Saml.SignRequests,
		SignatureMethod: s.Saml.SignMethod,

		Binding: s.Saml.Binding,

		IdentityPayload: saml.IdpIdentityPayload{
			Name:       s.Saml.IDP.IdentName,
			Handle:     s.Saml.IDP.IdentHandle,
			Identifier: s.Saml.IDP.IdentIdentifier,
		},
	})
}

func (svc *service) UpdateSettings(s *settings.Settings) {
	if svc.settings.LocalEnabled != s.LocalEnabled {
		svc.log.Debug("setting changed", zap.Bool("localEnabled", s.LocalEnabled))
	}

	if svc.settings.SignupEnabled != s.SignupEnabled {
		svc.log.Debug("setting changed", zap.Bool("signupEnabled", s.SignupEnabled))
	}

	if svc.settings.EmailConfirmationRequired != s.EmailConfirmationRequired {
		svc.log.Debug("setting changed", zap.Bool("emailConfirmationRequired", s.EmailConfirmationRequired))
	}

	if svc.settings.PasswordResetEnabled != s.PasswordResetEnabled {
		svc.log.Debug("setting changed", zap.Bool("passwordResetEnabled", s.PasswordResetEnabled))
	}

	if svc.settings.SplitCredentialsCheck != s.SplitCredentialsCheck {
		svc.log.Debug("setting changed", zap.Bool("splitCredentialsCheck", s.SplitCredentialsCheck))
	}

	if svc.settings.ExternalEnabled != s.ExternalEnabled {
		svc.log.Debug("setting changed", zap.Bool("externalEnabled", s.ExternalEnabled))
	}

	if svc.settings.MultiFactor != s.MultiFactor {
		svc.log.Debug("setting changed", zap.Any("mfa", s.MultiFactor))
	}

	if svc.settings.Saml != s.Saml {
		var (
			log = svc.log.Named("saml")
			ss  *saml.SamlSPService
			err error
		)

		log.Debug("setting updated")
		switch true {
		case s.Saml.Cert == "", s.Saml.Key == "":
			log.Warn("certificate private/public keys empty (see 'auth.external.saml' settings)")
			break

		case s.Saml.IDP.URL == "":
			log.Warn("could not get IDP url (see 'auth.external.saml.idp')")
			break

		default:
			ss, err = svc.LoadSamlService(context.Background(), s)

			if err != nil {
				log.Warn("could not reload service", zap.Error(err))
			}
		}

		if ss != nil {
			log.Info("reloading service")
			svc.handlers.SamlSPService = ss
		}
	}

	if len(svc.settings.Providers) != len(s.Providers) {
		svc.log.Debug("setting changed", zap.Int("providers", len(s.Providers)))
		external.SetupGothProviders(svc.log, svc.opt.ExternalRedirectURL, s.Providers...)
	}

	svc.settings = s
	svc.handlers.Settings = s
}

func (svc *service) Watch(ctx context.Context) {
	go svc.gc(ctx)
}

func (svc service) gc(ctx context.Context) {
	svc.log.Info("running startup garbage collection")
	go svc.gcSessions(ctx)
	go svc.gcOAuth2Tokens(ctx)

	i := svc.opt.GarbageCollectorInterval
	if i < time.Minute {
		svc.log.Warn("garbage collection interval less than 1 minute, disabling")
	} else {
		svc.log.Info("starting garbage collecting process", zap.Duration("interval", i))
	}

	tck := time.NewTicker(i)
	for {
		select {
		case <-ctx.Done():
			svc.log.Info("stopping gc", zap.Error(ctx.Err()))
			return
		case <-tck.C:
			svc.log.Info("garbage collector")
			go svc.gcSessions(ctx)
			go svc.gcOAuth2Tokens(ctx)
			return
		}

	}
}

func (svc service) gcSessions(ctx context.Context) {
	err := store.DeleteExpiredAuthSessions(ctx, svc.store)
	if err != nil {
		svc.log.Error("failed to collect session garbage", zap.Error(err))
	}
}
func (svc service) gcOAuth2Tokens(ctx context.Context) {
	err := store.DeleteExpiredAuthOA2Tokens(ctx, svc.store)
	if err != nil {
		svc.log.Error("failed to collect oauth2 token garbage", zap.Error(err))
	}
}

func (svc service) MountHttpRoutes(basePath string, r chi.Router) {
	basePath = strings.TrimRight(basePath, "/")
	svc.handlers.MountHttpRoutes(r)

	const uriRoot = "/auth/assets/public"
	var (
		assetHandler http.Handler
		useEmbedded  = len(svc.opt.AssetsPath) == 0
	)

	if useEmbedded {
		assetHandler = http.StripPrefix(basePath+"/auth/", http.FileServer(http.FS(PublicAssets)))
	} else {
		var root = strings.TrimRight(svc.opt.AssetsPath, "/") + "/public"

		if err := dirCheck(root); err != nil {
			svc.log.Error(
				"failed to configure auth assets handler",
				zap.Error(err),
				zap.String("AUTH_ASSETS_PATH", svc.opt.AssetsPath),
			)
		} else {
			assetHandler = http.StripPrefix(basePath+uriRoot, http.FileServer(http.Dir(root)))
		}
	}

	// fallback to embedded assets
	r.Handle(uriRoot+"/*", assetHandler)
}

// checks if directory exists & is readable
func dirCheck(path string) (err error) {
	_, err = os.Stat(path)
	if !os.IsNotExist(err) {
		return
	}

	return
}

func (svc service) WellKnownOpenIDConfiguration() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		_ = json.NewEncoder(w).Encode(map[string]interface{}{
			"issuer":                                svc.opt.BaseURL,
			"authorization_endpoint":                svc.opt.BaseURL + "/oauth2/authorize",
			"token_endpoint":                        svc.opt.BaseURL + "/oauth2/token",
			"jwks_uri":                              svc.opt.BaseURL + "/oauth2/public-keys",
			"scope_supported":                       []string{"profile", "api"},
			"id_token_signing_alg_values_supported": []string{"RS256", "HS512"},
			"response_types_supported":              []string{"code", "token"},
		})

		w.Header().Set("Content-Type", "application/json")
	}
}

// Profile fills map with user's data
//
// If scope supports it (contains "profile") user is loaded and
// map is filled with username (handle), email and name
func userProfile(ctx context.Context, s store.Users, ti oauth2def.TokenInfo, data map[string]interface{}) error {
	if !auth.CheckScope(ti.GetScope(), "profile") {
		return nil
	}

	userID, _ := auth.ExtractFromSubClaim(ti.GetUserID())
	if userID == 0 {
		return fmt.Errorf("invalid user ID in 'sub' claim")
	}

	user, err := store.LookupUserByID(ctx, s, userID)
	if err != nil {
		return err
	}

	data["handle"] = user.Handle
	data["name"] = user.Name
	data["email"] = user.Email

	if user.Meta != nil && user.Meta.PreferredLanguage != "" {
		data["preferred_language"] = user.Meta.PreferredLanguage
	}

	return nil
}