path: root/src/server/games/slots.rs

use super::traits::{Game, GameError, GamePhase, GameResult, GameState};
use rand::Rng;
use std::collections::HashMap;

pub const REELS: usize = 5;
pub const ROWS: usize = 3;
pub const SYMBOLS: [char; 6] = ['C', 'L', 'O', 'G', 'D', 'S'];

/// Five paylines, each entry is the row used on reel 0..4.
pub const PAYLINES: [[usize; REELS]; 5] = [
    [0, 0, 0, 0, 0], // line 1: top
    [1, 1, 1, 1, 1], // line 2: middle
    [2, 2, 2, 2, 2], // line 3: bottom
    [0, 1, 2, 1, 0], // line 4: V
    [2, 1, 0, 1, 2], // line 5: inverted V
];

#[derive(Clone, Copy)]
struct Payout {
    three: u64,
    four: u64,
    five: u64,
}

pub struct SlotsGame {
    payouts: HashMap<char, Payout>,
    /// Deterministic grid for tests and demos, in column-major order.
    fixed_grid: Option<Vec<char>>,
}

impl SlotsGame {
    pub fn new() -> Self {
        let mut payouts = HashMap::new();

        // RTP = 425/432 = 0.9838 (1.62% house edge) with five paylines.
        payouts.insert('C', Payout { three: 2, four: 5, five: 15 });
        payouts.insert('L', Payout { three: 3, four: 7, five: 20 });
        payouts.insert('O', Payout { three: 3, four: 8, five: 25 });
        payouts.insert('G', Payout { three: 4, four: 12, five: 40 });
        payouts.insert('D', Payout { three: 6, four: 18, five: 70 });
        payouts.insert('S', Payout { three: 9, four: 30, five: 150 });

        Self {
            payouts,
            fixed_grid: None,
        }
    }

    /// Build a slots game that always spins the given 15-symbol grid.
    /// The string is column-major: reel 0 top/middle/bottom, then reel 1...
    pub fn with_grid(grid: &str) -> Self {
        let mut game = Self::new();
        game.fixed_grid = Some(grid.chars().take(REELS * ROWS).collect());
        game
    }

    fn spin_grid(&self) -> Vec<char> {
        if let Some(grid) = &self.fixed_grid {
            return grid.clone();
        }

        let mut rng = rand::thread_rng();
        (0..REELS * ROWS)
            .map(|_| SYMBOLS[rng.gen_range(0..SYMBOLS.len())])
            .collect()
    }

    /// Evaluate one spin. Returns the total win and the 1-based winning lines.
    pub fn calculate_payout(&self, grid: &[char], bet: u64) -> (u64, Vec<usize>) {
        let mut total = 0u64;
        let mut winning_lines = Vec::new();

        for (index, pattern) in PAYLINES.iter().enumerate() {
            let Some(&first) = grid.get(pattern[0]) else {
                continue;
            };

            let mut run = 1;
            for (col, row) in pattern.iter().enumerate().skip(1) {
                let position = col * ROWS + row;
                if grid.get(position) == Some(&first) {
                    run += 1;
                } else {
                    break;
                }
            }

            if run < 3 {
                continue;
            }

            let Some(payout) = self.payouts.get(&first) else {
                continue;
            };
            let multiplier = match run {
                3 => payout.three,
                4 => payout.four,
                _ => payout.five,
            };

            total = total.saturating_add(bet.saturating_mul(multiplier));
            winning_lines.push(index + 1);
        }

        (total, winning_lines)
    }

    /// Exact theoretical return to player for the current paytable.
    pub fn theoretical_rtp(&self) -> f64 {
        // For one reel line and one symbol: exactly 3, 4 or 5 of a kind.
        let p3 = 5.0 / 1296.0;
        let p4 = 5.0 / 7776.0;
        let p5 = 1.0 / 7776.0;

        let per_line: f64 = self
            .payouts
            .values()
            .map(|payout| {
                p3 * payout.three as f64
                    + p4 * payout.four as f64
                    + p5 * payout.five as f64
            })
            .sum();

        per_line * PAYLINES.len() as f64
    }
}

impl Game for SlotsGame {
    fn game_type(&self) -> &'static str {
        "slots"
    }

    fn get_name(&self) -> &'static str {
        "Slots"
    }

    fn get_description(&self) -> &'static str {
        "5 reels x 3 rows, 5 paylines. Match 3, 4 or 5 symbols from the left."
    }

    fn prepare_state(&self, username: &str, bet_amount: u64) -> GameState {
        let mut data = HashMap::new();
        data.insert("username".to_string(), username.to_string());
        data.insert("status".to_string(), "ready".to_string());

        GameState {
            session_id: String::new(),
            game_type: "slots".to_string(),
            bet_amount,
            phase: GamePhase::WaitingToStart,
            data,
        }
    }

    fn process_action(
        &self,
        state: &GameState,
        action: &str,
        _params: &[&str],
    ) -> Result<GameState, GameError> {
        if state.phase == GamePhase::Finished {
            return Err(GameError::GameOver);
        }

        match action {
            "spin" => {
                if state.phase != GamePhase::WaitingToStart
                    && state.phase != GamePhase::Playing
                {
                    return Err(GameError::InvalidAction(
                        "Cannot spin in current phase".to_string(),
                    ));
                }

                let grid = self.spin_grid();
                let reels: String = grid.iter().collect();

                let mut new_data = state.data.clone();
                new_data.insert("reels".to_string(), reels);
                new_data.insert("status".to_string(), "spun".to_string());

                Ok(GameState {
                    session_id: state.session_id.clone(),
                    game_type: state.game_type.clone(),
                    bet_amount: state.bet_amount,
                    phase: GamePhase::Finished,
                    data: new_data,
                })
            }
            _ => Err(GameError::InvalidAction(format!(
                "Unknown action: {}",
                action
            ))),
        }
    }

    fn calculate_result(&self, state: &GameState) -> Result<GameResult, GameError> {
        if state.phase != GamePhase::Finished {
            return Err(GameError::InternalError("Game not finished".to_string()));
        }

        let reel_string = state
            .data
            .get("reels")
            .ok_or(GameError::InternalError("No reels found".to_string()))?;
        let grid: Vec<char> = reel_string.chars().collect();
        if grid.len() != REELS * ROWS {
            return Err(GameError::InternalError(format!(
                "Expected {} symbols, got {}",
                REELS * ROWS,
                grid.len()
            )));
        }

        let (winnings, winning_lines) = self.calculate_payout(&grid, state.bet_amount);
        let win_type = classify_win(winnings, state.bet_amount);
        let win_lines = if winning_lines.is_empty() {
            "-".to_string()
        } else {
            winning_lines
                .iter()
                .map(usize::to_string)
                .collect::<Vec<_>>()
                .join(",")
        };

        let mut result_data = HashMap::new();
        result_data.insert("reels".to_string(), reel_string.clone());
        result_data.insert("win_type".to_string(), win_type.to_string());
        result_data.insert("win_lines".to_string(), win_lines);

        Ok(GameResult {
            session_id: state.session_id.clone(),
            game_type: state.game_type.clone(),
            bet_amount: state.bet_amount,
            winnings,
            final_balance: 0,
            result_data,
        })
    }
}

fn classify_win(winnings: u64, bet: u64) -> &'static str {
    if winnings == 0 {
        "none"
    } else if bet > 0 && winnings >= bet.saturating_mul(50) {
        "mega"
    } else if bet > 0 && winnings >= bet.saturating_mul(10) {
        "big"
    } else {
        "win"
    }
}