Implement addreminder command

Author: laurentiuNiculae

cmd/gatekeeper/command.go

@@ -24,6 +24,10 @@ var (
 	CommandDef = "([a-zA-Z0-9\\-_]+)( +(.*))?"
 	CommandRegexp = regexp.MustCompile("^ *("+CommandPrefix+") *"+CommandDef+"$")
 	CommandNoPrefixRegexp = regexp.MustCompile("^ *"+CommandDef+"$")
+	ReminderDurationRegexpStr = `(\d+)(s|m|h|d|y)`
+	ReminderArgsRegexpStr = `^((\d+(s|m|h|d|y))+) +(.+)$`
+	ReminderDurationRegexp = regexp.MustCompile(ReminderDurationRegexpStr)
+	ReminderArgsRegexp = regexp.MustCompile(ReminderArgsRegexpStr)
 	Commit        = func() string {
 		if info, ok := debug.ReadBuildInfo(); ok {
 			for _, setting := range info.Settings {
@@ -752,6 +756,43 @@ func EvalBuiltinCommand(db *sql.DB, command Command, env CommandEnvironment, con
 		}
 		// TODO: report "added" instead of "updated" when the command didn't exist but was newly created
 		env.SendMessage(fmt.Sprintf("%s command %s is updated", env.AtAuthor(), name))
+	case "addreminder":
+		args := ReminderArgsRegexp.FindStringSubmatch(command.Args)
+		if (args == nil) {
+			env.SendMessage(env.AtAuthor() + " Coudn't parse the reminder arguments, expected `" + ReminderArgsRegexpStr + "`")
+			return
+		}
+
+		durationStr := args[1]
+		message := args[4]
+
+		delay := time.Duration(0)
+		for _, match := range ReminderDurationRegexp.FindAllStringSubmatch(durationStr, -1) {
+			ammount, err := strconv.ParseInt(match[1], 10, 64)
+			if err != nil {
+				log.Println("Reminder duration parsing: ", err)
+				env.SendMessage(env.AtAuthor() + " Delay ammount overflows." + "\n")
+				return
+			}
+			unit := match[2]
+
+			d, ok := MulDurationSafe(ammount, UnitDurations[unit])
+			if !ok {
+				env.SendMessage(env.AtAuthor() + "Duration specified caused an overflow.")
+				return
+			}
+
+			delay, ok = AddDurationSafe(delay, d)
+			if !ok {
+				env.SendMessage(env.AtAuthor() + "Duration specified caused an overflow.")
+				return
+			}
+		}
+
+		SetReminder(env, Reminder{
+			Delay:   delay,
+			Message: message,
+		})
 	case "delcmd":
 		if !env.IsAuthorAdmin() {
 			env.SendMessage(env.AtAuthor() + " only for " + env.AtAdmin())

cmd/gatekeeper/reminders.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"context"
+	"sync"
+	"time"
+	"log"
+	"math"
+)
+
+type Reminder struct {
+	Message string
+	Delay   time.Duration
+}
+
+var UnitDurations = map[string]time.Duration{
+	"s": time.Second,
+	"m": time.Minute,
+	"h": time.Hour,
+	"d": 24 * time.Hour,
+	"y": time.Duration(float64(365.2425) * float64(24 * time.Hour)),
+}
+
+type UserId = string
+
+var mutex = &sync.Mutex{}
+var reminders = map[UserId]context.CancelFunc{}
+
+func SetReminder(env CommandEnvironment, r Reminder) {
+	if !validateReminder(env, r) {
+		return
+	}
+
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	cancelOldReminder, ok := reminders[env.AuthorUserId()]
+	if ok {
+		cancelOldReminder()
+	}
+
+	reminders[env.AuthorUserId()] = cancel
+
+	go func() {
+		timer := time.NewTimer(r.Delay)
+		defer timer.Stop()
+
+		select {
+		case <-timer.C:
+			env.SendMessage(env.AtAuthor() + " " + r.Message + "\n")
+		case <-ctx.Done():
+			env.SendMessage(env.AtAuthor() + " Old reminder has been canceled: '" + r.Message + "'")
+		}
+	}()
+
+	env.SendMessage(env.AtAuthor() + " Reminder has been successfully set to fire in " + r.Delay.String() + ".")
+}
+
+func validateReminder(env CommandEnvironment, r Reminder) bool {
+	if (r.Delay < 1 * time.Second) {
+		log.Println("Smol reminder delay: " + r.Delay.String())
+		env.SendMessage(env.AtAuthor() + " Delay specified has an unexpected duration, check logs." + "\n")
+		return false
+	}
+
+	if (env.IsAuthorAdmin()) {
+		return true
+	}
+
+	if (len(r.Message) > 255) {
+		env.SendMessage(env.AtAuthor() + " Message body must be under 255 characters long" + "\n")
+		return false
+	}
+
+	return true
+}
+
+func AddDurationSafe(a, b time.Duration) (time.Duration, bool) {
+    if b > 0 && a > time.Duration(math.MaxInt64)-b {
+        return 0, false
+    }
+    if b < 0 && a < time.Duration(math.MinInt64)-b {
+        return 0, false
+    }
+    return a + b, true
+}
+
+func MulDurationSafe(ammount int64, d time.Duration) (time.Duration, bool) {
+    if d == 0 || ammount == 0 {
+        return 0, true
+    }
+    if ammount > 0 {
+        if d > time.Duration(math.MaxInt64)/time.Duration(ammount) {
+            return 0, false
+        }
+    } else {
+        if d < time.Duration(math.MinInt64)/time.Duration(ammount) {
+            return 0, false
+        }
+    }
+    return d * time.Duration(ammount), true
+}