mixmaker/backend/internal/adapter/discord/rolesync.go

package discord

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"sort"
	"strconv"
	"strings"
	"time"

	"mixmaker/backend/internal/application"
	"mixmaker/backend/internal/domain"
)

type RoleSyncConfig struct {
	BotToken     string
	GuildID      string
	Locale       string
	APIBaseURL   string
	HTTPClient   *http.Client
	PollInterval time.Duration
	JobTimeout   time.Duration
}

type RoleWorker struct {
	store        application.DiscordRoleStore
	manager      *RoleManager
	pollInterval time.Duration
	jobTimeout   time.Duration
	locale       string
	now          func() time.Time
}

type RoleManager struct {
	botToken   string
	guildID    string
	apiBaseURL string
	httpClient *http.Client
}

type discordRoleResponse struct {
	ID       string `json:"id"`
	Position int    `json:"position"`
}

type discordHTTPError struct {
	StatusCode int
	Status     string
	Body       string
	RetryAfter time.Duration
}

func (e *discordHTTPError) Error() string {
	return fmt.Sprintf("Discord returned %s: %s", e.Status, e.Body)
}

func NewRoleWorker(store application.DiscordRoleStore, config RoleSyncConfig) (*RoleWorker, error) {
	if store == nil {
		return nil, errors.New("Discord role store is required")
	}
	manager, err := newRoleManager(config)
	if err != nil {
		return nil, err
	}
	pollInterval := config.PollInterval
	if pollInterval <= 0 {
		pollInterval = 2 * time.Second
	}
	jobTimeout := config.JobTimeout
	if jobTimeout <= 0 {
		jobTimeout = 30 * time.Second
	}
	locale := strings.ToLower(strings.TrimSpace(config.Locale))
	if locale == "" {
		locale = "ru"
	}
	if locale != "ru" && locale != "en" {
		return nil, fmt.Errorf("unsupported Discord role locale %q", locale)
	}
	return &RoleWorker{
		store:        store,
		manager:      manager,
		pollInterval: pollInterval,
		jobTimeout:   jobTimeout,
		locale:       locale,
		now:          func() time.Time { return time.Now().UTC() },
	}, nil
}

func newRoleManager(config RoleSyncConfig) (*RoleManager, error) {
	if strings.TrimSpace(config.BotToken) == "" {
		return nil, errors.New("discord bot token is required for role sync")
	}
	if strings.TrimSpace(config.GuildID) == "" {
		return nil, errors.New("discord guild ID is required for role sync")
	}
	apiBaseURL := strings.TrimRight(config.APIBaseURL, "/")
	if apiBaseURL == "" {
		apiBaseURL = defaultAPIBaseURL
	}
	httpClient := config.HTTPClient
	if httpClient == nil {
		httpClient = http.DefaultClient
	}
	return &RoleManager{
		botToken:   config.BotToken,
		guildID:    config.GuildID,
		apiBaseURL: apiBaseURL,
		httpClient: httpClient,
	}, nil
}

func (w *RoleWorker) Run(ctx context.Context) {
	if err := w.store.SeedDiscordRoleSyncJobs(ctx); err != nil {
		slog.Error("Could not seed Discord role sync jobs", "error", err)
	}
	ticker := time.NewTicker(w.pollInterval)
	defer ticker.Stop()
	for {
		for {
			processed, err := w.ProcessNext(ctx)
			if err != nil {
				slog.Error("Discord role sync worker failed", "error", err)
			}
			if !processed {
				break
			}
		}
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
		}
	}
}

func (w *RoleWorker) ProcessNext(ctx context.Context) (bool, error) {
	job, err := w.store.ClaimDiscordRoleSyncJob(ctx)
	if errors.Is(err, domain.ErrNotFound) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	jobCtx, cancel := context.WithTimeout(ctx, w.jobTimeout)
	defer cancel()
	var warnings []string
	switch job.Action {
	case application.DiscordRoleActionTeardown:
		warnings, err = w.teardown(jobCtx, job)
	case application.DiscordRoleActionRSVP:
		warnings, err = w.reconcileRSVP(jobCtx, job.EventID)
	default:
		warnings, err = w.reconcile(jobCtx, job.EventID)
	}
	if err == nil {
		return true, w.store.CompleteDiscordRoleSyncJob(ctx, job.ID, strings.Join(warnings, "; "))
	}
	delay := retryDelay(job.Attempts, err)
	if retryErr := w.store.RetryDiscordRoleSyncJob(ctx, job.ID, err.Error(), w.now().Add(delay)); retryErr != nil {
		return true, fmt.Errorf("role sync failed: %v; schedule retry: %w", err, retryErr)
	}
	return true, nil
}

func (w *RoleWorker) reconcile(ctx context.Context, eventID string) ([]string, error) {
	current, err := w.store.GetDiscordRoleRoster(ctx, eventID)
	if errors.Is(err, domain.ErrNotFound) {
		return w.teardown(ctx, application.DiscordRoleSyncJob{EventID: eventID})
	}
	if err != nil {
		return nil, err
	}
	roles, err := w.store.ListDiscordManagedRoles(ctx, eventID)
	if err != nil {
		return nil, err
	}
	registeredRole := existingRole(roles, application.DiscordRoleKindRegistered)
	roles, err = w.ensureDesiredRoles(ctx, current.Roster, roles)
	if err != nil {
		return nil, err
	}
	if err = w.ensureTeamsAboveRegistered(ctx, roles, registeredRole); err != nil {
		return nil, err
	}
	desired, warnings, err := w.desiredAssignments(ctx, current, roles)
	if err != nil {
		return warnings, err
	}
	for _, role := range roles {
		if role.Scope == application.DiscordRoleScopeEvent && role.EventID != eventID {
			continue
		}
		roleWarnings, syncErr := w.syncAssignments(ctx, role.DiscordRoleID, desired[role.DiscordRoleID])
		warnings = append(warnings, roleWarnings...)
		if syncErr != nil {
			return warnings, syncErr
		}
	}
	return warnings, nil
}

func (w *RoleWorker) reconcileRSVP(ctx context.Context, eventID string) ([]string, error) {
	state, err := w.store.GetDiscordRoleRegistration(ctx, eventID)
	if errors.Is(err, domain.ErrNotFound) {
		return w.teardown(ctx, application.DiscordRoleSyncJob{EventID: eventID})
	}
	if err != nil {
		return nil, err
	}
	if state.Event.State == domain.Completed || state.Event.State == domain.Cancelled {
		return w.teardown(ctx, application.DiscordRoleSyncJob{EventID: eventID})
	}
	existing, err := w.store.ListDiscordManagedRoles(ctx, eventID)
	if err != nil {
		return nil, err
	}
	registrationKinds := map[string]bool{
		application.DiscordRoleKindRegistered: true,
		application.DiscordRoleKindGoing:      true,
		application.DiscordRoleKindMaybe:      true,
		application.DiscordRoleKindNotGoing:   true,
	}
	if len(state.Registrations) == 0 {
		hasRegistrationRoles := false
		for _, role := range existing {
			hasRegistrationRoles = hasRegistrationRoles || registrationKinds[role.Kind]
		}
		if !hasRegistrationRoles {
			return nil, nil
		}
	}
	names := rsvpRoleNames(w.locale, state.Event.Name)
	desiredRoles := []application.DiscordManagedRole{
		{Scope: application.DiscordRoleScopeEvent, EventID: eventID, Kind: application.DiscordRoleKindRegistered, RoleName: names[application.DiscordRoleKindRegistered], Hoist: true},
		{Scope: application.DiscordRoleScopeEvent, EventID: eventID, Kind: application.DiscordRoleKindGoing, RoleName: names[application.DiscordRoleKindGoing]},
		{Scope: application.DiscordRoleScopeEvent, EventID: eventID, Kind: application.DiscordRoleKindMaybe, RoleName: names[application.DiscordRoleKindMaybe]},
		{Scope: application.DiscordRoleScopeEvent, EventID: eventID, Kind: application.DiscordRoleKindNotGoing, RoleName: names[application.DiscordRoleKindNotGoing]},
	}
	roles, err := w.ensureRoles(ctx, desiredRoles, existing, registrationKinds)
	if err != nil {
		return nil, err
	}
	byKind := make(map[string]application.DiscordManagedRole, len(roles))
	desiredAssignments := make(map[string]map[string]bool, len(roles))
	for _, role := range roles {
		byKind[role.Kind] = role
		desiredAssignments[role.DiscordRoleID] = make(map[string]bool)
	}
	warnings := make([]string, 0)
	for _, registration := range state.Registrations {
		discordID := state.PlayerDiscordIDs[registration.PlayerID]
		if discordID == "" {
			warnings = append(warnings, "player "+registration.PlayerID+" has no linked Discord account")
			continue
		}
		desiredAssignments[byKind[application.DiscordRoleKindRegistered].DiscordRoleID][discordID] = true
		kind := rsvpStatusKind(registration.Status)
		if role := byKind[kind]; role.DiscordRoleID != "" {
			desiredAssignments[role.DiscordRoleID][discordID] = true
		}
	}
	for _, role := range roles {
		roleWarnings, syncErr := w.syncAssignments(ctx, role.DiscordRoleID, desiredAssignments[role.DiscordRoleID])
		warnings = append(warnings, roleWarnings...)
		if syncErr != nil {
			return warnings, syncErr
		}
	}
	return uniqueStrings(warnings), nil
}

func (w *RoleWorker) ensureDesiredRoles(ctx context.Context, roster domain.RosterDraft, existing []application.DiscordManagedRole) ([]application.DiscordManagedRole, error) {
	desired := []application.DiscordManagedRole{
		{Scope: application.DiscordRoleScopeGlobal, Kind: application.DiscordRoleKindTank, RoleName: "Tank"},
		{Scope: application.DiscordRoleScopeGlobal, Kind: application.DiscordRoleKindDamage, RoleName: "Damage"},
		{Scope: application.DiscordRoleScopeGlobal, Kind: application.DiscordRoleKindSupport, RoleName: "Support"},
	}
	for _, team := range roster.Teams {
		teamName := truncate(strings.TrimSpace(team.Name), 100)
		desired = append(desired,
			application.DiscordManagedRole{Scope: application.DiscordRoleScopeEvent, EventID: roster.EventID, TeamID: team.ID, Kind: application.DiscordRoleKindTeam, RoleName: teamName, Hoist: true},
			application.DiscordManagedRole{Scope: application.DiscordRoleScopeEvent, EventID: roster.EventID, TeamID: team.ID, Kind: application.DiscordRoleKindCaptain, RoleName: truncate(teamName+" Captain", 100)},
		)
	}
	return w.ensureRoles(ctx, desired, existing, map[string]bool{
		application.DiscordRoleKindTeam: true, application.DiscordRoleKindCaptain: true,
	})
}

func (w *RoleWorker) ensureRoles(ctx context.Context, desired, existing []application.DiscordManagedRole, removableKinds map[string]bool) ([]application.DiscordManagedRole, error) {
	existingByKey := make(map[string]application.DiscordManagedRole, len(existing))
	for _, role := range existing {
		existingByKey[managedRoleKey(role)] = role
	}
	desiredKeys := make(map[string]bool, len(desired))
	result := make([]application.DiscordManagedRole, 0, len(desired))
	for _, role := range desired {
		key := managedRoleKey(role)
		desiredKeys[key] = true
		if saved, ok := existingByKey[key]; ok {
			role.DiscordRoleID = saved.DiscordRoleID
			if saved.RoleName != role.RoleName || saved.Hoist != role.Hoist {
				if err := w.manager.UpdateRole(ctx, saved.DiscordRoleID, role.RoleName, role.Hoist); err != nil {
					return nil, err
				}
				if err := w.store.UpsertDiscordManagedRole(ctx, role); err != nil {
					return nil, err
				}
			}
		} else {
			roleID, err := w.manager.CreateRole(ctx, role.RoleName, role.Hoist)
			if err != nil {
				return nil, err
			}
			role.DiscordRoleID = roleID
			if err = w.store.UpsertDiscordManagedRole(ctx, role); err != nil {
				_ = w.manager.DeleteRole(ctx, roleID)
				return nil, err
			}
		}
		result = append(result, role)
	}
	for _, role := range existing {
		if !removableKinds[role.Kind] || desiredKeys[managedRoleKey(role)] {
			continue
		}
		if err := w.deleteManagedRole(ctx, role); err != nil {
			return nil, err
		}
	}
	return result, nil
}

func (w *RoleWorker) desiredAssignments(ctx context.Context, current application.DiscordRoleRoster, roles []application.DiscordManagedRole) (map[string]map[string]bool, []string, error) {
	desired := make(map[string]map[string]bool)
	byKey := make(map[string]application.DiscordManagedRole, len(roles))
	for _, role := range roles {
		byKey[managedRoleKey(role)] = role
		desired[role.DiscordRoleID] = make(map[string]bool)
	}
	warnings := appendRosterAssignments(desired, byKey, current, true)
	active, err := w.store.ListActiveDiscordRoleRosters(ctx)
	if err != nil {
		return nil, warnings, err
	}
	for _, roster := range active {
		warnings = append(warnings, appendRosterAssignments(desired, byKey, roster, false)...)
	}
	return desired, uniqueStrings(warnings), nil
}

func appendRosterAssignments(desired map[string]map[string]bool, roles map[string]application.DiscordManagedRole, item application.DiscordRoleRoster, includeEventRoles bool) []string {
	warnings := make([]string, 0)
	for _, team := range item.Roster.Teams {
		for _, slot := range team.Slots {
			if slot.PlayerID == "" {
				continue
			}
			discordID := item.PlayerDiscordIDs[slot.PlayerID]
			if discordID == "" {
				warnings = append(warnings, "player "+slot.PlayerID+" has no linked Discord account")
				continue
			}
			globalRole := roles[managedRoleKey(application.DiscordManagedRole{Scope: application.DiscordRoleScopeGlobal, Kind: roleKind(slot.Role)})]
			if globalRole.DiscordRoleID != "" {
				desired[globalRole.DiscordRoleID][discordID] = true
			}
			if !includeEventRoles {
				continue
			}
			teamRole := roles[managedRoleKey(application.DiscordManagedRole{Scope: application.DiscordRoleScopeEvent, EventID: item.Roster.EventID, TeamID: team.ID, Kind: application.DiscordRoleKindTeam})]
			if teamRole.DiscordRoleID != "" {
				desired[teamRole.DiscordRoleID][discordID] = true
			}
			if slot.PlayerID == team.CaptainPlayerID {
				captainRole := roles[managedRoleKey(application.DiscordManagedRole{Scope: application.DiscordRoleScopeEvent, EventID: item.Roster.EventID, TeamID: team.ID, Kind: application.DiscordRoleKindCaptain})]
				if captainRole.DiscordRoleID != "" {
					desired[captainRole.DiscordRoleID][discordID] = true
				}
			}
		}
	}
	return warnings
}

func (w *RoleWorker) syncAssignments(ctx context.Context, roleID string, desired map[string]bool) ([]string, error) {
	current, err := w.store.ListDiscordRoleAssignments(ctx, roleID)
	if err != nil {
		return nil, err
	}
	currentSet := make(map[string]bool, len(current))
	for _, userID := range current {
		currentSet[userID] = true
	}
	warnings := make([]string, 0)
	for userID := range desired {
		if currentSet[userID] {
			continue
		}
		if err = w.manager.AddMemberRole(ctx, userID, roleID); err != nil {
			var httpErr *discordHTTPError
			if errors.As(err, &httpErr) && httpErr.StatusCode == http.StatusNotFound {
				warnings = append(warnings, "Discord member "+userID+" is not in the guild")
				continue
			}
			return warnings, err
		}
		if err = w.store.UpsertDiscordRoleAssignment(ctx, roleID, userID); err != nil {
			return warnings, err
		}
	}
	for userID := range currentSet {
		if desired[userID] {
			continue
		}
		if err = w.manager.RemoveMemberRole(ctx, userID, roleID); err != nil && !isDiscordNotFound(err) {
			return warnings, err
		}
		if err = w.store.DeleteDiscordRoleAssignment(ctx, roleID, userID); err != nil {
			return warnings, err
		}
	}
	return warnings, nil
}

func (w *RoleWorker) teardown(ctx context.Context, job application.DiscordRoleSyncJob) ([]string, error) {
	roles, err := w.store.ListDiscordManagedRoles(ctx, job.EventID)
	if err != nil {
		return nil, err
	}
	deleted := make(map[string]bool)
	for _, role := range roles {
		if role.Scope != application.DiscordRoleScopeEvent || role.EventID != job.EventID {
			continue
		}
		if err = w.deleteManagedRole(ctx, role); err != nil {
			return nil, err
		}
		deleted[role.DiscordRoleID] = true
	}
	for _, roleID := range job.RoleSnapshot {
		if deleted[roleID] {
			continue
		}
		if err = w.manager.DeleteRole(ctx, roleID); err != nil && !isDiscordNotFound(err) {
			return nil, err
		}
	}
	globalRoles := make([]application.DiscordManagedRole, 0)
	for _, role := range roles {
		if role.Scope == application.DiscordRoleScopeGlobal {
			globalRoles = append(globalRoles, role)
		}
	}
	active, err := w.store.ListActiveDiscordRoleRosters(ctx)
	if err != nil {
		return nil, err
	}
	desired := make(map[string]map[string]bool)
	byKey := make(map[string]application.DiscordManagedRole)
	for _, role := range globalRoles {
		desired[role.DiscordRoleID] = make(map[string]bool)
		byKey[managedRoleKey(role)] = role
	}
	warnings := make([]string, 0)
	for _, roster := range active {
		warnings = append(warnings, appendRosterAssignments(desired, byKey, roster, false)...)
	}
	for _, role := range globalRoles {
		roleWarnings, syncErr := w.syncAssignments(ctx, role.DiscordRoleID, desired[role.DiscordRoleID])
		warnings = append(warnings, roleWarnings...)
		if syncErr != nil {
			return warnings, syncErr
		}
	}
	return uniqueStrings(warnings), nil
}

func (w *RoleWorker) deleteManagedRole(ctx context.Context, role application.DiscordManagedRole) error {
	if err := w.manager.DeleteRole(ctx, role.DiscordRoleID); err != nil && !isDiscordNotFound(err) {
		return err
	}
	return w.store.DeleteDiscordManagedRole(ctx, role)
}

func (w *RoleWorker) ensureTeamsAboveRegistered(ctx context.Context, roles []application.DiscordManagedRole, registered application.DiscordManagedRole) error {
	if registered.DiscordRoleID == "" {
		return nil
	}
	teamRoleIDs := make([]string, 0)
	for _, role := range roles {
		if role.Kind == application.DiscordRoleKindTeam {
			teamRoleIDs = append(teamRoleIDs, role.DiscordRoleID)
		}
	}
	if len(teamRoleIDs) == 0 {
		return nil
	}
	return w.manager.MoveRolesAbove(ctx, teamRoleIDs, registered.DiscordRoleID)
}

func (m *RoleManager) CreateRole(ctx context.Context, name string, hoist bool) (string, error) {
	var response discordRoleResponse
	if err := m.request(ctx, http.MethodPost, m.guildPath("/roles"), map[string]any{
		"name": name, "permissions": "0", "hoist": hoist, "mentionable": false,
	}, &response); err != nil {
		return "", err
	}
	if response.ID == "" {
		return "", errors.New("Discord create role response has no ID")
	}
	return response.ID, nil
}

func (m *RoleManager) UpdateRole(ctx context.Context, roleID, name string, hoist bool) error {
	return m.request(ctx, http.MethodPatch, m.guildPath("/roles/"+url.PathEscape(roleID)), map[string]any{"name": name, "hoist": hoist}, nil)
}

func (m *RoleManager) MoveRolesAbove(ctx context.Context, roleIDs []string, anchorRoleID string) error {
	var roles []discordRoleResponse
	if err := m.request(ctx, http.MethodGet, m.guildPath("/roles"), nil, &roles); err != nil {
		return err
	}
	positions := make(map[string]int, len(roles))
	for _, role := range roles {
		positions[role.ID] = role.Position
	}
	anchorPosition, ok := positions[anchorRoleID]
	if !ok {
		return nil
	}
	needsMove := false
	for _, roleID := range roleIDs {
		if position, found := positions[roleID]; !found || position <= anchorPosition {
			needsMove = true
			break
		}
	}
	if !needsMove {
		return nil
	}
	payload := make([]map[string]any, 0, len(roleIDs))
	for index, roleID := range roleIDs {
		payload = append(payload, map[string]any{"id": roleID, "position": anchorPosition + index + 1})
	}
	return m.request(ctx, http.MethodPatch, m.guildPath("/roles"), payload, nil)
}

func (m *RoleManager) DeleteRole(ctx context.Context, roleID string) error {
	return m.request(ctx, http.MethodDelete, m.guildPath("/roles/"+url.PathEscape(roleID)), nil, nil)
}

func (m *RoleManager) AddMemberRole(ctx context.Context, userID, roleID string) error {
	path := "/members/" + url.PathEscape(userID) + "/roles/" + url.PathEscape(roleID)
	return m.request(ctx, http.MethodPut, m.guildPath(path), nil, nil)
}

func (m *RoleManager) RemoveMemberRole(ctx context.Context, userID, roleID string) error {
	path := "/members/" + url.PathEscape(userID) + "/roles/" + url.PathEscape(roleID)
	return m.request(ctx, http.MethodDelete, m.guildPath(path), nil, nil)
}

func (m *RoleManager) guildPath(path string) string {
	return m.apiBaseURL + "/guilds/" + url.PathEscape(m.guildID) + path
}

func (m *RoleManager) request(ctx context.Context, method, endpoint string, payload any, result any) error {
	var body io.Reader
	if payload != nil {
		encoded, err := json.Marshal(payload)
		if err != nil {
			return err
		}
		body = bytes.NewReader(encoded)
	}
	request, err := http.NewRequestWithContext(ctx, method, endpoint, body)
	if err != nil {
		return err
	}
	request.Header.Set("Authorization", "Bot "+m.botToken)
	if payload != nil {
		request.Header.Set("Content-Type", "application/json")
	}
	response, err := m.httpClient.Do(request)
	if err != nil {
		return err
	}
	defer response.Body.Close()
	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
		responseBody, _ := io.ReadAll(io.LimitReader(response.Body, 4096))
		httpErr := &discordHTTPError{StatusCode: response.StatusCode, Status: response.Status, Body: strings.TrimSpace(string(responseBody))}
		if seconds, parseErr := strconv.ParseFloat(response.Header.Get("Retry-After"), 64); parseErr == nil {
			httpErr.RetryAfter = time.Duration(seconds * float64(time.Second))
		}
		return httpErr
	}
	if result != nil {
		return json.NewDecoder(response.Body).Decode(result)
	}
	return nil
}

func retryDelay(attempts int, err error) time.Duration {
	var httpErr *discordHTTPError
	if errors.As(err, &httpErr) && httpErr.RetryAfter > 0 {
		return httpErr.RetryAfter
	}
	if attempts < 1 {
		attempts = 1
	}
	if attempts > 6 {
		attempts = 6
	}
	return time.Duration(1<<uint(attempts-1)) * time.Second
}

func managedRoleKey(role application.DiscordManagedRole) string {
	return strings.Join([]string{role.Scope, role.EventID, role.TeamID, role.Kind}, "\x00")
}

func existingRole(roles []application.DiscordManagedRole, kind string) application.DiscordManagedRole {
	for _, role := range roles {
		if role.Kind == kind {
			return role
		}
	}
	return application.DiscordManagedRole{}
}

func roleKind(role domain.Role) string {
	switch role {
	case domain.Tank:
		return application.DiscordRoleKindTank
	case domain.Damage:
		return application.DiscordRoleKindDamage
	case domain.Support:
		return application.DiscordRoleKindSupport
	default:
		return ""
	}
}

func rsvpStatusKind(status domain.RSVPStatus) string {
	switch status {
	case domain.Going:
		return application.DiscordRoleKindGoing
	case domain.Maybe:
		return application.DiscordRoleKindMaybe
	case domain.NotGoing:
		return application.DiscordRoleKindNotGoing
	default:
		return ""
	}
}

func rsvpRoleNames(locale, eventName string) map[string]string {
	prefixes := map[string]string{
		application.DiscordRoleKindRegistered: "Зарегистрирован: ",
		application.DiscordRoleKindGoing:      "Идёт: ",
		application.DiscordRoleKindMaybe:      "Возможно: ",
		application.DiscordRoleKindNotGoing:   "Не идёт: ",
	}
	if locale == "en" {
		prefixes = map[string]string{
			application.DiscordRoleKindRegistered: "Registered: ",
			application.DiscordRoleKindGoing:      "Going: ",
			application.DiscordRoleKindMaybe:      "Maybe: ",
			application.DiscordRoleKindNotGoing:   "Not going: ",
		}
	}
	for kind, prefix := range prefixes {
		prefixes[kind] = truncate(prefix+strings.TrimSpace(eventName), 100)
	}
	return prefixes
}

func isDiscordNotFound(err error) bool {
	var httpErr *discordHTTPError
	return errors.As(err, &httpErr) && httpErr.StatusCode == http.StatusNotFound
}

func uniqueStrings(values []string) []string {
	seen := make(map[string]bool, len(values))
	out := make([]string, 0, len(values))
	for _, value := range values {
		if value != "" && !seen[value] {
			seen[value] = true
			out = append(out, value)
		}
	}
	sort.Strings(out)
	return out
}