use crate::*;

/// Performance counter
#[derive(Debug)]
pub struct PerfModel {
    pub clock: quanta::Clock,
    /// Measurement has a small cost. Disable it here.
    pub enabled: bool,
    // In nanoseconds. Time used by last iteration.
    pub used: AtomicF64,
    // In microseconds. Max prescribed time for iteration (frame, chunk...).
    pub window: AtomicF64,
}

impl_default!(PerfModel: Self {
    enabled: true,
    clock:   quanta::Clock::new(),
    used:    Default::default(),
    window:  Default::default(),
});

impl PerfModel {
    pub fn get_t0 (&self) -> Option<u64> {
        if self.enabled {
            Some(self.clock.raw())
        } else {
            None
        }
    }
    pub fn get_t1 (&self, t0: Option<u64>) -> Option<std::time::Duration> {
        if let Some(t0) = t0 {
            if self.enabled {
                Some(self.clock.delta(t0, self.clock.raw()))
            } else {
                None
            }
        } else {
            None
        }
    }
    pub fn update (&self, t0: Option<u64>, microseconds: f64) {
        if let Some(t0) = t0 {
            let t1 = self.clock.raw();
            self.used.store(self.clock.delta_as_nanos(t0, t1) as f64, Relaxed);
            self.window.store(microseconds, Relaxed,);
        }
    }
    pub fn percentage (&self) -> Option<f64> {
        let window = self.window.load(Relaxed) * 1000.0;
        if window > 0.0 {
            let used = self.used.load(Relaxed);
            Some(100.0 * used / window)
        } else {
            None
        }
    }
    pub fn cycle <F: FnMut(&Self)->T, T> (&self, call: &mut F) -> T {
        let t0 = self.get_t0();
        let result = call(self);
        let _t1 = self.get_t1(t0).unwrap();
        result
    }
}