Refactor ws_host_service_stats.rs to reduce cognitive_complexity and add test coverage

[mukeshblackhat]

ws_host_service_stats.rs has two suppressions: run_collector (line 83) and handle_stats_socket (line 166), both #[allow(clippy::cognitive_complexity)].

What they do

• run_collector (~50 lines) — streams stats from docker.stats() in a loop, computes CPU delta, inserts into history ring buffer, broadcasts to subscribers
• handle_stats_socket (~55 lines) — replays history buffer to a newly connected WebSocket client, then runs a tokio::select! loop relaying broadcast receiver output to the socket

What to do

1. Extract stats chunk processing in run_collector

Lines 105–125 process a single stats chunk: extract values, lock history, push to ring, send via broadcast. Extract:

async fn process_stats_chunk(
    state: &AppState,
    key: &str,
    stats: Stats,
    prev_cpu_total: &mut u64,
    prev_cpu_system: &mut u64,
    tx: &broadcast::Sender<serde_json::Value>,
)

2. Extract history replay in handle_stats_socket

Lines 170–180 replay the history ring to the socket. Extract:

async fn replay_stats_history(
    socket: &mut WebSocket,
    state: &AppState,
    key: &str,
) -> ControlFlow<()>

3. Extract broadcast forwarding loop

Lines 195–218 run the tokio::select! loop that either forwards a broadcast message or handles inbound WebSocket messages. This pattern is shared with ws_stats.rs and ws_service_stats.rs. Consider a shared helper:

async fn relay_broadcast_to_socket(
    socket: &mut WebSocket,
    rx: &mut broadcast::Receiver<serde_json::Value>,
    key: &str,
)

4. Add unit tests

process_stats_chunk (if extraction allows):

• Empty ring → new chunk inserted
• Ring at cap → oldest evicted, new pushed

Important

The workspace Cargo.toml sets cognitive_complexity, too_many_lines, too_many_arguments, and several other clippy lints to warn globally. Run make lint after every change and make sure the output is clean. Don't fix a suppression here only to create new warnings elsewhere.

Acceptance criteria

• process_stats_chunk extracted (from run_collector)
• replay_stats_history extracted (from handle_stats_socket)
• relay_broadcast_to_socket extracted (shared across WS stats handlers if possible)
• Both functions use the new helpers
• All tests pass (make test)
• make lint passes with zero new warnings
• Remove both #[allow(clippy::cognitive_complexity)] suppressions if make lint passes without them, keep any that are still needed (note why)

Related

Tracking issue pattern from previous PRs: #122, #133, #157, #158, #171, #172, #173, #174, #175