commit e03a70cfc833771d10842d804c41a0fc3692856c
Author: Maksim Pischulenok <pischule@outlook.com>
Date:   Tue May 18 00:04:51 2021 +0300

    Initial commit

diff --git a/main.go b/main.go
new file mode 100644
index 0000000..c76f0b8
--- /dev/null
+++ b/main.go
@@ -0,0 +1,133 @@
+package main
+
+import (
+	"fmt"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+	"log"
+	"os"
+	"strings"
+	"time"
+
+	tb "gopkg.in/tucnak/telebot.v2"
+)
+
+type ChatUser struct {
+	ChatID   int64 `gorm:"primaryKey"`
+	UserID   int   `gorm:"primaryKey"`
+	Username string
+}
+
+func main() {
+	db, err := gorm.Open(sqlite.Open("bot_db.db"), &gorm.Config{})
+	if err != nil {
+		panic("failed to connect database")
+	}
+
+	// Migrate the schema
+	err = db.AutoMigrate(&ChatUser{})
+	if err != nil {
+		panic("failed to migrate")
+	}
+
+	b, err := tb.NewBot(tb.Settings{
+		Token:  os.Getenv("TOKEN"),
+		Poller: &tb.LongPoller{Timeout: 10 * time.Second},
+	})
+
+	if err != nil {
+		log.Fatal(err)
+		return
+	}
+
+	b.Handle("/start", func(m *tb.Message) {
+		_, err := b.Send(
+			m.Sender, "Hey! I can help notify everyone 📢 in the group when someone needs them.\n"+
+				"Everyone who wishes to receive mentions needs to /in to opt-in. "+
+				"All opted-in users can then be mentioned using /all",
+		)
+		if err != nil {
+			log.Println(err)
+			return
+		}
+	})
+
+	b.Handle("/in", func(m *tb.Message) {
+		user := m.Sender
+
+		username := "anonymous"
+		if len(user.Username) > 0 {
+			username = user.Username
+		} else if len(user.FirstName) > 0 {
+			username = user.FirstName
+		}
+
+		db.Clauses(clause.OnConflict{
+			Columns:   []clause.Column{{Name: "chat_id"}, {Name: "user_id"}},
+			DoUpdates: clause.AssignmentColumns([]string{"username"}),
+		}).Create(&ChatUser{ChatID: m.Chat.ID, UserID: user.ID, Username: username})
+
+		msg := fmt.Sprintf("Thanks for opting in %s", username)
+
+		_, err := b.Send(m.Chat, msg)
+		if err != nil {
+			log.Println("/in", err)
+			return
+		}
+	})
+
+	b.Handle("/all", func(m *tb.Message) {
+		var users []ChatUser
+		db.Find(&users, ChatUser{ChatID: m.Chat.ID})
+
+		var usersList []string
+
+		for _, chatUser := range users {
+			usersList = append(usersList, fmt.Sprintf("[yolo](tg://user?id=%v)", chatUser.UserID))
+		}
+
+		msg := strings.Join(usersList, " ")
+
+		if len(users) == 0 {
+			msg = "There are no users\\. To opt in type /in command"
+		}
+
+		_, err := b.Send(m.Chat, msg, tb.ModeMarkdownV2)
+
+		if err != nil {
+			log.Println("/all", err)
+			return
+		}
+	})
+
+	b.Handle("/out", func(m *tb.Message) {
+		db.Where("chat_id = ? and user_id = ?", m.Chat.ID, m.Sender.ID).Delete(&ChatUser{})
+
+		msg := fmt.Sprintf("You've been opted out %v", m.Sender.ID)
+
+		_, err := b.Send(m.Chat, msg)
+		if err != nil {
+			log.Println("/out", err)
+			return
+		}
+	})
+
+	b.Handle("/stats", func(m *tb.Message) {
+		var userCount int64
+		var chatCount int64
+
+		db.Model(&ChatUser{}).Distinct("user_id").Count(&userCount)
+		db.Model(&ChatUser{}).Distinct("chat_id").Count(&chatCount)
+
+		msg := fmt.Sprintf("Users: %5d\nChats: %5d", userCount, chatCount)
+
+		_, err := b.Send(m.Chat, msg)
+		if err != nil {
+			log.Println(err)
+			return
+		}
+	})
+
+	b.Start()
+}