wip: experimental branch with finite-state machine processor (doesn't work yet)

.air.toml

@@ -0,0 +1,10 @@
+root = "."
+
+[build]
+exclude_regex = ["_test\\.go"]
+bin = "/usr/bin/make debug"
+cmd = "/usr/bin/make build"
+kill_delay = 0
+log = "build-errors.log"
+send_interrupt = true
+stop_on_error = true

.drone.yml

@@ -19,3 +19,5 @@ steps:
 trigger:
   event:
     - push
+  branch:
+    - master

.gitignore

@@ -22,6 +22,8 @@ vendor/
 # Go workspace file
 go.work
 .idea/
+.config/
+tmp/
 
 # Env files
 .env

Makefile

@@ -2,20 +2,37 @@ SHELL = /bin/bash -o pipefail
 export PATH := $(shell go env GOPATH)/bin:$(PATH)
 
 ROOT_DIR=$(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))
-BIN=$(ROOT_DIR)/build/vegapokerbot
+BIN_NAME=vegapokerbot
+BIN=$(ROOT_DIR)/build/$(BIN_NAME)
 GO_VERSION=$(shell go version | sed -e 's/go version //')
 BIN_DIR=$(ROOT_DIR)/build
 
 build: deps fmt
-	@echo "> building with ${GO_VERSION}"
+ifeq ($(DEBUG), true)
+	@echo "> building debug with ${GO_VERSION}"
+	@CGO_ENABLED=0 go build -buildvcs=false -gcflags "all=-N -l" -tags=release -o $(BIN) .
+else
+	@echo "> building release with ${GO_VERSION}"
 	@CGO_ENABLED=0 go build -buildvcs=false -tags=release -o $(BIN) .
+endif
 	@echo $(BIN)
 
 docker:
 	@docker buildx build --platform linux/amd64 --tag $CI_APP_IMAGE --file Dockerfile .
 
 run:
+ifeq ($(DEBUG), true)
+	@killall -s 9 dlv > /dev/null 2>&1 || true
+	@killall -s 9 ${BIN_NAME} > /dev/null 2>&1 || true
+	@air
+else
 	@${BIN} run
+endif
+
+debug:
+	@echo "> starting under delve"
+	@dlv --listen=:40000 --headless=true --api-version=2 --accept-multiclient --log exec ${BIN} run
+
 fmt:
 	@echo "> fmt"
 	@gofmt -l -s -w `go list -buildvcs=false -f '{{.Dir}}' ${ROOT_DIR}/... | grep -v /vendor/`

compose.prod.yml

@@ -1,29 +1,23 @@
 services:
   db:
     image: postgres:latest
+    restart: always
     environment:
       POSTGRES_USER: app
       POSTGRES_PASSWORD: app
       POSTGRES_DATABASE: app
-    networks:
-      - default
 
   app:
     image: "gitea.neur0tx.site/neur0toxine/vegapokerbot:latest"
-    networks:
-      - default
     links:
       - db
     env_file:
       - .env
+    restart: always
     labels:
       traefik.enable: "true"
-      traefik.http.routers.vegapokerbot.rule: Host(`vegapokerbot.neur0tx.site`) && PathPrefix(`/webhook8c31c4b2d65a87b4f3a6f10f8eb166fba9a2e5dc7696bc5291a7e69641dc5c21`)
+      traefik.http.routers.vegapokerbot.rule: Host(`vegapokerbot.example.com`) && PathPrefix(`/webhook`)
       traefik.http.routers.vegapokerbot.entrypoints: websecure
       traefik.http.services.vegapokerbot.loadbalancer.server.port: "3333"
       traefik.http.routers.vegapokerbot.tls: true
       traefik.http.routers.vegapokerbot.tls.certresolver: letsencrypt
-
-networks:
-  default:
-    driver: bridge

compose.yml

@@ -22,8 +22,10 @@ services:
       - db
     environment:
       GOCACHE: /go
+      DEBUG: true # Set to false to disable hot-reload & debugger.
     ports:
       - 3333:3333
+      - 40000:40000
     command: make build run
 
 networks:

go.mod

@@ -12,6 +12,7 @@ require (
 	github.com/maypok86/otter v1.2.1
 	github.com/mymmrac/telego v0.29.2
 	github.com/nicksnyder/go-i18n/v2 v2.4.0
+	github.com/stretchr/testify v1.9.0
 	go.uber.org/zap v1.27.0
 	golang.org/x/text v0.14.0
 	gopkg.in/yaml.v3 v3.0.1
@@ -26,6 +27,7 @@ require (
 	github.com/bytedance/sonic v1.11.3 // indirect
 	github.com/chenzhuoyu/base64x v0.0.0-20230717121745-296ad89f973d // indirect
 	github.com/chenzhuoyu/iasm v0.9.1 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dolthub/maphash v0.1.0 // indirect
 	github.com/fasthttp/router v1.5.0 // indirect
 	github.com/gammazero/deque v0.2.1 // indirect
@@ -42,6 +44,7 @@ require (
 	github.com/klauspost/compress v1.17.6 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.6 // indirect
 	github.com/lib/pq v1.10.9 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/savsgio/gotils v0.0.0-20240303185622-093b76447511 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect

internal/app/app.go

@@ -4,13 +4,16 @@ import (
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/config"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/db"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/fsmwizard"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/locale"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/logger"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/types"
 	"github.com/mymmrac/telego"
 	"go.uber.org/zap"
 	"gorm.io/gorm"
 	"net/url"
+	"time"
 )
 
 type App struct {
@@ -20,6 +23,7 @@ type App struct {
 	Config       *config.Config
 	Repositories *db.Repositories
 	Handlers     map[handler.Type]handler.Handler
+	updates      types.Queue[*telego.Update]
 	db           *gorm.DB
 }
 
@@ -113,6 +117,8 @@ func (a *App) initTelegram() error {
 }
 
 func (a *App) initHandlers() {
+	a.updates = types.NewQueue[*telego.Update]()
+	fsmwizard.PopulateStates(a)
 	a.Handlers = map[handler.Type]handler.Handler{
 		handler.Noop:              handler.NewNoopHandler(a.Logger, a.Config.Debug),
 		handler.Message:           handler.NewMessageHandler(a),
@@ -138,6 +144,17 @@ func (a *App) handler(update telego.Update) handler.Handler {
 	return a.Handlers[handler.Noop]
 }
 
+func (a *App) processUpdates() {
+	for {
+		item := a.updates.Dequeue()
+		if item == nil {
+			time.Sleep(time.Nanosecond * 200)
+			continue
+		}
+		a.processUpdate(*item)
+	}
+}
+
 func (a *App) processUpdate(update telego.Update) {
 	defer func() {
 		if r := recover(); r != nil {
@@ -155,9 +172,11 @@ func (a *App) longPoll() error {
 	if err != nil {
 		return err
 	}
+	go a.processUpdates()
 	defer a.Telegram.StopLongPolling()
 	for update := range updates {
-		go a.processUpdate(update)
+		update := update
+		a.updates.Enqueue(&update)
 	}
 	return nil
 }
@@ -182,8 +201,10 @@ func (a *App) listenWebhook() error {
 	defer func() {
 		_ = a.Telegram.StopWebhook()
 	}()
+	go a.processUpdates()
 	for update := range updates {
-		go a.processUpdate(update)
+		update := update
+		a.updates.Enqueue(&update)
 	}
 	return nil
 }

internal/handler/chat_member_updated_handler.go

@@ -2,6 +2,7 @@ package handler
 
 import (
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/db/model"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/fsmwizard"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/locale"
@@ -21,18 +22,25 @@ func NewChatMemberUpdatedHandler(app iface.App) *ChatMemberUpdatedHandler {
 }
 
 func (h *ChatMemberUpdatedHandler) Handle(wh telego.Update) error {
-	cm := wh.MyChatMember
-	if !cm.OldChatMember.MemberIsMember() && cm.OldChatMember.MemberUser().ID == h.App.TGProfile().ID &&
-		cm.NewChatMember.MemberIsMember() && cm.NewChatMember.MemberUser().ID == h.App.TGProfile().ID {
-		return h.handleAddToChat(wh.MyChatMember.Chat)
-	}
-	if cm.OldChatMember.MemberIsMember() && cm.OldChatMember.MemberUser().ID == h.App.TGProfile().ID &&
-		!cm.NewChatMember.MemberIsMember() && cm.NewChatMember.MemberUser().ID == h.App.TGProfile().ID {
-		return h.handleRemoveFromChat(wh.MyChatMember.Chat)
-	}
-
-	h.leaveChat(wh.MyChatMember.Chat.ID)
-	return nil
+	return fsmwizard.Get(wh.MyChatMember.From.ID).Handle(func(w *fsmwizard.Wizard) *fsmwizard.Wizard {
+		if w == nil {
+			return &fsmwizard.Wizard{Data: wh}
+		}
+		w.Data = wh
+		return w
+	})
+	// cm := wh.MyChatMember
+	// if !cm.OldChatMember.MemberIsMember() && cm.OldChatMember.MemberUser().ID == h.App.TGProfile().ID &&
+	// 	cm.NewChatMember.MemberIsMember() && cm.NewChatMember.MemberUser().ID == h.App.TGProfile().ID {
+	// 	return h.handleAddToChat(wh.MyChatMember.Chat)
+	// }
+	// if cm.OldChatMember.MemberIsMember() && cm.OldChatMember.MemberUser().ID == h.App.TGProfile().ID &&
+	// 	!cm.NewChatMember.MemberIsMember() && cm.NewChatMember.MemberUser().ID == h.App.TGProfile().ID {
+	// 	return h.handleRemoveFromChat(wh.MyChatMember.Chat)
+	// }
+	//
+	// h.leaveChat(wh.MyChatMember.Chat.ID)
+	// return nil
 }
 
 func (h *ChatMemberUpdatedHandler) handleAddToChat(tgChat telego.Chat) error {

internal/handler/fsmwizard/add_chat_member_state.go

@@ -0,0 +1,151 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/db/model"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+	"golang.org/x/text/language"
+)
+
+const MaxChatMembers = 32
+
+const AddChatMemberStateID fsm.StateID = "add_chat_member"
+
+type AddChatMemberState struct {
+	State
+}
+
+func NewAddChatMemberState(app iface.App) fsm.IState[Wizard] {
+	return &AddChatMemberState{newBase(app)}
+}
+
+func (s *AddChatMemberState) Enter(pl *Wizard, mc fsm.MachineControls[Wizard]) error {
+	if pl.Data.MyChatMember == nil {
+		s.Move(mc, WaitingForMemberWebhookStateID, pl)
+	}
+	return nil
+}
+
+func (s *AddChatMemberState) Handle(pl *Wizard, mc fsm.MachineControls[Wizard]) {
+	next := WaitingForMemberWebhookStateID
+	defer func() {
+		s.Move(mc, next, pl)
+	}()
+
+	cr := s.App.DB().ForChat()
+	tgChat := pl.Data.MyChatMember.Chat
+	user, chat := s.getUserAndChat(tgChat)
+	if user == nil || chat == nil {
+		return
+	}
+
+	s.Payload.Loc = s.Localizer(user.Language)
+	if s.handleTooManyMembers(tgChat.ID) {
+		return
+	}
+
+	if chat.ID == 0 {
+		chat = &model.Chat{
+			TelegramID: tgChat.ID,
+			UserID:     user.ID,
+		}
+		err := cr.Save(chat)
+		if err != nil {
+			s.curseAndLeave(tgChat.ID, err)
+			return
+		}
+	} else {
+		chat.UserID = user.ID
+		err := s.App.DB().ForIntegration().DeleteForChat(chat.ID)
+		if err != nil {
+			s.curseAndLeave(tgChat.ID, err)
+			return
+		}
+		err = cr.Save(chat)
+		if err != nil {
+			s.curseAndLeave(tgChat.ID, err)
+			return
+		}
+	}
+
+	_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+		ChatID:    tu.ID(user.ChatID),
+		Text:      s.Payload.Loc.Template("bot_was_added", map[string]interface{}{"Name": tgChat.Title}),
+		ParseMode: telego.ModeMarkdown,
+	})
+	s.LogError(err)
+	pl.User = user
+	pl.UserID = user.TelegramID
+	pl.Chat = chat
+	pl.ChatID = tgChat.ID
+	pl.TGChat = tgChat
+	pl.IsMaster = true
+	next = KeyboardChooserStateID
+}
+
+func (s *AddChatMemberState) handleTooManyMembers(chatID int64) bool {
+	totalMembers, err := s.App.TG().GetChatMemberCount(&telego.GetChatMemberCountParams{
+		ChatID: tu.ID(chatID),
+	})
+	if err != nil {
+		s.curseAndLeave(chatID, err)
+		return true
+	}
+	if *totalMembers > MaxChatMembers {
+		_, err = s.App.TG().SendMessage(&telego.SendMessageParams{
+			ChatID: tu.ID(chatID),
+			Text: s.Payload.Loc.Template(
+				"too_many_members_in_the_group", map[string]interface{}{"Limit": MaxChatMembers}),
+			ParseMode: telego.ModeMarkdown,
+		})
+		s.leaveChat(chatID)
+		s.LogError(err)
+		return true
+	}
+	return false
+}
+
+func (s *AddChatMemberState) getUserAndChat(tgChat telego.Chat) (*model.User, *model.Chat) {
+	user, err := s.App.DB().ForUser().ByTelegramID(s.Payload.Data.MyChatMember.From.ID)
+	if err != nil {
+		s.curseAndLeave(tgChat.ID, err)
+		return nil, nil
+	}
+	if user == nil || user.ID == 0 {
+		_, err = s.App.TG().SendMessage(&telego.SendMessageParams{
+			ChatID: tu.ID(tgChat.ID),
+			Text: s.Localizer(language.English.String()).
+				Template("you_should_register_first", map[string]interface{}{"Name": s.App.TGProfile().Username}),
+			ParseMode: telego.ModeMarkdown,
+		})
+		s.leaveChat(tgChat.ID)
+		s.LogError(err)
+		return nil, nil
+	}
+	cr := s.App.DB().ForChat()
+	chat, err := cr.ByTelegramID(tgChat.ID)
+	if err != nil {
+		s.curseAndLeave(tgChat.ID, err)
+		return nil, nil
+	}
+	return user, chat
+}
+
+func (s *AddChatMemberState) curseAndLeave(chatID int64, err error) {
+	s.LogError(util.SendInternalError(s.App.TG(), chatID, s.Localizer()))
+	s.leaveChat(chatID)
+	s.LogError(err)
+}
+
+func (s *AddChatMemberState) leaveChat(chatID int64) {
+	s.LogError(s.App.TG().LeaveChat(&telego.LeaveChatParams{
+		ChatID: tu.ID(chatID),
+	}))
+}
+
+func (s *AddChatMemberState) ID() fsm.StateID {
+	return AddChatMemberStateID
+}

internal/handler/fsmwizard/base.go

@@ -0,0 +1,88 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/db/model"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/locale"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	"golang.org/x/text/language"
+	"strings"
+)
+
+type Wizard struct {
+	UserID   int64
+	ChatID   int64
+	TGChat   telego.Chat
+	User     *model.User
+	Chat     *model.Chat
+	Loc      locale.Localizer
+	Data     telego.Update
+	KeyClick util.Payload
+	IsMaster bool
+}
+
+type State struct {
+	fsm.State[Wizard]
+	App iface.App
+}
+
+func newBase(app iface.App) State {
+	return State{App: app}
+}
+
+func (s State) Localizer(langCode ...string) locale.Localizer {
+	lang := language.English.String()
+	if len(langCode) > 0 {
+		lang = langCode[0]
+	} else {
+		if s.Payload != nil && s.Payload.User != nil {
+			lang = s.Payload.User.Language
+		} else if s.Payload != nil && s.Payload.UserID > 0 {
+			user, _ := s.App.DB().ForUser().ByTelegramID(s.Payload.UserID)
+			if user != nil && user.Language != "" {
+				lang = user.Language
+			}
+		}
+	}
+	if s.Payload != nil && s.Payload.Loc != nil && (len(langCode) == 0 || s.hasLocalizerWithLocale(lang)) {
+		return s.Payload.Loc
+	}
+	lang = strings.ToLower(lang)
+	if len(lang) > 2 {
+		lang = lang[:2]
+	}
+	switch lang {
+	case "en", "ru":
+		return s.App.Localizer(lang)
+	default:
+		return s.App.Localizer("en")
+	}
+}
+
+func (s State) hasLocalizerWithLocale(lang string) bool {
+	if s.Payload.Loc == nil {
+		return false
+	}
+	return s.Payload.Loc.Tag().String() == lang
+}
+
+func (s State) LogError(err error) {
+	if err == nil {
+		return
+	}
+	if s.App.Conf().Debug {
+		s.App.Log().Errorf("handler error: %s, payload: %#v", err, s.Payload)
+		return
+	}
+	s.App.Log().Errorf("handler error: %s, user id: %d, chat id: %d", err, s.Payload.UserID, s.Payload.ChatID)
+}
+
+func (s State) Move(mc fsm.MachineControls[Wizard], stateID fsm.StateID, pl *Wizard) {
+	s.LogError(mc.Move(stateID, pl))
+}
+
+func (s State) MoveForHandle(mc fsm.MachineControls[Wizard], stateID fsm.StateID, pl *Wizard) {
+	s.LogError(mc.MoveForHandle(stateID, pl))
+}

internal/handler/fsmwizard/configure_redmine_query_state.go

@@ -0,0 +1,47 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const ConfigureRedmineQueryStateID fsm.StateID = "configure_redmine_query"
+
+type ConfigureRedmineQueryState struct {
+	State
+}
+
+func NewConfigureRedmineQueryState(app iface.App) fsm.IState[Wizard] {
+	return &ConfigureRedmineQueryState{newBase(app)}
+}
+
+func (s *ConfigureRedmineQueryState) Enter(pl *Wizard, _ fsm.MachineControls[Wizard]) error {
+	_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+		ChatID:    tu.ID(pl.User.ChatID),
+		Text:      pl.Loc.Message("ask_for_redmine"),
+		ParseMode: telego.ModeMarkdown,
+		ReplyMarkup: &telego.InlineKeyboardMarkup{InlineKeyboard: [][]telego.InlineKeyboardButton{
+			{
+				{
+					Text: pl.Loc.Message("yes"),
+					CallbackData: util.NewRedmineQuestionPayload(
+						pl.User.TelegramID, pl.Chat.TelegramID, true).String(),
+				},
+				{
+					Text: pl.Loc.Message("no"),
+					CallbackData: util.NewRedmineQuestionPayload(
+						pl.User.TelegramID, pl.Chat.TelegramID, false).String(),
+				},
+			},
+		}},
+	})
+	s.LogError(err)
+	return err
+}
+
+func (s *ConfigureRedmineQueryState) ID() fsm.StateID {
+	return ConfigureRedmineQueryStateID
+}

internal/handler/fsmwizard/doc.go

@@ -0,0 +1,3 @@
+// Package fsmwizard contains setup wizard implementation written with finite-state machine.
+// Eventually it will replace wizard package (package name will be changed to wizard then).
+package fsmwizard

internal/handler/fsmwizard/error_state.go

@@ -0,0 +1,21 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"go.uber.org/zap"
+)
+
+type ErrorState struct {
+	fsm.ErrorState[Wizard]
+	log *zap.SugaredLogger
+}
+
+func NewErrorState(log *zap.SugaredLogger) *ErrorState {
+	return &ErrorState{log: log}
+}
+
+func (s *ErrorState) Handle(err error, cur fsm.StateID, next fsm.StateID, pl *Wizard, mc fsm.MachineControls[Wizard]) {
+	s.log.Errorf("critical wizard error: %s, current state: %s, next state: %s, payload: %#v",
+		err, cur, next, pl)
+	mc.Reset()
+}

internal/handler/fsmwizard/help_state.go

@@ -0,0 +1,33 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const HelpStateID fsm.StateID = "help"
+
+type HelpState struct {
+	State
+}
+
+func NewHelpState(app iface.App) fsm.IState[Wizard] {
+	return &HelpState{newBase(app)}
+}
+
+func (s *HelpState) Enter(pl *Wizard, _ fsm.MachineControls[Wizard]) error {
+	_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+		ChatID: tu.ID(pl.Data.Message.Chat.ID),
+		Text: s.Localizer(pl.Data.Message.From.LanguageCode).
+			Template("help_output", map[string]interface{}{"Name": s.App.TGProfile().Username}),
+		ParseMode: telego.ModeMarkdown,
+	})
+	s.LogError(err)
+	return fsm.ErrPreventTransition
+}
+
+func (s *HelpState) ID() fsm.StateID {
+	return HelpStateID
+}

internal/handler/fsmwizard/init.go

@@ -0,0 +1,99 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/types"
+	"time"
+
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+)
+
+var (
+	wizards    *types.TTLMap[int64, fsm.IMachine[Wizard]]
+	states     []fsm.IState[Wizard]
+	errorState *ErrorState
+	appPointer iface.App
+)
+
+func init() {
+	wizards = types.NewTTLMap[int64, fsm.IMachine[Wizard]](time.Hour * 24 * 7)
+}
+
+func Get(userID int64) fsm.IMachine[Wizard] {
+	if machine, ok := wizards.Get(userID); ok && machine != nil {
+		return machine
+	}
+	machine := newWizard()
+	wizards.Set(userID, machine)
+	return machine
+}
+
+func newWizard() fsm.IMachine[Wizard] {
+	return fsm.New[Wizard](states[0].ID(), wizardRouter, states, errorState)
+}
+
+// PopulateStates will init all state handlers for future use.
+func PopulateStates(app iface.App) {
+	appPointer = app
+	states = []fsm.IState[Wizard]{
+		NewRegisterState(app),
+		NewWaitingForMemberWebhookState(app),
+		NewAddChatMemberState(app),
+		NewKeyboardChooserState(app),
+		NewConfigureRedmineQueryState(app),
+		NewRemoveChatMemberState(app),
+		NewHelpState(app),
+		NewUnknownCommandState(app),
+	}
+	errorState = NewErrorState(app.Log())
+}
+
+func wizardRouter(w *Wizard, mc fsm.MachineControlsWithState[Wizard]) {
+	if w.Data.Message != nil {
+		if w.UserID == 0 {
+			w.UserID = w.Data.Message.From.ID
+		}
+		if w.ChatID == 0 {
+			w.ChatID = w.Data.Message.Chat.ID
+		}
+		if w.User == nil {
+			user, err := appPointer.DB().ForUser().ByTelegramID(w.Data.Message.From.ID)
+			if err != nil {
+				return
+			}
+
+			if user != nil && user.ID > 0 {
+				w.User = user
+			}
+		}
+		if w.Chat == nil {
+			chat, err := appPointer.DB().ForChat().ByTelegramID(w.Data.Message.Chat.ID)
+			if err != nil {
+				return
+			}
+
+			if chat != nil && chat.ID > 0 {
+				w.Chat = chat
+			}
+		}
+		if w.TGChat.ID == 0 {
+			w.TGChat = w.Data.Message.Chat
+		}
+
+		switch {
+		case util.MatchCommand("start", w.Data.Message):
+			_ = mc.Move(RegisterStateID, w)
+		case util.MatchCommand("help", w.Data.Message):
+			_ = mc.Move(HelpStateID, w)
+		case util.HasCommand(w.Data.Message):
+			_ = mc.Move(UnknownCommandStateID, w)
+		default:
+			return
+		}
+	}
+
+	if w.Data.MyChatMember != nil {
+		_ = mc.Move(WaitingForMemberWebhookStateID, w)
+	}
+}

internal/handler/fsmwizard/keyboard_chooser_state.go

@@ -0,0 +1,91 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/db/model"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const KeyboardChooserStateID fsm.StateID = "keyboard_chooser"
+
+type KeyboardChooserState struct {
+	State
+}
+
+func NewKeyboardChooserState(app iface.App) fsm.IState[Wizard] {
+	return &KeyboardChooserState{newBase(app)}
+}
+
+func (s *KeyboardChooserState) Enter(pl *Wizard, _ fsm.MachineControls[Wizard]) error {
+	_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+		ChatID:    tu.ID(pl.User.ChatID),
+		Text:      s.Localizer().Template("choose_keyboard", map[string]interface{}{"Name": pl.TGChat.Title}),
+		ParseMode: telego.ModeMarkdown,
+		ReplyMarkup: &telego.InlineKeyboardMarkup{
+			InlineKeyboard: [][]telego.InlineKeyboardButton{
+				{
+					{
+						Text: s.Localizer().Message("standard_vote_keyboard"),
+						CallbackData: util.NewKeyboardChooserPayload(
+							pl.User.TelegramID, pl.TGChat.ID, uint8(model.StandardKeyboard)).String(),
+					},
+				},
+				{
+					{
+						Text: s.Localizer().Message("sp_vote_keyboard"),
+						CallbackData: util.NewKeyboardChooserPayload(
+							pl.User.TelegramID, pl.TGChat.ID, uint8(model.StoryPointsKeyboard)).String(),
+					},
+				},
+			},
+		},
+	})
+	s.LogError(err)
+	return err
+}
+
+func (s *KeyboardChooserState) Handle(pl *Wizard, mc fsm.MachineControls[Wizard]) {
+	cr := s.App.DB().ForChat()
+	result := pl.KeyClick.KeyboardChoice()
+	if pl.KeyClick.User != pl.User.TelegramID {
+		return
+	}
+	chat, err := cr.ByTelegramID(pl.KeyClick.Chat)
+	if err != nil {
+		s.LogError(err)
+		return
+	}
+	if chat == nil || chat.ID == 0 {
+		return
+	}
+	chat.KeyboardType = model.KeyboardType(result.Type)
+	if err := cr.Save(chat); err != nil {
+		s.LogError(err)
+		return
+	}
+
+	kbTypeName := "standard_vote_keyboard"
+	if model.KeyboardType(result.Type) == model.StoryPointsKeyboard {
+		kbTypeName = "sp_vote_keyboard"
+	}
+	loc := s.Localizer(pl.User.Language)
+	_, err = s.App.TG().EditMessageText(&telego.EditMessageTextParams{
+		ChatID:    tu.ID(pl.User.ChatID),
+		MessageID: pl.Data.CallbackQuery.Message.GetMessageID(),
+		Text:      loc.Template("chosen_keyboard", map[string]interface{}{"Name": loc.Message(kbTypeName)}),
+	})
+	s.LogError(err)
+
+	if !s.Payload.IsMaster {
+		mc.Reset()
+		return
+	}
+	s.Move(mc, ConfigureRedmineQueryStateID, pl)
+}
+
+func (s *KeyboardChooserState) ID() fsm.StateID {
+	return KeyboardChooserStateID
+}

internal/handler/fsmwizard/register_state.go

@@ -0,0 +1,87 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/db/model"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const RegisterStateID fsm.StateID = "register"
+
+type RegisterState struct {
+	State
+}
+
+func NewRegisterState(app iface.App) fsm.IState[Wizard] {
+	return &RegisterState{newBase(app)}
+}
+
+func (s *RegisterState) Enter(pl *Wizard, _ fsm.MachineControls[Wizard]) error {
+	if pl.Data.Message != nil && pl.Data.Message.Chat.Type != telego.ChatTypePrivate {
+		return fsm.ErrPreventTransition
+	}
+	return nil
+}
+
+func (s *RegisterState) Handle(pl *Wizard, mc fsm.MachineControls[Wizard]) {
+	loc := s.Localizer(pl.Data.Message.From.LanguageCode)
+	userRepo := s.App.DB().ForUser()
+	user, err := userRepo.ByTelegramID(pl.Data.Message.From.ID)
+	if err != nil {
+		return
+	}
+
+	if user != nil && user.ID > 0 {
+		var shouldUpdate bool
+		if user.ChatID != pl.Data.Message.Chat.ID {
+			user.ChatID = pl.Data.Message.Chat.ID
+			shouldUpdate = true
+		}
+		if user.Language != pl.Data.Message.From.LanguageCode {
+			user.Language = pl.Data.Message.From.LanguageCode
+			shouldUpdate = true
+		}
+		if shouldUpdate {
+			s.LogError(userRepo.Save(user))
+		}
+		pl.User = user
+		s.Move(mc, WaitingForMemberWebhookStateID, pl)
+		return
+	}
+
+	err = userRepo.Save(&model.User{
+		TelegramID: pl.Data.Message.From.ID,
+		ChatID:     pl.Data.Message.Chat.ID,
+		Language:   pl.Data.Message.From.LanguageCode,
+	})
+	if err != nil {
+		s.LogError(err)
+		_, err = s.App.TG().SendMessage(&telego.SendMessageParams{
+			ChatID:    tu.ID(pl.Data.Message.Chat.ID),
+			Text:      loc.Message("internal_error"),
+			ParseMode: telego.ModeMarkdown,
+		})
+		s.LogError(err)
+	}
+	pl.User = user
+	s.Move(mc, WaitingForMemberWebhookStateID, pl)
+}
+
+func (s *RegisterState) Exit(pl *Wizard) {
+	if pl.Data.Message == nil {
+		return
+	}
+	loc := s.Localizer(pl.Data.Message.From.LanguageCode)
+	_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+		ChatID:    tu.ID(pl.Data.Message.Chat.ID),
+		Text:      loc.Message("welcome"),
+		ParseMode: telego.ModeMarkdown,
+	})
+	s.LogError(err)
+}
+
+func (s *RegisterState) ID() fsm.StateID {
+	return RegisterStateID
+}

internal/handler/fsmwizard/remove_chat_member_state.go

@@ -0,0 +1,56 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const RemoveChatMemberStateID fsm.StateID = "remove_chat_member"
+
+type RemoveChatMemberState struct {
+	State
+}
+
+func NewRemoveChatMemberState(app iface.App) fsm.IState[Wizard] {
+	return &RemoveChatMemberState{newBase(app)}
+}
+
+func (s *RemoveChatMemberState) Enter(pl *Wizard, mc fsm.MachineControls[Wizard]) error {
+	if pl.Data.MyChatMember == nil {
+		s.Move(mc, WaitingForMemberWebhookStateID, pl)
+	}
+	return nil
+}
+
+func (s *RemoveChatMemberState) Handle(pl *Wizard, mc fsm.MachineControls[Wizard]) {
+	if s.Payload.Chat == nil {
+		chat, err := s.App.DB().ForChat().ByTelegramID(s.Payload.Data.MyChatMember.Chat.ID)
+		if err != nil {
+			return
+		}
+
+		if chat != nil && chat.ID > 0 {
+			s.Payload.Chat = chat
+		}
+	}
+	if s.Payload.Chat != nil && s.Payload.Chat.ID > 0 {
+		user, _ := s.App.DB().ForUser().ByID(s.Payload.Chat.UserID)
+		if user != nil && user.ID > 0 && user.ChatID > 0 {
+			_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+				ChatID: tu.ID(user.ChatID),
+				Text: s.Localizer(user.Language).Template(
+					"bot_was_removed_from_group", map[string]interface{}{"Name": pl.Data.MyChatMember.Chat.Title}),
+				ParseMode: telego.ModeMarkdown,
+			})
+			s.LogError(err)
+		}
+		s.LogError(s.App.DB().ForChat().Delete(s.Payload.Chat))
+	}
+	s.Move(mc, WaitingForMemberWebhookStateID, pl)
+}
+
+func (s *RemoveChatMemberState) ID() fsm.StateID {
+	return RemoveChatMemberStateID
+}

internal/handler/fsmwizard/unknown_command_state.go

@@ -0,0 +1,32 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const UnknownCommandStateID fsm.StateID = "unknown_command"
+
+type UnknownCommandState struct {
+	State
+}
+
+func NewUnknownCommandState(app iface.App) fsm.IState[Wizard] {
+	return &UnknownCommandState{newBase(app)}
+}
+
+func (s *UnknownCommandState) Enter(pl *Wizard, _ fsm.MachineControls[Wizard]) error {
+	_, err := s.App.TG().SendMessage(&telego.SendMessageParams{
+		ChatID:    tu.ID(s.Payload.Data.Message.Chat.ID),
+		Text:      s.Localizer(s.Payload.Data.Message.From.LanguageCode).Message("unknown_command"),
+		ParseMode: telego.ModeMarkdown,
+	})
+	s.LogError(err)
+	return fsm.ErrPreventTransition
+}
+
+func (s *UnknownCommandState) ID() fsm.StateID {
+	return UnknownCommandStateID
+}

internal/handler/fsmwizard/waiting_for_member_webhook_state.go

@@ -0,0 +1,51 @@
+package fsmwizard
+
+import (
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/fsm"
+	"github.com/mymmrac/telego"
+	tu "github.com/mymmrac/telego/telegoutil"
+)
+
+const WaitingForMemberWebhookStateID fsm.StateID = "waiting_for_member_webhook"
+
+type WaitingForMemberWebhookState struct {
+	State
+}
+
+func NewWaitingForMemberWebhookState(app iface.App) fsm.IState[Wizard] {
+	return &WaitingForMemberWebhookState{newBase(app)}
+}
+
+func (s *WaitingForMemberWebhookState) Enter(pl *Wizard, mc fsm.MachineControls[Wizard]) error {
+	cm := pl.Data.MyChatMember
+	if cm == nil {
+		return nil
+	}
+	if !cm.OldChatMember.MemberIsMember() && cm.OldChatMember.MemberUser().ID == s.App.TGProfile().ID &&
+		cm.NewChatMember.MemberIsMember() && cm.NewChatMember.MemberUser().ID == s.App.TGProfile().ID {
+		s.MoveForHandle(mc, AddChatMemberStateID, pl)
+		return nil
+	}
+	if cm.OldChatMember.MemberIsMember() && cm.OldChatMember.MemberUser().ID == s.App.TGProfile().ID &&
+		!cm.NewChatMember.MemberIsMember() && cm.NewChatMember.MemberUser().ID == s.App.TGProfile().ID {
+		s.MoveForHandle(mc, RemoveChatMemberStateID, pl)
+		return nil
+	}
+
+	s.LogError(s.App.TG().LeaveChat(&telego.LeaveChatParams{
+		ChatID: tu.ID(pl.Data.MyChatMember.Chat.ID),
+	}))
+	return nil
+}
+
+func (s *WaitingForMemberWebhookState) Handle(pl *Wizard, mc fsm.MachineControls[Wizard]) {
+	// By using this we can handle both Move from Register state and Move from waiting for webhook state.
+	// The first one doesn't have data yet and it will be handled by Handle, the second one has data and will be
+	// handled by Enter.
+	_ = s.Enter(pl, mc)
+}
+
+func (s *WaitingForMemberWebhookState) ID() fsm.StateID {
+	return WaitingForMemberWebhookStateID
+}

internal/handler/new_message_handler.go

@@ -1,11 +1,8 @@
 package handler
 
 import (
-	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/group"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/fsmwizard"
 	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/iface"
-	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/store"
-	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/util"
-	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/internal/handler/wizard"
 	"github.com/mymmrac/telego"
 )
 
@@ -22,26 +19,30 @@ func (h *MessageHandler) Handle(wh telego.Update) error {
 		return nil
 	}
 
-	if util.MatchCommand("start", wh.Message) {
-		return wizard.NewRegister(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
-	}
+	return fsmwizard.Get(wh.Message.From.ID).Handle(func(w *fsmwizard.Wizard) *fsmwizard.Wizard {
+		if w == nil {
+			return &fsmwizard.Wizard{Data: wh}
+		}
+		w.Data = wh
+		return w
+	})
 
-	if util.MatchCommand("poll", wh.Message) {
-		return group.NewPoll(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
-	}
-
-	if util.MatchCommand("start", wh.Message) {
-		return wizard.NewRegister(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
-	}
-
-	setup, found := store.RedmineSetups.Get(wh.Message.Chat.ID)
-	if found {
-		return wizard.NewRedmineSetup(h.App, wh.Message.From.ID, wh.Message.Chat.ID, setup).Handle(wh)
-	}
-
-	if util.MatchCommand("help", wh.Message) {
-		return wizard.NewHelpCommand(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
-	}
-
-	return wizard.NewUnknownCommand(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
+	// if util.MatchCommand("start", wh.Message) {
+	// 	return wizard.NewRegister(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
+	// }
+	//
+	// if util.MatchCommand("poll", wh.Message) {
+	// 	return group.NewPoll(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
+	// }
+	//
+	// setup, found := store.RedmineSetups.Get(wh.Message.Chat.ID)
+	// if found {
+	// 	return wizard.NewRedmineSetup(h.App, wh.Message.From.ID, wh.Message.Chat.ID, setup).Handle(wh)
+	// }
+	//
+	// if util.MatchCommand("help", wh.Message) {
+	// 	return wizard.NewHelpCommand(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
+	// }
+	//
+	// return wizard.NewUnknownCommand(h.App, wh.Message.From.ID, wh.Message.Chat.ID).Handle(wh)
 }

internal/handler/util/command.go

@@ -8,3 +8,10 @@ import (
 func MatchCommand(command string, msg *telego.Message) bool {
 	return th.CommandEqual(command)(telego.Update{Message: msg})
 }
+
+func HasCommand(msg *telego.Message) bool {
+	if msg == nil {
+		return false
+	}
+	return th.CommandRegexp.MatchString(msg.Text)
+}

internal/handler/wizard/doc.go

@@ -0,0 +1,3 @@
+// Package wizard contains setup wizard implementation.
+// Deprecated: will be replaced with fsmwizard in the future.
+package wizard

internal/locale/load.go

@@ -32,7 +32,7 @@ func init() {
 	}
 
 	for _, tag := range tags {
-		localizers[tag.String()] = &localizer{loc: i18n.NewLocalizer(bundle, tag.String())}
+		localizers[tag.String()] = &localizer{loc: i18n.NewLocalizer(bundle, tag.String()), tag: tag}
 	}
 }
 

internal/locale/localizer.go

@@ -1,14 +1,19 @@
 package locale
 
-import "github.com/nicksnyder/go-i18n/v2/i18n"
+import (
+	"github.com/nicksnyder/go-i18n/v2/i18n"
+	"golang.org/x/text/language"
+)
 
 type Localizer interface {
 	Message(string) string
 	Template(string, interface{}) string
+	Tag() language.Tag
 }
 
 type localizer struct {
 	loc *i18n.Localizer
+	tag language.Tag
 }
 
 func (l *localizer) Message(str string) string {
@@ -21,3 +26,7 @@ func (l *localizer) Template(str string, tpl interface{}) string {
 		TemplateData: tpl,
 	})
 }
+
+func (l *localizer) Tag() language.Tag {
+	return l.tag
+}

pkg/fsm/machine.go

@@ -0,0 +1,147 @@
+package fsm
+
+import (
+	"errors"
+	"fmt"
+	"gitea.neur0tx.site/Neur0toxine/vegapokerbot/pkg/types"
+)
+
+var (
+	// ErrPreventTransition should be returned from Enter if you don't want to perform a state transition and
+	// everything that needed to be done has been done in Enter callback.
+	ErrPreventTransition = errors.New("prevents transition; this is not an error")
+	// ErrStateDoesNotExist will be returned if provided state ID does not exist in this machine.
+	ErrStateDoesNotExist = errors.New("state does not exist")
+)
+
+// MachineStateRouter should be provided to IMachine. This function can do two very useful things:
+// - It can modify Machine's payload.
+// - It can act as a router by changing Machine's state via provided controls.
+type MachineStateRouter[T any] func(*T, MachineControlsWithState[T])
+
+// MachineStateProvider provided to every Handle call. It can be used to set the initial state of the machine or to
+// update existing machine state.
+type MachineStateProvider[T any] func(*T) *T
+
+// IMachine is a Machine contract. The Machine should be able to do the following:
+//   - Move to another state (usually called by the IState itself).
+//   - Handle the state input.
+//   - Reset the machine.
+type IMachine[T any] interface {
+	MachineControlsWithState[T]
+	// Handle the state input. Handle func will accept the current payload and modify it based on user input.
+	Handle(MachineStateProvider[T]) error
+	// Reset the machine to its initial state.
+	Reset()
+}
+
+// Machine is a finite-state machine implementation.
+type Machine[T any] struct {
+	payload      *T
+	stateRouter  MachineStateRouter[T]
+	state        StateID
+	initialState StateID
+	states       *types.Map[StateID, IState[T]]
+	errHandler   ErrorState[T]
+	handleNow    bool
+}
+
+// New machine.
+func New[T any](initialState StateID, router MachineStateRouter[T], states []IState[T], errHandler ErrorState[T]) IMachine[T] {
+	stateMap := types.NewMap[StateID, IState[T]]()
+	for _, state := range states {
+		stateMap.Set(state.ID(), state)
+	}
+	return &Machine[T]{
+		state:        initialState,
+		stateRouter:  router,
+		initialState: initialState,
+		states:       stateMap,
+		errHandler:   errHandler,
+	}
+}
+
+// Move to another state.
+// Internal: should never be called outside state callbacks.
+func (m *Machine[T]) Move(id StateID, payload *T) error {
+	if id == m.state {
+		return nil
+	}
+	next, err := m.loadState(id, payload)
+	if next == nil || err != nil {
+		return err
+	}
+	cur, err := m.loadState(m.state, payload)
+	if err != nil {
+		return err
+	}
+	if cur != nil {
+		cur.Exit(payload)
+	}
+	if err := next.Enter(payload, m); err != nil {
+		if errors.Is(err, ErrPreventTransition) {
+			return nil
+		}
+		m.Reset()
+		return err
+	}
+	m.state = id
+	m.payload = payload
+	return nil
+}
+
+func (m *Machine[T]) MoveForHandle(id StateID, payload *T) error {
+	m.handleNow = true
+	return m.Move(id, payload)
+}
+
+// Handle the input.
+func (m *Machine[T]) Handle(provider MachineStateProvider[T]) error {
+	if provider != nil {
+		m.payload = provider(m.payload)
+	}
+	if m.stateRouter != nil {
+		m.stateRouter(m.payload, m)
+	}
+	st, err := m.loadState(m.state, m.payload)
+	if st == nil || err != nil {
+		return err
+	}
+	for {
+		st.Handle(m.payload, m)
+		if m.handleNow { // MoveForHandle was called, trying to handle again.
+			m.handleNow = false
+			continue
+		}
+		return nil
+	}
+}
+
+// State of the Machine.
+func (m *Machine[T]) State() *T {
+	return m.payload
+}
+
+// Reset the machine.
+func (m *Machine[T]) Reset() {
+	m.payload = nil
+	m.state = m.initialState
+}
+
+func (m *Machine[T]) loadState(id StateID, payload *T) (IState[T], error) {
+	if id == NilStateID {
+		return nil, nil
+	}
+	st, ok := m.states.Get(id)
+	if !ok {
+		return nil, m.fatalError(fmt.Errorf("%w: %s", ErrStateDoesNotExist, id), id, payload)
+	}
+	return st, nil
+}
+
+func (m *Machine[T]) fatalError(err error, id StateID, payload *T) error {
+	if m.errHandler != nil {
+		m.errHandler.Handle(err, m.state, id, payload, m)
+	}
+	return nil
+}

pkg/fsm/state.go

@@ -0,0 +1,85 @@
+package fsm
+
+// StateID is a state identifier. Machine with string state IDs can have *a lot of* states.
+type StateID string
+
+// NilStateID is a noop state. Machine won't do anything for this transition.
+const NilStateID = StateID("")
+
+// MachineControls is a fragment of IMachine implementation. This one can Move between the states or Reset the machine.
+// It may fail with an error which should be handled by the IState implementation.
+type MachineControls[T any] interface {
+	Move(StateID, *T) error
+	// MoveForHandle is the same as Move but it also triggers Handle immediately for the next state.
+	MoveForHandle(StateID, *T) error
+	Reset()
+}
+
+// MachineState returns machine state. This state should be immutable.
+type MachineState[T any] interface {
+	// State returns underlying state. This state SHOULD NOT be modified since there is no locking performed.
+	State() *T
+}
+
+// MachineControlsWithState is self-explanatory.
+type MachineControlsWithState[T any] interface {
+	MachineControls[T]
+	MachineState[T]
+}
+
+// IState is a State interface. This contract enforces that any state implementation should have three methods:
+// Enter, Handle and Exit. The first one is called right after the machine has moved to the state, the second one is
+// called when handling some state input, the last one is called right before leaving to a next state (which happens
+// if Handle has called Move on MachineControls.
+type IState[T any] interface {
+	// ID should return state identifier.
+	ID() StateID
+	// Enter is a state enter callback. Can be used to perform some sort of input query or to move to another
+	// state immediately. Also, if Enter fails the machine won't move to the state and MachineControls's Move will
+	// return an error which was returned from Enter.
+	Enter(*T, MachineControls[T]) error
+	// Handle is called when receiving some sort of input response. This one's signature is nearly identical to Enter,
+	// but it can wait for some sort of input (standard input? webhook) without locking inside the callback
+	// while Enter cannot do that.
+	Handle(*T, MachineControls[T])
+	// Exit is called right before leaving the state. It can be used to modify state's payload (T) or for some other
+	// miscellaneous tasks.
+	// Note: calling Exit doesn't mean that the machine will really transition to the next state.
+	// The next state's Enter callback can return an error which will reset the Machine to default state & payload.
+	Exit(*T)
+}
+
+// ErrorState is the Machine's fatal error handler which you should implement yourself.
+//
+// Error state is used by Machine in case of a fatal error (for example, for invalid state ID).
+// You can use ErrorState to make some kind of fatal error response like "Internal error has occurred"
+// or something similar. Also, ErrorState is special because neither Enter nor Exit exists in it.
+//
+// Machine without ErrorState will not do anything in case of fatal errors.
+type ErrorState[T any] interface {
+	Handle(err error, current StateID, next StateID, payload *T, machine MachineControls[T])
+}
+
+// State is the Machine's state. This implementation doesn't do anything and only helps with the
+// actual IState implementation (you don't need to write empty Enter and Exit callback if you don't use them).
+type State[T any] struct {
+	Payload *T
+}
+
+// ID panics because you need to implement it.
+func (s *State[T]) ID() StateID {
+	panic("implement ID() StateID method for your state")
+}
+
+// Enter here will immediately move the Machine to empty state.
+func (s *State[T]) Enter(payload *T, machine MachineControls[T]) error {
+	return machine.Move(NilStateID, payload)
+}
+
+// Handle here will immediately move the Machine to empty state.
+func (s *State[T]) Handle(payload *T, machine MachineControls[T]) {
+	_ = machine.Move(NilStateID, payload)
+}
+
+// Exit won't do anything.
+func (s *State[T]) Exit(*T) {}

pkg/types/map.go

@@ -0,0 +1,27 @@
+package types
+
+import (
+	"sync"
+)
+
+type Map[K comparable, V any] struct {
+	rw sync.RWMutex
+	m  map[K]V
+}
+
+func NewMap[K comparable, V any]() *Map[K, V] {
+	return &Map[K, V]{m: make(map[K]V)}
+}
+
+func (t *Map[K, V]) Set(k K, v V) {
+	defer t.rw.Unlock()
+	t.rw.Lock()
+	t.m[k] = v
+}
+
+func (t *Map[K, V]) Get(k K) (val V, ok bool) {
+	defer t.rw.RUnlock()
+	t.rw.RLock()
+	val, ok = t.m[k]
+	return
+}

pkg/types/queue.go

@@ -0,0 +1,62 @@
+package types
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+type node[T any] struct {
+	val  atomic.Pointer[T]
+	next atomic.Pointer[node[T]]
+}
+
+type Queue[T any] interface {
+	Enqueue(T)
+	Dequeue() T
+	Len() uint64
+}
+
+type queue[T any] struct {
+	head, tail *node[T]
+	length     atomic.Uint64
+}
+
+func NewQueue[T any]() Queue[T] {
+	n := node[T]{}
+	return &queue[T]{head: &n, tail: &n}
+}
+
+func (q *queue[T]) Enqueue(v T) {
+	n := node[T]{val: atomic.Pointer[T]{}}
+	n.val.Store(&v)
+	for {
+		if q.tail.next.CompareAndSwap(nil, &n) {
+			atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&q.tail)), unsafe.Pointer(&n))
+			q.length.Add(1)
+			return
+		}
+	}
+}
+
+func (q *queue[T]) Dequeue() T {
+	headAddr := (*unsafe.Pointer)(unsafe.Pointer(&q.head))
+	for {
+		var result T
+		head := atomic.LoadPointer(headAddr)
+		n := q.head.next.Load()
+		if n == nil {
+			return result
+		}
+		if atomic.CompareAndSwapPointer(headAddr, head, unsafe.Pointer(n)) {
+			q.length.Add(^uint64(0)) // Переполнение намеренное, это отнимает единицу от счетчика.
+			if r := n.val.Load(); r != nil {
+				return *r
+			}
+			return result
+		}
+	}
+}
+
+func (q *queue[T]) Len() uint64 {
+	return q.length.Load()
+}

pkg/types/queue_test.go

@@ -0,0 +1,19 @@
+package types
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestQueue(t *testing.T) {
+	q := NewQueue[uint8]()
+	assert.Equal(t, uint64(0), q.Len())
+	assert.Equal(t, uint8(0), q.Dequeue())
+
+	q.Enqueue(1)
+	q.Enqueue(2)
+	assert.Equal(t, uint64(2), q.Len())
+	assert.Equal(t, uint8(1), q.Dequeue())
+	assert.Equal(t, uint8(2), q.Dequeue())
+	assert.Equal(t, uint8(0), q.Dequeue())
+}

pkg/types/ttl_map.go

@@ -0,0 +1,63 @@
+package types
+
+import (
+	"sync"
+	"time"
+)
+
+type TTLMap[K comparable, V any] struct {
+	rw  sync.RWMutex
+	m   map[K]entry[V]
+	ttl time.Duration
+}
+
+type entry[V any] struct {
+	value    V
+	expireAt *time.Time
+}
+
+func (e *entry[V]) expired() bool {
+	if e.expireAt == nil {
+		return false
+	}
+	return time.Now().After(*e.expireAt)
+}
+
+func NewTTLMap[K comparable, V any](ttl time.Duration) *TTLMap[K, V] {
+	return &TTLMap[K, V]{m: make(map[K]entry[V]), ttl: ttl}
+}
+
+func (t *TTLMap[K, V]) Set(k K, v V) {
+	t.SetWithTTL(k, v, t.ttl)
+}
+
+func (t *TTLMap[K, V]) SetWithTTL(k K, v V, ttl time.Duration) {
+	defer t.rw.Unlock()
+	t.rw.Lock()
+	var expireAt *time.Time
+	if ttl > 0 {
+		at := time.Now().Add(ttl)
+		expireAt = &at
+	}
+	t.m[k] = entry[V]{value: v, expireAt: expireAt}
+}
+
+func (t *TTLMap[K, V]) Get(k K) (val V, ok bool) {
+	defer t.rw.RUnlock()
+	t.rw.RLock()
+	v, ok := t.m[k]
+	if !ok {
+		return
+	}
+	if v.expired() {
+		defer func() {
+			t.rw.RUnlock()
+			t.rw.Lock()
+			delete(t.m, k)
+			t.rw.Unlock()
+			t.rw.RLock()
+		}()
+		return
+	}
+	return v.value, true
+}