Dragon hoard question answer

hoard-answer.rs

#[derive(Debug, PartialEq, Eq, Hash, Clone)]
enum TreasureType {
    // ...
}

#[derive(Debug, Clone)]
struct Treasure {
    // ...
}

impl DragonHoard {
    fn new(name: &str) -> Self {
        DragonHoard {
            dragon_name: name.to_string(),
            treasures: Vec::new(),
        }
    }

    fn add_treasure(&mut self, treasure: Treasure) {
        self.treasures.push(treasure);
    }

    fn total_value(&self) -> u32 {
        self.treasures.iter().map(|t| t.value).sum()
    }

    fn rarest_treasures(&self, n: usize) -> Vec<&Treasure> {
        let mut treasures = self.treasures.iter().collect::<Vec<&Treasure>>();
        treasures.sort_by(|a, b| b.rarity.cmp(&a.rarity));
        treasures.truncate(n);
        treasures
    }

    fn value_by_type(&self) -> HashMap<TreasureType, u32> {
        let mut result = HashMap::new();
        for treasure in &self.treasures {
            *result.entry(treasure.treasure_type.clone()).or_insert(0) += treasure.value;
        }
        result
    }

    fn trade_treasure(&mut self, treasure_name: &str, other_dragon: &mut DragonHoard) -> Result<(), &'static str> {
        let pos = self.treasures.iter().position(|t| t.name == treasure_name)
            .ok_or("Treasure not found in hoard")?;
        let treasure = self.treasures.remove(pos);
        other_dragon.add_treasure(treasure);
        Ok(())
    }
}