//! Criterion benchmarks for IBLT set reconciliation.
//!
//! Groups:
//! - `iblt_manifest/encode/N`     — build + serialise an IBLT sketch
//! - `iblt_manifest/decode/D`     — decode a difference sketch with D elements
//! - `iblt_manifest/roundtrip/N/D` — full encode-send-decode cycle
//! - `iblt_manifest/size/N`       — report sketch bytes vs flat manifest bytes
//!
//! Run:
//!   cargo bench -p clawsync-onion -- iblt_bench

use clawsync_onion::iblt::{DEFAULT_HASH_COUNT, IbltSketch, MIN_CELLS};
use criterion::{BenchmarkId, Criterion, black_box, criterion_group, criterion_main};

// ─────────────────────────────────────────────────────────────────────────────

const SEED: u64 = 0x0123_4567_89AB_CDEF;

fn keys(n: usize) -> Vec<u64> {
    (0..n as u64).collect()
}

fn diff_sketches(n: usize, d: usize) -> (IbltSketch, Vec<u8>) {
    // A has keys 0..n, B has keys 0..(n-d)
    let a_keys = keys(n);
    let b_keys = keys(n.saturating_sub(d));
    // Use generous m to ensure reliable decode
    let m = ((d * 4).max(MIN_CELLS)).max(IbltSketch::recommended_cells(n));
    let mut a = IbltSketch::new(m, DEFAULT_HASH_COUNT, SEED);
    let mut b = IbltSketch::new(m, DEFAULT_HASH_COUNT, SEED);
    for &k in &a_keys {
        a.insert(k);
    }
    for &k in &b_keys {
        b.insert(k);
    }
    let b_bytes = b.to_bytes();
    a.subtract(&b);
    (a, b_bytes)
}

// ─────────────────────────────────────────────────────────────────────────────

fn bench_iblt(c: &mut Criterion) {
    let ns = [10usize, 100, 1_000, 10_000];
    let ds = [0usize, 1, 10, 50];

    // ── Encode (build + serialise) ────────────────────────────────────────────
    let mut group = c.benchmark_group("iblt_manifest/encode");
    for &n in &ns {
        let ks = keys(n);
        group.bench_with_input(BenchmarkId::from_parameter(n), &ks, |b, k| {
            b.iter(|| {
                let s = IbltSketch::from_keys(black_box(k), SEED);
                black_box(s.to_bytes())
            });
        });
    }
    group.finish();

    // ── Decode diff sketch ────────────────────────────────────────────────────
    let mut group = c.benchmark_group("iblt_manifest/decode");
    for &d in &ds {
        let n = 1_000usize;
        let (diff_sketch, _) = diff_sketches(n, d);
        group.bench_with_input(BenchmarkId::from_parameter(d), &diff_sketch, |b, s| {
            b.iter(|| black_box(s.decode()));
        });
    }
    group.finish();

    // ── Full roundtrip (encode A, encode B, subtract, decode) ─────────────────
    let mut group = c.benchmark_group("iblt_manifest/roundtrip");
    for &n in &[100usize, 1_000, 10_000] {
        for &d in &[0usize, 10] {
            let a_keys = keys(n);
            let b_keys = keys(n.saturating_sub(d));
            group.bench_with_input(
                BenchmarkId::new(format!("n{n}"), format!("d{d}")),
                &(a_keys, b_keys),
                |b, (ak, bk)| {
                    b.iter(|| {
                        let m = (d * 4).max(MIN_CELLS).max(IbltSketch::recommended_cells(n));
                        let mut a = IbltSketch::new(m, DEFAULT_HASH_COUNT, SEED);
                        let mut b_sk = IbltSketch::new(m, DEFAULT_HASH_COUNT, SEED);
                        for &k in black_box(ak) {
                            a.insert(k);
                        }
                        for &k in black_box(bk) {
                            b_sk.insert(k);
                        }
                        a.subtract(&b_sk);
                        black_box(a.decode())
                    });
                },
            );
        }
    }
    group.finish();

    // ── Wire size table (not timed) ───────────────────────────────────────────
    println!("\n=== IBLT sketch size vs flat manifest (N × 60 B) ===");
    println!(
        "{:>8}  {:>10}  {:>12}  {:>10}",
        "N", "IBLT (B)", "Flat (B)", "ratio"
    );
    for &n in &[10usize, 100, 1_000, 10_000, 100_000] {
        let ks = keys(n);
        let sz = IbltSketch::from_keys(&ks, SEED).to_bytes().len();
        let flat = n * 60;
        println!(
            "{:>8}  {:>10}  {:>12}  {:>9.1}×",
            n,
            sz,
            flat,
            flat as f64 / sz as f64
        );
    }
}

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