Made the root Widget a separate entity.

cmd/test/main.go

@@ -110,9 +110,6 @@ var beh = tg.NewBehaviour().
 		// The session initialization.
 		c.Session.Data = &SessionData{}
 
-	}). // On any message update before the bot created session.
-	WithPreStartFunc(func(c *tg.Context){
-		c.Sendf("Please, use the /start command to start the bot")
 	}).WithScreens(
 		tg.NewScreen("start", tg.NewPage(
 				"The bot started!",
@@ -187,13 +184,17 @@ var beh = tg.NewBehaviour().
 			}),
 		tg.NewCommand("read").
 			Desc("reads a string and sends it back").
-			ActionFunc(func(c *tg.Context) {
-				/*c.Sendf("Type some text:")
-				msg, err := c.ReadTextMessage()
-				if err != nil {
-					return
+			WidgetFunc(func(c *tg.Context, updates chan *tg.Update) error {
+				c.Sendf("Type text and I will send it back to you")
+				for u := range updates {
+					if u.Message == nil {
+						continue
 					}
-				c.Sendf("You typed %q", msg)*/
+					c.Sendf("You typed %q", u.Message.Text)
+					break
+				}
+				c.Sendf("Done")
+				return nil
 			}),
 		tg.NewCommand("image").
 			Desc("sends a sample image").

tg/beh.go

@@ -5,20 +5,24 @@ package tg
 
 // The type describes behaviour for the bot in personal chats.
 type Behaviour struct {
-	PreStart *action
+	Root Widget
 	Init      *action
 	Screens   ScreenMap
-	Commands  CommandMap
 }
 
 // Returns new empty behaviour.
 func NewBehaviour() *Behaviour {
 	return &Behaviour{
 		Screens: make(ScreenMap),
-		Commands:  make(CommandMap),
 	}
 }
 
+// Set the root widget. Mostly the CommandWidget is used.
+func (b *Behaviour) WithRoot(root Widget) *Behaviour {
+	b.Root = root
+	return b
+}
+
 // The Action will be called on session creation,
 // not when starting or restarting the bot with the Start Action.
 func (b *Behaviour) WithInit(a Action) *Behaviour {
@@ -33,20 +37,6 @@ func (b *Behaviour) WithInitFunc(
 	return b.WithInit(fn)
 }
 
-// Defines pre-start action.
-// E. g. when the user has not type the "/start" command.
-// Mostly used to send the "/start" command back
-// with some warning.
-func (b *Behaviour) WithPreStart(a Action) *Behaviour {
-	b.PreStart = newAction(a)
-	return b
-}
-
-// Alias for WithPreStart to be used with function inside.
-func (b *Behaviour) WithPreStartFunc(fn ActionFunc) *Behaviour {
-	return b.WithPreStart(fn)
-}
-
 // The function sets screens.
 func (b *Behaviour) WithScreens(
 	screens ...*Screen,
@@ -64,18 +54,17 @@ func (b *Behaviour) WithScreens(
 	return b
 }
 
-// The function sets commands.
+// The function sets as the standard root widget CommandWidget
+// and its commands..
 func (b *Behaviour) WithCommands(cmds ...*Command) *Behaviour {
-	for _, cmd := range cmds {
-		if cmd.Name == "" {
-			panic("empty command name")
-		}
-		_, ok := b.Commands[cmd.Name]
-		if ok {
-			panic("duplicate command definition")
-		}
-		b.Commands[cmd.Name] = cmd
-	}
+	b.Root = NewCommandWidget().
+		WithCommands(cmds...).
+		WithPreStartFunc(func(c *Context){
+			c.Sendf("Please, use the /start command to start")
+		}).WithUsageFunc(func(c *Context){
+			c.Sendf("No such command")
+		})
+
 	return b
 }
 

tg/bot.go

@@ -117,7 +117,7 @@ func (b *Bot) WithGroupSessions(sessions GroupSessionMap) *Bot {
 }
 
 // Setting the command on the user side.
-func (bot *Bot) setCommands(
+func (bot *Bot) SetCommands(
 	scope tgbotapi.BotCommandScope,
 	cmdMap map[CommandName] BotCommander,
 ) {
@@ -156,20 +156,17 @@ func (bot *Bot) Run() error {
 		bot.groupBehaviour == nil {
 		return errors.New("no behaviour defined")
 	}
+
+	if bot.behaviour != nil && bot.behaviour.Root == nil {
+		return errors.New("the root widget is not set, cannot run")
+	}
+
 	uc := tgbotapi.NewUpdate(0)
 	uc.Timeout = 60
 	updates := bot.Api.GetUpdatesChan(uc)
 	handles := make(map[string]chan *Update)
 
 	if bot.behaviour != nil {
-		commanders := make(map[CommandName] BotCommander)
-		for k, v := range bot.behaviour.Commands {
-			commanders[k] = v
-		}
-		bot.setCommands(
-			tgbotapi.NewBotCommandScopeAllPrivateChats(),
-			commanders,
-		)
 		chn := make(chan *Update)
 		handles["private"] = chn
 		go bot.handlePrivate(chn)
@@ -180,7 +177,7 @@ func (bot *Bot) Run() error {
 		for k, v := range bot.groupBehaviour.Commands {
 			commanders[k] = v
 		}
-		bot.setCommands(
+		bot.SetCommands(
 			tgbotapi.NewBotCommandScopeAllGroupChats(),
 			commanders,
 		)

tg/command.go

@@ -89,3 +89,113 @@ func (c *GroupCommand) ToApi() tgbotapi.BotCommand {
 	ret.Description = c.Description
 	return ret
 }
+
+// The type is used to recognize commands and execute
+// its actions and widgets .
+type CommandWidget struct {
+	PreStart Action
+	Commands  CommandMap
+	Usage Action
+}
+
+// Returns new empty CommandWidget.
+func NewCommandWidget() *CommandWidget {
+	ret := &CommandWidget{}
+	ret.Commands = make(CommandMap)
+	return ret
+}
+
+// Set the commands to handle.
+func (w *CommandWidget) WithCommands(cmds ...*Command) *CommandWidget {
+	for _, cmd := range cmds {
+		if cmd.Name == "" {
+			panic("empty command name")
+		}
+		_, ok := w.Commands[cmd.Name]
+		if ok {
+			panic("duplicate command definition")
+		}
+		w.Commands[cmd.Name] = cmd
+	}
+	return w
+}
+
+// Set the prestart action.
+func (w *CommandWidget) WithPreStart(a Action) *CommandWidget {
+	w.PreStart = a
+	return w
+}
+
+// Set the prestart action with function.
+func (w *CommandWidget) WithPreStartFunc(fn ActionFunc) *CommandWidget {
+	return w.WithPreStart(fn)
+}
+
+// Set the usage action.
+func (w *CommandWidget) WithUsage(a Action) *CommandWidget {
+	w.Usage = a
+	return w
+}
+
+// Set the usage action with function.
+func (w *CommandWidget) WithUsageFunc(fn ActionFunc) *CommandWidget {
+	return w.WithUsage(fn)
+}
+
+func (widget *CommandWidget) Serve(c *Context, updates chan *Update) error {
+	commanders := make(map[CommandName] BotCommander)
+	for k, v := range widget.Commands {
+		commanders[k] = v
+	}
+	c.Bot.SetCommands(
+		tgbotapi.NewBotCommandScopeAllPrivateChats(),
+		commanders,
+	)
+
+	var cmdUpdates chan *Update
+	for u := range updates {
+		if c.ScreenId() == "" && u.Message != nil {
+			// Skipping and executing the preinit action
+			// while we have the empty screen.
+			// E. g. the session did not start.
+			if !(u.Message.IsCommand() && u.Message.Command() == "start") {
+				c.Run(widget.PreStart, u)
+				continue
+			}
+		}
+
+		if u.Message != nil && u.Message.IsCommand() {
+			// Command handling.
+			cmdName := CommandName(u.Message.Command())
+			cmd, ok := widget.Commands[cmdName]
+			if !ok {
+				c.Run(widget.Usage, u)
+				continue
+			} 
+			c.Run(cmd.Action, u)
+			if cmd.Widget != nil {
+				if cmdUpdates != nil {
+					close(cmdUpdates)
+				}
+				cmdUpdates = make(chan *Update)
+				go func() {
+					cmd.Widget.Serve(
+						&Context{context: c.context, Update: u},
+						cmdUpdates,
+					)
+					close(cmdUpdates)
+					cmdUpdates = nil
+				}()
+			}
+		}
+		
+		if cmdUpdates != nil {
+			// Send to the commands channel if we are
+			// executing one.
+			cmdUpdates <- u
+		} else {
+			c.Skip(u)
+		}
+	}
+	return nil
+}

tg/page.go

@@ -141,9 +141,7 @@ func (p *Page) Serve(
 				act = kbd.Action
 			}
 		}
-		if act != nil {
-			c.run(act, u)
-		} 
+		c.Run(act, u)
 	}
 	return nil
 }

tg/private.go

@@ -10,100 +10,67 @@ type context struct {
 	Session *Session
 	// To reach the bot abilities inside callbacks.
 	Bot     *Bot
-	widgetUpdates chan *Update
-	curScreen, prevScreen *Screen
+	skippedUpdates chan *Update
+	// Current screen ID.
+	screenId, prevScreenId ScreenId
 }
 
+
 // The type represents way to interact with user in
 // handling functions. Is provided to Act() function always.
 
 // Goroutie function to handle each user.
 func (c *context) handleUpdateChan(updates chan *Update) {
 	beh := c.Bot.behaviour
-
-	session := c.Session
-	preStart := beh.PreStart
 	if beh.Init != nil {
 		c.run(beh.Init, nil)
 	}
-	var cmdUpdates chan *Update
-	for u := range updates {
-		// The part is added to implement custom update handling.
-		if !session.started {
-			if u.Message.IsCommand() &&
-					u.Message.Command() == "start" {
-				// Special treatment for the "/start"
-				// command.
-				session.started = true
-				cmdName := CommandName("start")
-				cmd, ok := beh.Commands[cmdName]
-				if ok {
-					if cmd.Action != nil {
-						c.run(cmd.Action, u)
-					}
-				} else {
-					// Some usage.
-				}
-			} else {
-				// Prestart handling.
-				c.run(preStart, u)
+	beh.Root.Serve(&Context{
+		context: c,
+	}, updates)
 }
 
-			continue
-		}
-
-		if u.Message != nil && u.Message.IsCommand() {
-			// Command handling.
-			cmdName := CommandName(u.Message.Command())
-			cmd, ok := beh.Commands[cmdName]
-			if ok {
-				if cmd.Action != nil {
-					c.run(cmd.Action, u)
-				}
-				if cmd.Widget != nil {
-					if cmdUpdates != nil {
-						close(cmdUpdates)
-					}
-					cmdUpdates = make(chan *Update)
-					go func() {
-						cmd.Widget.Serve(
-							&Context{context: c, Update: u},
-							cmdUpdates,
-						)
-						close(cmdUpdates)
-						cmdUpdates = nil
-					}()
-				}
-			} else {
-				// Some usage.
-			}
-			continue
-		}
-		
-		// The standard thing - send messages to widgets.
-		if cmdUpdates != nil {
-			cmdUpdates <- u
-		} else {
-			c.widgetUpdates <- u
-		}
-	}
-}
 
 func (c *context) run(a Action, u *Update) {
 	a.Act(&Context{context: c, Update:  u})
 }
 
-func (c *context) Render(v Renderable) ([]*Message, error) {
+func (c *Context) ScreenId() ScreenId {
+	return c.screenId
+}
+
+func (c *Context) PrevScreenId() ScreenId {
+	return c.prevScreenId
+}
+
+func (c *Context) Run(a Action, u *Update) {
+	if a != nil {
+		a.Act(&Context{context: c.context, Update: u})
+	}
+}
+
+// Only for the root widget usage.
+// Skip the update sending it down to
+// the underlying widget.
+func (c *Context) Skip(u *Update) {
+	if c.skippedUpdates != nil {
+		c.skippedUpdates <- u
+	}
+}
+
+// Renders the Renedrable object to the side of client
+// and returns the messages it sent.
+func (c *Context) Render(v Renderable) ([]*Message, error) {
 	return c.Bot.Render(c.Session.Id, v)
 }
 
 // Sends to the Sendable object.
-func (c *context) Send(v Sendable) (*Message, error) {
+func (c *Context) Send(v Sendable) (*Message, error) {
 	return c.Bot.Send(c.Session.Id, v)
 }
 
 // Sends the formatted with fmt.Sprintf message to the user.
-func (c *context) Sendf(format string, v ...any) (*Message, error) {
+func (c *Context) Sendf(format string, v ...any) (*Message, error) {
 	msg, err := c.Send(NewMessage(
 		c.Session.Id, fmt.Sprintf(format, v...),
 	))
@@ -165,29 +132,22 @@ func (c *Context) ChangeScreen(screenId ScreenId) error {
 	// Getting the screen and changing to
 	// then executing its widget.
 	screen := c.Bot.behaviour.Screens[screenId]
-	c.prevScreen = c.curScreen
-	c.curScreen = screen
+	c.prevScreenId = c.screenId
+	c.screenId = screenId
 
 	// Making the new channel for the widget.
-	if c.widgetUpdates != nil {
-		close(c.widgetUpdates)
+	if c.skippedUpdates != nil {
+		close(c.skippedUpdates)
 	}
-	c.widgetUpdates = make(chan *Update)
+	c.skippedUpdates = make(chan *Update)
 	if screen.Widget != nil {
 		// Running the widget if the screen has one.
-		go screen.Widget.Serve(c, c.widgetUpdates)
-	} else {
-		// Skipping updates if there is no
-		// widget to handle them.
 		go func() {
-			for _ = range c.widgetUpdates {}
+			screen.Widget.Serve(c, c.skippedUpdates)
 		}()
+	} else {
+		panic("no widget defined for the screen")
 	}
 
-	//c.Bot.Render(c.Session.Id, screen)
-	//if screen.Action != nil {
-		//c.run(screen.Action, c.Update)
-	//}
-
 	return nil
 }