graph TD

    SubscribeIndex0[Subscribe, index = 0, no snapshot]
    SubscribeIndexNot0[Subscribe, index > 0, with snapshot]

    SubscribeIndex0 --->|if events in topic| Snapshot
    Snapshot --> EndOfSnapshot
    SubscribeIndex0 ------->|no events in topic| EndOfSnapshot
    EndOfSnapshot --> EventStream

    SubscribeIndexNot0 -->|if index != TopicBuffer.Head| NewSnapshotToFollow
    NewSnapshotToFollow ---> Snapshot

    SubscribeIndexNot0 -->|if index == TopicBuffer.Head| EventStream

    class EndOfSnapshot,NewSnapshotToFollow framing
    classDef framing fill:#FFD700,stroke:#333