use criterion::{criterion_group, criterion_main, Criterion};
use rand::{
    distributions::{Alphanumeric, DistString},
    thread_rng, Rng,
};

use cover::library::{Artist, Library, Song};

// actual benchmarks

fn bench_random_library(c: &mut Criterion) {
    bench_random_library_with_sizes(c, "small", 5, 25);
    bench_random_library_with_sizes(c, "medium", 25, 100);
    bench_random_library_with_sizes(c, "large", 100, 1000);
    bench_random_library_with_sizes(c, "massive", 1000, 2500);
}

// benchmark helpers

fn bench_random_library_with_sizes(c: &mut Criterion, size: &str, artists: usize, songs: usize) {
    let id = format!("{size} random library ({artists} artists x {songs} songs/artist)");
    let library = random_library(artists, songs);
    c.bench_function(id.as_str(), |b| {
        b.iter(|| {
            library.library_covers();
        })
    });
}

// test data generators

fn random_string() -> String {
    let mut rng = thread_rng();
    let length = rng.gen_range(1..=20);
    Alphanumeric.sample_string(&mut rng, length)
}

fn generate_iter<T: Clone>(generator: impl Fn() -> T, length: usize) -> impl Iterator<Item = T> {
    let mut ts = Vec::with_capacity(length);
    for _ in 0..length {
        ts.push(generator())
    }
    ts.into_iter()
}

fn random_song() -> Song {
    Song::new(
        random_string(),
        random_string(),
        generate_iter(random_string, 5),
    )
}

fn random_artist(songs: usize) -> Artist {
    Artist::new(
        random_string(),
        generate_iter(random_string, 5),
        generate_iter(random_song, songs),
    )
}

fn random_library(artists: usize, songs_per_artist: usize) -> Library {
    Library::new(generate_iter(|| random_artist(songs_per_artist), artists))
}

// entrypoint

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