chat

type Chat struct {
	ID            *commonpb.ChatId
	Type          chatpb.Metadata_ChatType
	Members       []*commonpb.UserId
	LastActivity  time.Time
	LastMessageID *messagingpb.MessageId
}

type DmFeedCursor struct {
	LastActivity time.Time
	ChatID       *commonpb.ChatId
}

type MessageRef struct {
	ChatID    *commonpb.ChatId
	MessageID *messagingpb.MessageId
}

type MessagingReader interface {
	// LastMessages returns the message for each ref that exists, keyed by
	// string(chatID.Value). Refs without a message are absent from the map.
	LastMessages(ctx context.Context, refs []MessageRef) (map[string]*messagingpb.Message, error)

	// Pointers returns the delivered/read pointers for each chat, keyed by
	// string(chatID.Value). Chats with no pointers are absent from the map.
	Pointers(ctx context.Context, chatIDs []*commonpb.ChatId) (map[string][]*messagingpb.Pointer, error)
}

type Server struct {
	chatpb.UnimplementedChatServer
	// contains filtered or unexported fields
}

type Store interface {
	// PutChat persists a new chat and its membership. It returns ErrChatExists
	// if a chat with the same ID already exists.
	PutChat(ctx context.Context, chat *Chat) error

	// GetChatByID returns the chat with the given ID, or ErrChatNotFound.
	GetChatByID(ctx context.Context, chatID *commonpb.ChatId) (*Chat, error)

	// GetDmFeedPage returns one page of userID's DM feed pinned to a snapshot:
	// the DMs userID is a member of whose last_activity is at or before snapshot,
	// ordered by (last_activity, chat_id) descending (most recent first), at most
	// limit chats (limit <= 0 means unbounded). When cursor is nil the page starts
	// at the most recent chat in the snapshot; otherwise it resumes strictly after
	// cursor. An empty result (no error) is returned when no chats remain.
	//
	// Pinning to a fixed watermark makes a multi-page read internally consistent.
	// last_activity only ever advances to a wall-clock send time, so any chat that
	// becomes active after the snapshot moves strictly above the watermark and
	// leaves the window — it can be neither duplicated onto nor skipped within a
	// later page. Those freshly-active chats are surfaced through the live
	// MetadataUpdate event stream instead (see the Chat service's GetDmChatFeed).
	//
	// It is scoped to DMs because the per-user inbox is split by chat type (see
	// the dynamodb store). Group chats will have a parallel accessor, and the
	// server merges the two descending streams into one feed.
	GetDmFeedPage(ctx context.Context, userID *commonpb.UserId, snapshot time.Time, cursor *DmFeedCursor, limit int) ([]*Chat, error)

	// GetMembers returns the member user IDs of a chat, or ErrChatNotFound.
	GetMembers(ctx context.Context, chatID *commonpb.ChatId) ([]*commonpb.UserId, error)

	// IsMember reports whether userID is a member of chatID. It returns false
	// (no error) when the chat does not exist.
	IsMember(ctx context.Context, chatID *commonpb.ChatId, userID *commonpb.UserId) (bool, error)

	// AdvanceLastMessage records messageID as the chat's most recent message,
	// moving last_activity forward to ts and last_message_id to messageID, and
	// reports whether it advanced. The two fields are two views of the same event
	// (the newest message) and are updated together. If the stored last_activity
	// is already at or after ts, it is a no-op and returns false. It returns
	// ErrChatNotFound if the chat does not exist.
	AdvanceLastMessage(ctx context.Context, chatID *commonpb.ChatId, messageID *messagingpb.MessageId, ts time.Time) (bool, error)
}