roguelike-game/src/random_table.rs

use rltk::RandomNumberGenerator;

pub struct RandomEntry {
    name: String,
    weight: i32,
}

impl RandomEntry {
    pub fn new<S: ToString>(name: S, weight: i32) -> RandomEntry {
        RandomEntry {
            name: name.to_string(),
            weight,
        }
    }
}

#[derive(Default)]
pub struct RandomTable {
    entries: Vec<RandomEntry>,
    total_weight: i32,
}

impl RandomTable {
    pub fn new() -> RandomTable {
        RandomTable {
            entries: Vec::new(),
            total_weight: 0,
        }
    }

    pub fn add<S: ToString>(mut self, name: S, weight: i32) -> Self {
        if weight > 0 {
            self.total_weight += weight;
            self.entries.push(RandomEntry::new(name, weight));
        }

        self
    }

    pub fn roll(&self, rng: &mut RandomNumberGenerator) -> String {
        if self.total_weight == 0 {
            return "None".to_string();
        }

        let mut roll = rng.roll_dice(1, self.total_weight) - 1;
        let mut index: usize = 0;

        while roll > 0 {
            if roll < self.entries[index].weight {
                return self.entries[index].name.clone();
            }

            roll -= self.entries[index].weight;
            index += 1;
        }

        "None".to_string()
    }
}