//! Runtime comparison benchmarks
//!
//! Compares announcement performance across different async runtimes.
//! This verifies the runtime-agnostic design works consistently.
//!
//! Runtimes tested:
//! - tokio (most popular)
//! - smol (lightweight alternative)
//!
//! Expected result: Similar performance across runtimes since announcement
//! uses event-listener which abstracts runtime details.

#![allow(unused_must_use)]

use announcement::Announcement;
use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion, Throughput};
use std::hint::black_box;
use std::sync::Arc;

/// Benchmark: Basic announce and listen - tokio vs smol
fn bench_basic(c: &mut Criterion) {
    let rt = tokio::runtime::Runtime::new().unwrap();
    let mut group = c.benchmark_group("runtimes/basic");

    // Tokio version
    group.bench_function("tokio", |b| {
        b.to_async(&rt).iter(|| async {
            let (announcer, announcement) = Announcement::new();
            let listener = announcement.listener();

            let handle = tokio::spawn(async move { listener.listen().await });
            announcer.announce(Arc::new(42)).unwrap();

            black_box(handle.await.unwrap());
        });
    });

    // Smol version
    group.bench_function("smol", |b| {
        b.iter(|| {
            smol::block_on(async {
                let (announcer, announcement) = Announcement::new();
                let listener = announcement.listener();

                let handle = smol::spawn(async move { listener.listen().await });
                announcer.announce(Arc::new(42)).unwrap();

                black_box(handle.await);
            });
        });
    });

    group.finish();
}

/// Benchmark: Fanout to multiple listeners - tokio vs smol
fn bench_fanout(c: &mut Criterion) {
    let rt = tokio::runtime::Runtime::new().unwrap();
    let mut group = c.benchmark_group("runtimes/fanout");

    for n in [10, 100, 500].iter() {
        group.throughput(Throughput::Elements(*n as u64));

        // Tokio version
        group.bench_with_input(BenchmarkId::new("tokio", n), n, |b, &n| {
            b.to_async(&rt).iter(|| async move {
                let (announcer, announcement) = Announcement::new();

                let mut handles = Vec::with_capacity(n);
                for _ in 0..n {
                    let listener = announcement.listener();
                    handles.push(tokio::spawn(async move { listener.listen().await }));
                }

                announcer.announce(Arc::new(42)).unwrap();

                for h in handles {
                    black_box(h.await.unwrap());
                }
            });
        });

        // Smol version
        group.bench_with_input(BenchmarkId::new("smol", n), n, |b, &n| {
            b.iter(|| {
                smol::block_on(async {
                    let (announcer, announcement) = Announcement::new();

                    let mut handles = Vec::with_capacity(n);
                    for _ in 0..n {
                        let listener = announcement.listener();
                        handles.push(smol::spawn(async move { listener.listen().await }));
                    }

                    announcer.announce(Arc::new(42)).unwrap();

                    for h in handles {
                        black_box(h.await);
                    }
                });
            });
        });
    }

    group.finish();
}

/// Benchmark: Concurrent announcements - tokio vs smol
fn bench_concurrent(c: &mut Criterion) {
    let rt = tokio::runtime::Runtime::new().unwrap();
    let mut group = c.benchmark_group("runtimes/concurrent");

    // Tokio version
    group.bench_function("tokio", |b| {
        b.to_async(&rt).iter(|| async {
            let mut handles = Vec::with_capacity(100);

            for i in 0..100 {
                handles.push(tokio::spawn(async move {
                    let (announcer, announcement) = Announcement::new();
                    let listener = announcement.listener();

                    let recv_handle = tokio::spawn(async move { listener.listen().await });
                    announcer.announce(Arc::new(i)).unwrap();

                    recv_handle.await.unwrap()
                }));
            }

            for h in handles {
                black_box(h.await.unwrap());
            }
        });
    });

    // Smol version
    group.bench_function("smol", |b| {
        b.iter(|| {
            smol::block_on(async {
                let mut handles = Vec::with_capacity(100);

                for i in 0..100 {
                    handles.push(smol::spawn(async move {
                        let (announcer, announcement) = Announcement::new();
                        let listener = announcement.listener();

                        let recv_handle = smol::spawn(async move { listener.listen().await });
                        announcer.announce(Arc::new(i)).unwrap();

                        recv_handle.await
                    }));
                }

                for h in handles {
                    black_box(h.await);
                }
            });
        });
    });

    group.finish();
}

criterion_group!(benches, bench_basic, bench_fanout, bench_concurrent,);
criterion_main!(benches);