//! Criterion bench for mmap-strategy wins (waves 1-3).
//!
//! Measures the per-tensor-hint application time + the
//! end-to-end load time under different PrefetchPolicy
//! variants. Page-cache state is not controlled (no easy
//! way to evict from userspace); for cold-cache TTFT
//! numbers, run on a freshly-booted box or use `drop_caches`
//! between iterations.

use std::hint::black_box;

use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
use jouleclaw_loader_gguf::synthetic::{synthesize_llama_gguf, SyntheticConfig};
use jouleclaw_loader_gguf::{
    read_gguf_file, read_gguf_file_with_policy, PrefetchPolicy,
};
use std::io::Write;
use std::path::PathBuf;

fn write_synth_gguf(tag: &str) -> PathBuf {
    let bytes = synthesize_llama_gguf(&SyntheticConfig::default());
    let dir = std::env::temp_dir();
    let pid = std::process::id();
    let path = dir.join(format!("jouleclaw-bench-{}-{}.gguf", tag, pid));
    let mut f = std::fs::File::create(&path).unwrap();
    f.write_all(&bytes).unwrap();
    f.sync_all().unwrap();
    path
}

fn bench_policies(c: &mut Criterion) {
    let path = write_synth_gguf("policies");
    let mut g = c.benchmark_group("read_gguf_file_with_policy");
    let policies = [
        ("none", PrefetchPolicy::None),
        ("all", PrefetchPolicy::All),
        ("per_tensor_only", PrefetchPolicy::PerTensorOnly),
        ("top_n_3", PrefetchPolicy::TopN(3)),
        ("top_n_10", PrefetchPolicy::TopN(10)),
    ];
    for (label, policy) in policies {
        g.bench_with_input(
            BenchmarkId::from_parameter(label),
            &policy,
            |b, &policy| {
                b.iter(|| {
                    let m = read_gguf_file_with_policy(black_box(&path), policy)
                        .expect("parse");
                    black_box(&m);
                });
            },
        );
    }
    g.finish();
    // Default-API path baseline.
    c.bench_function("read_gguf_file_default", |b| {
        b.iter(|| {
            let m = read_gguf_file(black_box(&path)).expect("parse");
            black_box(&m);
        });
    });
    let _ = std::fs::remove_file(path);
}

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