pub trait Locatable {
    fn get_xy(&self) -> (usize, usize);
}

pub trait LocatableFactory<T:Locatable> {
    fn create(x:usize, y:usize) -> T;
}

#[derive(Clone)]
pub struct LocatableVec<T:Locatable + std::marker::Copy> {
    arr: [Option<T>; 81],
    len: usize,
}

pub struct LocatableVecIter<'a, T:Locatable + std::marker::Copy> {
    vec : &'a LocatableVec<T>,
    idx: usize,
} // (&'a LocatableVec<T>, usize);


impl<T:Locatable + std::marker::Copy> LocatableVec<T> {
    
    pub fn new() -> LocatableVec<T> {
        LocatableVec{arr: [None; 81], len: 0}
    }
    
    pub fn iter(&self) -> LocatableVecIter<'_, T>  {
        LocatableVecIter{vec: self, idx: 0}
    }
    
    pub fn len(&self) -> usize {
        self.len
    }
    
    pub fn put(&mut self, value : T) {
        let (x,y) = value.get_xy();
        let idx = y * 9 + x;
        if self.arr[idx].is_none() {
            self.len += 1;
        }
        self.arr[idx] = Some(value);
    }
    
    pub fn remove(&mut self, value : &T) -> bool{
        let (x,y) = value.get_xy();
        let idx = y * 9 + x;
        if self.arr[idx].is_some() {
            self.arr[idx] = None;
            self.len -= 1;
            return true;
        }
        false
    }
    
}

impl<'a, T:Locatable + std::marker::Copy> Iterator for LocatableVecIter<'a, T> {
    type Item = &'a T;
    
    fn next(&mut self) -> Option<Self::Item> {
        for i in self.idx..self.vec.arr.len() {
            let pos = &self.vec.arr[i];
            if pos.is_some() {
                self.idx = i + 1;
                return pos.as_ref();
            }
        }
        None
    }
}