use crate::defines::LevelInt;

/// A growth rate defines how much experience is required per level.
pub trait GrowthRate {
    /// Calculate the level something with this growth rate would have at a certain experience.
    fn calculate_level(&self, experience: u32) -> LevelInt;
    /// Calculate the experience something with this growth rate would have at a certain level.
    fn calculate_experience(&self, level: LevelInt) -> u32;
}

/// An implementation of the growth rate that uses a lookup table for experience.
pub struct LookupGrowthRate {
    /// The lookup Vec.
    experience: Vec<u32>,
}

impl LookupGrowthRate {
    /// Instantiates a new lookup growth rate.
    pub fn new(experience: Vec<u32>) -> LookupGrowthRate {
        LookupGrowthRate { experience }
    }
}

impl GrowthRate for LookupGrowthRate {
    fn calculate_level(&self, experience: u32) -> LevelInt {
        for (i, v) in self.experience.iter().enumerate() {
            if *v > experience {
                return i as LevelInt;
            }
        }
        self.experience.len() as LevelInt
    }

    fn calculate_experience(&self, level: LevelInt) -> u32 {
        if level >= self.experience.len() as LevelInt {
            *self.experience.last().unwrap()
        } else {
            self.experience[(level - 1) as usize]
        }
    }
}