// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

package app

import (
	"errors"
	"net/http"
	"path"
	"strings"

	"github.com/mattermost/mattermost/server/public/model"
	"github.com/mattermost/mattermost/server/public/shared/mlog"
	"github.com/mattermost/mattermost/server/public/shared/request"
	"github.com/mattermost/mattermost/server/v8/channels/app/password/hashers"
	"github.com/mattermost/mattermost/server/v8/channels/app/users"
	"github.com/mattermost/mattermost/server/v8/channels/utils"
	"github.com/mattermost/mattermost/server/v8/platform/shared/mfa"
)

type TokenLocation int

const (
	TokenLocationNotFound TokenLocation = iota
	TokenLocationHeader
	TokenLocationCookie
	TokenLocationQueryString
	TokenLocationCloudHeader
	TokenLocationRemoteClusterHeader
)

func (tl TokenLocation) String() string {
	switch tl {
	case TokenLocationNotFound:
		return "Not Found"
	case TokenLocationHeader:
		return "Header"
	case TokenLocationCookie:
		return "Cookie"
	case TokenLocationQueryString:
		return "QueryString"
	case TokenLocationCloudHeader:
		return "CloudHeader"
	case TokenLocationRemoteClusterHeader:
		return "RemoteClusterHeader"
	default:
		return "Unknown"
	}
}

func (a *App) IsPasswordValid(rctx request.CTX, password string) *model.AppError {
	if err := users.IsPasswordValidWithSettings(password, &a.Config().PasswordSettings); err != nil {
		var invErr *users.ErrInvalidPassword
		switch {
		case errors.As(err, &invErr):
			return model.NewAppError("User.IsValid", invErr.Id(), map[string]any{"Min": *a.Config().PasswordSettings.MinimumLength}, "", http.StatusBadRequest).Wrap(err)
		default:
			return model.NewAppError("User.IsValid", "app.valid_password_generic.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
		}
	}

	return nil
}

func (a *App) checkUserPassword(user *model.User, password string) *model.AppError {
	if user.Password == "" || password == "" {
		return model.NewAppError("checkUserPassword", "api.user.check_user_password.invalid.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}

	// Get the hasher and parsed PHC
	hasher, phc, err := hashers.GetHasherFromPHCString(user.Password)
	if err != nil {
		return model.NewAppError("checkUserPassword", "api.user.check_user_password.invalid_hash.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}

	// Compare the password using the hasher that generated it
	err = hasher.CompareHashAndPassword(phc, password)
	if err != nil && errors.Is(err, hashers.ErrMismatchedHashAndPassword) {
		return model.NewAppError("checkUserPassword", "api.user.check_user_password.invalid.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized).Wrap(err)
	} else if err != nil {
		return model.NewAppError("checkUserPassword", "app.valid_password_generic.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Migrate the password if needed
	if !hashers.IsLatestHasher(hasher) {
		return a.migratePassword(user, password)
	}

	return nil
}

// migratePassword updates the database with the user's password hashed with the
// latest hashing method. It assumes that the password has been already validated.
func (a *App) migratePassword(user *model.User, password string) *model.AppError {
	// Compute the new hash with the latest hashing method
	newHash, err := hashers.Hash(password)
	if err != nil {
		return model.NewAppError("migratePassword", "app.user.check_user_password.failed_migration", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	// Update the password
	if err := a.Srv().Store().User().UpdatePassword(user.Id, newHash); err != nil {
		return model.NewAppError("migratePassword", "app.user.check_user_password.failed_update", nil, "", http.StatusInternalServerError).Wrap(err)
	}
	a.InvalidateCacheForUser(user.Id)

	return nil
}

func (a *App) CheckPasswordAndAllCriteria(rctx request.CTX, userID string, password string, mfaToken string) *model.AppError {
	user, err := a.GetUser(userID)
	if err != nil {
		if err.Id != MissingAccountError {
			err.StatusCode = http.StatusInternalServerError
			return err
		}
		err.StatusCode = http.StatusBadRequest
		return err
	}

	if err := a.CheckUserPreflightAuthenticationCriteria(rctx, user, mfaToken); err != nil {
		return err
	}

	maxAttempts := *a.Config().ServiceSettings.MaximumLoginAttempts
	claimed, claimErr := a.Srv().Store().User().TryIncrementFailedPasswordAttempts(user.Id, maxAttempts)
	if claimErr != nil {
		return model.NewAppError("CheckPasswordAndAllCriteria", "app.user.update_failed_pwd_attempts.app_error", nil, "", http.StatusInternalServerError).Wrap(claimErr)
	}
	if !claimed {
		return model.NewAppError("checkUserLoginAttempts", "api.user.check_user_login_attempts.too_many.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}

	if err := a.checkUserPassword(user, password); err != nil {
		// Only keep the claimed slot when the failure is an actual
		// credential mismatch; backend errors (hasher failures, migration
		// failures, malformed stored hash) must not consume a slot or a
		// transient infra issue could lock out a user with valid creds.
		if err.Id != "api.user.check_user_password.invalid.app_error" {
			if passErr := a.Srv().Store().User().DecrementFailedPasswordAttempts(user.Id); passErr != nil {
				rctx.Logger().Warn("failed to refund login attempt slot", mlog.String("user_id", user.Id), mlog.Err(passErr))
			}
		}
		return err
	}

	if err := a.CheckUserMfa(rctx, user, mfaToken); err != nil {
		// The slot we claimed already counts this as a failed attempt;
		// the only special case is when no mfaToken was provided, which
		// is treated as a pre-flight MFA-state probe rather than a real
		// attempt — refund the slot so the probe is not counted.
		if mfaToken == "" {
			if passErr := a.Srv().Store().User().DecrementFailedPasswordAttempts(user.Id); passErr != nil {
				rctx.Logger().Warn("failed to refund MFA probe slot", mlog.String("user_id", user.Id), mlog.Err(passErr))
			}
		}

		return err
	}

	if passErr := a.Srv().Store().User().UpdateFailedPasswordAttempts(user.Id, 0); passErr != nil {
		return model.NewAppError("CheckPasswordAndAllCriteria", "app.user.update_failed_pwd_attempts.app_error", nil, "", http.StatusInternalServerError).Wrap(passErr)
	}

	if err := a.CheckUserPostflightAuthenticationCriteria(rctx, user); err != nil {
		return err
	}

	return nil
}

// This to be used for places we check the users password when they are already logged in
func (a *App) DoubleCheckPassword(rctx request.CTX, user *model.User, password string) *model.AppError {
	maxAttempts := *a.Config().ServiceSettings.MaximumLoginAttempts
	claimed, claimErr := a.Srv().Store().User().TryIncrementFailedPasswordAttempts(user.Id, maxAttempts)
	if claimErr != nil {
		return model.NewAppError("DoubleCheckPassword", "app.user.update_failed_pwd_attempts.app_error", nil, "", http.StatusInternalServerError).Wrap(claimErr)
	}
	if !claimed {
		return model.NewAppError("checkUserLoginAttempts", "api.user.check_user_login_attempts.too_many.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}

	if err := a.checkUserPassword(user, password); err != nil {
		if err.Id != "api.user.check_user_password.invalid.app_error" {
			if passErr := a.Srv().Store().User().DecrementFailedPasswordAttempts(user.Id); passErr != nil {
				rctx.Logger().Warn("failed to refund login attempt slot", mlog.String("user_id", user.Id), mlog.Err(passErr))
			}
		}
		return err
	}

	if passErr := a.Srv().Store().User().UpdateFailedPasswordAttempts(user.Id, 0); passErr != nil {
		return model.NewAppError("DoubleCheckPassword", "app.user.update_failed_pwd_attempts.app_error", nil, "", http.StatusInternalServerError).Wrap(passErr)
	}

	a.InvalidateCacheForUser(user.Id)

	return nil
}

func (a *App) checkLdapUserPasswordAndAllCriteria(rctx request.CTX, user *model.User, password, mfaToken string) (*model.User, *model.AppError) {
	// We need to get the latest value of the user from the database. user.Id is empty for first-time LDAP users.
	if user.Id != "" {
		var err *model.AppError
		user, err = a.GetUser(user.Id)
		if err != nil {
			if err.Id != MissingAccountError {
				err.StatusCode = http.StatusInternalServerError
				return nil, err
			}
			err.StatusCode = http.StatusBadRequest
			return nil, err
		}
	}

	ldapID := user.AuthData

	if a.Ldap() == nil || ldapID == nil {
		err := model.NewAppError("doLdapAuthentication", "api.user.login_ldap.not_available.app_error", nil, "", http.StatusNotImplemented)
		return nil, err
	}

	maxAttempts := *a.Config().LdapSettings.MaximumLoginAttempts

	// First-time LDAP users have no local row yet to pre-claim against.
	if user.Id != "" {
		claimed, claimErr := a.Srv().Store().User().TryIncrementFailedPasswordAttempts(user.Id, maxAttempts)
		if claimErr != nil {
			return nil, model.NewAppError("checkLdapUserPasswordAndAllCriteria", "app.user.update_failed_pwd_attempts.app_error", nil, "", http.StatusInternalServerError).Wrap(claimErr)
		}
		if !claimed {
			return nil, model.NewAppError("checkUserLoginAttempts", "api.user.check_user_login_attempts.too_many_ldap.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
		}
	}

	ldapUser, err := a.Ldap().DoLogin(rctx, *ldapID, password)
	if err != nil {
		// If this is a new LDAP user, we need to get the user from the database because DoLogin will have created the user.
		if user.Id == "" {
			var getUserByAuthErr *model.AppError
			ldapUser, getUserByAuthErr = a.GetUserByAuth(ldapID, model.UserAuthServiceLdap)
			if getUserByAuthErr != nil {
				return nil, getUserByAuthErr
			}
		} else {
			ldapUser = user
		}

		// Log a info to make it easier to admin to spot that a user tried to log in with a legitimate user name.
		if err.Id == "ent.ldap.do_login.invalid_password.app_error" {
			rctx.Logger().LogM(mlog.MlvlLDAPInfo, "A user tried to sign in, which matched an LDAP account, but the password was incorrect.", mlog.String("ldap_id", *ldapID))

			// For existing users we already claimed the slot above, so the
			// counter has already been bumped. For first-time users (the
			// row was just created by DoLogin) we still need to count the
			// failed attempt explicitly, using the atomic primitive so
			// concurrent first-attempt requests cannot overwrite each
			// other's increments.
			if user.Id == "" {
				if _, passErr := a.Srv().Store().User().TryIncrementFailedPasswordAttempts(ldapUser.Id, maxAttempts); passErr != nil {
					rctx.Logger().Warn("failed to record failed attempt for first-time LDAP user", mlog.String("user_id", ldapUser.Id), mlog.Err(passErr))
				}
			}
		} else if user.Id != "" {
			// Non-credential failure (LDAP unreachable, transient error,
			// etc.) on an existing user must not consume the slot we
			// pre-claimed, or an LDAP outage could lock out everyone.
			if passErr := a.Srv().Store().User().DecrementFailedPasswordAttempts(user.Id); passErr != nil {
				rctx.Logger().Warn("failed to refund LDAP login attempt slot", mlog.String("user_id", user.Id), mlog.Err(passErr))
			}
		}

		err.StatusCode = http.StatusUnauthorized
		return nil, err
	}

	if err = a.CheckUserMfa(rctx, ldapUser, mfaToken); err != nil {
		// For existing LDAP users we pre-claimed a slot, so it already
		// counts as a failed attempt. The only special case is when no
		// mfaToken was provided, which is treated as a pre-flight
		// MFA-state probe rather than a real attempt — refund the slot
		// so the probe is not counted.
		//
		// For first-time LDAP users we did not pre-claim (no row to
		// claim against), so a real MFA attempt with a non-empty token
		// still needs to be counted explicitly against the freshly
		// created row.
		switch {
		case user.Id == "" && mfaToken != "":
			if _, passErr := a.Srv().Store().User().TryIncrementFailedPasswordAttempts(ldapUser.Id, maxAttempts); passErr != nil {
				rctx.Logger().Warn("failed to record failed MFA attempt for first-time LDAP user", mlog.String("user_id", ldapUser.Id), mlog.Err(passErr))
			}
		case user.Id != "" && mfaToken == "":
			if passErr := a.Srv().Store().User().DecrementFailedPasswordAttempts(ldapUser.Id); passErr != nil {
				rctx.Logger().Warn("failed to refund LDAP MFA probe slot", mlog.String("user_id", ldapUser.Id), mlog.Err(passErr))
			}
		}
		return nil, err
	}

	if err = checkUserNotDisabled(ldapUser); err != nil {
		// Existing LDAP users had a slot pre-claimed; a disabled-account
		// rejection is not a credential failure, so refund the slot so a
		// reactivated user is not immediately rate-limited.
		if user.Id != "" {
			if passErr := a.Srv().Store().User().DecrementFailedPasswordAttempts(ldapUser.Id); passErr != nil {
				rctx.Logger().Warn("failed to refund disabled LDAP login attempt slot", mlog.String("user_id", ldapUser.Id), mlog.Err(passErr))
			}
		}
		return nil, err
	}

	if passErr := a.Srv().Store().User().UpdateFailedPasswordAttempts(ldapUser.Id, 0); passErr != nil {
		return nil, model.NewAppError("checkLdapUserPasswordAndAllCriteria", "app.user.update_failed_pwd_attempts.app_error", nil, "", http.StatusInternalServerError).Wrap(passErr)
	}

	// user successfully authenticated
	return ldapUser, nil
}

func (a *App) CheckUserAllAuthenticationCriteria(rctx request.CTX, user *model.User, mfaToken string) *model.AppError {
	if err := a.CheckUserPreflightAuthenticationCriteria(rctx, user, mfaToken); err != nil {
		return err
	}

	if err := a.CheckUserPostflightAuthenticationCriteria(rctx, user); err != nil {
		return err
	}

	return nil
}

func (a *App) CheckUserPreflightAuthenticationCriteria(rctx request.CTX, user *model.User, mfaToken string) *model.AppError {
	if err := checkUserNotDisabled(user); err != nil {
		return err
	}

	if err := checkUserNotBot(user); err != nil {
		return err
	}

	if err := checkUserLoginAttempts(user, *a.Config().ServiceSettings.MaximumLoginAttempts); err != nil {
		return err
	}

	return nil
}

func (a *App) CheckUserPostflightAuthenticationCriteria(rctx request.CTX, user *model.User) *model.AppError {
	if !user.EmailVerified && *a.Config().EmailSettings.RequireEmailVerification {
		return model.NewAppError("Login", "api.user.login.not_verified.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}

	return nil
}

func (a *App) CheckUserMfa(rctx request.CTX, user *model.User, token string) *model.AppError {
	if !user.MfaActive || !*a.Config().ServiceSettings.EnableMultifactorAuthentication {
		return nil
	}

	if !*a.Config().ServiceSettings.EnableMultifactorAuthentication {
		return model.NewAppError("CheckUserMfa", "mfa.mfa_disabled.app_error", nil, "", http.StatusNotImplemented)
	}

	ok, err := mfa.New(a.Srv().Store().User()).ValidateToken(user, token)
	if err != nil {
		return model.NewAppError("CheckUserMfa", "mfa.validate_token.authenticate.app_error", nil, "", http.StatusBadRequest).Wrap(err)
	}

	if !ok {
		return model.NewAppError("checkUserMfa", "api.user.check_user_mfa.bad_code.app_error", nil, "", http.StatusUnauthorized)
	}

	return nil
}

func (a *App) MFARequired(rctx request.CTX) *model.AppError {
	if license := a.Channels().License(); license == nil || !*license.Features.MFA || !*a.Config().ServiceSettings.EnableMultifactorAuthentication || !*a.Config().ServiceSettings.EnforceMultifactorAuthentication {
		return nil
	}

	session := rctx.Session()
	// Session cannot be nil or empty if MFA is to be enforced.
	if session == nil || session.Id == "" {
		return model.NewAppError("MfaRequired", "api.context.get_session.app_error", nil, "", http.StatusUnauthorized)
	}

	// OAuth integrations are excepted
	if session.IsOAuth {
		return nil
	}

	user, err := a.GetUser(session.UserId)
	if err != nil {
		return model.NewAppError("MfaRequired", "api.context.get_user.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
	}

	if user.IsGuest() && !*a.Config().GuestAccountsSettings.EnforceMultifactorAuthentication {
		return nil
	}
	// Only required for email and ldap accounts
	if user.AuthService != "" &&
		user.AuthService != model.UserAuthServiceEmail &&
		user.AuthService != model.UserAuthServiceLdap {
		return nil
	}

	// Special case to let user get themself
	subpath, _ := utils.GetSubpathFromConfig(a.Config())
	if rctx.Path() == path.Join(subpath, "/api/v4/users/me") {
		return nil
	}

	// Bots are exempt
	if user.IsBot {
		return nil
	}

	if !user.MfaActive {
		return model.NewAppError("MfaRequired", "api.context.mfa_required.app_error", nil, "", http.StatusForbidden)
	}

	return nil
}

func checkUserLoginAttempts(user *model.User, maxAttempts int) *model.AppError {
	if user.FailedAttempts >= maxAttempts {
		if user.AuthService == model.UserAuthServiceLdap {
			return model.NewAppError("checkUserLoginAttempts", "api.user.check_user_login_attempts.too_many_ldap.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
		}
		return model.NewAppError("checkUserLoginAttempts", "api.user.check_user_login_attempts.too_many.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}

	return nil
}

func checkUserNotDisabled(user *model.User) *model.AppError {
	if user.DeleteAt > 0 {
		return model.NewAppError("Login", "api.user.login.inactive.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}
	return nil
}

func checkUserNotBot(user *model.User) *model.AppError {
	if user.IsBot {
		return model.NewAppError("Login", "api.user.login.bot_login_forbidden.app_error", nil, "user_id="+user.Id, http.StatusUnauthorized)
	}
	return nil
}

func (a *App) authenticateUser(rctx request.CTX, user *model.User, password, mfaToken string) (*model.User, *model.AppError) {
	license := a.Srv().License()
	ldapAvailable := *a.Config().LdapSettings.Enable && a.Ldap() != nil && license != nil && *license.Features.LDAP

	if user.AuthService == model.UserAuthServiceLdap {
		if !ldapAvailable {
			err := model.NewAppError("login", "api.user.login_ldap.not_available.app_error", nil, "", http.StatusNotImplemented)
			return user, err
		}

		ldapUser, err := a.checkLdapUserPasswordAndAllCriteria(rctx, user, password, mfaToken)
		if err != nil {
			err.StatusCode = http.StatusUnauthorized
			return user, err
		}

		// slightly redundant to get the user again, but we need to get it from the LDAP server
		return ldapUser, nil
	}

	if user.AuthService != "" {
		authService := user.AuthService
		if authService == model.UserAuthServiceSaml {
			authService = strings.ToUpper(authService)
		}
		err := model.NewAppError("login", "api.user.login.use_auth_service.app_error", map[string]any{"AuthService": authService}, "", http.StatusBadRequest)
		return user, err
	}

	if err := a.CheckPasswordAndAllCriteria(rctx, user.Id, password, mfaToken); err != nil {
		if err.Id == "api.user.check_user_password.invalid.app_error" {
			rctx.Logger().LogM(mlog.MlvlLDAPInfo, "A user tried to sign in, which matched a Mattermost account, but the password was incorrect.", mlog.String("username", user.Username))
		}

		err.StatusCode = http.StatusUnauthorized
		return user, err
	}

	return user, nil
}

func ParseAuthTokenFromRequest(r *http.Request) (token string, loc TokenLocation) {
	defer func() {
		// Stripping off tokens of large sizes
		// to prevent logging a large string.
		if len(token) > 50 {
			token = token[:50]
		}
	}()

	authHeader := r.Header.Get(model.HeaderAuth)

	// Attempt to parse the token from the cookie
	if cookie, err := r.Cookie(model.SessionCookieToken); err == nil {
		return cookie.Value, TokenLocationCookie
	}

	// Parse the token from the header
	if len(authHeader) > 6 && strings.ToUpper(authHeader[0:6]) == model.HeaderBearer {
		// Default session token
		return authHeader[7:], TokenLocationHeader
	}

	if len(authHeader) > 5 && strings.ToLower(authHeader[0:5]) == model.HeaderToken {
		// OAuth token
		return authHeader[6:], TokenLocationHeader
	}

	// Attempt to parse token out of the query string
	if token := r.URL.Query().Get("access_token"); token != "" {
		return token, TokenLocationQueryString
	}

	if token := r.Header.Get(model.HeaderCloudToken); token != "" {
		return token, TokenLocationCloudHeader
	}

	if token := r.Header.Get(model.HeaderRemoteclusterToken); token != "" {
		return token, TokenLocationRemoteClusterHeader
	}

	return "", TokenLocationNotFound
}