coup/src/lib.rs

use rand::seq::SliceRandom;

use std::fmt;

use Action::*;
use Card::*;

pub type CoupResult<T> = Result<T, &'static str>;

#[repr(u8)]
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
pub enum Card {
    Duke,
    Assassin,
    Captain,
    Ambassador,
    Contessa,
}

impl Card {
    pub fn allows_action(self, action: Action) -> bool {
        matches!((self, action),
                 (_, Income) |
                 (_, ForeignAid) |
                 (Duke, Tax) |
                 (Assassin, Assassinate) |
                 (Ambassador, Exchange) |
                 (Captain, Steal))
    }
    pub fn blocks_action(self, action: Action) -> bool {
        matches!((self, action),
                 (Duke, Income) |
                 (Captain, Steal) |
                 (Ambassador, Steal) |
                 (Contessa, Assassinate))
    }
}

trait Stack {
    fn draw(&mut self, player: &mut Player) -> CoupResult<()>;
    fn draw_first(&mut self, card: Card) -> bool;
    fn shuffle(&mut self);
}

impl Stack for Vec<Card> {
    fn draw(&mut self, player: &mut Player) -> CoupResult<()> {
        match self.pop() {
            Some(card) => {
                player.cards.push(card);
                Ok(())
            },
            None => Err("Tried to draw from an empty deck!"),
        }
    }

    fn draw_first(&mut self, card: Card) -> bool {
        match self.iter().position(|c| *c == card) {
            Some(i) => {
                self.remove(i);
                true
            },
            None => false,
        }
    }
    
    fn shuffle(&mut self) {
        let deck = self.as_mut_slice();
        let mut rng = rand::thread_rng();
        deck.shuffle(&mut rng);
    }
}

impl fmt::Display for Card {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let name = match self {
            Duke => "Duke",
            Assassin => "Assassin",
            Captain => "Captain",
            Ambassador => "Ambassador",
            Contessa => "Contessa",
        };
        write!(f, "{}", name)
    }
}

#[repr(u8)]
#[derive(Clone, Copy)]
pub enum Action {
    Income,
    ForeignAid,
    Coup,
    Tax,
    Assassinate,
    Exchange,
    Steal,
}

impl Action {
    pub fn is_targeted(self) -> bool {
        matches!(self, Coup | Steal | Assassinate)
    }

    pub fn challenger_mode(self) -> ResMode {
        match self {
            Income | ForeignAid | Coup => ResMode::None,
            Assassinate | Steal | Tax | Exchange => ResMode::Anyone,
        }
    }

    pub fn blocker_mode(self) -> ResMode {
        match self {
            Income | Tax | Exchange | Coup => ResMode::None,
            Assassinate | Steal => ResMode::Target,
            ForeignAid => ResMode::Anyone,
        }
    }

    pub fn coin_cost(self) -> u8 {
        match self {
            Assassinate => 3,
            Coup => 7,
            _ => 0,
        }
    }
}

impl fmt::Display for Action {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let name = match self {
            Income => "Income",
            ForeignAid => "Foreign Aid",
            Coup => "Coup",
            Tax => "Tax",
            Assassinate => "Assassinate",
            Exchange => "Exchange",
            Steal => "Steal",
        };
        write!(f, "{}", name)
    }
}

#[repr(u8)]
#[derive(Clone, Copy)]
pub enum ResMode {
    None,
    Target,
    Anyone,
}

#[derive(Clone)]
pub struct Player {
    pub coins: u8,
    pub cards: Vec<Card>,
}

impl Player {
    pub fn is_alive(&self) -> bool {
        !self.cards.is_empty()
    }
    pub fn lose(&mut self, card: Card, deck: &mut Vec<Card>) {
        self.cards.draw_first(card);
        deck.push(card);
    }
}

impl Default for Player {
    fn default() -> Self {
        Player {
            cards: Vec::new(),
            coins: 2,
        }
    }
}

#[derive(Clone)]
pub struct Game {
    pub players: Vec<Player>,
    pub deck: Vec<Card>,
    pub discard: Vec<Card>,
    pub turn: usize,
}

macro_rules! thrice {
    ($($e:expr),*) => {
        vec![$($e, $e, $e),*]
    }
}

impl Game {
    pub fn new(num_players: usize) -> Self {
        let mut deck = thrice![Duke, Assassin, Captain, Ambassador, Contessa];
        deck.shuffle();
        let mut players = Vec::new();
        players.resize_with(num_players, Player::default);
        for player in &mut players {
            deck.draw(player).unwrap();
            deck.draw(player).unwrap();
        }
        Game {
            deck,
            players,
            discard: Vec::new(),
            turn: 0,
        }
    }
    pub fn is_game_over(&self) -> bool {
        self.players.iter().filter(|p| p.is_alive()).count() == 1
    }
    
    fn turn_iterator(&self) -> impl Iterator<Item = usize> + '_ {
        let players_turn_order = std::iter::successors(Some(self.turn), |p| {
            let next = (p + 1) % self.players.len();
            if next == self.turn {
                None
            } else {
                Some(next)
            }
        });
        players_turn_order.skip(1).filter(|p| self.players[*p].is_alive())
    }

    fn resolution(&mut self, resolution: Resolution, agents: &[&dyn Agent]) -> CoupResult<Phase> {
        let current_player = &mut self.players.get_mut(self.turn).unwrap();
        let current_agent = agents[self.turn];
        match resolution.action {
            Income => current_player.coins += 1,
            ForeignAid => current_player.coins += 2,
            Coup | Assassinate => match resolution.target {
                Some(target) => {
                    let target_player = &self.players[target];
                    let card = agents[target].choose_lost_influence(&target_player.cards);
                    self.players[target].lose(card, &mut self.discard);
                }
                _ => return Err("Coup/Assassinate resolution has no target"),
            },
            Tax => current_player.coins += 3,
            Exchange => {
                let drawn = vec![self.deck.pop().unwrap(), self.deck.pop().unwrap()];
                let hand = current_player.cards.clone();
                let mut choices = [drawn, hand].concat();
                let discarded = current_agent.exchange(&choices);
                for card in discarded {
                    if !choices.draw_first(card) {
                        return Err("Exchanged a card that was not in choices");
                    } else {
                        self.deck.push(card);
                    }
                }
                current_player.cards = choices;
                self.deck.shuffle();
            }
            Steal => match resolution.target {
                Some(target) => {
                    let val = self.players[target].coins.min(2);
                    self.players[self.turn].coins += val;
                    self.players[target].coins -= val;
                    
                }
                _ => return Err("Steal resolution has no target"),
            }        
        }
        let next = self.turn_iterator().next();
        if let Some(next) = next {
            self.turn = next;
        }
        Ok(Phase::Done)
    }
}

enum Phase {
    Action(Action),
    //ActionChallenge(ActionChallenge),
    //Block(Block),
    //BlockChallenge(BlockChallenge),
    Resolution(Resolution),
    Done,
}

pub struct Resolution {
    action: Action,
    target: Option<usize>,
}

pub trait Agent : fmt::Debug {
    fn exchange(&self, cards: &[Card]) -> [Card; 2];
    fn choose_lost_influence(&self, cards: &[Card]) -> Card;
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_resolution() {
        #[derive(Debug)]
        struct DummyAgent;
        impl Agent for DummyAgent {
            fn exchange(&self, cards: &[Card]) -> [Card; 2] {
                [Contessa, Duke]
            }
            fn choose_lost_influence(&self, cards: &[Card]) -> Card {
                Captain
            }
        }
        let deck = vec![Contessa, Contessa];
        let discard = vec![];
        let players = vec![
            Player { coins: 2, cards: vec![Duke, Assassin] },
            Player { coins: 1, cards: vec![Captain] },
        ];
        let game = Game {
            deck,
            discard,
            players,
            turn: 0,
        };

        // Test income
        {
            let mut game = game.clone();
            game.resolution(Resolution {
                action: Income,
                target: None,
            }, &[&DummyAgent, &DummyAgent]).unwrap();
            assert_eq!(game.players[0].coins, 3);
        }

        // Test foreign aid
        {
            let mut game = game.clone();
            game.resolution(Resolution {
                action: ForeignAid,
                target: None,
            }, &[&DummyAgent, &DummyAgent]).unwrap();
            assert_eq!(game.players[0].coins, 4);
        }

        // Test coup / assassinate
        {
            let mut game = game.clone();
            game.resolution(Resolution {
                action: Coup,
                target: Some(1),
            }, &[&DummyAgent, &DummyAgent]).unwrap();
            assert!(game.players[1].cards.is_empty());
            assert_eq!(game.discard, vec![Captain]);
        }

        // Test steal
        {
            let mut game = game.clone();
            game.resolution(Resolution {
                action: Steal,
                target: Some(1),
            }, &[&DummyAgent, &DummyAgent]).unwrap();
            assert_eq!(game.players[0].coins, 3);
            assert_eq!(game.players[1].coins, 0);
        }

        // Test exchange
        {
            let mut game = game.clone();
            game.resolution(Resolution {
                action: Exchange,
                target: Some(1),
            }, &[&DummyAgent, &DummyAgent]).unwrap();
            game.players[0].cards.sort();
            assert_eq!(game.players[0].cards, vec![Assassin, Contessa]);
            game.deck.sort();
            assert_eq!(game.deck, vec![Duke, Contessa]);
            assert!(game.discard.is_empty());
        }
    }
}