//! Inner Fenrir tracking
//! This is meant to be **async-free** so that others might use it
//! without the tokio runtime

pub(crate) mod worker;

use crate::inner::worker::Work;
use ::std::{collections::BTreeMap, vec::Vec};
use ::tokio::time::Instant;

/// Track the total number of threads and our index
/// 65K cpus should be enough for anybody
#[derive(Debug, Clone, Copy)]
pub(crate) struct ThreadTracker {
    pub total: u16,
    /// Note: starts from 1
    pub id: u16,
}

pub(crate) static mut SLEEP_RESOLUTION: ::std::time::Duration =
    if cfg!(linux) || cfg!(macos) {
        ::std::time::Duration::from_millis(1)
    } else {
        // windows
        ::std::time::Duration::from_millis(16)
    };

pub(crate) async fn set_minimum_sleep_resolution() {
    let nanosleep = ::std::time::Duration::from_nanos(1);
    let mut tests: usize = 3;

    while tests > 0 {
        let pre_sleep = ::std::time::Instant::now();
        ::tokio::time::sleep(nanosleep).await;
        let post_sleep = ::std::time::Instant::now();
        let slept_for = post_sleep - pre_sleep;
        #[allow(unsafe_code)]
        unsafe {
            if slept_for < SLEEP_RESOLUTION {
                SLEEP_RESOLUTION = slept_for;
            }
        }
        tests = tests - 1;
    }
}

/// Sleeping has a higher resolution that we would like for packet pacing.
/// So we sleep for however log we need, then chunk up all the work here
/// we will end up chunking the work in SLEEP_RESOLUTION, then we will busy wait
/// for more precise timing
pub(crate) struct Timers {
    times: BTreeMap<Instant, Work>,
}

impl Timers {
    pub(crate) fn new() -> Self {
        Self {
            times: BTreeMap::new(),
        }
    }
    pub(crate) fn get_next(&self) -> ::tokio::time::Sleep {
        match self.times.keys().next() {
            Some(entry) => ::tokio::time::sleep_until((*entry).into()),
            None => {
                ::tokio::time::sleep(::std::time::Duration::from_secs(3600))
            }
        }
    }
    pub(crate) fn add(
        &mut self,
        duration: ::tokio::time::Duration,
        work: Work,
    ) -> ::tokio::time::Instant {
        // the returned time is the key in the map.
        // Make sure it is unique.
        //
        // We can be pretty sure we won't do a lot of stuff
        // in a single nanosecond, so if we hit a time that is already present
        // just add a nanosecond and retry
        let mut time = ::tokio::time::Instant::now() + duration;
        let mut work = work;
        loop {
            if let Some(old_val) = self.times.insert(time, work) {
                work = self.times.insert(time, old_val).unwrap();
                time = time + ::std::time::Duration::from_nanos(1);
            } else {
                break;
            }
        }
        time
    }
    pub(crate) fn remove(&mut self, time: ::tokio::time::Instant) {
        let _ = self.times.remove(&time);
    }
    /// Get all the work from now up until now + SLEEP_RESOLUTION
    pub(crate) fn get_work(&mut self) -> Vec<Work> {
        let now: ::tokio::time::Instant = ::std::time::Instant::now().into();
        let mut ret = Vec::with_capacity(4);
        let mut count_rm = 0;
        #[allow(unsafe_code)]
        let next_instant = unsafe { now + SLEEP_RESOLUTION };
        let mut iter = self.times.iter_mut().peekable();
        loop {
            match iter.peek() {
                None => break,
                Some(next) => {
                    if *next.0 > next_instant {
                        break;
                    }
                }
            }
            let mut work = Work::DropHandshake(crate::enc::asym::KeyID(0));
            let mut entry = iter.next().unwrap();
            ::core::mem::swap(&mut work, &mut entry.1);
            ret.push(work);
            count_rm = count_rm + 1;
        }
        while count_rm > 0 {
            self.times.pop_first();
            count_rm = count_rm - 1;
        }
        ret
    }
}