Commands can now be limited to a channel or set of Channels (fixes #5)

Also extracted the command permission logic to a separate function
because it was getting ridiculous. It might be a by slower now, but I
really don’t care. Readabiliy should be much better, except now it’s
even more obvious how bad the entire idea behind that logic was/is.
Shikata ga nai, I guess.

CHANGELOG.md

@@ -5,6 +5,9 @@ Updates are listed in reverse chronological order.
 - a copy of each deleted message is now send via DM to the author (suggested by CommanderLook)
 - seasonal fluff
 - finally use gofmt
+- better logging of own messages
+- redirect function is much cleaner now
+- commands can be limited to certain channels
 
 ### 1.3
 - use global array of pointers to commands to allow easier modification and avoid unnecessary memcpy

command.go

@@ -40,7 +40,8 @@ type Command struct {
 	AdminOnly       bool
 	IgnoreCase      bool
 	// for custom commands that go beyond prints and deletions
-	Function func(*discordgo.Session, *discordgo.MessageCreate)
+	Function        func(*discordgo.Session, *discordgo.MessageCreate)
+	AllowedChannels mapset.Set // allowed everywhere if blank
 
 	UsersOnCooldown mapset.Set // don’t set this manually (it’s overwritten anyway)
 }
@@ -114,10 +115,7 @@ func evaluateMessage(s *discordgo.Session, m *discordgo.MessageCreate) {
    Sets command cooldowns if necessary and also clears them again.
 */
 func executeCommand(session *discordgo.Session, message *discordgo.MessageCreate, command *Command) {
-	if isAdmin(message.Author) || // no restrictions for admins
-		(!command.AdminOnly && (isDM(session, message) || !command.UsersOnCooldown.Contains(message.Author.ID)) &&
-			(!command.DMOnly || isDM(session, message))) {
-
+	if commandAllowed(session, message, command) {
 		log.Printf("Executed command %s triggered by user %s", command.Trigger, userToString(message.Author))
 		if command.Cooldown > 0 && !isDM(session, message) && !isAdmin(message.Author) {
 			command.UsersOnCooldown.Add(message.Author.ID)
@@ -143,6 +141,35 @@ func executeCommand(session *discordgo.Session, message *discordgo.MessageCreate
 	}
 }
 
+/*
+ * Check if a user has the permission to trigger a given command.
+ * To be honest, this whole logic is a mess, but I don’t know a better way to handle it.
+ */
+func commandAllowed(session *discordgo.Session, message *discordgo.MessageCreate, command *Command) bool {
+	// no restrictions for admins
+	if isAdmin(message.Author) {
+		return true
+	}
+	// blacklist admin commands for everyone else
+	if command.AdminOnly {
+		return false
+	}
+	// cooldowns are irrelevant in DMs
+	if !isDM(session, message) && command.UsersOnCooldown.Contains(message.Author.ID) {
+		return false
+	}
+	// the command is not limited to DMs or we are inside a DM chat
+	if command.DMOnly && !isDM(session, message) {
+		return false
+	}
+	// no allowed channels = all channels are allowed.
+	// DMs are whitelisted by default
+	if command.AllowedChannels.Cardinality() != 0 && !command.AllowedChannels.Contains(message.ChannelID) && !isDM(session, message) {
+		return false
+	}
+	return true
+}
+
 func removeCooldown(command *Command, uid string) {
 	time.Sleep(time.Duration(command.Cooldown) * time.Second)
 	if command.UsersOnCooldown.Contains(uid) {