//! cb-sim — scenario runner binary (GameKernel K17; precursor of `cb sim`).
//! Parses scenario files, dispatches each to its game by the `<game>/`
//! prefix of its `scenario` field, and executes it. Exit codes: 0 all
//! passed, 1 any failure — including a scenario whose game prefix is not
//! registered, and a run in which nothing executed. There is deliberately
//! no "tolerable" non-zero exit: a silent skip is the failure mode this
//! binary exists to catch.

use cb_game_runtime::{replay, scenario, RunOutcome, ScenarioFile};
use games_ground::GroundState;
use std::path::{Path, PathBuf};

/// Where a failing run drops its `.cbreplay` bundle
/// (MetricsAndScenarios §2).
const REPLAY_DIR: &str = "replays";

fn main() {
    let argv: Vec<String> = std::env::args().skip(1).collect();
    if argv.is_empty() {
        eprintln!("usage: cb-sim [--runs <n>] <scenario.yaml>...");
        eprintln!("       cb-sim --replay <bundle.cbreplay>...");
        std::process::exit(64);
    }

    // K10: until CB-WP-0006 T06 this binary had no flag parsing at all, so
    // `--replay` had nowhere to go — every argument was treated as a
    // scenario path.
    if argv[0] == "--replay" {
        std::process::exit(replay_bundles(&argv[1..]));
    }

    // AM-8 (CB-WP-0015 T02): the replay count. Defaults to K8's two, so
    // `make sim` is unchanged; `make am8` passes 10 on one scenario.
    let mut runs = scenario::K8_RUNS;
    let mut args = argv;
    if args[0] == "--runs" {
        if args.len() < 3 {
            eprintln!("usage: cb-sim --runs <n> <scenario.yaml>...");
            std::process::exit(64);
        }
        runs = match args[1].parse::<usize>() {
            Ok(n) if n >= 2 => n,
            // A --runs that silently fell back to 2 would report an
            // N=10 result after doing an N=2 check — the harness-does-
            // nothing class this binary's header is about.
            _ => {
                eprintln!("--runs needs an integer >= 2, got {:?}", args[1]);
                std::process::exit(64);
            }
        };
        args = args.split_off(2);
    }

    let mut failed = false;
    let mut passed = 0usize;
    let mut covered: Vec<String> = Vec::new();

    for path in &args {
        let text = match std::fs::read_to_string(path) {
            Ok(t) => t,
            Err(e) => {
                eprintln!("{path}: read error: {e}");
                failed = true;
                continue;
            }
        };
        let sc = match ScenarioFile::from_yaml(&text) {
            Err(e) => {
                eprintln!("{path}: parse error: {e}");
                failed = true;
                continue;
            }
            Ok(sc) => sc,
        };

        let outcome = match sc.scenario.split('/').next() {
            Some("ground") => scenario::run_n::<GroundState>(&sc, runs),
            _ => {
                // A renamed or typo'd prefix would otherwise skip every
                // scenario while the run still looked clean.
                eprintln!(
                    "FAIL {} — no game registered for prefix {:?}",
                    sc.scenario,
                    sc.scenario.split('/').next().unwrap_or("")
                );
                failed = true;
                continue;
            }
        };

        match outcome {
            RunOutcome::Passed { covers } => {
                println!(
                    "PASS {} covers={}{}",
                    sc.scenario,
                    covers.join(","),
                    if sc.provisional { " provisional" } else { "" }
                );
                covered.extend(covers);
                passed += 1;
            }
            RunOutcome::Failed { reason, evidence } => {
                println!("FAIL {} — {reason}", sc.scenario);
                // K10: a failure becomes work an agent can start, not just
                // information (MetricsAndScenarios §4).
                if let Some(ev) = evidence {
                    match std::fs::create_dir_all(REPLAY_DIR)
                        .map_err(|e| e.to_string())
                        .and_then(|()| {
                            replay::write_bundle(
                                Path::new(REPLAY_DIR),
                                &sc,
                                &ev.initial,
                                &ev.initial_hash,
                                &ev.end_state,
                                &ev.end_state_hash,
                                &reason,
                            )
                        }) {
                        Ok(path) => println!("     bundle {}", path.display()),
                        Err(e) => eprintln!("     bundle NOT written: {e}"),
                    }
                }
                failed = true;
            }
        }
    }

    covered.sort();
    covered.dedup();
    println!("{passed} passed, {} rules covered", covered.len());

    // Positive control: a run that executed nothing must not pass. This
    // is the same class of error as a benchmark timing rejected work.
    if passed == 0 {
        eprintln!("FAIL — no scenario executed; refusing to report success");
        failed = true;
    }

    if failed {
        std::process::exit(1);
    }
}

/// `cb-sim --replay <bundle>...` — re-execute recorded bundles.
fn replay_bundles(paths: &[String]) -> i32 {
    if paths.is_empty() {
        eprintln!("usage: cb-sim --replay <bundle.cbreplay>...");
        return 64;
    }
    let mut ok = 0usize;
    let mut bad = false;
    for p in paths {
        let bundle = PathBuf::from(p);
        match replay::replay::<GroundState>(&bundle) {
            Ok(r) => {
                println!(
                    "REPLAY {} — {} commands, hash {} reproduced",
                    r.scenario,
                    r.commands,
                    &r.hash[..12]
                );
                ok += 1;
            }
            Err(e) => {
                println!("REPLAY FAIL {} — {e}", bundle.display());
                bad = true;
            }
        }
    }
    // Same positive control as the scenario path: a run that replayed
    // nothing must not report success.
    if ok == 0 {
        eprintln!("FAIL — no bundle replayed; refusing to report success");
        bad = true;
    }
    i32::from(bad)
}