//! 不可撤销的定时器

use std::{cmp::Reverse, fmt};

use pi_ext_heap::{empty as heap_empty, ExtHeap};
use pi_wheel::{TimeoutItem, Wheel};

/// 不可撤销的定时器
pub struct Timer<T, const N0: usize, const N: usize, const L: usize> {
    wheel: Wheel<T, N0, N, L>, // 定时轮
    heap: ExtHeap<Reverse<TimeoutItem<T>>>, // 最小堆
    add_count: usize,
    remove_count: usize,
    roll_count: u64,
}

impl<T: fmt::Debug, const N0: usize, const N: usize, const L: usize> fmt::Debug
    for Timer<T, N0, N, L>
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Timer")
            .field("wheel", &self.wheel)
            .field("heap", &self.heap)
            .field("add_count", &self.add_count)
            .field("remove_count", &self.remove_count)
            .field("roll_count", &self.roll_count)
            .finish()
    }
}
impl<T, const N0: usize, const N: usize, const L: usize> Default for Timer<T, N0, N, L> {
    fn default() -> Self {
        Timer {
            wheel: Default::default(),
            heap: Default::default(),
            add_count: 0,
            remove_count: 0,
            roll_count: 0,
        }
    }
}

impl<T, const N0: usize, const N: usize, const L: usize> Timer<T, N0, N, L> {
    /// 获得添加任务数量
    pub fn add_count(&self) -> usize {
        self.add_count
    }
    /// 获得移除任务数量
    pub fn remove_count(&self) -> usize {
        self.remove_count
    }
    /// 获得滚动次数
    pub fn roll_count(&self) -> u64 {
        self.roll_count
    }
    /// 放入一个定时任务
    pub fn push(&mut self, timeout: usize, el: T) {
        self.add_count += 1;
        if let Some(r) = self.wheel.push(TimeoutItem::new(timeout, el)) {
            // 没有放入的定时任务的时间已经被转换成绝对时间，放入堆中
            self.heap.push(Reverse(r), &mut (), heap_empty);
        }
    }
    /// 弹出一个定时任务
    /// * `now` 当前时间
    /// * @return `Option<T>` 弹出的定时元素
    pub fn pop(&mut self, now: u64) -> Option<T> {
        loop {
            if let Some(r) = self.wheel.pop() {
                self.remove_count += 1;
                return Some(r.el)
            }
            if self.roll_count >= now {
                return None
            }
            self.roll();
        }
    }
    /// 判断指定时间内是否还有定时任务
    pub fn is_ok(&mut self, now: u64) -> bool {
        loop {
            if !self.wheel.is_cur_over() {
                return true
            }
            if self.roll_count >= now {
                return false
            }
            self.roll();
        }
    }
    /// 轮滚动 - 向后滚动一个最小粒度, 可能会造成轮的逐层滚动。如果滚动到底，则修正堆上全部的定时任务，并将堆上的到期任务放入轮中
    pub fn roll(&mut self) {
        self.roll_count += 1;
        if self.wheel.roll() {
            // 修正堆上全部的定时任务
            for i in 0..self.heap.len() {
                unsafe { self.heap.get_unchecked_mut(i).0.timeout -= self.wheel.max_time() };
            }
            // 如果滚到轮的最后一层的最后一个， 则将堆上的到期任务放入轮中
            // 检查堆顶的最近的任务
            while let Some(it) = self.heap.peek() {
                // 判断任务是否需要放入轮中
                if it.0.timeout >= self.wheel.max_time() {
                    break;
                }
                let it = self.heap.pop(&mut (), heap_empty).unwrap();
                // 时间已经修正过了，可以直接放入定时轮中
                self.wheel.push(it.0);
            }
        }
    }
}

// 测试定时器得延时情况
#[cfg(test)]
mod test_mod {
    extern crate pcg_rand;
    extern crate rand_core;

    use std::{
        thread,
        time::{Duration, Instant},
    };

    use self::rand_core::{RngCore, SeedableRng};
    use crate::*;

    #[test]
    fn test() {
        let mut timer: Timer<(u64, u64), 128, 16, 1> = Default::default();
        let mut rng = pcg_rand::Pcg32::seed_from_u64(22222);
        let start = Instant::now();
        println!("max_time:{}", timer.wheel.max_time());
        for i in 1..100000 {
            let t = (rng.next_u32() % 16100) as u64;
            let now = Instant::now();
            let tt = now.duration_since(start).as_millis() as u64;
            if i < 100 {
                println!("push: timeout:{} realtime:{:?}", t, (i, t + tt));
                timer.push(t as usize, (i, t + tt));
            }
            if t == 9937 || t == 15280 {
                println!("{:?}", timer.wheel);
            }
            //while let Some(it) = timer.pop(tt) {
            while timer.is_ok(tt) {
                let it = timer.pop(tt).unwrap();
                println!("ppp:{:?}, now:{}", it, tt);
            }
            if i > 100 && timer.add_count == timer.remove_count {
                //println!("vec:{:?}", vec);
                println!(
                    "return: add_count:{:?}",
                    timer.add_count
                );
                return;
            }
            thread::sleep(Duration::from_millis(1 as u64));
        }
    }

}