Institute Inform-style rulebooks

src/irc/globals.go

@@ -1,11 +1,13 @@
 package irc
 
 import (
+	"git.chromaticdragon.app/pyrex/minimal-irc-server/v2/src/logic"
 	"git.chromaticdragon.app/pyrex/minimal-irc-server/v2/src/transport"
 )
 
 type Globals struct {
 	Server        *transport.Server
+	Rulebook      *logic.Rulebook
 	Users         *UsersSystem
 	Notifications *NotificationsSystem
 }
@@ -15,9 +17,12 @@ var globals *Globals = nil
 func InitializeGlobals(server *transport.Server) {
 	globals = &Globals{
 		Server:        server,
+		Rulebook:      logic.NewRulebook(),
 		Users:         NewUsersSystem(),
 		Notifications: NewNotificationsSystem(),
 	}
+	globals.Users.InitializeRules()
+	globals.Notifications.InitializeRules()
 }
 
 func GetGlobals() *Globals {
@@ -27,29 +32,10 @@ func GetGlobals() *Globals {
 	return globals
 }
 
-func (g *Globals) getHandlers() []Handler {
-	return []Handler{
-		g.Users,
-		g.Notifications,
-	}
+func AddNewRule[T any](check func(T) error, carryOut func(T)) {
+	GetGlobals().Rulebook.Add(logic.NewRule(check, carryOut))
 }
 
-func Dispatch[T any](askPermission func(T) error, act func(T)) error {
-	globals := GetGlobals()
-	handlers := globals.getHandlers()
-
-	for _, handler := range handlers {
-		if h, ok := handler.(T); ok {
-			err := askPermission(h)
-			if err != nil {
-				return err
-			}
-		}
-	}
-	for _, handler := range handlers {
-		if h, ok := handler.(T); ok {
-			act(h)
-		}
-	}
-	return nil
+func Perform[T any](action T) error {
+	return GetGlobals().Rulebook.Perform(action)
 }

src/irc/handlerTypes.go

@@ -4,16 +4,21 @@ type Handler interface {
 	AssertTypes()
 }
 
-type NickChangeHandler interface {
-	AskPermissionForNickChange(user *User, oldNick *Nick, newNick *Nick) error
-	HandleNickChange(user *User, oldNick *Nick, newNick *Nick)
+type NickChangeAction struct {
+	User    *User
+	OldNick *Nick
+	NewNick *Nick
 }
 
-type PartJoinHandler interface {
-	AskPermissionForPart(user *User, channelName ChannelName, reason *string) error
-	HandlePart(user *User, channelName ChannelName, reason *string)
-	AskPermissionForJoin(user *User, channelName ChannelName) error
-	HandleJoin(user *User, channelName ChannelName)
+type PartAction struct {
+	User        *User
+	ChannelName ChannelName
+	Reason      *string
+}
+
+type JoinAction struct {
+	User        *User
+	ChannelName ChannelName
 }
 
 type ChatMode string
@@ -23,16 +28,16 @@ const (
 	ChatModeNotice  ChatMode = "NOTICE"
 )
 
-type ChatHandler interface {
-	AskPermissionForUserMessage(user *User, mode ChatMode, destination *User, message string) error
-	HandleUserMessage(user *User, mode ChatMode, destination *User, message string)
-
-	AskPermissionForChannelMessage(user *User, mode ChatMode, destination canonicalChannelName, message string) error
-	HandleChannelMessage(user *User, mode ChatMode, destination canonicalChannelName, message string)
+type SendMessageToUserAction struct {
+	User        *User
+	Mode        ChatMode
+	Destination *User
+	Message     string
 }
 
-/*
-type BroadcastHandler interface {
-	HandleBroadcastMessage(channel string) error
+type SendMessageToChannelAction struct {
+	User        *User
+	Mode        ChatMode
+	Destination canonicalChannelName
+	Message     string
 }
-*/

src/irc/main.go

@@ -179,23 +179,19 @@ func parseChannelList(arg string) []ChannelName {
 }
 
 func handleChannelMessage(sender *User, mode ChatMode, destination canonicalChannelName, message string) error {
-	return Dispatch(
-		func(ch ChatHandler) error {
-			return ch.AskPermissionForChannelMessage(sender, mode, destination, message)
-		},
-		func(ch ChatHandler) {
-			ch.HandleChannelMessage(sender, mode, destination, message)
-		},
-	)
+	return Perform(SendMessageToChannelAction{
+		User:        sender,
+		Mode:        mode,
+		Destination: destination,
+		Message:     message,
+	})
 }
 
 func handleUserMessage(sender *User, mode ChatMode, destination *User, message string) error {
-	return Dispatch(
-		func(ch ChatHandler) error {
-			return ch.AskPermissionForUserMessage(sender, mode, destination, message)
-		},
-		func(ch ChatHandler) {
-			ch.HandleUserMessage(sender, mode, destination, message)
-		},
-	)
+	return Perform(SendMessageToUserAction{
+		User:        sender,
+		Mode:        mode,
+		Destination: destination,
+		Message:     message,
+	})
 }

src/irc/notificationsSystem.go

@@ -13,143 +13,138 @@ func NewNotificationsSystem() *NotificationsSystem {
 	return &NotificationsSystem{}
 }
 
-func (notifications *NotificationsSystem) AssertTypes() {
-	var _ NickChangeHandler = notifications
-	var _ PartJoinHandler = notifications
-	var _ ChatHandler = notifications
-}
+func (notifications *NotificationsSystem) InitializeRules() {
+	// nick changes
+	AddNewRule(
+		func(nc NickChangeAction) error { return nil },
+		func(nc NickChangeAction) {
+			if nc.NewNick == nil {
+				return // not expressible in the IRC protocol; probably shouldn't be allowed?
+			}
 
-func (notifications *NotificationsSystem) AskPermissionForNickChange(user *User, oldNick *Nick, newNick *Nick) error {
-	return nil
-}
-
-func (notifications *NotificationsSystem) HandleNickChange(user *User, oldNick *Nick, newNick *Nick) {
-	if newNick == nil {
-		return // not expressible in the IRC protocol; probably shouldn't be allowed?
-	}
-
-	src := user.GetSourceString()
-	content := transport.Content{
-		Source:    &src,
-		Command:   "NICK",
-		Arguments: []string{newNick.Value},
-	}
-	group := NewBroadcastGroup()
-	group.AddChannels(user.GetChannels()...)
-	group.AddUsers(user)
-	Broadcast(group, content)
-}
-
-// TODO: Always present the channel name in its _established_ notation
-func (notifications *NotificationsSystem) AskPermissionForPart(user *User, channelName ChannelName, reason *string) error {
-	return nil
-}
-
-func (notifications *NotificationsSystem) HandlePart(user *User, channelName ChannelName, reason *string) {
-	src := user.GetSourceString()
-
-	var args []string
-	args = append(args, string(channelName.Value))
-	if reason != nil {
-		args = append(args, *reason)
-	}
-	content := transport.Content{
-		Source:    &src,
-		Command:   "PART",
-		Arguments: args,
-	}
-	group := NewBroadcastGroup()
-	group.AddChannels(channelName.canonical)
-	group.AddUsers(user)
-	Broadcast(group, content)
-}
-
-func (notifications *NotificationsSystem) AskPermissionForJoin(user *User, channelName ChannelName) error {
-	return nil
-}
-
-func (notifications *NotificationsSystem) HandleJoin(user *User, channelName ChannelName) {
-	src := user.GetSourceString()
-
-	content := transport.Content{
-		Source:    &src,
-		Command:   "JOIN",
-		Arguments: []string{string(channelName.Value)},
-	}
-	group := NewBroadcastGroup()
-	group.AddChannels(channelName.canonical)
-	group.AddUsers(user)
-	Broadcast(group, content)
-
-	// tell the user who is here
-	group = NewBroadcastGroup()
-	group.AddUsers(user)
-	src2 := "server"
-
-	var nameList strings.Builder
-	var i = 0
-	for user := range GetGlobals().Users.ByChannel(channelName) {
-		if i != 0 {
-			nameList.WriteString(" ")
-		}
-		nameList.WriteString(user.nick.Value)
-		i += 1
-	}
-
-	Broadcast(group, transport.Content{
-		Source:  &src2,
-		Command: "332",
-		Arguments: []string{
-			user.nick.Value, channelName.Value, "TODO: topic!",
+			src := nc.User.GetSourceString()
+			content := transport.Content{
+				Source:    &src,
+				Command:   "NICK",
+				Arguments: []string{nc.NewNick.Value},
+			}
+			group := NewBroadcastGroup()
+			group.AddChannels(nc.User.GetChannels()...)
+			group.AddUsers(nc.User)
+			Broadcast(group, content)
 		},
-	})
-	Broadcast(group, transport.Content{
-		Source:  &src2,
-		Command: "353",
-		Arguments: []string{
-			user.nick.Value, "=", channelName.Value, nameList.String(),
+	)
+
+	// joins
+	AddNewRule(
+		func(j JoinAction) error { return nil },
+		func(j JoinAction) {
+			src := j.User.GetSourceString()
+
+			content := transport.Content{
+				Source:    &src,
+				Command:   "JOIN",
+				Arguments: []string{string(j.ChannelName.Value)},
+			}
+			group := NewBroadcastGroup()
+			group.AddChannels(j.ChannelName.canonical)
+			group.AddUsers(j.User)
+			Broadcast(group, content)
+
+			// tell the user who is here
+			group = NewBroadcastGroup()
+			group.AddUsers(j.User)
+			src2 := "server"
+
+			var nameList strings.Builder
+			var i = 0
+			for user := range GetGlobals().Users.ByChannel(j.ChannelName) {
+				if i != 0 {
+					nameList.WriteString(" ")
+				}
+				nameList.WriteString(user.nick.Value)
+				i += 1
+			}
+
+			Broadcast(group, transport.Content{
+				Source:  &src2,
+				Command: "332",
+				Arguments: []string{
+					j.User.nick.Value, j.ChannelName.Value, "TODO: topic!",
+				},
+			})
+			Broadcast(group, transport.Content{
+				Source:  &src2,
+				Command: "353",
+				Arguments: []string{
+					j.User.nick.Value, "=", j.ChannelName.Value, nameList.String(),
+				},
+			})
+			Broadcast(group, transport.Content{
+				Source:  &src2,
+				Command: "366",
+				Arguments: []string{
+					j.User.nick.Value, j.ChannelName.Value, "End of /NAMES list",
+				},
+			})
 		},
-	})
-	Broadcast(group, transport.Content{
-		Source:  &src2,
-		Command: "366",
-		Arguments: []string{
-			user.nick.Value, channelName.Value, "End of /NAMES list",
+	)
+
+	// parts
+	AddNewRule(
+		func(p PartAction) error { return nil },
+		func(p PartAction) {
+			src := p.User.GetSourceString()
+
+			var args []string
+			args = append(args, string(p.ChannelName.Value))
+			if p.Reason != nil {
+				args = append(args, *p.Reason)
+			}
+			content := transport.Content{
+				Source:    &src,
+				Command:   "PART",
+				Arguments: args,
+			}
+			group := NewBroadcastGroup()
+			group.AddChannels(p.ChannelName.canonical)
+			group.AddUsers(p.User)
+			Broadcast(group, content)
 		},
-	})
-}
-
-func (notifications *NotificationsSystem) AskPermissionForUserMessage(user *User, mode ChatMode, destination *User, message string) error {
-	return nil
-}
-
-func (notifications *NotificationsSystem) HandleUserMessage(user *User, mode ChatMode, destination *User, message string) {
-	src := user.GetSourceString()
-
-	content := transport.Content{
-		Source:    &src,
-		Command:   string(mode),
-		Arguments: []string{destination.GetNick().Value, message},
-	}
-	group := NewBroadcastGroup()
-	group.AddUsers(destination)
-	Broadcast(group, content)
-}
-
-func (notifications *NotificationsSystem) AskPermissionForChannelMessage(user *User, mode ChatMode, destination canonicalChannelName, message string) error {
-	return nil
-}
-
-func (notifications *NotificationsSystem) HandleChannelMessage(user *User, mode ChatMode, destination canonicalChannelName, message string) {
-	src := user.GetSourceString()
-
-	content := transport.Content{
-		Source:    &src,
-		Command:   string(mode),
-		Arguments: []string{string(destination), message},
-	}
-	group := NewBroadcastGroup()
-	group.AddChannels(destination)
-	group.AddSpecificallyExcludedUsers(user)
-	Broadcast(group, content)
+	)
+
+	// messages (to user)
+	AddNewRule(
+		func(s SendMessageToUserAction) error { return nil },
+		func(s SendMessageToUserAction) {
+			src := s.User.GetSourceString()
+
+			content := transport.Content{
+				Source:    &src,
+				Command:   string(s.Mode),
+				Arguments: []string{s.Destination.GetNick().Value, s.Message},
+			}
+			group := NewBroadcastGroup()
+			group.AddUsers(s.Destination)
+			Broadcast(group, content)
+		},
+	)
+
+	// messages (to channel)
+	AddNewRule(
+		func(s SendMessageToChannelAction) error { return nil },
+		func(s SendMessageToChannelAction) {
+			src := s.User.GetSourceString()
+
+			content := transport.Content{
+				Source:    &src,
+				Command:   string(s.Mode),
+				Arguments: []string{string(s.Destination), s.Message},
+			}
+			group := NewBroadcastGroup()
+			group.AddChannels(s.Destination)
+			group.AddSpecificallyExcludedUsers(s.User)
+			Broadcast(group, content)
+		},
+	)
 }

src/irc/user.go

@@ -20,14 +20,6 @@ type User struct {
 	channels []canonicalChannelName
 }
 
-func NewUsersSystem() *UsersSystem {
-	return &UsersSystem{
-		clientIdIndex:    make(map[transport.ClientId]*User),
-		nickIndex:        make(map[canonicalNick]*User),
-		channelNameIndex: make(map[canonicalChannelName]map[*User]struct{}),
-	}
-}
-
 func (user *User) recomputeSourceString() {
 	nick := "unknown"
 	if user.nick != nil {
@@ -56,15 +48,7 @@ func (user *User) GetNick() *Nick {
 }
 
 func (user *User) SetNick(newNick *Nick) error {
-	oldNick := user.nick
-	return Dispatch(
-		func(nch NickChangeHandler) error {
-			return nch.AskPermissionForNickChange(user, oldNick, newNick)
-		},
-		func(nch NickChangeHandler) {
-			nch.HandleNickChange(user, oldNick, newNick)
-		},
-	)
+	return Perform(NickChangeAction{User: user, OldNick: user.nick, NewNick: newNick})
 }
 
 func (user *User) GetUsername() *string {
@@ -103,23 +87,9 @@ func (user *User) GetChannels() []canonicalChannelName {
 }
 
 func (user *User) Join(channelName ChannelName) error {
-	return Dispatch(
-		func(pjh PartJoinHandler) error {
-			return pjh.AskPermissionForJoin(user, channelName)
-		},
-		func(pjh PartJoinHandler) {
-			pjh.HandleJoin(user, channelName)
-		},
-	)
+	return Perform(JoinAction{User: user, ChannelName: channelName})
 }
 
 func (user *User) Part(channelName ChannelName, reason *string) error {
-	return Dispatch(
-		func(pjh PartJoinHandler) error {
-			return pjh.AskPermissionForPart(user, channelName, reason)
-		},
-		func(pjh PartJoinHandler) {
-			pjh.HandlePart(user, channelName, reason)
-		},
-	)
+	return Perform(PartAction{User: user, ChannelName: channelName, Reason: reason})
 }

src/irc/usersSystem.go

@@ -13,6 +13,14 @@ type UsersSystem struct {
 	channelNameIndex map[canonicalChannelName](map[*User]struct{})
 }
 
+func NewUsersSystem() *UsersSystem {
+	return &UsersSystem{
+		clientIdIndex:    make(map[transport.ClientId]*User),
+		nickIndex:        make(map[canonicalNick]*User),
+		channelNameIndex: make(map[canonicalChannelName]map[*User]struct{}),
+	}
+}
+
 func (users *UsersSystem) ByClientIdOrCreate(clientId transport.ClientId) *User {
 	existing, ok := users.clientIdIndex[clientId]
 
@@ -47,73 +55,75 @@ func (users *UsersSystem) ByCanonicalChannel(channelName canonicalChannelName) m
 	return users.channelNameIndex[channelName]
 }
 
-func (users *UsersSystem) AssertTypes() {
-	// statically assert that we implement the types we believe we do
-	var _ NickChangeHandler = users
-	var _ PartJoinHandler = users
+func (users *UsersSystem) InitializeRules() {
+	// nick changes
+	AddNewRule(
+		func(nc NickChangeAction) error {
+			// users can always change from one nick to the same nick
+			if nc.OldNick != nil && nc.NewNick != nil && nc.OldNick.canonical == nc.NewNick.canonical {
+				return nil
+			}
 
-}
-
-func (users *UsersSystem) AskPermissionForNickChange(user *User, oldNick *Nick, newNick *Nick) error {
-	if oldNick != nil && newNick != nil && oldNick.canonical == newNick.canonical {
-		// you're _always_ allowed to change your nick to the nick you currently have
-		return nil
-	}
-
-	// is this someone else's nick?
-	_, ok := users.nickIndex[newNick.canonical]
-	if ok {
-		return fmt.Errorf("%w: %s", ErrNickAlreadyInUse, newNick.Value)
-	}
-
-	return nil
-}
-
-func (users *UsersSystem) HandleNickChange(user *User, oldNick *Nick, newNick *Nick) {
-	if oldNick != nil {
-		delete(users.nickIndex, oldNick.canonical)
-	}
-	user.nick = newNick
-	user.recomputeSourceString()
-
-	if newNick != nil {
-		users.nickIndex[newNick.canonical] = user
-	}
-}
-
-func (users *UsersSystem) AskPermissionForPart(user *User, channelName ChannelName, reason *string) error {
-	if !slices.Contains(user.channels, channelName.canonical) {
-		return fmt.Errorf("%w: %s", ErrNotInChannel, channelName)
-	}
-	return nil
-}
-
-func (users *UsersSystem) HandlePart(user *User, channelName ChannelName, reason *string) {
-	name := channelName.canonical
-	user.channels = slices.DeleteFunc(user.channels, func(ccn canonicalChannelName) bool {
-		return ccn == name
-	})
-
-	channelUsers := users.channelNameIndex[name]
-	delete(channelUsers, user)
-	if len(channelUsers) == 0 {
-		delete(users.channelNameIndex, name)
-	}
-}
-
-func (users *UsersSystem) AskPermissionForJoin(user *User, channelName ChannelName) error {
-	if slices.Contains(user.channels, channelName.canonical) {
-		return fmt.Errorf("%w: %s", ErrAlreadyInChannel, channelName)
-	}
-	return nil
-}
-
-func (users *UsersSystem) HandleJoin(user *User, channelName ChannelName) {
-	name := channelName.canonical
-	existing, ok := users.channelNameIndex[name]
-	if !ok {
-		existing = make(map[*User]struct{})
-		users.channelNameIndex[name] = existing
-	}
-	existing[user] = struct{}{}
+			// is this someone else's nick?
+			_, ok := users.nickIndex[nc.NewNick.canonical]
+			if ok {
+				return fmt.Errorf("%w: %s", ErrNickAlreadyInUse, nc.NewNick.Value)
+			}
+
+			return nil
+
+		},
+		func(nc NickChangeAction) {
+			if nc.OldNick != nil {
+				delete(users.nickIndex, nc.OldNick.canonical)
+			}
+			nc.User.nick = nc.NewNick
+			nc.User.recomputeSourceString()
+
+			if nc.NewNick != nil {
+				users.nickIndex[nc.NewNick.canonical] = nc.User
+			}
+		},
+	)
+
+	// joining channel
+	AddNewRule(
+		func(j JoinAction) error {
+			if slices.Contains(j.User.channels, j.ChannelName.canonical) {
+				return fmt.Errorf("%w: %s", ErrAlreadyInChannel, j.ChannelName)
+			}
+			return nil
+		},
+		func(j JoinAction) {
+			name := j.ChannelName.canonical
+			existing, ok := users.channelNameIndex[name]
+			if !ok {
+				existing = make(map[*User]struct{})
+				users.channelNameIndex[name] = existing
+			}
+			existing[j.User] = struct{}{}
+		},
+	)
+
+	// parting channel
+	AddNewRule(
+		func(p PartAction) error {
+			if !slices.Contains(p.User.channels, p.ChannelName.canonical) {
+				return fmt.Errorf("%w: %s", ErrNotInChannel, p.ChannelName.Value)
+			}
+			return nil
+		},
+		func(p PartAction) {
+			name := p.ChannelName.canonical
+			p.User.channels = slices.DeleteFunc(p.User.channels, func(ccn canonicalChannelName) bool {
+				return ccn == name
+			})
+
+			channelUsers := users.channelNameIndex[name]
+			delete(channelUsers, p.User)
+			if len(channelUsers) == 0 {
+				delete(users.channelNameIndex, name)
+			}
+		},
+	)
 }

src/logic/rules.go

@@ -0,0 +1,115 @@
+package logic
+
+/// An Inform 7-style rulebook.
+///
+/// This is pretty icky, but basically the concept here:
+///
+/// For any action type, you can make a series of rules to:
+///
+/// (1) check if it's permissible
+/// (2) actually carry it out
+///
+/// These rules will be fired off in the order that they were added
+/// with the rule that a failed check results in an error,
+/// and a successful check results in all of the carryOut steps
+/// actually being caused to occur. (They are not allowed to fail.)
+type Rulebook struct {
+	chapters []anyChapter
+}
+
+type chapter[T any] struct {
+	check    []func(T) error
+	carryOut []func(T)
+}
+
+type anyChapter interface {
+	dispatchOn(interface{}) (bool, error)
+}
+
+type rule[T any] struct {
+	check    *func(T) error
+	carryOut *func(T)
+}
+
+type AnyRule interface {
+	addTo(rb *Rulebook)
+}
+
+func NewRulebook() *Rulebook {
+	return &Rulebook{}
+}
+
+func NewRule[T any](check func(T) error, carryOut func(T)) *rule[T] {
+	return &rule[T]{
+		check:    &check,
+		carryOut: &carryOut,
+	}
+
+}
+
+// why is this done in the rule and not the rulebook?
+// because go lacks parameterized types on methods, so we _have_ to
+// flip the control flow to put this logic in the type with the most knowledge
+// of the generic type
+func (r *rule[T]) addTo(rb *Rulebook) {
+	for i, ch := range rb.chapters {
+		if chSpecific, ok := ch.(chapter[T]); ok {
+			r.addToChapter(&chSpecific)
+			rb.chapters[i] = chSpecific
+			return
+		}
+	}
+
+	newChapter := chapter[T]{}
+	r.addToChapter(&newChapter)
+	rb.chapters = append(rb.chapters, newChapter)
+}
+
+func (r *rule[T]) addToChapter(chapter *chapter[T]) {
+	if check := r.check; check != nil {
+		chapter.check = append(chapter.check, *check)
+	}
+	if carryOut := r.carryOut; carryOut != nil {
+		chapter.carryOut = append(chapter.carryOut, *carryOut)
+	}
+}
+
+func (rb *Rulebook) Add(r AnyRule) {
+	r.addTo(rb)
+}
+
+func (rb *Rulebook) Perform(action interface{}) error {
+	for _, ch := range rb.chapters {
+		handled, err := ch.dispatchOn(action)
+		if handled {
+			return err
+		}
+	}
+
+	// there were zero rules
+	return nil
+}
+
+func (ch chapter[T]) dispatchOn(action interface{}) (bool, error) {
+	if specializedAction, ok := action.(T); ok {
+		return true, ch.dispatchOnSpecific(specializedAction)
+	}
+
+	// false: wrong dispatcher
+	return false, nil
+}
+
+func (ch chapter[T]) dispatchOnSpecific(item T) error {
+	for _, checkRule := range ch.check {
+		err := checkRule(item)
+		if err != nil {
+			return err
+		}
+	}
+
+	for _, carryOutRule := range ch.carryOut {
+		carryOutRule(item)
+	}
+
+	return nil
+}