clay-borg/tools/cb-play/src/table.rs

//! The playable loop: render one seat's projection, offer it the legal
//! commands, read one, apply it (CB-WP-0008 T02).
//!
//! Everything a human sees comes from `GroundState::project` — K13's
//! projection, whose first consumer this is. The process itself holds
//! full state, because it is the referee: legality is decided by
//! `validate`, and hidden information is withheld at the *rendering*
//! boundary, which is where it leaks.
//!
//! **Stated non-goal:** no TUI, no colour, no readline. Stage 1 is the
//! inspectable 2D table; this is the smallest thing that makes the rules
//! playable. Dressing it up now would be inventing a UI before a player
//! has used one.

use cb_game_runtime::{Project, Setup, Viewer};
use cb_kernel::{Actor, PlayerId};
use games_ground::bot::{BotError, Choice, GreedyPolicy, Policy, RandomPolicy};
use games_ground::record::to_step;
use games_ground::{GroundCommand, GroundState};

use crate::inspect::{render, seat_name};
use std::io::{BufRead, Write};

pub struct Config {
    pub seed: u64,
    pub players: u8,
    /// Seats a human plays, 0-based (`PlayerId(0)` is P1).
    pub human_seats: Vec<u8>,
    pub bot: String,
    /// Where to write a `.cbreplay` bundle of the finished game.
    pub replay_dir: Option<std::path::PathBuf>,
    /// Where to write the finished game as a scenario file. A session
    /// somebody played becomes a regression test.
    pub record: Option<std::path::PathBuf>,
    /// Serve human seats in a browser instead of on the terminal
    /// (ADR-0007). `Some(0)` lets the OS pick the port.
    pub serve: Option<u16>,
}

impl Default for Config {
    fn default() -> Self {
        Self {
            seed: 1,
            players: 3,
            human_seats: vec![0],
            bot: "greedy".into(),
            replay_dir: None,
            record: None,
            serve: None,
        }
    }
}

/// What a finished game reports back.
/// The end-state hash is what makes a session comparable to its replay.
#[derive(Debug)]
pub struct Summary {
    pub rounds: u8,
    pub end_state_hash: String,
    pub scenario: cb_game_runtime::ScenarioFile,
    pub bundle: Option<std::path::PathBuf>,
    pub recorded: Option<std::path::PathBuf>,
}

// ------------------------------------------------------------- rendering
//
// The table itself is rendered by `inspect`. What stays here is the
// vocabulary a *chooser* needs: how a legal command is described in the
// menu. Rendering the state and naming a move are different jobs, and
// T02 needs the first without the second.

fn describe(command: &GroundCommand) -> String {
    // Reuse the recorder's vocabulary rather than inventing a third one:
    // what the player reads is what the scenario file will say.
    let step = to_step(Actor::System, command);
    let mut out = step.cmd.clone();
    for (key, value) in &step.args {
        let rendered = match value {
            serde_yaml::Value::String(s) => s.clone(),
            other => serde_yaml::to_string(other)
                .unwrap_or_default()
                .trim()
                .to_string(),
        };
        out.push_str(&format!(" {key}={rendered}"));
    }
    out
}

// --------------------------------------------------------------- policies

/// A seat driven from stdin. Implements the same `Policy` the bots do, so
/// a human and a bot are interchangeable and the driver stays one loop.
pub struct HumanPolicy<'a, R: BufRead, W: Write> {
    input: &'a std::cell::RefCell<R>,
    out: &'a std::cell::RefCell<W>,
    /// `Policy::choose` cannot fail, so an unreadable input is parked
    /// here and turned into a loud error by [`play`]. Returning some
    /// default move instead would let a broken session play itself.
    ///
    /// A shared slot rather than a trait method: widening `Policy` so one
    /// implementor can fail would push a CLI concern into every bot.
    failure: Failure,
}

/// Where a human seat parks the reason it could not answer.
pub type Failure = std::rc::Rc<std::cell::RefCell<Option<String>>>;

impl<'a, R: BufRead, W: Write> HumanPolicy<'a, R, W> {
    pub fn new(
        input: &'a std::cell::RefCell<R>,
        out: &'a std::cell::RefCell<W>,
        failure: Failure,
    ) -> Self {
        Self {
            input,
            out,
            failure,
        }
    }
}

impl<R: BufRead, W: Write> Policy for HumanPolicy<'_, R, W> {
    fn name(&self) -> &'static str {
        "human"
    }

    fn choose(
        &mut self,
        state: &GroundState,
        seat: PlayerId,
        legal: &[GroundCommand],
        may_pass: bool,
    ) -> Choice {
        let mut w = self.out.borrow_mut();
        let _ = write!(w, "{}", render(&state.project(Viewer::Player(seat))));
        let _ = writeln!(w, "  you are {}", seat_name(seat));
        for (i, cmd) in legal.iter().enumerate() {
            let _ = writeln!(w, "    [{i}] {}", describe(cmd));
        }
        let _ = writeln!(
            w,
            "  choose a number{}:",
            if may_pass { " or `pass`" } else { "" }
        );
        let _ = w.flush();
        drop(w);

        let mut line = String::new();
        loop {
            line.clear();
            match self.input.borrow_mut().read_line(&mut line) {
                Ok(0) => {
                    *self.failure.borrow_mut() =
                        Some(format!("input ended while {} had to act", seat_name(seat)));
                    // Out of range on purpose: the driver reports it.
                    return Choice::Command(usize::MAX);
                }
                Err(e) => {
                    *self.failure.borrow_mut() = Some(format!("read error: {e}"));
                    return Choice::Command(usize::MAX);
                }
                Ok(_) => {}
            }
            let word = line.trim();
            if word.is_empty() {
                continue;
            }
            if word.eq_ignore_ascii_case("pass") {
                return Choice::Pass;
            }
            match word.parse::<usize>() {
                Ok(i) => return Choice::Command(i),
                Err(_) => {
                    let mut w = self.out.borrow_mut();
                    let _ = writeln!(w, "  not a number: {word:?}");
                    let _ = w.flush();
                }
            }
        }
    }
}

/// How long the terminal page stays available for an abandoned tab.
///
/// A server that never exits is its own defect; a short timeout races a
/// player reading the result. So it serves until the page posts `done`,
/// with this only as the bound.
const END_LINGER: std::time::Duration = std::time::Duration::from_secs(600);

/// Show the browser that the game ended badly, then return the error.
///
/// CB-WP-0018 T01: this path used to `return Err(...)` straight to a
/// terminal nobody was reading, and the browser got a refused connection —
/// identical to a normal win. An error the only interface cannot see is
/// not reported.
fn end_badly<T>(
    server: &Option<std::rc::Rc<crate::hotseat::Server>>,
    msg: String,
) -> Result<T, String> {
    if let Some(s) = server {
        let _ = s.serve_end(None, &msg, END_LINGER);
    }
    Err(msg)
}

fn bot_policy<'a>(kind: &str, seed: u64) -> Result<Box<dyn Policy + 'a>, String> {
    match kind {
        "greedy" => Ok(Box::new(GreedyPolicy)),
        "random" => Ok(Box::new(RandomPolicy::new(seed))),
        other => Err(format!("unknown bot policy {other:?} (greedy, random)")),
    }
}

// ----------------------------------------------------------------- driver

/// Play one game. The human seats read from `input`; the rest are bots.
pub fn play<R: BufRead, W: Write>(config: &Config, input: R, out: W) -> Result<Summary, String> {
    // The shared reader and writer must outlive the policy objects that
    // borrow them, so ownership stays here and the game runs one frame in.
    let input = std::cell::RefCell::new(input);
    let out = std::cell::RefCell::new(out);
    run_game(config, &input, &out)
}

fn run_game<'a, R: BufRead + 'a, W: Write + 'a>(
    config: &Config,
    input: &'a std::cell::RefCell<R>,
    out: &'a std::cell::RefCell<W>,
) -> Result<Summary, String> {
    let setup = Setup {
        players: config.players,
        preset: format!("standard-{}p", config.players),
        patch: Default::default(),
    };
    let initial = <GroundState as cb_game_runtime::ScenarioGame>::setup(&setup, config.seed)?;
    let initial_json = serde_json::to_value(&initial).map_err(|e| e.to_string())?;
    let initial_hash = cb_events::state_hash_hex(&initial);

    // Human seats and bot seats fill one policy vector; the driver does
    // not know which is which, which is the point.
    let failure: Failure = Default::default();
    // ADR-0007: a browser seat and a CLI seat are both just a Policy, so
    // the driver cannot tell them apart — which is the property that lets
    // a browser game replay as a scenario like any other.
    let server = match config.serve {
        Some(port) => {
            let s = std::rc::Rc::new(crate::hotseat::Server::bind(port)?);
            let _ = writeln!(out.borrow_mut(), "  open {}", s.url());
            let _ = out.borrow_mut().flush();
            Some(s)
        }
        None => None,
    };
    let mut policies: Vec<Box<dyn Policy + 'a>> = Vec::new();
    for seat in 0..config.players {
        if config.human_seats.contains(&seat) {
            match &server {
                Some(s) => policies.push(Box::new(crate::hotseat::SeatPolicy::new(
                    s.clone(),
                    failure.clone(),
                ))),
                None => policies.push(Box::new(HumanPolicy::new(input, out, failure.clone()))),
            }
        } else {
            policies.push(bot_policy(&config.bot, config.seed + u64::from(seat))?);
        }
    }

    // CB-WP-0018 T02: the browser seat's page renders the journal as it
    // fills, so a player sees what each command produced -- including the
    // commands that produced nothing.
    let result = match &server {
        Some(srv) => games_ground::bot::play_journaled(initial, &mut policies, Some(srv.journal())),
        None => games_ground::bot::play(initial, &mut policies),
    };

    // A human seat that ran out of input reports *that*, not the
    // out-of-range index it had to return to get here.
    let human_failure = failure.borrow().clone();
    let game = match (result, human_failure) {
        (_, Some(msg)) => return end_badly(&server, msg),
        (Err(BotError::IllegalChoice { seat, offered, .. }), None) => {
            return end_badly(
                &server,
                format!(
                    "{} chose a command outside the {offered} offered",
                    seat_name(seat)
                ),
            )
        }
        (Err(e), None) => return end_badly(&server, e.to_string()),
        (Ok(game), None) => game,
    };

    let end_hash = cb_events::state_hash_hex(&game.state);
    let mut w = out.borrow_mut();
    let _ = write!(w, "{}", render(&game.state.project(Viewer::Spectator)));
    let _ = writeln!(
        w,
        "  game over — {} commands, hash {}",
        game.commands,
        &end_hash[..12]
    );
    // ADR-0007 control 1 leaves evidence rather than only a 403: a
    // session that was probed says so, so a player finds out from the
    // transcript rather than from nothing at all.
    if let Some(s) = &server {
        let refusals = s.refusals();
        if refusals.is_empty() {
            let _ = writeln!(w, "  no requests were refused this session");
        } else {
            let _ = writeln!(w, "  {} request(s) refused:", refusals.len());
            for r in &refusals {
                let _ = writeln!(w, "    {r}");
            }
        }
    }
    let _ = w.flush();
    drop(w);

    // CB-WP-0018 T01: the browser sees the end of its own game. Measured
    // before this: a game ended at 5 rounds / 30 commands, the result went
    // to stdout, and the page's post-`ok` reload got Connection refused.
    if let Some(srv) = &server {
        let ended = game.state.project(Viewer::Spectator);
        let msg = format!("{} commands, hash {}", game.commands, &end_hash[..12]);
        let _ = srv.serve_end(Some(&ended), &msg, END_LINGER);
    }

    let scenario = games_ground::record::to_scenario(
        "ground/cb-play-session",
        config.seed,
        config.players,
        &game.steps,
        Some(end_hash.clone()),
    );

    let bundle = match &config.replay_dir {
        None => None,
        Some(dir) => {
            let end_json = serde_json::to_value(&game.state).map_err(|e| e.to_string())?;
            Some(cb_game_runtime::replay::write_bundle(
                dir,
                &scenario,
                &initial_json,
                &initial_hash,
                &end_json,
                &end_hash,
                "recorded by cb-play",
            )?)
        }
    };

    let recorded = match &config.record {
        None => None,
        Some(path) => {
            let yaml = serde_yaml::to_string(&scenario).map_err(|e| e.to_string())?;
            std::fs::write(path, yaml).map_err(|e| format!("write {}: {e}", path.display()))?;
            Some(path.clone())
        }
    };

    Ok(Summary {
        rounds: game.rounds,
        end_state_hash: end_hash,
        scenario,
        bundle,
        recorded,
    })
}