Add endpoint to fetch user recommendations

endpoint/user/endpoint.go

@@ -47,6 +47,13 @@ func SetupUserRoutes(group *gin.RouterGroup, repository UserQuery, titleReposito
 	})
 	// endpoint used to search for users by username
 	group.GET("/search", searchForUsers(repository))
+
+	group.OPTIONS("/recommended", func(ctx *gin.Context) {
+		ctx.Header("Allow", "GET")
+		ctx.Status(200)
+	})
+	// endpoint to fetch user recommendations
+	group.GET("/recommended", getRecommendedUsers(repository))
 }
 
 /*
@@ -369,6 +376,44 @@ func searchForUsers(repository UserQuery) gin.HandlerFunc {
 	}
 }
 
+func getRecommendedUsers(repository UserQuery) gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		const DefaultCount = 3
+		const MaxCount = 10
+
+		var req struct {
+			Count int32 `form:"c"`
+		}
+
+		if err := ctx.BindQuery(&req); err != nil {
+			return
+		}
+
+		// Only accept numbers in range [0-10]
+		if req.Count <= 0 {
+			req.Count = DefaultCount
+		} else if req.Count > MaxCount {
+			req.Count = MaxCount
+		}
+
+		userID, err := endpoint.GetUserID(ctx)
+		if err != nil {
+			return
+		}
+
+		// fetch matching users from database
+		users, err := repository.SelectUserRecommendations(userID, uint32(req.Count))
+
+		if err != nil {
+			eventID := raven.CaptureError(err, nil)
+			ctx.String(http.StatusInternalServerError, "Failed fetching data from DB. "+eventID)
+			return
+		}
+
+		ctx.JSON(http.StatusOK, users)
+	}
+}
+
 func ForgotPassword(repository UserQuery, tokenFactory otp.TokenFactory, templatemail *sendmail.TemplateMail) gin.HandlerFunc {
 	return func(ctx *gin.Context) {
 		var req ForgotPasswordRequest

endpoint/user/query.go

@@ -32,6 +32,7 @@ type UserQuery interface {
 	Select(id uint32) ([]schemas.FullUserSchema, error)
 	SelectByUsername(username string) ([]schemas.InfoUserSchema, error)
 	SelectByUsernameLike(username string) ([]schemas.InfoUserSchema, error)
+	SelectUserRecommendations(userID uint32, count uint32) ([]schemas.InfoUserSchema, error)
 	SelectCredentialsByField(field UserField, value interface{}) (*schemas.CredentialsSchema, error)
 	Authenticate(name string, password string) (uint32, error)
 	Update(userID uint32, params PatchUserRequest, titleRepository title.TitleQuery) error
@@ -405,6 +406,55 @@ func (MySQLUserQuery) SelectByUsernameLike(username string) ([]schemas.InfoUserS
 	return users, nil
 }
 
+// SelectUserRecommendations fetches and returns a limited list of userdata for possible recommendations
+func (MySQLUserQuery) SelectUserRecommendations(userID uint32, count uint32) ([]schemas.InfoUserSchema, error) {
+	db, connectionError := dbhandler.GetDBConnection()
+	if connectionError != nil {
+		return nil, errors.New("Unable to connect to database. " + connectionError.Error())
+	}
+
+	stmt, prepareError := db.Prepare(`
+		SELECT iduser, username, idavatar, avatar.image, avatar.level, title.idtitle,
+			title.name, subject.idsubject, subject.name, subject.shortform,
+			subject.department, subject.description, title.unlock_score, title.unlock_win
+		FROM user
+		LEFT JOIN title ON (title.idtitle=selected_title)
+		LEFT JOIN subject ON (idsubject=title.subject)
+		LEFT JOIN avatar ON (idavatar=selected_avatar)
+		WHERE iduser NOT IN (SELECT friend FROM friend WHERE user = ?) 
+			AND iduser != ? AND verified = 1
+		ORDER BY RAND()
+		LIMIT ?`)
+
+	if prepareError != nil {
+		return nil, errors.New(
+			"An error occurred while preparing database access. " + prepareError.Error())
+	}
+	defer stmt.Close()
+
+	// execute sql query
+	rows, queryError := stmt.Query(userID, userID, count)
+	if queryError != nil {
+		return nil, errors.New("Cannot execute database query. " + queryError.Error())
+	}
+	defer rows.Close()
+
+	users := []schemas.InfoUserSchema{}
+
+	for rows.Next() {
+		var tmpUser schemas.InfoUserSchema
+
+		scanError := scanUser(rows.Scan, &tmpUser)
+		if scanError != nil {
+			return nil, errors.New("Cannot scan db values into users list. " + scanError.Error())
+		}
+
+		users = append(users, tmpUser)
+	}
+
+	return users, nil
+}
+
 func scanUser(scanFn func(dest ...interface{}) error, tmpUser *schemas.InfoUserSchema) error {
 	// Temporary subject
 	var tmpSubjectID sql.NullInt32