Added rate limiter

discord/discord.go

@@ -11,7 +11,15 @@ func (app *application) messageCreate(s *discordgo.Session, m *discordgo.Message
 		return
 	}
 
-	/* Checking if the message starts with the trigger specified in application struct 
+	/* Check if the user is even allowed by the rate limiter */
+	err := app.limiter.CheckAllowed(m.Author.ID)
+	if err != nil {
+		/* normally don't send, but now do for debug purposes. This is the admin bot channel */
+		app.unknownError(err, s, true, "815952128106430514")
+		return
+	}
+
+	/* Checking if the message starts with the trigger specified in application struct
 	if it does then we start the switch statement to trigger the appropriate function
 	if it does not then we check if it contains a triggerword from the database */
 	if strings.HasPrefix(m.Content, app.trigger) {
@@ -52,14 +60,13 @@ func (app *application) messageCreate(s *discordgo.Session, m *discordgo.Message
 			case "removeadmin":
 				app.removeAdmin(s, m, splitCommand)
 			}
-			
+
 		}
 	} else {
 		/* If the trigger wasn't the prefix of the message, we need to check all the words for a trigger */
 		app.findTrigger(s, m)
 	}
 
-	
-	
-}
+	app.limiter.LogInteraction(m.Author.ID, "messagecreate")
 
+}

discord/main.go

@@ -6,8 +6,10 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"time"
 
 	"github.com/bwmarrin/discordgo"
+	"quenten.nl/pepebot/limiter"
 	"quenten.nl/pepebot/models/mysql"
 )
 
@@ -15,15 +17,16 @@ import (
 It also has many methods for the different functions of the bot.
 These methods are mostly located in discord.go */
 type application struct {
-	errorLog *log.Logger
-	infoLog  *log.Logger
-	badwords *mysql.BadwordModel
-	adminroles *mysql.AdminRolesModel
-	trigger string
+	errorLog    *log.Logger
+	infoLog     *log.Logger
+	badwords    *mysql.BadwordModel
+	adminroles  *mysql.AdminRolesModel
+	trigger     string
 	allBadWords map[string][]string
+	limiter     *limiter.Limiter
 
 	active bool
-	stop bool
+	stop   bool
 }
 
 func main() {
@@ -39,12 +42,18 @@ func main() {
 		errorLog.Fatal(err)
 	}
 
+	limiter := &limiter.Limiter{
+		RateLimit: 5,
+		TimeLimit: time.Second * 15,
+	}
+
 	app := &application{
-		infoLog: infoLog,
-		errorLog: errorLog,
-		badwords: &mysql.BadwordModel{DB: db},
+		infoLog:    infoLog,
+		errorLog:   errorLog,
+		badwords:   &mysql.BadwordModel{DB: db},
 		adminroles: &mysql.AdminRolesModel{DB: db},
-		trigger: "!pepe",
+		trigger:    "!pepe",
+		limiter:    limiter,
 	}
 
 	app.allBadWords, err = app.badwords.AllWords()

limiter/action.go

@@ -0,0 +1,8 @@
+package limiter
+
+import "time"
+
+type Action struct {
+	Type      string
+	Timestamp time.Time
+}

limiter/limiter.go

@@ -0,0 +1,55 @@
+package limiter
+
+import (
+	"errors"
+	"time"
+)
+
+/* The Limiter struct saves all interactions in a map of lists indexed by user id going back the time limit.
+When checking if a user is allowed to perform an action, it traverses the list for that userid.
+If an item is older than the time limit, remove it and don't count.
+If it is in the limit, then count. If the amount of interactions is higher than the limit, return an error */
+type Limiter struct {
+	TimeLimit time.Duration
+	RateLimit int
+	Logs      map[string][]Action
+}
+
+func (l *Limiter) LogInteraction(userid string, action string) {
+	l.Logs[userid] = append(l.Logs[userid], Action{
+		Timestamp: time.Now(),
+		Type:      action,
+	})
+}
+
+/* CheckAllowed counts the amount of log entries for a given userid, making sure to delete and not count the expired ones.
+Returns an error if the amount of log entries exceeds the ratelimit */
+func (l *Limiter) CheckAllowed(userid string) error {
+	counter := 0
+	expiredEntries := make([]int, 0)
+	for i := 0; i < len(l.Logs[userid]); i++ {
+		/* If the timestamp plus the timelimit is happened before "Now" */
+		if l.Logs[userid][i].Timestamp.Add(l.TimeLimit).Before(time.Now()) {
+			expiredEntries = append(expiredEntries, i)
+			continue
+		} else {
+			counter++
+			continue
+		}
+	}
+	/* remove entries */
+	for i := 0; i < len(expiredEntries); i++ {
+		l.removeAction(userid, expiredEntries[i])
+	}
+
+	if counter >= l.RateLimit {
+		return errors.New("rate limit exceeded")
+	} else {
+		return nil
+	}
+}
+
+func (l *Limiter) removeAction(userid string, i int) {
+	l.Logs[userid][i] = l.Logs[userid][len(l.Logs[userid])-1]
+	l.Logs[userid] = l.Logs[userid][:len(l.Logs[userid])-1]
+}