use std::sync::atomic::Ordering;
use std::time::Instant;

use histogram::Histogram;

use crate::common::*;
use crate::config::Config;


pub fn clean_connections_and_torrents(state: &State){
    let now = Instant::now();

    let mut connections = state.connections.lock();

    connections.retain(|_, v| v.0 > now);
    connections.shrink_to_fit();

    ::std::mem::drop(connections);

    let mut torrents = state.torrents.lock();

    torrents.retain(|_, torrent| {
        let num_seeders = &mut torrent.num_seeders;
        let num_leechers = &mut torrent.num_leechers;

        torrent.peers.retain(|_, peer| {
            let keep = peer.valid_until.0 > now;

            if !keep {
                match peer.status {
                    PeerStatus::Seeding => {
                        *num_seeders -= 1;
                    },
                    PeerStatus::Leeching => {
                        *num_leechers -= 1;
                    },
                    _ => (),
                };
            }

            keep
        });

        !torrent.peers.is_empty()
    });

    torrents.shrink_to_fit();
}


pub fn gather_and_print_statistics(
    state: &State,
    config: &Config,
){
    let interval = config.statistics.interval;

    let requests_received: f64 = state.statistics.requests_received
        .fetch_and(0, Ordering::SeqCst) as f64;
    let responses_sent: f64 = state.statistics.responses_sent
        .fetch_and(0, Ordering::SeqCst) as f64;
    let bytes_received: f64 = state.statistics.bytes_received
        .fetch_and(0, Ordering::SeqCst) as f64;
    let bytes_sent: f64 = state.statistics.bytes_sent
        .fetch_and(0, Ordering::SeqCst) as f64;

    let requests_per_second = requests_received / interval as f64;
    let responses_per_second: f64 = responses_sent / interval as f64;
    let bytes_received_per_second: f64 = bytes_received / interval as f64;
    let bytes_sent_per_second: f64 = bytes_sent / interval as f64;

    let readable_events: f64 = state.statistics.readable_events
        .fetch_and(0, Ordering::SeqCst) as f64;
    let requests_per_readable_event = if readable_events == 0.0 {
        0.0
    } else {
        requests_received / readable_events
    };

    println!(
        "stats: {:.2} requests/second, {:.2} responses/second, {:.2} requests/readable event",
        requests_per_second,
        responses_per_second,
        requests_per_readable_event
    );

    println!(
        "bandwidth: {:7.2} Mbit/s in, {:7.2} Mbit/s out",
        bytes_received_per_second * 8.0 / 1_000_000.0,
        bytes_sent_per_second * 8.0 / 1_000_000.0,
    );

    let mut peers_per_torrent = Histogram::new();

    let torrents = &mut state.torrents.lock();

    for torrent in torrents.values(){
        let num_peers = (torrent.num_seeders + torrent.num_leechers) as u64;

        if let Err(err) = peers_per_torrent.increment(num_peers){
            eprintln!("error incrementing peers_per_torrent histogram: {}", err)
        }
    }

    ::std::mem::drop(torrents);

    if peers_per_torrent.entries() != 0 {
        println!(
            "peers per torrent: min: {}, p50: {}, p75: {}, p90: {}, p99: {}, p999: {}, max: {}",
            peers_per_torrent.minimum().unwrap(),
            peers_per_torrent.percentile(50.0).unwrap(),
            peers_per_torrent.percentile(75.0).unwrap(),
            peers_per_torrent.percentile(90.0).unwrap(),
            peers_per_torrent.percentile(99.0).unwrap(),
            peers_per_torrent.percentile(99.9).unwrap(),
            peers_per_torrent.maximum().unwrap(),
        );
    }

    println!();
}