//! AM-6/AM-7 benchmarks (GameKernel §4): the real GROUND aggregate under
//! the CB-RES-0001 synthetic workload (3-player commit/reveal rounds).
//!
//! The baseline is boardgame.io, recorded in
//! research/CB-RES-0001-harness/boardgame-io/results-260731.json. That
//! harness measured moves/second *while history grew*, and its headline
//! finding was that throughput halved as history doubled. AM-7 exists
//! because of that finding, so the same workload sizes are run here:
//! what matters is the shape of the curve, not only the peak number.

use cb_events::state_hash_hex;
use cb_game_runtime::{ScenarioFile, ScenarioGame, Setup};
use cb_kernel::{Actor, Aggregate, PlayerId};
use criterion::{criterion_group, criterion_main, BatchSize, Criterion, Throughput};
use games_ground::{Action, GroundCommand, GroundMode, GroundState};
use std::collections::BTreeMap;

fn setup(seed: u64) -> GroundState {
    GroundState::setup(
        &Setup {
            players: 3,
            preset: "standard-3p".to_string(),
            patch: BTreeMap::new(),
        },
        seed,
    )
    .expect("standard-3p setup")
}

fn apply(state: &mut GroundState, actor: Actor, command: &GroundCommand) -> usize {
    match state.validate(actor, command) {
        Ok(events) => {
            for event in &events {
                state.fold(event);
            }
            events.len()
        }
        Err(_) => 0,
    }
}

/// K18: the benchmark workload, **loaded from the scenario format**.
///
/// Until CB-WP-0006 T07 this function hardcoded the command sequence in
/// Rust and never touched `ScenarioFile`, so K18 — "Criterion benches
/// driving the same scenario format at scale" — was false. Embedding the
/// file at compile time keeps the bench self-contained while making the
/// workload *data*: editing `benchmarks/synthetic-3p.yaml` changes what
/// AM-6 and AM-7 measure, and `bench_shape` in the aggregate crate breaks
/// if that changes the round's shape.
const WORKLOAD_YAML: &str = include_str!("../../../benchmarks/synthetic-3p.yaml");

fn workload() -> Vec<(Actor, GroundCommand)> {
    let sc = ScenarioFile::from_yaml(WORKLOAD_YAML).expect("bench workload parses");
    // Positive control: an empty or mis-parsed workload would benchmark
    // nothing while still reporting a rate.
    assert!(
        !sc.commands.is_empty(),
        "K18: the bench workload has no commands"
    );
    sc.commands
        .iter()
        .map(|step| GroundState::parse_command(step).expect("bench command parses"))
        .collect()
}

/// One full round for three players, replayed from the scenario workload.
/// Returns the number of events applied.
fn play_round(state: &mut GroundState, round: &[(Actor, GroundCommand)]) -> usize {
    let mut applied = 0;
    for (actor, command) in round {
        applied += apply(state, *actor, command);
    }
    applied
}

fn run_rounds(rounds: usize) -> usize {
    let mut applied = 0;
    let mut state = setup(42);
    let script = workload();
    for round in 0..rounds {
        if state.outcome.is_some() {
            state = setup(42 + round as u64);
        }
        let produced = play_round(&mut state, &script);
        // A workload whose commands get rejected still "runs", but it
        // measures nothing. An earlier version of this bench stalled on
        // the GR-R03 stress gate and reported throughput for rounds that
        // never happened, so refuse to measure that.
        assert!(
            produced == EVENTS_PER_ROUND || produced == FINAL_ROUND_EVENTS,
            "round {round} produced {produced} events, expected {EVENTS_PER_ROUND} \
             (or {FINAL_ROUND_EVENTS} on a game's last round)"
        );
        applied += produced;
    }
    applied
}

/// Pinned by the `bench_shape` test in the aggregate crate.
const EVENTS_PER_ROUND: usize = 13;
/// GR-R09: a game's fifth round emits GameEnded instead of RoundEnded
/// plus StepAdvanced, so it is one event shorter.
const FINAL_ROUND_EVENTS: usize = 12;
/// Mean events per round over a 5-round game, scaled by 5 to stay in
/// integers: (4 x 13 + 12) = 64.
const EVENTS_PER_5_ROUNDS: usize = 64;

/// Play one round, appending every applied event to `log`.
fn record_round(state: &mut GroundState, log: &mut Vec<games_ground::GroundEvent>) {
    let mut run = |state: &mut GroundState, actor: Actor, cmd: &GroundCommand| {
        if let Ok(produced) = state.validate(actor, cmd) {
            for event in &produced {
                state.fold(event);
                log.push(event.clone());
            }
        }
    };
    for (seat, action, target) in [
        (0u8, Action::Attack, Some(PlayerId(1))),
        (2, Action::Support, Some(PlayerId(1))),
        (1, Action::Ground, None),
    ] {
        run(
            state,
            Actor::Player(PlayerId(seat)),
            &GroundCommand::SelectAction {
                action,
                target,
                problem: None,
            },
        );
    }
    run(state, Actor::System, &GroundCommand::Reveal);
    run(
        state,
        Actor::Player(PlayerId(1)),
        &GroundCommand::ChooseGroundMode {
            mode: GroundMode::Gr,
            choice: None,
        },
    );
    run(state, Actor::System, &GroundCommand::Resolve);
    run(state, Actor::System, &GroundCommand::EndRound);
}

fn bench_synthetic(c: &mut Criterion) {
    // Events per round is fixed by the workload, so throughput can be
    // reported in events/second — the AM-6 unit.
    assert_eq!(play_round(&mut setup(1), &workload()), EVENTS_PER_ROUND);

    let mut group = c.benchmark_group("synthetic-ground-3p");
    // AM-6 headline throughput and AM-7 scaling, at the sizes the
    // boardgame.io harness used so the curves line up.
    for &rounds in &[5_000usize, 10_000, 20_000, 40_000, 100_000] {
        group.throughput(Throughput::Elements(
            (rounds * EVENTS_PER_5_ROUNDS / 5) as u64,
        ));
        group.bench_function(format!("rounds-{rounds}"), |b| {
            b.iter_batched(|| rounds, run_rounds, BatchSize::SmallInput)
        });
    }
    group.finish();

    // AM-7 replay, and the honest analogue of the boardgame.io finding:
    // a *single* growing event log folded back into state. The round
    // benches above restart the game every 5 rounds (GR-R09), so their
    // flat curve is partly by construction — this one is not, because
    // the log here grows without bound.
    let mut replay = c.benchmark_group("replay-ground-3p");
    for &target_events in &[10_000usize, 100_000] {
        // Build one log by playing real rounds, then measure folding it
        // back. Must use the full command sequence: a shortened one
        // stalls, because Reveal needs every seat's selection and
        // EndRound is gated on Resolve.
        let mut log = Vec::with_capacity(target_events);
        let mut source = setup(42);
        let mut games = 0u64;
        while log.len() < target_events {
            if source.outcome.is_some() {
                games += 1;
                source = setup(42 + games);
            }
            let before = log.len();
            record_round(&mut source, &mut log);
            // Positive control: a round that yields nothing means the
            // workload stalled, and the loop above would spin forever.
            assert!(
                log.len() > before,
                "replay workload stalled: a round produced no events"
            );
        }
        replay.throughput(Throughput::Elements(log.len() as u64));
        replay.bench_function(format!("fold-{target_events}-events"), |b| {
            b.iter(|| {
                let mut state = setup(42);
                for event in &log {
                    state.fold(event);
                }
                state_hash_hex(&state)
            })
        });
    }
    replay.finish();

    // AM-7: hashing the full aggregate, the per-round determinism cost.
    let mut hashing = c.benchmark_group("state-hash-ground-3p");
    hashing.throughput(Throughput::Elements(1));
    hashing.bench_function("hash-one-state", |b| {
        let state = setup(42);
        b.iter(|| state_hash_hex(&state))
    });
    hashing.finish();
}

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