Reapply "feat: 实现身份资料、对话密码、在线目录与群管理"

This reverts commit 16ece09a97.
2026-09-30 07:44:50 +08:00
parent 16ece09a97
commit 14e2e65a8c
14 changed files with 2777 additions and 65 deletions
@@ -0,0 +1,727 @@
+package group
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"database/sql"
+	"errors"
+	"time"
+
+	"git.asio.asia/nixevol/NixMsg/internal/app/port"
+	"git.asio.asia/nixevol/NixMsg/internal/protocol"
+	"git.asio.asia/nixevol/NixMsg/internal/store"
+)
+
+const (
+	eventMemberAdded   = "member_added"
+	eventMemberRemoved = "member_removed"
+	eventLeft          = "left"
+	eventOwnerChanged  = "owner_changed"
+	eventRenamed       = "renamed"
+	eventDissolved     = "dissolved"
+
+	reasonLeftGroup      = "left_group"
+	reasonGroupDissolved = "group_dissolved"
+
+	idAlphabet = "abcdefghijklmnopqrstuvwxyz0123456789"
+)
+
+// TalkGate checks talk password when adding members (implemented by identity).
+type TalkGate interface {
+	CheckTalkPasswordForJoin(ctx context.Context, actorID, targetID, talkPassword, remoteIP string) error
+}
+
+// OnlineLookup reports member online status.
+type OnlineLookup interface {
+	IsOnline(endpointID string) bool
+}
+
+// Config holds group service dependencies.
+type Config struct {
+	DB              *store.DB
+	Talk            TalkGate
+	Online          OnlineLookup
+	Downlink        port.Downlink
+	MaxGroupMembers int
+	Now             func() time.Time
+	DefaultRemoteIP string
+}
+
+// App implements group.Service.
+type App struct {
+	db       *store.DB
+	talk     TalkGate
+	online   OnlineLookup
+	down     port.Downlink
+	maxMem   int
+	nowFn    func() time.Time
+	remoteIP string
+}
+
+// New constructs the group service.
+func New(cfg Config) *App {
+	now := cfg.Now
+	if now == nil {
+		now = time.Now
+	}
+	max := cfg.MaxGroupMembers
+	if max <= 0 {
+		max = 1000
+	}
+	return &App{
+		db:       cfg.DB,
+		talk:     cfg.Talk,
+		online:   cfg.Online,
+		down:     cfg.Downlink,
+		maxMem:   max,
+		nowFn:    now,
+		remoteIP: cfg.DefaultRemoteIP,
+	}
+}
+
+func (a *App) nowMs() int64 { return a.nowFn().UnixMilli() }
+
+func errCode(code, msg string) *protocol.Error {
+	return &protocol.Error{Code: code, Message: msg}
+}
+
+func protoCode(err error) string {
+	var pe *protocol.Error
+	if errors.As(err, &pe) {
+		return pe.Code
+	}
+	return ""
+}
+
+// Create creates a group; creator becomes owner and member. Partial member failures still create the group.
+func (a *App) Create(ctx context.Context, actorID string, req *protocol.GroupCreate) (CreateResult, error) {
+	if req == nil {
+		return CreateResult{}, errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return CreateResult{}, err
+	}
+	if !protocol.ValidEndpointID(actorID) {
+		return CreateResult{}, errCode(protocol.CodeBadRequest, "invalid actor")
+	}
+	gid := req.ID
+	if gid == "" {
+		var genErr error
+		gid, genErr = generateGroupID()
+		if genErr != nil {
+			return CreateResult{}, genErr
+		}
+	}
+	now := a.nowMs()
+	failed := make([]MemberFail, 0)
+	added := make([]string, 0, len(req.Members))
+
+	for _, m := range req.Members {
+		if m.ID == actorID {
+			continue
+		}
+		if checkErr := a.checkAddMember(ctx, actorID, m.ID, m.TalkPassword); checkErr != nil {
+			failed = append(failed, MemberFail{ID: m.ID, Code: failCode(checkErr)})
+			continue
+		}
+		added = append(added, m.ID)
+	}
+
+	if 1+len(added) > a.maxMem {
+		return CreateResult{}, errCode(protocol.CodeGroupFull, "group full")
+	}
+
+	err := a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		var exists int
+		qErr := tx.QueryRow(`SELECT 1 FROM groups WHERE id = ?`, gid).Scan(&exists)
+		if qErr == nil {
+			return errCode(protocol.CodeIDTaken, "group id taken")
+		}
+		if !errors.Is(qErr, sql.ErrNoRows) {
+			return qErr
+		}
+		if _, e := tx.Exec(`INSERT INTO groups(id, name, owner_id, created_at) VALUES(?,?,?,?)`,
+			gid, req.Name, actorID, now); e != nil {
+			if isUnique(e) {
+				return errCode(protocol.CodeIDTaken, "group id taken")
+			}
+			return e
+		}
+		if _, e := tx.Exec(`INSERT INTO group_members(group_id, endpoint_id, joined_at) VALUES(?,?,?)`,
+			gid, actorID, now); e != nil {
+			return e
+		}
+		for _, id := range added {
+			if _, e := tx.Exec(`INSERT INTO group_members(group_id, endpoint_id, joined_at) VALUES(?,?,?)`,
+				gid, id, now); e != nil {
+				return e
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return CreateResult{}, err
+	}
+
+	for _, id := range added {
+		a.emit(ctx, append([]string{actorID}, added...), gid, eventMemberAdded, id, now)
+	}
+	return CreateResult{ID: gid, Name: req.Name, OwnerID: actorID, Failed: failed}, nil
+}
+
+// Add adds members (owner only).
+func (a *App) Add(ctx context.Context, actorID string, req *protocol.GroupAdd) (AddResult, error) {
+	if req == nil {
+		return AddResult{}, errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return AddResult{}, err
+	}
+	owner, members, err := a.loadGroup(ctx, req.GroupID)
+	if err != nil {
+		return AddResult{}, err
+	}
+	if owner != actorID {
+		return AddResult{}, errCode(protocol.CodeForbidden, "not owner")
+	}
+
+	failed := make([]MemberFail, 0)
+	added := make([]string, 0)
+	now := a.nowMs()
+
+	for _, m := range req.Members {
+		if contains(members, m.ID) {
+			continue
+		}
+		if len(members)+len(added) >= a.maxMem {
+			failed = append(failed, MemberFail{ID: m.ID, Code: protocol.CodeGroupFull})
+			continue
+		}
+		if checkErr := a.checkAddMember(ctx, actorID, m.ID, m.TalkPassword); checkErr != nil {
+			failed = append(failed, MemberFail{ID: m.ID, Code: failCode(checkErr)})
+			continue
+		}
+		added = append(added, m.ID)
+	}
+
+	if len(added) > 0 {
+		err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+			for _, id := range added {
+				if _, e := tx.Exec(`INSERT OR IGNORE INTO group_members(group_id, endpoint_id, joined_at) VALUES(?,?,?)`,
+					req.GroupID, id, now); e != nil {
+					return e
+				}
+			}
+			return nil
+		})
+		if err != nil {
+			return AddResult{}, err
+		}
+		all := append(append([]string{}, members...), added...)
+		for _, id := range added {
+			a.emit(ctx, all, req.GroupID, eventMemberAdded, id, now)
+		}
+	}
+	return AddResult{Failed: failed}, nil
+}
+
+// Remove kicks a member (owner only).
+func (a *App) Remove(ctx context.Context, actorID string, req *protocol.GroupRemove) error {
+	if req == nil {
+		return errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return err
+	}
+	owner, members, err := a.loadGroup(ctx, req.GroupID)
+	if err != nil {
+		return err
+	}
+	if owner != actorID {
+		return errCode(protocol.CodeForbidden, "not owner")
+	}
+	if req.EndpointID == owner {
+		return errCode(protocol.CodeBadRequest, "cannot remove owner")
+	}
+	if !contains(members, req.EndpointID) {
+		return errCode(protocol.CodeNotFound, "member not found")
+	}
+	now := a.nowMs()
+	var revokes []revokeItem
+	err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		if _, e := tx.Exec(`DELETE FROM group_members WHERE group_id = ? AND endpoint_id = ?`,
+			req.GroupID, req.EndpointID); e != nil {
+			return e
+		}
+		return voidMemberDeliveriesTx(tx, req.GroupID, req.EndpointID, reasonLeftGroup, now, &revokes)
+	})
+	if err != nil {
+		return err
+	}
+	a.publishRevokes(ctx, revokes)
+	left := without(members, req.EndpointID)
+	notify := append(left, req.EndpointID)
+	a.emit(ctx, notify, req.GroupID, eventMemberRemoved, req.EndpointID, now)
+	return nil
+}
+
+// Leave lets a non-owner member leave.
+func (a *App) Leave(ctx context.Context, actorID string, req *protocol.GroupLeave) error {
+	if req == nil {
+		return errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return err
+	}
+	owner, members, err := a.loadGroup(ctx, req.GroupID)
+	if err != nil {
+		return err
+	}
+	if !contains(members, actorID) {
+		return errCode(protocol.CodeNotMember, "not a member")
+	}
+	if owner == actorID {
+		return errCode(protocol.CodeOwnerCannotLeave, "owner cannot leave")
+	}
+	now := a.nowMs()
+	var revokes []revokeItem
+	err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		if _, e := tx.Exec(`DELETE FROM group_members WHERE group_id = ? AND endpoint_id = ?`,
+			req.GroupID, actorID); e != nil {
+			return e
+		}
+		return voidMemberDeliveriesTx(tx, req.GroupID, actorID, reasonLeftGroup, now, &revokes)
+	})
+	if err != nil {
+		return err
+	}
+	a.publishRevokes(ctx, revokes)
+	left := without(members, actorID)
+	notify := append(left, actorID)
+	a.emit(ctx, notify, req.GroupID, eventLeft, actorID, now)
+	return nil
+}
+
+// Transfer transfers ownership.
+func (a *App) Transfer(ctx context.Context, actorID string, req *protocol.GroupTransfer) error {
+	if req == nil {
+		return errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return err
+	}
+	owner, members, err := a.loadGroup(ctx, req.GroupID)
+	if err != nil {
+		return err
+	}
+	if owner != actorID {
+		return errCode(protocol.CodeForbidden, "not owner")
+	}
+	if !contains(members, req.EndpointID) {
+		return errCode(protocol.CodeNotFound, "member not found")
+	}
+	now := a.nowMs()
+	err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		_, e := tx.Exec(`UPDATE groups SET owner_id = ? WHERE id = ?`, req.EndpointID, req.GroupID)
+		return e
+	})
+	if err != nil {
+		return err
+	}
+	a.emit(ctx, members, req.GroupID, eventOwnerChanged, req.EndpointID, now)
+	return nil
+}
+
+// Rename renames the group.
+func (a *App) Rename(ctx context.Context, actorID string, req *protocol.GroupRename) error {
+	if req == nil {
+		return errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return err
+	}
+	owner, members, err := a.loadGroup(ctx, req.GroupID)
+	if err != nil {
+		return err
+	}
+	if owner != actorID {
+		return errCode(protocol.CodeForbidden, "not owner")
+	}
+	now := a.nowMs()
+	err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		_, e := tx.Exec(`UPDATE groups SET name = ? WHERE id = ?`, req.Name, req.GroupID)
+		return e
+	})
+	if err != nil {
+		return err
+	}
+	a.emit(ctx, members, req.GroupID, eventRenamed, "", now)
+	return nil
+}
+
+// Dissolve dissolves the group and voids unfinished deliveries / scheduled messages.
+func (a *App) Dissolve(ctx context.Context, actorID string, req *protocol.GroupDissolve) error {
+	if req == nil {
+		return errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return err
+	}
+	owner, members, err := a.loadGroup(ctx, req.GroupID)
+	if err != nil {
+		return err
+	}
+	if owner != actorID {
+		return errCode(protocol.CodeForbidden, "not owner")
+	}
+	now := a.nowMs()
+	var revokes []revokeItem
+	err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		if e := voidGroupAllTx(tx, req.GroupID, now, &revokes); e != nil {
+			return e
+		}
+		if _, e := tx.Exec(`DELETE FROM group_members WHERE group_id = ?`, req.GroupID); e != nil {
+			return e
+		}
+		_, e := tx.Exec(`DELETE FROM groups WHERE id = ?`, req.GroupID)
+		return e
+	})
+	if err != nil {
+		return err
+	}
+	a.publishRevokes(ctx, revokes)
+	a.emit(ctx, members, req.GroupID, eventDissolved, "", now)
+	return nil
+}
+
+// List lists groups the actor belongs to.
+func (a *App) List(ctx context.Context, actorID string, req *protocol.GroupList) ([]ListItem, string, error) {
+	if req == nil {
+		req = &protocol.GroupList{V: protocol.Version, Type: protocol.TypeGroupList, RID: "x", Limit: 100}
+	}
+	if err := req.Validate(); err != nil {
+		return nil, "", err
+	}
+	limit := req.Limit
+	if limit <= 0 {
+		limit = 100
+	}
+	if limit > protocol.MaxPageLimit {
+		limit = protocol.MaxPageLimit
+	}
+	rows, err := a.db.Read.QueryContext(ctx, `
+SELECT g.id, g.name, g.owner_id,
+  (SELECT COUNT(*) FROM group_members gm2 WHERE gm2.group_id = g.id) AS cnt
+FROM groups g
+JOIN group_members gm ON gm.group_id = g.id AND gm.endpoint_id = ?
+WHERE g.id > ?
+ORDER BY g.id ASC
+LIMIT ?`, actorID, req.Cursor, limit+1)
+	if err != nil {
+		return nil, "", err
+	}
+	defer func() { _ = rows.Close() }()
+	items := make([]ListItem, 0, limit)
+	for rows.Next() {
+		var it ListItem
+		if scanErr := rows.Scan(&it.ID, &it.Name, &it.OwnerID, &it.MemberCount); scanErr != nil {
+			return nil, "", scanErr
+		}
+		items = append(items, it)
+	}
+	next := ""
+	if len(items) > limit {
+		items = items[:limit]
+		next = items[len(items)-1].ID
+	}
+	return items, next, rows.Err()
+}
+
+// Get returns group details; caller must be a member.
+func (a *App) Get(ctx context.Context, actorID string, req *protocol.GroupGet) (GetResult, error) {
+	if req == nil {
+		return GetResult{}, errCode(protocol.CodeBadRequest, "nil request")
+	}
+	if err := req.Validate(); err != nil {
+		return GetResult{}, err
+	}
+	var name, owner string
+	err := a.db.Read.QueryRowContext(ctx, `SELECT name, owner_id FROM groups WHERE id = ?`, req.GroupID).
+		Scan(&name, &owner)
+	if errors.Is(err, sql.ErrNoRows) {
+		return GetResult{}, errCode(protocol.CodeNotFound, "group not found")
+	}
+	if err != nil {
+		return GetResult{}, err
+	}
+	var one int
+	err = a.db.Read.QueryRowContext(ctx,
+		`SELECT 1 FROM group_members WHERE group_id = ? AND endpoint_id = ?`, req.GroupID, actorID).Scan(&one)
+	if errors.Is(err, sql.ErrNoRows) {
+		return GetResult{}, errCode(protocol.CodeNotMember, "not a member")
+	}
+	if err != nil {
+		return GetResult{}, err
+	}
+	limit := req.Limit
+	if limit <= 0 {
+		limit = 100
+	}
+	if limit > protocol.MaxPageLimit {
+		limit = protocol.MaxPageLimit
+	}
+	rows, err := a.db.Read.QueryContext(ctx, `
+SELECT gm.endpoint_id, e.name
+FROM group_members gm
+JOIN endpoints e ON e.id = gm.endpoint_id
+WHERE gm.group_id = ? AND gm.endpoint_id > ?
+ORDER BY gm.endpoint_id ASC
+LIMIT ?`, req.GroupID, req.Cursor, limit+1)
+	if err != nil {
+		return GetResult{}, err
+	}
+	defer func() { _ = rows.Close() }()
+	members := make([]MemberItem, 0, limit)
+	for rows.Next() {
+		var m MemberItem
+		if scanErr := rows.Scan(&m.ID, &m.Name); scanErr != nil {
+			return GetResult{}, scanErr
+		}
+		if a.online != nil {
+			m.Online = a.online.IsOnline(m.ID)
+		}
+		members = append(members, m)
+	}
+	next := ""
+	if len(members) > limit {
+		members = members[:limit]
+		next = members[len(members)-1].ID
+	}
+	return GetResult{ID: req.GroupID, Name: name, OwnerID: owner, Members: members, NextCursor: next}, rows.Err()
+}
+
+// AdminCreate creates a group without talk-password checks.
+func (a *App) AdminCreate(ctx context.Context, name, ownerID string, memberIDs []string) (CreateResult, error) {
+	members := make([]protocol.GroupMemberIn, 0, len(memberIDs))
+	for _, id := range memberIDs {
+		members = append(members, protocol.GroupMemberIn{ID: id})
+	}
+	return a.createAdmin(ctx, ownerID, name, "", members)
+}
+
+// AdminAddMembers adds members without talk-password checks.
+func (a *App) AdminAddMembers(ctx context.Context, groupID string, memberIDs []string) (AddResult, error) {
+	_, members, err := a.loadGroup(ctx, groupID)
+	if err != nil {
+		return AddResult{}, err
+	}
+	failed := make([]MemberFail, 0)
+	added := make([]string, 0)
+	now := a.nowMs()
+	for _, id := range memberIDs {
+		if contains(members, id) {
+			continue
+		}
+		var enabled int
+		e := a.db.Read.QueryRowContext(ctx, `SELECT enabled FROM endpoints WHERE id = ?`, id).Scan(&enabled)
+		if errors.Is(e, sql.ErrNoRows) {
+			failed = append(failed, MemberFail{ID: id, Code: protocol.CodeInvalidTarget})
+			continue
+		}
+		if e != nil {
+			return AddResult{}, e
+		}
+		if enabled == 0 {
+			failed = append(failed, MemberFail{ID: id, Code: protocol.CodeEndpointDisabled})
+			continue
+		}
+		if len(members)+len(added) >= a.maxMem {
+			failed = append(failed, MemberFail{ID: id, Code: protocol.CodeGroupFull})
+			continue
+		}
+		added = append(added, id)
+	}
+	if len(added) == 0 {
+		return AddResult{Failed: failed}, nil
+	}
+	err = a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		for _, id := range added {
+			if _, e := tx.Exec(`INSERT OR IGNORE INTO group_members(group_id, endpoint_id, joined_at) VALUES(?,?,?)`,
+				groupID, id, now); e != nil {
+				return e
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return AddResult{}, err
+	}
+	all := append(append([]string{}, members...), added...)
+	for _, id := range added {
+		a.emit(ctx, all, groupID, eventMemberAdded, id, now)
+	}
+	return AddResult{Failed: failed}, nil
+}
+
+func (a *App) createAdmin(ctx context.Context, ownerID, name, gid string, members []protocol.GroupMemberIn) (CreateResult, error) {
+	if gid == "" {
+		var genErr error
+		gid, genErr = generateGroupID()
+		if genErr != nil {
+			return CreateResult{}, genErr
+		}
+	}
+	if !protocol.ValidName(name) || name == "" {
+		return CreateResult{}, errCode(protocol.CodeBadRequest, "invalid name")
+	}
+	now := a.nowMs()
+	failed := make([]MemberFail, 0)
+	added := make([]string, 0)
+	for _, m := range members {
+		if m.ID == ownerID {
+			continue
+		}
+		var enabled int
+		e := a.db.Read.QueryRowContext(ctx, `SELECT enabled FROM endpoints WHERE id = ?`, m.ID).Scan(&enabled)
+		if errors.Is(e, sql.ErrNoRows) {
+			failed = append(failed, MemberFail{ID: m.ID, Code: protocol.CodeInvalidTarget})
+			continue
+		}
+		if e != nil {
+			return CreateResult{}, e
+		}
+		if enabled == 0 {
+			failed = append(failed, MemberFail{ID: m.ID, Code: protocol.CodeEndpointDisabled})
+			continue
+		}
+		added = append(added, m.ID)
+	}
+	if 1+len(added) > a.maxMem {
+		return CreateResult{}, errCode(protocol.CodeGroupFull, "group full")
+	}
+	err := a.db.Queue.Do(ctx, func(tx *sql.Tx) error {
+		if _, e := tx.Exec(`INSERT INTO groups(id, name, owner_id, created_at) VALUES(?,?,?,?)`,
+			gid, name, ownerID, now); e != nil {
+			if isUnique(e) {
+				return errCode(protocol.CodeIDTaken, "group id taken")
+			}
+			return e
+		}
+		if _, e := tx.Exec(`INSERT INTO group_members(group_id, endpoint_id, joined_at) VALUES(?,?,?)`,
+			gid, ownerID, now); e != nil {
+			return e
+		}
+		for _, id := range added {
+			if _, e := tx.Exec(`INSERT INTO group_members(group_id, endpoint_id, joined_at) VALUES(?,?,?)`,
+				gid, id, now); e != nil {
+				return e
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return CreateResult{}, err
+	}
+	return CreateResult{ID: gid, Name: name, OwnerID: ownerID, Failed: failed}, nil
+}
+
+func (a *App) checkAddMember(ctx context.Context, actorID, targetID, talkPassword string) error {
+	if a.talk == nil {
+		return errCode(protocol.CodeBusy, "talk gate not configured")
+	}
+	return a.talk.CheckTalkPasswordForJoin(ctx, actorID, targetID, talkPassword, a.remoteIP)
+}
+
+func (a *App) loadGroup(ctx context.Context, groupID string) (owner string, members []string, err error) {
+	err = a.db.Read.QueryRowContext(ctx, `SELECT owner_id FROM groups WHERE id = ?`, groupID).Scan(&owner)
+	if errors.Is(err, sql.ErrNoRows) {
+		return "", nil, errCode(protocol.CodeNotFound, "group not found")
+	}
+	if err != nil {
+		return "", nil, err
+	}
+	rows, qErr := a.db.Read.QueryContext(ctx, `SELECT endpoint_id FROM group_members WHERE group_id = ?`, groupID)
+	if qErr != nil {
+		return "", nil, qErr
+	}
+	defer func() { _ = rows.Close() }()
+	for rows.Next() {
+		var id string
+		if scanErr := rows.Scan(&id); scanErr != nil {
+			return "", nil, scanErr
+		}
+		members = append(members, id)
+	}
+	return owner, members, rows.Err()
+}
+
+func (a *App) emit(ctx context.Context, recipients []string, groupID, event, endpointID string, atMs int64) {
+	if a.down == nil {
+		return
+	}
+	frame := protocol.GroupEvent{
+		V: protocol.Version, Type: protocol.TypeGroupEvent,
+		GroupID: groupID, Event: event, EndpointID: endpointID, AtMs: atMs,
+	}
+	payload, encErr := encodeFrame(frame)
+	if encErr != nil {
+		return
+	}
+	seen := map[string]struct{}{}
+	for _, id := range recipients {
+		if _, ok := seen[id]; ok {
+			continue
+		}
+		seen[id] = struct{}{}
+		_ = a.down.PublishDown(ctx, id, "", payload, port.PublishOpts{QoS: 0})
+	}
+}
+
+func encodeFrame(v any) ([]byte, error) {
+	var buf bytes.Buffer
+	if err := protocol.Encode(&buf, v); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func generateGroupID() (string, error) {
+	b := make([]byte, 8)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	out := make([]byte, 8)
+	for i := range b {
+		out[i] = idAlphabet[int(b[i])%len(idAlphabet)]
+	}
+	return "g_" + string(out), nil
+}
+
+func failCode(err error) string {
+	if c := protoCode(err); c != "" {
+		return c
+	}
+	return protocol.CodeBusy
+}
+
+func contains(ss []string, x string) bool {
+	for _, s := range ss {
+		if s == x {
+			return true
+		}
+	}
+	return false
+}
+
+func without(ss []string, x string) []string {
+	out := make([]string, 0, len(ss))
+	for _, s := range ss {
+		if s != x {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
+var _ Service = (*App)(nil)