use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};

fn generate_data(n: usize) -> Vec<u64> {
    use rand::prelude::*;
    let mut rng = thread_rng();
    let mut res = vec![0u64; n];
    rng.fill(&mut res[..]);
    res
}

const N: usize = 1000;

pub fn criterion_benchmark(c: &mut Criterion) {
    let data = generate_data(N);
    let mut group = c.benchmark_group("vec_fill");
    group.bench_function(BenchmarkId::new("with_capacity_extend", ""), |b| {
        b.iter(|| {
            let mut result = Vec::with_capacity(data.len() + 1);
            result.push(0);
            result.extend(data.iter());
            result
        })
    });
    group.bench_function(BenchmarkId::new("clone_insert", ""), |b| {
        b.iter(|| {
            let mut result = data.clone();
            result.insert(0, 0);
            result
        })
    });
    group.bench_function(BenchmarkId::new("chain_collect", ""), |b| {
        b.iter(|| {
            let result: Vec<u64> = std::iter::once(0).chain(data.iter().copied()).collect();
            result
        })
    });
    group.finish();
}

criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);