vyre-foundation 0.4.1

use std::cell::RefCell;
use std::collections::HashMap;
use std::time::Instant;

thread_local! {
    static METRICS: RefCell<HashMap<&'static str, u64>> = RefCell::new(HashMap::new());
}

/// RAII guard returned by [`span`].
pub struct SpanGuard {
    name: &'static str,
    start: Instant,
}

/// Completed performance timing sample.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct PerfMeasurement {
    /// Elapsed nanoseconds.
    pub elapsed_ns: u64,
}

/// Explicitly-finished performance scope used by hot paths that need the
/// elapsed value in addition to thread-local accumulation.
pub struct PerfScope {
    name: &'static str,
    start: Instant,
}

impl PerfScope {
    /// Start a named performance scope.
    #[must_use]
    pub fn start(_crate_name: &'static str, name: &'static str) -> Self {
        Self {
            name,
            start: Instant::now(),
        }
    }

    /// Finish this scope and accumulate its elapsed time.
    #[must_use]
    pub fn finish(self) -> PerfMeasurement {
        let elapsed_ns = self.start.elapsed().as_nanos() as u64;
        METRICS.with(|metrics| {
            let mut map = metrics.borrow_mut();
            *map.entry(self.name).or_insert(0) += elapsed_ns;
        });
        PerfMeasurement { elapsed_ns }
    }
}

impl Drop for SpanGuard {
    fn drop(&mut self) {
        let elapsed = self.start.elapsed().as_nanos() as u64;
        METRICS.with(|metrics| {
            let mut map = metrics.borrow_mut();
            *map.entry(self.name).or_insert(0) += elapsed;
        });
    }
}

/// Start a performance span. When the returned guard is dropped, the elapsed time
/// is accumulated into the thread-local metric named `name`.
pub fn span(name: &'static str) -> SpanGuard {
    SpanGuard {
        name,
        start: Instant::now(),
    }
}

/// Retrieve all accumulated metrics for the current thread.
pub fn get_metrics() -> HashMap<&'static str, u64> {
    METRICS.with(|metrics| metrics.borrow().clone())
}

/// Reset all accumulated metrics for the current thread.
pub fn reset_metrics() {
    METRICS.with(|metrics| metrics.borrow_mut().clear());
}