feat: add a new command - /monitor create (#21)

Reviewed-on: #21

cmd/dcbot/internal/run/run.go

@@ -39,15 +39,17 @@ func New() *cli.Command {
 			}
 
 			groupRepo := bundb.NewGroup(db)
+			monitorRepo := bundb.NewMonitor(db)
 
 			groupSvc := service.NewGroup(groupRepo, client)
+			monitorSvc := service.NewMonitor(monitorRepo, groupRepo, client)
 
 			cfg, err := newBotConfig()
 			if err != nil {
 				return fmt.Errorf("newBotConfig: %w", err)
 			}
 
-			bot, err := discord.NewBot(cfg.Token, groupSvc, client)
+			bot, err := discord.NewBot(cfg.Token, groupSvc, monitorSvc, client)
 			if err != nil {
 				return fmt.Errorf("discord.NewBot: %w", err)
 			}

internal/bundb/group.go

@@ -79,12 +79,35 @@ func (g *Group) List(ctx context.Context, params domain.ListGroupsParams) ([]dom
 	}
 
 	result := make([]domain.Group, 0, len(groups))
-	for _, version := range groups {
-		result = append(result, version.ToDomain())
+	for _, group := range groups {
+		result = append(result, group.ToDomain())
 	}
+
 	return result, nil
 }
 
+func (g *Group) Get(ctx context.Context, id, serverID string) (domain.Group, error) {
+	if _, err := uuid.Parse(id); err != nil {
+		return domain.Group{}, domain.GroupNotFoundError{ID: id}
+	}
+
+	var group model.Group
+
+	err := g.db.NewSelect().
+		Model(&group).
+		Where("id = ?", id).
+		Where("server_id = ?", serverID).
+		Scan(ctx)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return domain.Group{}, domain.GroupNotFoundError{ID: id}
+		}
+		return domain.Group{}, fmt.Errorf("couldn't select group (id=%s,serverID=%s) from the db: %w", id, serverID, err)
+	}
+
+	return group.ToDomain(), nil
+}
+
 func (g *Group) Delete(ctx context.Context, id, serverID string) error {
 	if _, err := uuid.Parse(id); err != nil {
 		return domain.GroupNotFoundError{ID: id}

internal/bundb/group_test.go

@@ -50,7 +50,7 @@ func TestGroup_Update(t *testing.T) {
 	db := newDB(t)
 	fixture := loadFixtures(t, db)
 	repo := bundb.NewGroup(db)
-	group := getGroupFromFixture(t, fixture, "group-server-1-1")
+	group := getGroupFromFixture(t, fixture, "group-1-server-1")
 
 	t.Run("OK", func(t *testing.T) {
 		t.Parallel()
@@ -80,45 +80,47 @@ func TestGroup_Update(t *testing.T) {
 		assert.Zero(t, updatedGroup)
 	})
 
-	t.Run("ERR: invalid UUID", func(t *testing.T) {
+	t.Run("ERR: group not found", func(t *testing.T) {
 		t.Parallel()
 
-		id := "12345"
-		updatedGroup, err := repo.Update(context.Background(), id, "", domain.UpdateGroupParams{
-			ChannelGains: domain.NullString{
-				String: "update",
-				Valid:  true,
+		tests := []struct {
+			name     string
+			id       string
+			serverID string
+		}{
+			{
+				name:     "ID - not UUID",
+				id:       "test",
+				serverID: group.ServerID,
 			},
-		})
-		assert.ErrorIs(t, err, domain.GroupNotFoundError{ID: id})
-		assert.Zero(t, updatedGroup)
-	})
-
-	t.Run("ERR: group not found (unknown ID)", func(t *testing.T) {
-		t.Parallel()
-
-		id := uuid.NewString()
-		updatedGroup, err := repo.Update(context.Background(), id, group.ServerID, domain.UpdateGroupParams{
-			ChannelGains: domain.NullString{
-				String: "update",
-				Valid:  true,
+			{
+				name:     "ID - random UUID",
+				id:       uuid.NewString(),
+				serverID: group.ServerID,
 			},
-		})
-		assert.ErrorIs(t, err, domain.GroupNotFoundError{ID: id})
-		assert.Zero(t, updatedGroup)
-	})
-
-	t.Run("ERR: group not found (unknown ServerID)", func(t *testing.T) {
-		t.Parallel()
-
-		updatedGroup, err := repo.Update(context.Background(), group.ID.String(), uuid.NewString(), domain.UpdateGroupParams{
-			ChannelGains: domain.NullString{
-				String: "update",
-				Valid:  true,
+			{
+				name:     "ServerID - random UUID",
+				id:       group.ID.String(),
+				serverID: uuid.NewString(),
 			},
-		})
-		assert.ErrorIs(t, err, domain.GroupNotFoundError{ID: group.ID.String()})
-		assert.Zero(t, updatedGroup)
+		}
+
+		for _, tt := range tests {
+			tt := tt
+
+			t.Run(tt.name, func(t *testing.T) {
+				t.Parallel()
+
+				updatedGroup, err := repo.Update(context.Background(), tt.id, tt.serverID, domain.UpdateGroupParams{
+					ChannelGains: domain.NullString{
+						String: "update",
+						Valid:  true,
+					},
+				})
+				assert.ErrorIs(t, err, domain.GroupNotFoundError{ID: tt.id})
+				assert.Zero(t, updatedGroup)
+			})
+		}
 	})
 }
 
@@ -180,13 +182,65 @@ func TestGroup_List(t *testing.T) {
 	}
 }
 
+func TestGroup_Get(t *testing.T) {
+	t.Parallel()
+
+	db := newDB(t)
+	fixture := loadFixtures(t, db)
+	repo := bundb.NewGroup(db)
+	group := getGroupFromFixture(t, fixture, "group-1-server-1")
+
+	t.Run("OK", func(t *testing.T) {
+		t.Parallel()
+
+	})
+
+	t.Run("ERR: group not found (unknown ID)", func(t *testing.T) {
+		t.Parallel()
+
+		tests := []struct {
+			name     string
+			id       string
+			serverID string
+		}{
+			{
+				name:     "ID - not UUID",
+				id:       "test",
+				serverID: group.ServerID,
+			},
+			{
+				name:     "ID - random UUID",
+				id:       uuid.NewString(),
+				serverID: group.ServerID,
+			},
+			{
+				name:     "ServerID - random UUID",
+				id:       group.ID.String(),
+				serverID: uuid.NewString(),
+			},
+		}
+
+		for _, tt := range tests {
+			tt := tt
+
+			t.Run(tt.name, func(t *testing.T) {
+				t.Parallel()
+
+				g, err := repo.Get(context.Background(), tt.id, tt.serverID)
+				assert.ErrorIs(t, err, domain.GroupNotFoundError{ID: tt.id})
+				assert.Zero(t, g)
+			})
+		}
+	})
+}
+
 func TestGroup_Delete(t *testing.T) {
 	t.Parallel()
 
 	db := newDB(t)
 	fixture := loadFixtures(t, db)
 	repo := bundb.NewGroup(db)
-	group := getGroupFromFixture(t, fixture, "group-server-1-1")
+	group := getGroupFromFixture(t, fixture, "group-1-server-1")
 
 	t.Run("OK", func(t *testing.T) {
 		t.Parallel()
@@ -200,32 +254,44 @@ func TestGroup_Delete(t *testing.T) {
 		assert.Len(t, groups, 0)
 	})
 
-	t.Run("ERR: invalid UUID", func(t *testing.T) {
+	t.Run("ERR: group not found", func(t *testing.T) {
 		t.Parallel()
 
-		id := "12345"
-		assert.ErrorIs(t, repo.Delete(context.Background(), id, ""), domain.GroupNotFoundError{ID: id})
-	})
+		tests := []struct {
+			name     string
+			id       string
+			serverID string
+		}{
+			{
+				name:     "ID - not UUID",
+				id:       "test",
+				serverID: group.ServerID,
+			},
+			{
+				name:     "ID - random UUID",
+				id:       uuid.NewString(),
+				serverID: group.ServerID,
+			},
+			{
+				name:     "ServerID - random UUID",
+				id:       group.ID.String(),
+				serverID: uuid.NewString(),
+			},
+		}
 
-	t.Run("ERR: group not found (unknown ID)", func(t *testing.T) {
-		t.Parallel()
+		for _, tt := range tests {
+			tt := tt
 
-		id := uuid.NewString()
-		assert.ErrorIs(
-			t,
-			repo.Delete(context.Background(), id, group.ServerID),
-			domain.GroupNotFoundError{ID: id},
-		)
-	})
+			t.Run(tt.name, func(t *testing.T) {
+				t.Parallel()
 
-	t.Run("ERR: group not found (unknown ServerID)", func(t *testing.T) {
-		t.Parallel()
-
-		assert.ErrorIs(
-			t,
-			repo.Delete(context.Background(), group.ID.String(), uuid.NewString()),
-			domain.GroupNotFoundError{ID: group.ID.String()},
-		)
+				assert.ErrorIs(
+					t,
+					repo.Delete(context.Background(), tt.id, tt.serverID),
+					domain.GroupNotFoundError{ID: tt.id},
+				)
+			})
+		}
 	})
 }
 
@@ -233,7 +299,7 @@ func getAllGroupsFromFixture(tb testing.TB, fixture *dbfixture.Fixture) []model.
 	tb.Helper()
 
 	//nolint:lll
-	ids := []string{"group-server-1-1", "group-server-1-2", "group-server-2-1", "group-server-2-2"}
+	ids := []string{"group-1-server-1", "group-2-server-1", "group-1-server-2", "group-2-server-2"}
 
 	groups := make([]model.Group, 0, len(ids))
 	for _, id := range ids {

internal/bundb/internal/model/monitor.go

@@ -0,0 +1,27 @@
+package model
+
+import (
+	"time"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
+	"github.com/google/uuid"
+	"github.com/uptrace/bun"
+)
+
+type Monitor struct {
+	bun.BaseModel `bun:"base_model,table:monitors,alias:monitor"`
+
+	ID        uuid.UUID `bun:"id,type:uuid,pk,default:gen_random_uuid()"`
+	GroupID   uuid.UUID `bun:"group_id,type:uuid,notnull,unique:monitors_group_id_tribe_id_key"`
+	TribeID   int64     `bun:"tribe_id,notnull,unique:monitors_group_id_tribe_id_key"`
+	CreatedAt time.Time `bun:"created_at,nullzero,notnull,default:current_timestamp"`
+}
+
+func (m Monitor) ToDomain() domain.Monitor {
+	return domain.Monitor{
+		ID:        m.ID.String(),
+		GroupID:   m.GroupID.String(),
+		TribeID:   m.TribeID,
+		CreatedAt: m.CreatedAt,
+	}
+}

internal/bundb/migrations/20221022051838_create_monitors_table.go

@@ -0,0 +1,31 @@
+package migrations
+
+import (
+	"context"
+	"fmt"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/bundb/internal/model"
+	"github.com/uptrace/bun"
+)
+
+func init() {
+	Migrations.MustRegister(func(ctx context.Context, db *bun.DB) error {
+		if _, err := db.NewCreateTable().
+			Model(&model.Monitor{}).
+			Varchar(defaultVarcharLength).
+			ForeignKey(`(group_id) REFERENCES groups (id) ON DELETE CASCADE`).
+			Exec(ctx); err != nil {
+			return fmt.Errorf("couldn't create the 'monitors' table: %w", err)
+		}
+		return nil
+	}, func(ctx context.Context, db *bun.DB) error {
+		if _, err := db.NewDropTable().
+			Model(&model.Group{}).
+			IfExists().
+			Cascade().
+			Exec(ctx); err != nil {
+			return fmt.Errorf("couldn't drop the 'monitors' table: %w", err)
+		}
+		return nil
+	})
+}

internal/bundb/monitor.go

@@ -0,0 +1,95 @@
+package bundb
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/bundb/internal/model"
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
+	"github.com/google/uuid"
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/driver/pgdriver"
+)
+
+type Monitor struct {
+	db *bun.DB
+}
+
+func NewMonitor(db *bun.DB) *Monitor {
+	return &Monitor{db: db}
+}
+
+func (m *Monitor) Create(ctx context.Context, params domain.CreateMonitorParams) (domain.Monitor, error) {
+	groupID, err := uuid.Parse(params.GroupID())
+	if err != nil {
+		return domain.Monitor{}, domain.GroupDoesNotExistError{
+			ID: params.GroupID(),
+		}
+	}
+
+	monitor := model.Monitor{
+		GroupID: groupID,
+		TribeID: params.TribeID(),
+	}
+
+	if _, err = m.db.NewInsert().
+		Model(&monitor).
+		Returning("*").
+		Exec(ctx); err != nil {
+
+		return domain.Monitor{}, fmt.Errorf(
+			"something went wrong while inserting monitor into the db: %w",
+			mapCreateMonitorError(err, params),
+		)
+	}
+
+	return monitor.ToDomain(), nil
+}
+
+func (m *Monitor) List(ctx context.Context, groupID string) ([]domain.Monitor, error) {
+	if _, err := uuid.Parse(groupID); err != nil {
+		return nil, nil
+	}
+
+	var monitors []model.Monitor
+
+	if err := m.db.NewSelect().
+		Model(&monitors).
+		Order("created_at ASC").
+		Where("group_id = ?", groupID).
+		Scan(ctx); err != nil && !errors.Is(err, sql.ErrNoRows) {
+		return nil, fmt.Errorf("couldn't select monitors from the db: %w", err)
+	}
+
+	result := make([]domain.Monitor, 0, len(monitors))
+	for _, monitor := range monitors {
+		result = append(result, monitor.ToDomain())
+	}
+
+	return result, nil
+}
+
+func mapCreateMonitorError(err error, params domain.CreateMonitorParams) error {
+	var pgError pgdriver.Error
+	if !errors.As(err, &pgError) {
+		return err
+	}
+
+	code := pgError.Field('C')
+	constraint := pgError.Field('n')
+	switch {
+	case code == "23503" && constraint == "monitors_group_id_fkey":
+		return domain.GroupDoesNotExistError{
+			ID: params.GroupID(),
+		}
+	case code == "23505" && constraint == "monitors_group_id_tribe_id_key":
+		return domain.MonitorAlreadyExistsError{
+			TribeID: params.TribeID(),
+			GroupID: params.GroupID(),
+		}
+	default:
+		return err
+	}
+}

internal/bundb/monitor_test.go

@@ -0,0 +1,140 @@
+package bundb_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/bundb"
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMonitor_Create(t *testing.T) {
+	t.Parallel()
+
+	db := newDB(t)
+	fixture := loadFixtures(t, db)
+	repo := bundb.NewMonitor(db)
+
+	t.Run("OK", func(t *testing.T) {
+		t.Parallel()
+
+		group := getGroupFromFixture(t, fixture, "group-1-server-1")
+
+		params, err := domain.NewCreateMonitorParams(group.ID.String(), 1234)
+		require.Zero(t, err)
+
+		monitor, err := repo.Create(context.Background(), params)
+		assert.NoError(t, err)
+		_, err = uuid.Parse(monitor.ID)
+		assert.NoError(t, err)
+		assert.Equal(t, params.GroupID(), monitor.GroupID)
+		assert.Equal(t, params.TribeID(), monitor.TribeID)
+		assert.WithinDuration(t, time.Now(), monitor.CreatedAt, 1*time.Second)
+
+		// check unique index
+		monitor, err = repo.Create(context.Background(), params)
+		assert.ErrorIs(t, err, domain.MonitorAlreadyExistsError{
+			TribeID: params.TribeID(),
+			GroupID: params.GroupID(),
+		})
+		assert.Zero(t, monitor)
+	})
+
+	t.Run("ERR: group doesn't exist", func(t *testing.T) {
+		t.Parallel()
+
+		t.Run("foreign key violation", func(t *testing.T) {
+			t.Parallel()
+
+			groupID := uuid.NewString()
+			params, err := domain.NewCreateMonitorParams(groupID, 1234)
+			require.Zero(t, err)
+
+			monitor, err := repo.Create(context.Background(), params)
+			assert.ErrorIs(t, err, domain.GroupDoesNotExistError{
+				ID: groupID,
+			})
+			assert.Zero(t, monitor)
+		})
+
+		t.Run("not UUID", func(t *testing.T) {
+			t.Parallel()
+
+			groupID := "592292203234328587"
+			params, err := domain.NewCreateMonitorParams(groupID, 1234)
+			require.Zero(t, err)
+
+			monitor, err := repo.Create(context.Background(), params)
+			assert.ErrorIs(t, err, domain.GroupDoesNotExistError{
+				ID: groupID,
+			})
+			assert.Zero(t, monitor)
+		})
+	})
+}
+
+func TestMonitor_List(t *testing.T) {
+	t.Parallel()
+
+	db := newDB(t)
+	fixture := loadFixtures(t, db)
+	repo := bundb.NewMonitor(db)
+
+	tests := []struct {
+		name             string
+		groupID          string
+		expectedMonitors []string
+	}{
+		{
+			name:    "group-1-server-1",
+			groupID: getGroupFromFixture(t, fixture, "group-1-server-1").ID.String(),
+			expectedMonitors: []string{
+				"e3017ba8-4fba-4bb1-ac8d-e4e9477a04d2",
+				"89719460-58ab-46b8-8682-46f161546949",
+			},
+		},
+		{
+			name:    "group-2-server-2",
+			groupID: getGroupFromFixture(t, fixture, "group-2-server-2").ID.String(),
+			expectedMonitors: []string{
+				"c7d63c3d-55f6-432e-b9d8-006f8c5ab407",
+			},
+		},
+		{
+			name:             "random UUID",
+			groupID:          uuid.NewString(),
+			expectedMonitors: nil,
+		},
+		{
+			name:             "not UUID",
+			groupID:          "test",
+			expectedMonitors: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			res, err := repo.List(context.Background(), tt.groupID)
+			assert.NoError(t, err)
+			assert.Len(t, res, len(tt.expectedMonitors))
+			for _, id := range tt.expectedMonitors {
+				found := false
+				for _, m := range res {
+					if m.ID == id {
+						found = true
+						break
+					}
+				}
+				assert.True(t, found, "monitor (id=%s) not found", id)
+			}
+		})
+	}
+}

internal/bundb/testdata/fixture.yml

@@ -1,26 +1,43 @@
 - model: Group
   rows:
-    - _id: group-server-1-1
+    - _id: group-1-server-1
       id: d56ad37f-2637-48ea-98f8-79627f3fcc96
       server_id: server-1
       server_key: pl181
       version_code: pl
       created_at: 2022-03-15T15:00:10.000Z
-    - _id: group-server-1-2
+    - _id: group-2-server-1
       id: 429b790e-7186-4106-b531-4cc4931ce2ba
       server_id: server-1
       server_key: pl181
       version_code: pl
       created_at: 2022-03-15T15:03:10.000Z
-    - _id: group-server-2-1
+    - _id: group-1-server-2
       id: abeb6c8e-70b6-445c-989f-890cd2a1f87a
       server_id: server-2
       server_key: pl181
       version_code: pl
       created_at: 2022-03-18T15:03:10.000Z
-    - _id: group-server-2-2
+    - _id: group-2-server-2
       id: 0be82203-4ca3-4b4c-a0c8-3a70099d88f7
       server_id: server-2
       server_key: pl181
       version_code: pl
-      created_at: 2022-03-19T15:03:10.000Z
+      created_at: 2022-03-19T15:03:10.000Z
+- model: Monitor
+  rows:
+    - _id: monitor-1-group-1-server-1
+      id: e3017ba8-4fba-4bb1-ac8d-e4e9477a04d2
+      group_id: d56ad37f-2637-48ea-98f8-79627f3fcc96
+      tribe_id: 123
+      created_at: 2022-03-15T15:01:10.000Z
+    - _id: monitor-2-group-1-server-1
+      id: 89719460-58ab-46b8-8682-46f161546949
+      group_id: d56ad37f-2637-48ea-98f8-79627f3fcc96
+      tribe_id: 15
+      created_at: 2022-03-15T15:02:10.000Z
+    - _id: monitor-1-group-2-server-2
+      id: c7d63c3d-55f6-432e-b9d8-006f8c5ab407
+      group_id: 0be82203-4ca3-4b4c-a0c8-3a70099d88f7
+      tribe_id: 121
+      created_at: 2022-03-19T15:10:10.000Z

internal/discord/bot.go

@@ -17,36 +17,52 @@ type GroupService interface {
 	Delete(ctx context.Context, id, serverID string) error
 }
 
+type MonitorService interface {
+	Create(ctx context.Context, groupID, serverID, tribeTag string) (domain.Monitor, error)
+}
+
 type TWHelpClient interface {
 	ListVersions(ctx context.Context) ([]twhelp.Version, error)
 }
 
 type Bot struct {
-	s        *discordgo.Session
-	groupSvc GroupService
-	client   TWHelpClient
+	s          *discordgo.Session
+	groupSvc   GroupService
+	monitorSvc MonitorService
+	client     TWHelpClient
 }
 
-func NewBot(token string, groupSvc GroupService, client TWHelpClient) (*Bot, error) {
+func NewBot(token string, groupSvc GroupService, monitorSvc MonitorService, client TWHelpClient) (*Bot, error) {
 	s, err := discordgo.New("Bot " + token)
 	if err != nil {
 		return nil, fmt.Errorf("discordgo.New: %w", err)
 	}
+
 	if err = s.Open(); err != nil {
 		return nil, fmt.Errorf("s.Open: %w", err)
 	}
-	b := &Bot{s: s, groupSvc: groupSvc, client: client}
+
+	b := &Bot{s: s, groupSvc: groupSvc, monitorSvc: monitorSvc, client: client}
 	if err = b.registerCommands(); err != nil {
 		_ = s.Close()
 		return nil, fmt.Errorf("couldn't register commands: %w", err)
 	}
+
 	return b, nil
 }
 
 func (b *Bot) registerCommands() error {
-	if err := b.registerCommand(&groupCommand{svc: b.groupSvc, client: b.client}); err != nil {
-		return err
+	commands := []command{
+		&groupCommand{svc: b.groupSvc, client: b.client},
+		&monitorCommand{svc: b.monitorSvc},
 	}
+
+	for _, c := range commands {
+		if err := b.registerCommand(c); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 

internal/discord/command_group.go

@@ -35,9 +35,10 @@ func (c *groupCommand) create(s *discordgo.Session) error {
 	}
 
 	var perm int64 = discordgo.PermissionAdministrator
+
 	_, err = s.ApplicationCommandCreate(s.State.User.ID, "", &discordgo.ApplicationCommand{
 		Name:                     c.name(),
-		Description:              "Manages monitor groups on this server",
+		Description:              "Manages groups on this server",
 		DefaultMemberPermissions: &perm,
 		Options: []*discordgo.ApplicationCommandOption{
 			{
@@ -185,6 +186,7 @@ func (c *groupCommand) create(s *discordgo.Session) error {
 	if err != nil {
 		return fmt.Errorf("s.ApplicationCommandCreate: %w", err)
 	}
+
 	return nil
 }
 

internal/discord/command_monitor.go

@@ -0,0 +1,118 @@
+package discord
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/bwmarrin/discordgo"
+)
+
+const (
+	tribeTagMaxLength = 10
+)
+
+type monitorCommand struct {
+	svc MonitorService
+}
+
+func (c *monitorCommand) name() string {
+	return "monitor"
+}
+
+func (c *monitorCommand) register(s *discordgo.Session) error {
+	if err := c.create(s); err != nil {
+		return err
+	}
+
+	s.AddHandler(c.handle)
+
+	return nil
+}
+
+func (c *monitorCommand) create(s *discordgo.Session) error {
+	var perm int64 = discordgo.PermissionAdministrator
+
+	_, err := s.ApplicationCommandCreate(s.State.User.ID, "", &discordgo.ApplicationCommand{
+		Name:                     c.name(),
+		Description:              "Manages monitors",
+		DefaultMemberPermissions: &perm,
+		Options: []*discordgo.ApplicationCommandOption{
+			{
+				Name:        "create",
+				Description: "Creates a new monitor",
+				Type:        discordgo.ApplicationCommandOptionSubCommand,
+				Options: []*discordgo.ApplicationCommandOption{
+					{
+						Name:        "group",
+						Description: "Group ID",
+						Type:        discordgo.ApplicationCommandOptionString,
+						Required:    true,
+					},
+					{
+						Name:        "tag",
+						Description: "Tribe tag",
+						Type:        discordgo.ApplicationCommandOptionString,
+						Required:    true,
+						MaxLength:   tribeTagMaxLength,
+					},
+				},
+			},
+		},
+	})
+	if err != nil {
+		return fmt.Errorf("s.ApplicationCommandCreate: %w", err)
+	}
+
+	return nil
+}
+
+func (c *monitorCommand) handle(s *discordgo.Session, i *discordgo.InteractionCreate) {
+	cmdData := i.ApplicationCommandData()
+
+	if cmdData.Name != c.name() {
+		return
+	}
+
+	switch cmdData.Options[0].Name {
+	case "create":
+		c.handleCreate(s, i)
+		return
+	default:
+	}
+}
+
+func (c *monitorCommand) handleCreate(s *discordgo.Session, i *discordgo.InteractionCreate) {
+	ctx := context.Background()
+
+	group := ""
+	tag := ""
+	for _, opt := range i.ApplicationCommandData().Options[0].Options {
+		if opt == nil {
+			continue
+		}
+		switch opt.Name {
+		case "group":
+			group = opt.StringValue()
+		case "tag":
+			tag = opt.StringValue()
+		}
+	}
+
+	monitor, err := c.svc.Create(ctx, group, i.GuildID, tag)
+	if err != nil {
+		_ = s.InteractionRespond(i.Interaction, &discordgo.InteractionResponse{
+			Type: discordgo.InteractionResponseChannelMessageWithSource,
+			Data: &discordgo.InteractionResponseData{
+				Content: messageFromError(err),
+			},
+		})
+		return
+	}
+
+	_ = s.InteractionRespond(i.Interaction, &discordgo.InteractionResponse{
+		Type: discordgo.InteractionResponseChannelMessageWithSource,
+		Data: &discordgo.InteractionResponseData{
+			Content: "monitor has been successfully created (ID=" + monitor.ID + ")",
+		},
+	})
+}

internal/domain/error.go

@@ -1,9 +1,13 @@
 package domain
 
-import "errors"
+import (
+	"errors"
+	"fmt"
+)
 
 var (
 	ErrNothingToUpdate = errors.New("nothing to update")
+	ErrRequired        = errors.New("cannot be blank")
 )
 
 type ErrorCode uint8
@@ -12,6 +16,7 @@ const (
 	ErrorCodeUnknown ErrorCode = iota
 	ErrorCodeEntityNotFound
 	ErrorCodeValidationError
+	ErrorCodeAlreadyExists
 )
 
 type UserError interface {
@@ -20,18 +25,39 @@ type UserError interface {
 	Code() ErrorCode
 }
 
-type RequiredError struct {
+type ValidationError struct {
 	Field string
+	Err   error
 }
 
-func (e RequiredError) Error() string {
-	return e.Field + ": cannot be blank"
+func (e ValidationError) Error() string {
+	return fmt.Sprintf("%s: %s", e.Field, e.Err)
 }
 
-func (e RequiredError) UserError() string {
+func (e ValidationError) UserError() string {
 	return e.Error()
 }
 
-func (e RequiredError) Code() ErrorCode {
+func (e ValidationError) Code() ErrorCode {
+	return ErrorCodeValidationError
+}
+
+func (e ValidationError) Unwrap() error {
+	return e.Err
+}
+
+type MinError struct {
+	Min int
+}
+
+func (e MinError) Error() string {
+	return fmt.Sprintf("must be no less than %d", e.Min)
+}
+
+func (e MinError) UserError() string {
+	return e.Error()
+}
+
+func (e MinError) Code() ErrorCode {
 	return ErrorCodeValidationError
 }

internal/domain/error_test.go

@@ -1,20 +1,37 @@
 package domain_test
 
 import (
+	"fmt"
 	"testing"
 
 	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
 	"github.com/stretchr/testify/assert"
 )
 
-func TestRequiredError(t *testing.T) {
+func TestValidationError(t *testing.T) {
 	t.Parallel()
 
-	err := domain.RequiredError{
-		Field: "123",
+	err := domain.ValidationError{
+		Field: "test",
+		Err: domain.MinError{
+			Min: 25,
+		},
 	}
 	var _ domain.UserError = err
-	assert.Equal(t, err.Field+": cannot be blank", err.Error())
+	assert.Equal(t, fmt.Sprintf("%s: %s", err.Field, err.Err.Error()), err.Error())
+	assert.Equal(t, err.Error(), err.UserError())
+	assert.ErrorIs(t, err, err.Err)
+	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
+}
+
+func TestMinError(t *testing.T) {
+	t.Parallel()
+
+	err := domain.MinError{
+		Min: 25,
+	}
+	var _ domain.UserError = err
+	assert.Equal(t, "must be no less than 25", err.Error())
 	assert.Equal(t, err.Error(), err.UserError())
 	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
 }

internal/domain/group.go

@@ -25,20 +25,23 @@ type CreateGroupParams struct {
 
 func NewCreateGroupParams(serverID, versionCode, serverKey, channelGains, channelLosses string) (CreateGroupParams, error) {
 	if serverID == "" {
-		return CreateGroupParams{}, RequiredError{
+		return CreateGroupParams{}, ValidationError{
 			Field: "ServerID",
+			Err:   ErrRequired,
 		}
 	}
 
 	if versionCode == "" {
-		return CreateGroupParams{}, RequiredError{
+		return CreateGroupParams{}, ValidationError{
 			Field: "VersionCode",
+			Err:   ErrRequired,
 		}
 	}
 
 	if serverKey == "" {
-		return CreateGroupParams{}, RequiredError{
+		return CreateGroupParams{}, ValidationError{
 			Field: "ServerKey",
+			Err:   ErrRequired,
 		}
 	}
 
@@ -117,3 +120,19 @@ func (e GroupNotFoundError) UserError() string {
 func (e GroupNotFoundError) Code() ErrorCode {
 	return ErrorCodeEntityNotFound
 }
+
+type GroupDoesNotExistError struct {
+	ID string
+}
+
+func (e GroupDoesNotExistError) Error() string {
+	return fmt.Sprintf("group (ID=%s) doesn't exist", e.ID)
+}
+
+func (e GroupDoesNotExistError) UserError() string {
+	return e.Error()
+}
+
+func (e GroupDoesNotExistError) Code() ErrorCode {
+	return ErrorCodeValidationError
+}

internal/domain/group_test.go

@@ -34,20 +34,29 @@ func TestNewCreateGroupParams(t *testing.T) {
 			name:        "ERR: ServerID cannot be blank",
 			versionCode: "",
 			serverID:    "",
-			err:         domain.RequiredError{Field: "ServerID"},
+			err: domain.ValidationError{
+				Field: "ServerID",
+				Err:   domain.ErrRequired,
+			},
 		},
 		{
 			name:        "ERR: VersionCode cannot be blank",
 			serverID:    "1234",
 			versionCode: "",
-			err:         domain.RequiredError{Field: "VersionCode"},
+			err: domain.ValidationError{
+				Field: "VersionCode",
+				Err:   domain.ErrRequired,
+			},
 		},
 		{
 			name:        "ERR: ServerKey cannot be blank",
 			serverID:    "1234",
 			versionCode: "en",
 			serverKey:   "",
-			err:         domain.RequiredError{Field: "ServerKey"},
+			err: domain.ValidationError{
+				Field: "ServerKey",
+				Err:   domain.ErrRequired,
+			},
 		},
 	}
 
@@ -163,3 +172,15 @@ func TestGroupNotFoundError(t *testing.T) {
 	assert.Equal(t, err.Error(), err.UserError())
 	assert.Equal(t, domain.ErrorCodeEntityNotFound, err.Code())
 }
+
+func TestGroupDoesNotExistError(t *testing.T) {
+	t.Parallel()
+
+	err := domain.GroupDoesNotExistError{
+		ID: uuid.NewString(),
+	}
+	var _ domain.UserError = err
+	assert.Equal(t, fmt.Sprintf("group (ID=%s) doesn't exist", err.ID), err.Error())
+	assert.Equal(t, err.Error(), err.UserError())
+	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
+}

internal/domain/monitor.go

@@ -0,0 +1,84 @@
+package domain
+
+import (
+	"fmt"
+	"time"
+)
+
+const (
+	tribeIDMin = 1
+)
+
+type Monitor struct {
+	ID        string
+	TribeID   int64
+	GroupID   string
+	CreatedAt time.Time
+}
+
+type CreateMonitorParams struct {
+	tribeID int64
+	groupID string
+}
+
+func NewCreateMonitorParams(groupID string, tribeID int64) (CreateMonitorParams, error) {
+	if groupID == "" {
+		return CreateMonitorParams{}, ValidationError{
+			Field: "GroupID",
+			Err:   ErrRequired,
+		}
+	}
+
+	if tribeID < tribeIDMin {
+		return CreateMonitorParams{}, ValidationError{
+			Field: "TribeID",
+			Err: MinError{
+				Min: tribeIDMin,
+			},
+		}
+	}
+
+	return CreateMonitorParams{tribeID: tribeID, groupID: groupID}, nil
+}
+
+func (c CreateMonitorParams) TribeID() int64 {
+	return c.tribeID
+}
+
+func (c CreateMonitorParams) GroupID() string {
+	return c.groupID
+}
+
+type MonitorAlreadyExistsError struct {
+	TribeID int64
+	GroupID string
+}
+
+func (e MonitorAlreadyExistsError) Error() string {
+	return fmt.Sprintf("monitor (GroupID=%s,TribeID=%d) already exists", e.GroupID, e.TribeID)
+}
+
+func (e MonitorAlreadyExistsError) UserError() string {
+	return e.Error()
+}
+
+func (e MonitorAlreadyExistsError) Code() ErrorCode {
+	return ErrorCodeAlreadyExists
+}
+
+type MonitorLimitReachedError struct {
+	Current int // current number of groups
+	Limit   int // maximum number of groups
+}
+
+func (e MonitorLimitReachedError) Error() string {
+	return fmt.Sprintf("monitor limit has been reached (%d/%d)", e.Current, e.Limit)
+}
+
+func (e MonitorLimitReachedError) UserError() string {
+	return e.Error()
+}
+
+func (e MonitorLimitReachedError) Code() ErrorCode {
+	return ErrorCodeValidationError
+}

internal/domain/monitor_test.go

@@ -0,0 +1,93 @@
+package domain_test
+
+import (
+	"fmt"
+	"testing"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewCreateMonitorParams(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		tribeID int64
+		groupID string
+		err     error
+	}{
+		{
+			name:    "OK",
+			tribeID: 15,
+			groupID: uuid.NewString(),
+		},
+		{
+			name:    "ERR: GroupID cannot be blank",
+			groupID: "",
+			err: domain.ValidationError{
+				Field: "GroupID",
+				Err:   domain.ErrRequired,
+			},
+		},
+		{
+			name:    "ERR: TribeID < 1",
+			groupID: uuid.NewString(),
+			tribeID: 0,
+			err: domain.ValidationError{
+				Field: "TribeID",
+				Err: domain.MinError{
+					Min: 1,
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			res, err := domain.NewCreateMonitorParams(
+				tt.groupID,
+				tt.tribeID,
+			)
+			if tt.err != nil {
+				assert.ErrorIs(t, err, tt.err)
+				assert.Zero(t, res)
+				return
+			}
+			assert.NoError(t, err)
+			assert.Equal(t, tt.groupID, res.GroupID())
+			assert.Equal(t, tt.tribeID, res.TribeID())
+		})
+	}
+}
+
+func TestMonitorAlreadyExistsError(t *testing.T) {
+	t.Parallel()
+
+	err := domain.MonitorAlreadyExistsError{
+		GroupID: uuid.NewString(),
+		TribeID: 1234,
+	}
+	var _ domain.UserError = err
+	assert.Equal(t, fmt.Sprintf("monitor (GroupID=%s,TribeID=%d) already exists", err.GroupID, err.TribeID), err.Error())
+	assert.Equal(t, err.Error(), err.UserError())
+	assert.Equal(t, domain.ErrorCodeAlreadyExists, err.Code())
+}
+
+func TestMonitorLimitReachedError(t *testing.T) {
+	t.Parallel()
+
+	err := domain.MonitorLimitReachedError{
+		Current: 10,
+		Limit:   10,
+	}
+	var _ domain.UserError = err
+	assert.Equal(t, fmt.Sprintf("monitor limit has been reached (%d/%d)", err.Current, err.Limit), err.Error())
+	assert.Equal(t, err.Error(), err.UserError())
+	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
+}

internal/domain/tw.go

@@ -35,3 +35,19 @@ func (e ServerIsClosedError) UserError() string {
 func (e ServerIsClosedError) Code() ErrorCode {
 	return ErrorCodeValidationError
 }
+
+type TribeDoesNotExistError struct {
+	Tag string
+}
+
+func (e TribeDoesNotExistError) Error() string {
+	return fmt.Sprintf("tribe (Tag=%s) doesn't exist", e.Tag)
+}
+
+func (e TribeDoesNotExistError) UserError() string {
+	return e.Error()
+}
+
+func (e TribeDoesNotExistError) Code() ErrorCode {
+	return ErrorCodeValidationError
+}

internal/domain/tw_test.go

@@ -33,3 +33,15 @@ func TestServerIsClosedError(t *testing.T) {
 	assert.Equal(t, err.Error(), err.UserError())
 	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
 }
+
+func TestTribeDoesNotExistError(t *testing.T) {
+	t.Parallel()
+
+	err := domain.TribeDoesNotExistError{
+		Tag: "*TAG*",
+	}
+	var _ domain.UserError = err
+	assert.Equal(t, fmt.Sprintf("tribe (Tag=%s) doesn't exist", err.Tag), err.Error())
+	assert.Equal(t, err.Error(), err.UserError())
+	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
+}

internal/service/group.go

@@ -18,6 +18,7 @@ type GroupRepository interface {
 	Create(ctx context.Context, params domain.CreateGroupParams) (domain.Group, error)
 	Update(ctx context.Context, id, serverID string, params domain.UpdateGroupParams) (domain.Group, error)
 	List(ctx context.Context, params domain.ListGroupsParams) ([]domain.Group, error)
+	Get(ctx context.Context, id, serverID string) (domain.Group, error)
 	Delete(ctx context.Context, id, serverID string) error
 }
 
@@ -91,6 +92,14 @@ func (g *Group) List(ctx context.Context, params domain.ListGroupsParams) ([]dom
 	return groups, nil
 }
 
+func (g *Group) Get(ctx context.Context, id, serverID string) (domain.Group, error) {
+	group, err := g.repo.Get(ctx, id, serverID)
+	if err != nil {
+		return domain.Group{}, fmt.Errorf("GroupRepository.Get: %w", err)
+	}
+	return group, nil
+}
+
 func (g *Group) Delete(ctx context.Context, id, serverID string) error {
 	if err := g.repo.Delete(ctx, id, serverID); err != nil {
 		return fmt.Errorf("GroupRepository.Delete: %w", err)

internal/service/monitor.go

@@ -0,0 +1,89 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/twhelp"
+)
+
+const (
+	maxMonitorsPerGroup = 10
+)
+
+//counterfeiter:generate -o internal/mock/monitor_repository.gen.go . MonitorRepository
+type MonitorRepository interface {
+	Create(ctx context.Context, params domain.CreateMonitorParams) (domain.Monitor, error)
+	List(ctx context.Context, groupID string) ([]domain.Monitor, error)
+}
+
+//counterfeiter:generate -o internal/mock/group_getter.gen.go . GroupGetter
+type GroupGetter interface {
+	Get(ctx context.Context, id, serverID string) (domain.Group, error)
+}
+
+type Monitor struct {
+	repo     MonitorRepository
+	client   TWHelpClient
+	groupSvc GroupGetter
+}
+
+func NewMonitor(repo MonitorRepository, groupSvc GroupGetter, client TWHelpClient) *Monitor {
+	return &Monitor{repo: repo, client: client, groupSvc: groupSvc}
+}
+
+func (m *Monitor) Create(ctx context.Context, groupID, serverID, tribeTag string) (domain.Monitor, error) {
+	// check if group exists
+	group, err := m.groupSvc.Get(ctx, groupID, serverID)
+	if err != nil {
+		if errors.Is(err, domain.GroupNotFoundError{ID: groupID}) {
+			return domain.Monitor{}, domain.GroupDoesNotExistError{ID: groupID}
+		}
+		return domain.Monitor{}, fmt.Errorf("GroupService.Get: %w", err)
+	}
+
+	// check limit
+	monitors, err := m.repo.List(ctx, group.ID)
+	if err != nil {
+		return domain.Monitor{}, fmt.Errorf("MonitorRepository.List: %w", err)
+	}
+
+	if len(monitors) >= maxMonitorsPerGroup {
+		return domain.Monitor{}, domain.MonitorLimitReachedError{
+			Current: len(monitors),
+			Limit:   maxMonitorsPerGroup,
+		}
+	}
+
+	// check if tribe exists
+	tribe, err := m.client.GetTribeByTag(ctx, group.VersionCode, group.ServerKey, tribeTag)
+	if err != nil {
+		var apiErr twhelp.APIError
+		if !errors.As(err, &apiErr) {
+			return domain.Monitor{}, fmt.Errorf("TWHelpClient.GetServer: %w", err)
+		}
+		return domain.Monitor{}, domain.TribeDoesNotExistError{
+			Tag: tribeTag,
+		}
+	}
+
+	if !tribe.DeletedAt.IsZero() {
+		return domain.Monitor{}, domain.TribeDoesNotExistError{
+			Tag: tribeTag,
+		}
+	}
+
+	params, err := domain.NewCreateMonitorParams(group.ID, tribe.ID)
+	if err != nil {
+		return domain.Monitor{}, fmt.Errorf("domain.NewCreateMonitorParams: %w", err)
+	}
+
+	monitor, err := m.repo.Create(ctx, params)
+	if err != nil {
+		return domain.Monitor{}, fmt.Errorf("MonitorRepository.Create: %w", err)
+	}
+
+	return monitor, nil
+}

internal/service/monitor_test.go

@@ -0,0 +1,195 @@
+package service_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/domain"
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/service"
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/service/internal/mock"
+	"gitea.dwysokinski.me/twhelp/dcbot/internal/twhelp"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonitor_Create(t *testing.T) {
+	t.Parallel()
+
+	t.Run("OK", func(t *testing.T) {
+		t.Parallel()
+
+		repo := &mock.FakeMonitorRepository{}
+		repo.ListReturns(nil, nil)
+		repo.CreateCalls(func(ctx context.Context, params domain.CreateMonitorParams) (domain.Monitor, error) {
+			return domain.Monitor{
+				ID:        uuid.NewString(),
+				TribeID:   params.TribeID(),
+				GroupID:   params.GroupID(),
+				CreatedAt: time.Now(),
+			}, nil
+		})
+
+		groupSvc := &mock.FakeGroupGetter{}
+		groupSvc.GetCalls(func(ctx context.Context, groupID, serverID string) (domain.Group, error) {
+			return domain.Group{
+				ID:            groupID,
+				ServerID:      serverID,
+				ChannelGains:  "",
+				ChannelLosses: "",
+				ServerKey:     "pl151",
+				VersionCode:   "pl",
+				CreatedAt:     time.Now(),
+			}, nil
+		})
+
+		client := &mock.FakeTWHelpClient{}
+		tribe := twhelp.Tribe{
+			ID:         150,
+			Tag:        "*TAG*",
+			Name:       uuid.NewString(),
+			ProfileURL: "https://pl151.plemiona.pl/game.php?screen=info_player&id=150",
+			DeletedAt:  time.Time{},
+		}
+		client.GetTribeByTagReturns(tribe, nil)
+
+		groupID := uuid.NewString()
+
+		monitor, err := service.NewMonitor(repo, groupSvc, client).
+			Create(context.Background(), groupID, uuid.NewString(), tribe.Tag)
+		assert.NoError(t, err)
+		assert.NotEmpty(t, monitor.ID)
+		assert.Equal(t, groupID, monitor.GroupID)
+		assert.Equal(t, tribe.ID, monitor.TribeID)
+		assert.NotEmpty(t, monitor.CreatedAt)
+	})
+
+	t.Run("ERR: group doesn't exist", func(t *testing.T) {
+		t.Parallel()
+
+		groupID := uuid.NewString()
+		groupSvc := &mock.FakeGroupGetter{}
+		groupSvc.GetReturns(domain.Group{}, domain.GroupNotFoundError{ID: groupID})
+
+		monitor, err := service.NewMonitor(nil, groupSvc, nil).
+			Create(context.Background(), groupID, uuid.NewString(), "tag")
+		assert.ErrorIs(t, err, domain.GroupDoesNotExistError{
+			ID: groupID,
+		})
+		assert.Zero(t, monitor)
+	})
+
+	t.Run("ERR: monitor limit has been reached", func(t *testing.T) {
+		t.Parallel()
+
+		const maxMonitorsPerGroup = 10
+
+		repo := &mock.FakeMonitorRepository{}
+		repo.ListReturns(make([]domain.Monitor, maxMonitorsPerGroup), nil)
+
+		groupSvc := &mock.FakeGroupGetter{}
+		groupSvc.GetCalls(func(ctx context.Context, groupID, serverID string) (domain.Group, error) {
+			return domain.Group{
+				ID:            groupID,
+				ServerID:      serverID,
+				ChannelGains:  "",
+				ChannelLosses: "",
+				ServerKey:     "pl151",
+				VersionCode:   "pl",
+				CreatedAt:     time.Now(),
+			}, nil
+		})
+
+		monitor, err := service.NewMonitor(repo, groupSvc, nil).
+			Create(context.Background(), uuid.NewString(), uuid.NewString(), "TAG")
+		assert.ErrorIs(t, err, domain.MonitorLimitReachedError{
+			Current: maxMonitorsPerGroup,
+			Limit:   maxMonitorsPerGroup,
+		})
+		assert.Zero(t, monitor)
+	})
+
+	t.Run("ERR: tribe doesn't exist", func(t *testing.T) {
+		t.Parallel()
+
+		t.Run("API error", func(t *testing.T) {
+			t.Parallel()
+
+			repo := &mock.FakeMonitorRepository{}
+			repo.ListReturns(nil, nil)
+			repo.CreateCalls(func(ctx context.Context, params domain.CreateMonitorParams) (domain.Monitor, error) {
+				return domain.Monitor{
+					ID:        uuid.NewString(),
+					TribeID:   params.TribeID(),
+					GroupID:   params.GroupID(),
+					CreatedAt: time.Now(),
+				}, nil
+			})
+
+			groupSvc := &mock.FakeGroupGetter{}
+			groupSvc.GetCalls(func(ctx context.Context, groupID, serverID string) (domain.Group, error) {
+				return domain.Group{
+					ID:            groupID,
+					ServerID:      serverID,
+					ChannelGains:  "",
+					ChannelLosses: "",
+					ServerKey:     "pl151",
+					VersionCode:   "pl",
+					CreatedAt:     time.Now(),
+				}, nil
+			})
+
+			client := &mock.FakeTWHelpClient{}
+			client.GetTribeByTagReturns(twhelp.Tribe{}, twhelp.APIError{
+				Code:    twhelp.ErrorCodeEntityNotFound,
+				Message: "tribe not found",
+			})
+
+			tag := "TAG"
+
+			monitor, err := service.NewMonitor(repo, groupSvc, client).
+				Create(context.Background(), uuid.NewString(), uuid.NewString(), tag)
+			assert.ErrorIs(t, err, domain.TribeDoesNotExistError{
+				Tag: tag,
+			})
+			assert.Zero(t, monitor)
+		})
+
+		t.Run("tribe is deleted", func(t *testing.T) {
+			t.Parallel()
+
+			repo := &mock.FakeMonitorRepository{}
+			repo.ListReturns(nil, nil)
+
+			groupSvc := &mock.FakeGroupGetter{}
+			groupSvc.GetCalls(func(ctx context.Context, groupID, serverID string) (domain.Group, error) {
+				return domain.Group{
+					ID:            groupID,
+					ServerID:      serverID,
+					ChannelGains:  "",
+					ChannelLosses: "",
+					ServerKey:     "pl151",
+					VersionCode:   "pl",
+					CreatedAt:     time.Now(),
+				}, nil
+			})
+
+			client := &mock.FakeTWHelpClient{}
+			tribe := twhelp.Tribe{
+				ID:         150,
+				Tag:        "*TAG*",
+				Name:       uuid.NewString(),
+				ProfileURL: "https://pl151.plemiona.pl/game.php?screen=info_player&id=150",
+				DeletedAt:  time.Now(),
+			}
+			client.GetTribeByTagReturns(tribe, nil)
+
+			monitor, err := service.NewMonitor(repo, groupSvc, client).
+				Create(context.Background(), uuid.NewString(), uuid.NewString(), tribe.Tag)
+			assert.ErrorIs(t, err, domain.TribeDoesNotExistError{
+				Tag: tribe.Tag,
+			})
+			assert.Zero(t, monitor)
+		})
+	})
+}

internal/service/service.go

@@ -11,4 +11,5 @@ import (
 //counterfeiter:generate -o internal/mock/twhelp_client.gen.go . TWHelpClient
 type TWHelpClient interface {
 	GetServer(ctx context.Context, version, server string) (twhelp.Server, error)
+	GetTribeByTag(ctx context.Context, version, server, tag string) (twhelp.Tribe, error)
 }

internal/twhelp/client.go

@@ -14,8 +14,9 @@ const (
 	defaultUserAgent = "TWHelpDCBot/development"
 	defaultTimeout   = 10 * time.Second
 
-	endpointListVersions = "/api/v1/versions"
-	endpointGetServer    = "/api/v1/versions/%s/servers/%s"
+	endpointListVersions  = "/api/v1/versions"
+	endpointGetServer     = "/api/v1/versions/%s/servers/%s"
+	endpointGetTribeByTag = "/api/v1/versions/%s/servers/%s/tribes/tag/%s"
 )
 
 type Client struct {
@@ -68,6 +69,14 @@ func (c *Client) GetServer(ctx context.Context, version, server string) (Server,
 	return resp.Data, nil
 }
 
+func (c *Client) GetTribeByTag(ctx context.Context, version, server, tag string) (Tribe, error) {
+	var resp getTribeResp
+	if err := c.getJSON(ctx, fmt.Sprintf(endpointGetTribeByTag, version, server, tag), &resp); err != nil {
+		return Tribe{}, err
+	}
+	return resp.Data, nil
+}
+
 func (c *Client) getJSON(ctx context.Context, urlStr string, v any) error {
 	u, err := c.baseURL.Parse(urlStr)
 	if err != nil {

internal/twhelp/types.go

@@ -1,5 +1,7 @@
 package twhelp
 
+import "time"
+
 type ErrorCode string
 
 const (
@@ -47,3 +49,15 @@ type Server struct {
 type getServerResp struct {
 	Data Server `json:"data"`
 }
+
+type Tribe struct {
+	ID         int64     `json:"id"`
+	Tag        string    `json:"tag"`
+	Name       string    `json:"name"`
+	ProfileURL string    `json:"profileUrl"`
+	DeletedAt  time.Time `json:"deletedAt"`
+}
+
+type getTribeResp struct {
+	Data Tribe `json:"data"`
+}