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

package app

import (
	"errors"
	"math"
	"net/http"
	"time"

	"github.com/mattermost/mattermost-server/v5/audit"
	"github.com/mattermost/mattermost-server/v5/mlog"
	"github.com/mattermost/mattermost-server/v5/model"
	"github.com/mattermost/mattermost-server/v5/store"
)

func (a *App) CreateSession(session *model.Session) (*model.Session, *model.AppError) {
	session.Token = ""

	session, err := a.Srv().Store.Session().Save(session)
	if err != nil {
		var invErr *store.ErrInvalidInput
		switch {
		case errors.As(err, &invErr):
			return nil, model.NewAppError("CreateSession", "app.session.save.existing.app_error", nil, invErr.Error(), http.StatusBadRequest)
		default:
			return nil, model.NewAppError("CreateSession", "app.session.save.app_error", nil, err.Error(), http.StatusInternalServerError)
		}
	}

	a.AddSessionToCache(session)

	return session, nil
}

func (a *App) GetSession(token string) (*model.Session, *model.AppError) {
	metrics := a.Metrics()

	var session *model.Session
	var err *model.AppError
	if err := a.Srv().sessionCache.Get(token, &session); err == nil {
		if metrics != nil {
			metrics.IncrementMemCacheHitCounterSession()
		}
	} else {
		if metrics != nil {
			metrics.IncrementMemCacheMissCounterSession()
		}
	}

	if session == nil {
		var nErr error
		if session, nErr = a.Srv().Store.Session().Get(token); nErr == nil {
			if session != nil {
				if session.Token != token {
					return nil, model.NewAppError("GetSession", "api.context.invalid_token.error", map[string]interface{}{"Token": token, "Error": ""}, "session token is different from the one in DB", http.StatusUnauthorized)
				}

				if !session.IsExpired() {
					a.AddSessionToCache(session)
				}
			}
		} else if nfErr := new(store.ErrNotFound); !errors.As(nErr, &nfErr) {
			return nil, model.NewAppError("GetSession", "app.session.get.app_error", nil, nErr.Error(), http.StatusInternalServerError)
		}
	}

	if session == nil {
		session, err = a.createSessionForUserAccessToken(token)
		if err != nil {
			detailedError := ""
			statusCode := http.StatusUnauthorized
			if err.Id != "app.user_access_token.invalid_or_missing" {
				detailedError = err.Error()
				statusCode = err.StatusCode
			} else {
				mlog.Warn("Error while creating session for user access token", mlog.Err(err))
			}
			return nil, model.NewAppError("GetSession", "api.context.invalid_token.error", map[string]interface{}{"Token": token, "Error": detailedError}, "", statusCode)
		}
	}

	if session == nil || session.IsExpired() {
		return nil, model.NewAppError("GetSession", "api.context.invalid_token.error", map[string]interface{}{"Token": token, "Error": ""}, "session is either nil or expired", http.StatusUnauthorized)
	}

	if *a.Config().ServiceSettings.SessionIdleTimeoutInMinutes > 0 &&
		!session.IsOAuth && !session.IsMobileApp() &&
		session.Props[model.SESSION_PROP_TYPE] != model.SESSION_TYPE_USER_ACCESS_TOKEN &&
		!*a.Config().ServiceSettings.ExtendSessionLengthWithActivity {

		timeout := int64(*a.Config().ServiceSettings.SessionIdleTimeoutInMinutes) * 1000 * 60
		if (model.GetMillis() - session.LastActivityAt) > timeout {
			// Revoking the session is an asynchronous task anyways since we are not checking
			// for the return value of the call before returning the error.
			// So moving this to a goroutine has 2 advantages:
			// 1. We are treating this as a proper asynchronous task.
			// 2. This also fixes a race condition in the web hub, where GetSession
			// gets called from (*WebConn).isMemberOfTeam and revoking a session involves
			// clearing the webconn cache, which needs the hub again.
			a.Srv().Go(func() {
				err := a.RevokeSessionById(session.Id)
				if err != nil {
					mlog.Warn("Error while revoking session", mlog.Err(err))
				}
			})
			return nil, model.NewAppError("GetSession", "api.context.invalid_token.error", map[string]interface{}{"Token": token, "Error": ""}, "idle timeout", http.StatusUnauthorized)
		}
	}

	return session, nil
}

func (a *App) GetSessions(userId string) ([]*model.Session, *model.AppError) {

	sessions, err := a.Srv().Store.Session().GetSessions(userId)
	if err != nil {
		return nil, model.NewAppError("GetSessions", "app.session.get_sessions.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	return sessions, nil
}

func (a *App) UpdateSessionsIsGuest(userId string, isGuest bool) {
	sessions, err := a.Srv().Store.Session().GetSessions(userId)
	if err != nil {
		mlog.Error("Unable to get user sessions", mlog.String("user_id", userId), mlog.Err(err))
	}

	for _, session := range sessions {
		if isGuest {
			session.AddProp(model.SESSION_PROP_IS_GUEST, "true")
		} else {
			session.AddProp(model.SESSION_PROP_IS_GUEST, "false")
		}
		err := a.Srv().Store.Session().UpdateProps(session)
		if err != nil {
			mlog.Error("Unable to update isGuest session", mlog.Err(err))
			continue
		}
		a.AddSessionToCache(session)
	}
}

func (a *App) RevokeAllSessions(userId string) *model.AppError {
	sessions, err := a.Srv().Store.Session().GetSessions(userId)
	if err != nil {
		return model.NewAppError("RevokeAllSessions", "app.session.get_sessions.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	for _, session := range sessions {
		if session.IsOAuth {
			a.RevokeAccessToken(session.Token)
		} else {
			if err := a.Srv().Store.Session().Remove(session.Id); err != nil {
				return model.NewAppError("RevokeAllSessions", "app.session.remove.app_error", nil, err.Error(), http.StatusInternalServerError)
			}
		}
	}

	a.ClearSessionCacheForUser(userId)

	return nil
}

// RevokeSessionsFromAllUsers will go through all the sessions active
// in the server and revoke them
func (a *App) RevokeSessionsFromAllUsers() *model.AppError {
	// revoke tokens before sessions so they can't be used to relogin
	nErr := a.Srv().Store.OAuth().RemoveAllAccessData()
	if nErr != nil {
		return model.NewAppError("RevokeSessionsFromAllUsers", "app.oauth.remove_access_data.app_error", nil, nErr.Error(), http.StatusInternalServerError)
	}
	err := a.Srv().Store.Session().RemoveAllSessions()
	if err != nil {
		return model.NewAppError("RevokeSessionsFromAllUsers", "app.session.remove_all_sessions_for_team.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	a.ClearSessionCacheForAllUsers()

	return nil
}

func (a *App) ClearSessionCacheForUser(userId string) {
	a.ClearSessionCacheForUserSkipClusterSend(userId)

	if a.Cluster() != nil {
		msg := &model.ClusterMessage{
			Event:    model.CLUSTER_EVENT_CLEAR_SESSION_CACHE_FOR_USER,
			SendType: model.CLUSTER_SEND_RELIABLE,
			Data:     userId,
		}
		a.Cluster().SendClusterMessage(msg)
	}
}

func (a *App) ClearSessionCacheForAllUsers() {
	a.ClearSessionCacheForAllUsersSkipClusterSend()

	if a.Cluster() != nil {
		msg := &model.ClusterMessage{
			Event:    model.CLUSTER_EVENT_CLEAR_SESSION_CACHE_FOR_ALL_USERS,
			SendType: model.CLUSTER_SEND_RELIABLE,
		}
		a.Cluster().SendClusterMessage(msg)
	}
}

func (a *App) ClearSessionCacheForUserSkipClusterSend(userId string) {
	if keys, err := a.Srv().sessionCache.Keys(); err == nil {
		var session *model.Session
		for _, key := range keys {
			if err := a.Srv().sessionCache.Get(key, &session); err == nil {
				if session.UserId == userId {
					a.Srv().sessionCache.Remove(key)
					if a.Metrics() != nil {
						a.Metrics().IncrementMemCacheInvalidationCounterSession()
					}
				}
			}
		}
	}

	a.InvalidateWebConnSessionCacheForUser(userId)
}

func (a *App) ClearSessionCacheForAllUsersSkipClusterSend() {
	mlog.Info("Purging sessions cache")
	a.Srv().sessionCache.Purge()
}

func (a *App) AddSessionToCache(session *model.Session) {
	a.Srv().sessionCache.SetWithExpiry(session.Token, session, time.Duration(int64(*a.Config().ServiceSettings.SessionCacheInMinutes))*time.Minute)
}

func (a *App) SessionCacheLength() int {
	if l, err := a.Srv().sessionCache.Len(); err == nil {
		return l
	}
	return 0
}

func (a *App) RevokeSessionsForDeviceId(userId string, deviceId string, currentSessionId string) *model.AppError {
	sessions, err := a.Srv().Store.Session().GetSessions(userId)
	if err != nil {
		return model.NewAppError("RevokeSessionsForDeviceId", "app.session.get_sessions.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	for _, session := range sessions {
		if session.DeviceId == deviceId && session.Id != currentSessionId {
			mlog.Debug("Revoking sessionId for userId. Re-login with the same device Id", mlog.String("session_id", session.Id), mlog.String("user_id", userId))
			if err := a.RevokeSession(session); err != nil {
				// Soft error so we still remove the other sessions
				mlog.Error(err.Error())
			}
		}
	}

	return nil
}

func (a *App) GetSessionById(sessionId string) (*model.Session, *model.AppError) {
	session, err := a.Srv().Store.Session().Get(sessionId)
	if err != nil {
		return nil, model.NewAppError("GetSessionById", "app.session.get.app_error", nil, err.Error(), http.StatusBadRequest)
	}

	return session, nil
}

func (a *App) RevokeSessionById(sessionId string) *model.AppError {
	session, err := a.Srv().Store.Session().Get(sessionId)
	if err != nil {
		return model.NewAppError("RevokeSessionById", "app.session.get.app_error", nil, err.Error(), http.StatusBadRequest)
	}
	return a.RevokeSession(session)

}

func (a *App) RevokeSession(session *model.Session) *model.AppError {
	if session.IsOAuth {
		if err := a.RevokeAccessToken(session.Token); err != nil {
			return err
		}
	} else {
		if err := a.Srv().Store.Session().Remove(session.Id); err != nil {
			return model.NewAppError("RevokeSession", "app.session.remove.app_error", nil, err.Error(), http.StatusInternalServerError)
		}
	}

	a.ClearSessionCacheForUser(session.UserId)

	return nil
}

func (a *App) AttachDeviceId(sessionId string, deviceId string, expiresAt int64) *model.AppError {
	_, err := a.Srv().Store.Session().UpdateDeviceId(sessionId, deviceId, expiresAt)
	if err != nil {
		return model.NewAppError("AttachDeviceId", "app.session.update_device_id.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	return nil
}

func (a *App) UpdateLastActivityAtIfNeeded(session model.Session) {
	now := model.GetMillis()

	a.UpdateWebConnUserActivity(session, now)

	if now-session.LastActivityAt < model.SESSION_ACTIVITY_TIMEOUT {
		return
	}

	if err := a.Srv().Store.Session().UpdateLastActivityAt(session.Id, now); err != nil {
		mlog.Error("Failed to update LastActivityAt", mlog.String("user_id", session.UserId), mlog.String("session_id", session.Id), mlog.Err(err))
	}

	session.LastActivityAt = now
	a.AddSessionToCache(&session)
}

// ExtendSessionExpiryIfNeeded extends Session.ExpiresAt based on session lengths in config.
// A new ExpiresAt is only written if enough time has elapsed since last update.
// Returns true only if the session was extended.
func (a *App) ExtendSessionExpiryIfNeeded(session *model.Session) bool {
	if session == nil || session.IsExpired() {
		return false
	}

	sessionLength := a.GetSessionLengthInMillis(session)

	// Only extend the expiry if the lessor of 1% or 1 day has elapsed within the
	// current session duration.
	threshold := int64(math.Min(float64(sessionLength)*0.01, float64(24*60*60*1000)))
	// Minimum session length is 1 day as of this writing, therefore a minimum ~14 minutes threshold.
	// However we'll add a sanity check here in case that changes. Minimum 5 minute threshold,
	// meaning we won't write a new expiry more than every 5 minutes.
	if threshold < 5*60*1000 {
		threshold = 5 * 60 * 1000
	}

	now := model.GetMillis()
	elapsed := now - (session.ExpiresAt - sessionLength)
	if elapsed < threshold {
		return false
	}

	auditRec := a.MakeAuditRecord("extendSessionExpiry", audit.Fail)
	defer a.LogAuditRec(auditRec, nil)
	auditRec.AddMeta("session", session)

	newExpiry := now + sessionLength
	if err := a.Srv().Store.Session().UpdateExpiresAt(session.Id, newExpiry); err != nil {
		mlog.Error("Failed to update ExpiresAt", mlog.String("user_id", session.UserId), mlog.String("session_id", session.Id), mlog.Err(err))
		auditRec.AddMeta("err", err.Error())
		return false
	}

	// Update local cache. No need to invalidate cache for cluster as the session cache timeout
	// ensures each node will get an extended expiry within the next 10 minutes.
	// Worst case is another node may generate a redundant expiry update.
	session.ExpiresAt = newExpiry
	a.AddSessionToCache(session)

	mlog.Debug("Session extended", mlog.String("user_id", session.UserId), mlog.String("session_id", session.Id),
		mlog.Int64("newExpiry", newExpiry), mlog.Int64("session_length", sessionLength))

	auditRec.Success()
	auditRec.AddMeta("extended_session", session)
	return true
}

// GetSessionLengthInMillis returns the session length, in milliseconds,
// based on the type of session (Mobile, SSO, Web/LDAP).
func (a *App) GetSessionLengthInMillis(session *model.Session) int64 {
	if session == nil {
		return 0
	}

	var days int
	if session.IsMobileApp() {
		days = *a.Config().ServiceSettings.SessionLengthMobileInDays
	} else if session.IsSSOLogin() {
		days = *a.Config().ServiceSettings.SessionLengthSSOInDays
	} else {
		days = *a.Config().ServiceSettings.SessionLengthWebInDays
	}
	return int64(days * 24 * 60 * 60 * 1000)
}

// SetSessionExpireInDays sets the session's expiry the specified number of days
// relative to either the session creation date or the current time, depending
// on the `ExtendSessionOnActivity` config setting.
func (a *App) SetSessionExpireInDays(session *model.Session, days int) {
	if session.CreateAt == 0 || *a.Config().ServiceSettings.ExtendSessionLengthWithActivity {
		session.ExpiresAt = model.GetMillis() + (1000 * 60 * 60 * 24 * int64(days))
	} else {
		session.ExpiresAt = session.CreateAt + (1000 * 60 * 60 * 24 * int64(days))
	}
}

func (a *App) CreateUserAccessToken(token *model.UserAccessToken) (*model.UserAccessToken, *model.AppError) {

	user, err := a.Srv().Store.User().Get(token.UserId)
	if err != nil {
		return nil, err
	}

	if !*a.Config().ServiceSettings.EnableUserAccessTokens && !user.IsBot {
		return nil, model.NewAppError("CreateUserAccessToken", "app.user_access_token.disabled", nil, "", http.StatusNotImplemented)
	}

	token.Token = model.NewId()

	token, nErr := a.Srv().Store.UserAccessToken().Save(token)
	if nErr != nil {
		var appErr *model.AppError
		switch {
		case errors.As(nErr, &appErr):
			return nil, appErr
		default:
			return nil, model.NewAppError("CreateUserAccessToken", "app.user_access_token.save.app_error", nil, err.Error(), http.StatusInternalServerError)
		}
	}

	// Don't send emails to bot users.
	if !user.IsBot {
		if err := a.Srv().EmailService.sendUserAccessTokenAddedEmail(user.Email, user.Locale, a.GetSiteURL()); err != nil {
			a.Log().Error("Unable to send user access token added email", mlog.Err(err), mlog.String("user_id", user.Id))
		}
	}

	return token, nil

}

func (a *App) createSessionForUserAccessToken(tokenString string) (*model.Session, *model.AppError) {
	token, nErr := a.Srv().Store.UserAccessToken().GetByToken(tokenString)
	if nErr != nil {
		return nil, model.NewAppError("createSessionForUserAccessToken", "app.user_access_token.invalid_or_missing", nil, nErr.Error(), http.StatusUnauthorized)
	}

	if !token.IsActive {
		return nil, model.NewAppError("createSessionForUserAccessToken", "app.user_access_token.invalid_or_missing", nil, "inactive_token", http.StatusUnauthorized)
	}

	user, err := a.Srv().Store.User().Get(token.UserId)
	if err != nil {
		return nil, err
	}

	if !*a.Config().ServiceSettings.EnableUserAccessTokens && !user.IsBot {
		return nil, model.NewAppError("createSessionForUserAccessToken", "app.user_access_token.invalid_or_missing", nil, "EnableUserAccessTokens=false", http.StatusUnauthorized)
	}

	if user.DeleteAt != 0 {
		return nil, model.NewAppError("createSessionForUserAccessToken", "app.user_access_token.invalid_or_missing", nil, "inactive_user_id="+user.Id, http.StatusUnauthorized)
	}

	session := &model.Session{
		Token:   token.Token,
		UserId:  user.Id,
		Roles:   user.GetRawRoles(),
		IsOAuth: false,
	}

	session.AddProp(model.SESSION_PROP_USER_ACCESS_TOKEN_ID, token.Id)
	session.AddProp(model.SESSION_PROP_TYPE, model.SESSION_TYPE_USER_ACCESS_TOKEN)
	if user.IsBot {
		session.AddProp(model.SESSION_PROP_IS_BOT, model.SESSION_PROP_IS_BOT_VALUE)
	}
	if user.IsGuest() {
		session.AddProp(model.SESSION_PROP_IS_GUEST, "true")
	} else {
		session.AddProp(model.SESSION_PROP_IS_GUEST, "false")
	}
	a.SetSessionExpireInDays(session, model.SESSION_USER_ACCESS_TOKEN_EXPIRY)

	session, nErr = a.Srv().Store.Session().Save(session)
	if nErr != nil {
		var invErr *store.ErrInvalidInput
		switch {
		case errors.As(nErr, &invErr):
			return nil, model.NewAppError("CreateSession", "app.session.save.existing.app_error", nil, invErr.Error(), http.StatusBadRequest)
		default:
			return nil, model.NewAppError("CreateSession", "app.session.save.app_error", nil, nErr.Error(), http.StatusInternalServerError)
		}
	}

	a.AddSessionToCache(session)

	return session, nil

}

func (a *App) RevokeUserAccessToken(token *model.UserAccessToken) *model.AppError {
	var session *model.Session
	session, _ = a.Srv().Store.Session().Get(token.Token)

	if err := a.Srv().Store.UserAccessToken().Delete(token.Id); err != nil {
		return model.NewAppError("RevokeUserAccessToken", "app.user_access_token.delete.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if session == nil {
		return nil
	}

	return a.RevokeSession(session)
}

func (a *App) DisableUserAccessToken(token *model.UserAccessToken) *model.AppError {
	var session *model.Session
	session, _ = a.Srv().Store.Session().Get(token.Token)

	if err := a.Srv().Store.UserAccessToken().UpdateTokenDisable(token.Id); err != nil {
		return model.NewAppError("DisableUserAccessToken", "app.user_access_token.update_token_disable.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if session == nil {
		return nil
	}

	return a.RevokeSession(session)
}

func (a *App) EnableUserAccessToken(token *model.UserAccessToken) *model.AppError {
	var session *model.Session
	session, _ = a.Srv().Store.Session().Get(token.Token)

	err := a.Srv().Store.UserAccessToken().UpdateTokenEnable(token.Id)
	if err != nil {
		return model.NewAppError("EnableUserAccessToken", "app.user_access_token.update_token_enable.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	if session == nil {
		return nil
	}

	return nil
}

func (a *App) GetUserAccessTokens(page, perPage int) ([]*model.UserAccessToken, *model.AppError) {
	tokens, err := a.Srv().Store.UserAccessToken().GetAll(page*perPage, perPage)
	if err != nil {
		return nil, model.NewAppError("GetUserAccessTokens", "app.user_access_token.get_all.app_error", nil, err.Error(), http.StatusInternalServerError)
	}

	for _, token := range tokens {
		token.Token = ""
	}

	return tokens, nil
}

func (a *App) GetUserAccessTokensForUser(userId string, page, perPage int) ([]*model.UserAccessToken, *model.AppError) {
	tokens, err := a.Srv().Store.UserAccessToken().GetByUser(userId, page*perPage, perPage)
	if err != nil {
		return nil, model.NewAppError("GetUserAccessTokensForUser", "app.user_access_token.get_by_user.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	for _, token := range tokens {
		token.Token = ""
	}

	return tokens, nil

}

func (a *App) GetUserAccessToken(tokenId string, sanitize bool) (*model.UserAccessToken, *model.AppError) {
	token, err := a.Srv().Store.UserAccessToken().Get(tokenId)
	if err != nil {
		var nfErr *store.ErrNotFound
		switch {
		case errors.As(err, &nfErr):
			return nil, model.NewAppError("GetUserAccessToken", "app.user_access_token.get_by_user.app_error", nil, nfErr.Error(), http.StatusNotFound)
		default:
			return nil, model.NewAppError("GetUserAccessToken", "app.user_access_token.get_by_user.app_error", nil, err.Error(), http.StatusInternalServerError)
		}
	}

	if sanitize {
		token.Token = ""
	}
	return token, nil
}

func (a *App) SearchUserAccessTokens(term string) ([]*model.UserAccessToken, *model.AppError) {
	tokens, err := a.Srv().Store.UserAccessToken().Search(term)
	if err != nil {
		return nil, model.NewAppError("SearchUserAccessTokens", "app.user_access_token.search.app_error", nil, err.Error(), http.StatusInternalServerError)
	}
	for _, token := range tokens {
		token.Token = ""
	}
	return tokens, nil
}