nanoreth/docs/mermaid/fetch-client.mmd

sequenceDiagram
    participant Client as FetchClient
    participant Fetcher as StateFetcher
    participant State as NetworkState
    participant Session as Active Peer Session
    participant Peers as PeerManager
    loop Send Request, retry if retriable and remaining retries
        Client->>Fetcher: DownloadRequest{GetHeaders, GetBodies}
        Note over Client,Fetcher: Request and oneshot Sender sent via `request_tx` channel
        loop Process buffered requests
            State->>Fetcher: poll action
            Fetcher->>Fetcher: Select Available Peer
            Note over Fetcher: Peer is available if it's currently idle, no inflight requests
            Fetcher->>State: FetchAction::BlockDownloadRequest
            State->>Session: Delegate Request
            Note over State,Session: Request and oneshot Sender sent via `to_session_tx` channel
        end
        Session->>Session: Send Request to remote
        Session->>Session: Enforce Request timeout
        Session-->>State: Send Response Result via channel
        State->>Fetcher: Delegate Response
        Fetcher-->>Client: Send Response via channel
        opt Bad Response
            Client->>Peers: Penalize Peer
        end
        Peers->>Peers: Apply Reputation Change
        opt reputation dropped below threshold
            Peers->>State: Disconnect Session
            State->>Session: Delegate Disconnect
        end
    end