PLAT-39403 connector: bridge Reddit avatars from the chat web API

pkg/connector/avatars.go

@@ -0,0 +1,119 @@
+package connector
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/rs/zerolog"
+	"maunium.net/go/mautrix/bridgev2"
+	"maunium.net/go/mautrix/bridgev2/networkid"
+)
+
+const (
+	redditorBatchSize = 50
+	avatarRetryDelay  = 5 * time.Minute
+)
+
+var avatarHTTPClient = &http.Client{Timeout: 30 * time.Second}
+
+// Reddit's chat Matrix server returns no avatars, so they come from the web
+// session. A missing icon is cached as empty so it isn't requested on every
+// resync, and failed lookups back off rather than repeat on every sync batch.
+func (r *RedditClient) redditorAvatars(ctx context.Context, userIDs []networkid.UserID) map[networkid.UserID]*bridgev2.Avatar {
+	if r.session == nil {
+		return nil
+	}
+	if missing := r.claimUncachedRedditors(userIDs); len(missing) > 0 {
+		r.fetchRedditorIcons(ctx, missing)
+	}
+	r.avatarMu.Lock()
+	defer r.avatarMu.Unlock()
+	avatars := make(map[networkid.UserID]*bridgev2.Avatar, len(userIDs))
+	for _, userID := range userIDs {
+		if url := r.avatarURLs[userID]; url != "" {
+			avatars[userID] = &bridgev2.Avatar{
+				ID:  networkid.AvatarID(url),
+				Get: func(ctx context.Context) ([]byte, error) { return downloadRedditorAvatar(ctx, url) },
+			}
+		}
+	}
+	return avatars
+}
+
+// The lookup itself runs without avatarMu, which the sync path takes. Claimed
+// IDs are skipped by concurrent callers until it finishes.
+func (r *RedditClient) claimUncachedRedditors(userIDs []networkid.UserID) []string {
+	r.avatarMu.Lock()
+	defer r.avatarMu.Unlock()
+	if time.Now().Before(r.avatarRetryAt) {
+		return nil
+	}
+	if r.avatarURLs == nil {
+		r.avatarURLs = make(map[networkid.UserID]string)
+		r.avatarFetching = make(map[networkid.UserID]bool)
+	}
+	var missing []string
+	for _, userID := range userIDs {
+		if len(missing) == redditorBatchSize {
+			break
+		}
+		if _, cached := r.avatarURLs[userID]; !cached && !r.avatarFetching[userID] && isRedditUserID(userID) {
+			r.avatarFetching[userID] = true
+			missing = append(missing, string(userID))
+		}
+	}
+	return missing
+}
+
+func (r *RedditClient) fetchRedditorIcons(ctx context.Context, redditorIDs []string) {
+	icons, err := r.session.GetRedditorIcons(ctx, redditorIDs)
+	if err != nil {
+		zerolog.Ctx(ctx).Warn().Err(err).Msg("Failed to fetch Reddit avatars")
+	}
+	r.avatarMu.Lock()
+	defer r.avatarMu.Unlock()
+	if err != nil {
+		r.avatarRetryAt = time.Now().Add(avatarRetryDelay)
+	}
+	for _, redditorID := range redditorIDs {
+		delete(r.avatarFetching, networkid.UserID(redditorID))
+		if err == nil {
+			r.avatarURLs[networkid.UserID(redditorID)] = icons[redditorID]
+		}
+	}
+}
+
+func (r *RedditClient) addMemberAvatars(ctx context.Context, info *bridgev2.ChatInfo) *bridgev2.ChatInfo {
+	if info.Members == nil {
+		return info
+	}
+	userIDs := make([]networkid.UserID, 0, len(info.Members.MemberMap))
+	for _, member := range info.Members.MemberMap {
+		userIDs = append(userIDs, member.Sender)
+	}
+	avatars := r.redditorAvatars(ctx, userIDs)
+	for _, member := range info.Members.MemberMap {
+		if avatar := avatars[member.Sender]; avatar != nil && member.UserInfo != nil {
+			member.UserInfo.Avatar = avatar
+		}
+	}
+	return info
+}
+
+func downloadRedditorAvatar(ctx context.Context, url string) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := avatarHTTPClient.Do(req)
+	if err != nil {
+		return nil, mediaError(ctx, "Reddit avatar download", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("reddit avatar is unavailable (HTTP %d)", resp.StatusCode)
+	}
+	return readMediaBounded(resp.Body, 2*1024*1024)
+}

pkg/connector/chatinfo.go

@@ -21,7 +21,7 @@ func (r *RedditClient) GetChatInfo(ctx context.Context, portal *bridgev2.Portal)
 	if key != portal.PortalKey {
 		return nil, errors.New("chat ownership does not match Reddit room state")
 	}
-	return r.chatInfoFromState(state), nil
+	return r.addMemberAvatars(ctx, r.chatInfoFromState(state)), nil
 }
 
 // GetUserInfo fetches profile info for a ghost (a Reddit user puppeted into
@@ -40,19 +40,10 @@ func (r *RedditClient) GetUserInfo(ctx context.Context, ghost *bridgev2.Ghost) (
 		Username: stripUserPrefix(name),
 		UserID:   string(ghost.ID),
 	})
-	info := &bridgev2.UserInfo{Name: ptr.Ptr(formatted)}
-	if !resp.AvatarURL.IsEmpty() {
-		mxc := resp.AvatarURL.CUString()
-		info.Avatar = &bridgev2.Avatar{
-			ID:  networkid.AvatarID(mxc),
-			Get: func(ctx context.Context) ([]byte, error) { return r.downloadRedditMedia(ctx, mxc, nil) },
-		}
-		if r.main.directMedia {
-			// Retain the normal download fallback if the identity cannot fit.
-			info.Avatar.MXC, _ = r.directMediaURI(ctx, mxc)
-		}
-	}
-	return info, nil
+	return &bridgev2.UserInfo{
+		Name:   ptr.Ptr(formatted),
+		Avatar: r.redditorAvatars(ctx, []networkid.UserID{ghost.ID})[ghost.ID],
+	}, nil
 }
 
 func stripUserPrefix(name string) string {

pkg/connector/chatsync.go

@@ -329,9 +329,9 @@ func (r *RedditClient) joinedRoomEvent(state *RoomState, key networkid.PortalKey
 	info := r.chatInfoFromState(state)
 	return &simplevent.ChatResync{
 		EventMeta: simplevent.EventMeta{Type: bridgev2.RemoteEventChatResync, PortalKey: key, CreatePortal: true},
-		GetChatInfoFunc: func(context.Context, *bridgev2.Portal) (*bridgev2.ChatInfo, error) {
+		GetChatInfoFunc: func(ctx context.Context, _ *bridgev2.Portal) (*bridgev2.ChatInfo, error) {
 			// Account block state may change while this room snapshot is queued.
-			return r.chatInfoFromState(state), nil
+			return r.addMemberAvatars(ctx, r.chatInfoFromState(state)), nil
 		},
 		CheckNeedsBackfillFunc: func(_ context.Context, latest *database.Message) (bool, error) {
 			return info.CanBackfill && (limited || latest == nil), nil

pkg/connector/client.go

@@ -48,6 +48,11 @@ type RedditClient struct {
 
 	typingMu sync.Mutex
 	typing   map[networkid.PortalKey][]id.UserID
+
+	avatarMu       sync.Mutex
+	avatarURLs     map[networkid.UserID]string
+	avatarFetching map[networkid.UserID]bool
+	avatarRetryAt  time.Time
 }
 
 var _ bridgev2.NetworkAPI = (*RedditClient)(nil)

pkg/connector/requests.go

@@ -143,8 +143,8 @@ func (r *RedditClient) pendingRequestEvent(state *RoomState, key networkid.Porta
 	info := r.chatInfoFromState(state)
 	return &simplevent.ChatResync{
 		EventMeta: simplevent.EventMeta{Type: bridgev2.RemoteEventChatResync, PortalKey: key, CreatePortal: true},
-		GetChatInfoFunc: func(context.Context, *bridgev2.Portal) (*bridgev2.ChatInfo, error) {
-			return r.chatInfoFromState(state), nil
+		GetChatInfoFunc: func(ctx context.Context, _ *bridgev2.Portal) (*bridgev2.ChatInfo, error) {
+			return r.addMemberAvatars(ctx, r.chatInfoFromState(state)), nil
 		},
 		CheckNeedsBackfillFunc: func(_ context.Context, latest *database.Message) (bool, error) {
 			// Populate an existing empty request room too. Subsequent resyncs

pkg/redditchat/redditors.go

@@ -0,0 +1,27 @@
+package redditchat
+
+import "context"
+
+// GetRedditorIcons returns avatar URLs keyed by t2_ ID. Reddit's chat Matrix
+// server has no avatars; the integrated chat UI reads them from here.
+func (s *RedditSession) GetRedditorIcons(ctx context.Context, redditorIDs []string) (map[string]string, error) {
+	var data struct {
+		RedditorsInfoByIDs []struct {
+			ID   string `json:"id"`
+			Icon *struct {
+				URL string `json:"url"`
+			} `json:"icon"`
+		} `json:"redditorsInfoByIds"`
+	}
+	err := s.chatGraphQL(ctx, "ChatRedditors", map[string]any{"ids": redditorIDs, "includeRedditorAttributes": true}, &data)
+	if err != nil {
+		return nil, err
+	}
+	icons := make(map[string]string, len(data.RedditorsInfoByIDs))
+	for _, redditor := range data.RedditorsInfoByIDs {
+		if redditor.Icon != nil && redditor.Icon.URL != "" {
+			icons[redditor.ID] = redditor.Icon.URL
+		}
+	}
+	return icons, nil
+}