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//! Play game with random selection.
//!
//! # Examples
//! ```rust
//! # extern crate connect6;
//! # use connect6::{agent::Agent, policy::RandomPolicy};
//! let mut policy = RandomPolicy::new();
//! let result = Agent::new(&mut policy).play();
//! assert!(result.is_ok());
//! ```
use game::Game;
use policy::{Policy, Simulate};

use rand;
use rand::prelude::SliceRandom;

#[cfg(test)]
mod tests;

/// Play game with random selection.
///
/// # Examples
/// ```rust
/// # extern crate connect6;
/// # use connect6::{agent::Agent, policy::RandomPolicy};
/// let mut policy = RandomPolicy::new();
/// let result = Agent::new(&mut policy).play();
/// assert!(result.is_ok());
/// ```
pub struct RandomPolicy {}

impl RandomPolicy {
    /// Construct a new RandomPolicy
    pub fn new() -> RandomPolicy {
        RandomPolicy {}
    }
}

impl Policy for RandomPolicy {
    /// make random selection
    fn next(&mut self, game: &Game) -> Option<(usize, usize)> {
        let sim = Simulate::from_game(game);
        let node = sim.node.borrow();
        // choose position from vector `possible`
        node.possible.choose(&mut rand::thread_rng()).map(|x| *x)
    }
}