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#[macro_use]
extern crate serde_derive;

use std::marker::PhantomData;
use std::ops::{Range, Index, IndexMut};
use std::iter::Map;
use std::usize::MAX;

pub trait Id: Copy + From<usize> + Into<usize> {
    fn index(&self) -> usize {
        Into::<usize>::into(*self) 
    }

    fn is_valid(&self) -> bool {
        self.index() != MAX
    }

    fn is_invalid(&self) -> bool {
        self.index() == MAX
    }

    fn invalid() -> Self {
        Self::from(MAX)
    }
}

pub type IdsIter<I> = Map<Range<usize>, fn(usize) -> I>;

#[derive(Debug)]
#[derive(Serialize, Deserialize)]
pub struct IdVec<I: Id, T> {
    items: Vec<T>,
    marker: PhantomData<I>,
}

impl<I: Id, T> IdVec<I, T> {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn push(&mut self, item: T) -> I {
        self.items.push(item);
        I::from(self.len() - 1)
    }

    pub fn len(&self) -> usize {
        self.items.len()
    }
    
    pub fn ids(&self) -> IdsIter<I> {
        (0 .. self.len()).map(I::from)
    }

    pub fn items(&self) -> &[T] {
        &self.items
    }
}

impl<I: Id, T> Index<I> for IdVec<I, T> {
    type Output = T;

    fn index(&self, id: I) -> &Self::Output {
        &self.items[id.index()]
    }
}

impl<I: Id, T> IndexMut<I> for IdVec<I, T> {
    fn index_mut(&mut self, id: I) -> &mut Self::Output {
        &mut self.items[id.index()]
    }
}

impl<I: Id, T> Default for IdVec<I, T> {
    fn default() -> Self {
        Self {
            items: Default::default(),
            marker: Default::default(),
        }
    }
}

impl<I: Id, T> From<Vec<T>> for IdVec<I, T> {
    fn from(items: Vec<T>) -> Self {
        Self {
            items: items,
            marker: Default::default(),
        }
    }
}

impl<I: Id, T> Into<Vec<T>> for IdVec<I, T> {
    fn into(self) -> Vec<T> {
        self.items
    }
}

#[macro_export]
macro_rules! create_id {
    ($id: ident) => {
        #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
        #[derive(Serialize, Deserialize)]
        pub struct $id(pub usize);

        impl $crate::Id for $id {}

        impl From<usize> for $id {
            fn from(index: usize) -> Self {
                $id(index)
            }
        }

        impl Into<usize> for $id {
            fn into(self) -> usize {
                self.0
            }
        }

        impl Default for $id {
            fn default() -> Self {
                $crate::Id::invalid()
            }
        }
    }
}

create_id!(Test);