// Non-disruptive HID latency budget coverage.
//
// Scope: measure fake endpoint write latency on local temp files only.
// Targets: server HID handoff path and Phase 7 latency budget.
// Why: input responsiveness needs a concrete p95 number; this keeps us from
// tuning by vibes while staying safe on the active desktop.

use std::{sync::Arc, time::Instant};

use lesavka_server::runtime_support::write_hid_report;
use tokio::sync::Mutex;

fn percentile_95(mut values: Vec<u128>) -> u128 {
    values.sort_unstable();
    let index = ((values.len() - 1) as f64 * 0.95).ceil() as usize;
    values[index]
}

#[tokio::test]
async fn fake_hid_loopback_p95_stays_under_interactive_budget() {
    let dir = tempfile::tempdir().expect("tempdir");
    let endpoint = dir.path().join("hidg0");
    std::fs::File::create(&endpoint).expect("create fake HID endpoint");
    let endpoint = endpoint.to_string_lossy().to_string();
    let handle = Arc::new(Mutex::new(None));
    let reports: Vec<[u8; 8]> = (0..96)
        .map(|idx| [0, 0, 0x04 + (idx % 26) as u8, 0, 0, 0, 0, 0])
        .collect();
    let mut samples_ms = Vec::with_capacity(reports.len());

    for report in reports {
        let started = Instant::now();
        write_hid_report(&handle, &endpoint, &report)
            .await
            .expect("write fake HID report");
        samples_ms.push(started.elapsed().as_millis());
    }

    let p95_ms = percentile_95(samples_ms);
    assert!(
        p95_ms < 150,
        "fake HID write p95 should stay below 150ms, got {p95_ms}ms"
    );
}