// Copyright 2018 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![feature(test)]
#![allow(non_snake_case)]

extern crate test;

use test::Bencher;

use rand::prelude::*;
use rand::seq::*;
use std::mem::size_of;

// We force use of 32-bit RNG since seq code is optimised for use with 32-bit
// generators on all platforms.
use rand_pcg::Pcg32 as SmallRng;

const RAND_BENCH_N: u64 = 1000;

#[bench]
fn seq_shuffle_100(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &mut [usize] = &mut [1; 100];
    b.iter(|| {
        x.shuffle(&mut rng);
        x[0]
    })
}

#[bench]
fn seq_slice_choose_1_of_1000(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &mut [usize] = &mut [1; 1000];
    for i in 0..1000 {
        x[i] = i;
    }
    b.iter(|| {
        let mut s = 0;
        for _ in 0..RAND_BENCH_N {
            s += x.choose(&mut rng).unwrap();
        }
        s
    });
    b.bytes = size_of::<usize>() as u64 * crate::RAND_BENCH_N;
}

macro_rules! seq_slice_choose_multiple {
    ($name:ident, $amount:expr, $length:expr) => {
        #[bench]
        fn $name(b: &mut Bencher) {
            let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
            let x : &[i32] = &[$amount; $length];
            let mut result = [0i32; $amount];
            b.iter(|| {
                // Collect full result to prevent unwanted shortcuts getting
                // first element (in case sample_indices returns an iterator).
                for (slot, sample) in result.iter_mut().zip(
                    x.choose_multiple(&mut rng, $amount)) {
                    *slot = *sample;
                }
                result[$amount-1]
            })
        }
    }
}

seq_slice_choose_multiple!(seq_slice_choose_multiple_1_of_1000, 1, 1000);
seq_slice_choose_multiple!(seq_slice_choose_multiple_950_of_1000, 950, 1000);
seq_slice_choose_multiple!(seq_slice_choose_multiple_10_of_100, 10, 100);
seq_slice_choose_multiple!(seq_slice_choose_multiple_90_of_100, 90, 100);

#[bench]
fn seq_iter_choose_from_1000(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &mut [usize] = &mut [1; 1000];
    for i in 0..1000 {
        x[i] = i;
    }
    b.iter(|| {
        let mut s = 0;
        for _ in 0..RAND_BENCH_N {
            s += x.iter().choose(&mut rng).unwrap();
        }
        s
    });
    b.bytes = size_of::<usize>() as u64 * crate::RAND_BENCH_N;
}

#[derive(Clone)]
struct UnhintedIterator<I: Iterator + Clone> {
    iter: I,
}
impl<I: Iterator + Clone> Iterator for UnhintedIterator<I> {
    type Item = I::Item;
    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next()
    }
}

#[derive(Clone)]
struct WindowHintedIterator<I: ExactSizeIterator + Iterator + Clone> {
    iter: I,
    window_size: usize,
}
impl<I: ExactSizeIterator + Iterator + Clone> Iterator for WindowHintedIterator<I> {
    type Item = I::Item;
    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        (std::cmp::min(self.iter.len(), self.window_size), None)
    }
}

#[bench]
fn seq_iter_unhinted_choose_from_1000(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &[usize] = &[1; 1000];
    b.iter(|| {
        UnhintedIterator { iter: x.iter() }.choose(&mut rng).unwrap()
    })
}

#[bench]
fn seq_iter_window_hinted_choose_from_1000(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &[usize] = &[1; 1000];
    b.iter(|| {
        WindowHintedIterator { iter: x.iter(), window_size: 7 }.choose(&mut rng)
    })
}

#[bench]
fn seq_iter_choose_multiple_10_of_100(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &[usize] = &[1; 100];
    b.iter(|| {
        x.iter().cloned().choose_multiple(&mut rng, 10)
    })
}

#[bench]
fn seq_iter_choose_multiple_fill_10_of_100(b: &mut Bencher) {
    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
    let x : &[usize] = &[1; 100];
    let mut buf = [0; 10];
    b.iter(|| {
        x.iter().cloned().choose_multiple_fill(&mut rng, &mut buf)
    })
}

macro_rules! sample_indices {
    ($name:ident, $fn:ident, $amount:expr, $length:expr) => {
        #[bench]
        fn $name(b: &mut Bencher) {
            let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
            b.iter(|| {
                index::$fn(&mut rng, $length, $amount)
            })
        }
    }
}

sample_indices!(misc_sample_indices_1_of_1k, sample, 1, 1000);
sample_indices!(misc_sample_indices_10_of_1k, sample, 10, 1000);
sample_indices!(misc_sample_indices_100_of_1k, sample, 100, 1000);
sample_indices!(misc_sample_indices_100_of_1M, sample, 100, 1000_000);
sample_indices!(misc_sample_indices_100_of_1G, sample, 100, 1000_000_000);
sample_indices!(misc_sample_indices_200_of_1G, sample, 200, 1000_000_000);
sample_indices!(misc_sample_indices_400_of_1G, sample, 400, 1000_000_000);
sample_indices!(misc_sample_indices_600_of_1G, sample, 600, 1000_000_000);