trees 0.2.1

General purpose tree data structures
Documentation 
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/// breadth first search

use super::Size;

use rust::*;

/// A struct for one visit in breadth first search.
#[derive(Debug,PartialEq,Eq)]
pub struct Visit<T> {
    pub data : T,
    pub size : Size,
}

pub struct BfsTree<Iter> {
    pub iter : Iter,
    pub size : Size,
}

impl<Item,Iter> BfsTree<Splitted<Iter>>
    where Iter: Iterator<Item=Item>
{
    pub fn from<Treelike>( treelike: Treelike, size: Size ) -> Self
        where Treelike: IntoIterator<Item=Item,IntoIter=Iter>
    {
        Self{ iter: Splitted::<Iter>::from( treelike ), size: size }
    }
}

impl<Iter> BfsTree<Iter> {
    pub fn wrap( self ) -> Bfs<Iter> { Bfs::Tree( self )}
}

pub struct BfsForest<Iter> {
    pub iter : Iter,
    pub size : Size,
}

impl<Item,Iter> BfsForest<Splitted<Iter>>
    where Iter: Iterator<Item=Item>
{
    pub fn from<Treelike>( treelike: Treelike, size: Size ) -> Self
        where Treelike: IntoIterator<Item=Item,IntoIter=Iter>
    {
        Self{ iter: Splitted::<Iter>::from( treelike ), size: size }
    }
}

impl<Iter> BfsForest<Iter> {
    pub fn wrap( self ) -> Bfs<Iter> { Bfs::Forest( self )}
}

pub enum Bfs<Iter> {
    Tree(   BfsTree  <Iter> ),
    Forest( BfsForest<Iter> ),
}

impl<T,Iter> Bfs<Iter>
    where Iter: Iterator<Item=Visit<T>>
{
    pub fn iter( self ) -> Iter {
        match self {
            Bfs::Tree(   tree   ) => tree.iter,
            Bfs::Forest( forest ) => forest.iter,
        }
    }

    pub fn iter_and_size( self ) -> ( Iter, Size ) {
        match self {
            Bfs::Tree(   tree   ) => (tree.iter,   tree.size),
            Bfs::Forest( forest ) => (forest.iter, forest.size),
        }
    }

    pub fn tree_iter( self ) -> Option<Iter> {
        match self {
            Bfs::Tree( tree ) => Some( tree.iter ),
            _ => None,
        }
    }

    pub fn forest_iter( self ) -> Option<Iter> {
        match self {
            Bfs::Forest( forest ) => Some( forest.iter ),
            _ => None,
        }
    }
}

pub trait Split {
    type Item;
    type Iter: ExactSizeIterator;

    fn split( self ) -> ( Self::Item, Self::Iter, u32 );
}

/// An iterator in breadth-first manner
pub struct Splitted<Iter> {
    pub(crate) iters : VecDeque<Iter>,
}

impl<Treelike,Item,Iter> From<Treelike> for Splitted<Iter>
    where Treelike : IntoIterator<Item=Item,IntoIter=Iter>
        ,     Iter : Iterator<Item=Item>
{
    fn from( treelike: Treelike ) -> Self {
        let mut iters = VecDeque::new();
        iters.push_back( treelike.into_iter() );
        Splitted{ iters }
    }
}

impl<T,Item,Iter> Iterator for Splitted<Iter>
    where Iter : ExactSizeIterator<Item=Item>
        , Item : Split<Iter=Iter,Item=T>
{
    type Item = Visit<T>;

    #[inline] fn next( &mut self ) -> Option<Self::Item> {
        loop {
            let next_item = 
                if let Some( ref mut iter ) = self.iters.front_mut() {
                    iter.next()
                } else {
                    return None;
                };
            if let Some( item ) = next_item {
                let ( data, iter, node_cnt ) = item.split();
                let degree = iter.len();
                self.iters.push_back( iter );
                return Some( Visit{ data, size: Size{ degree: degree as u32, node_cnt }});
            } else {
                self.iters.pop_front();
            }
        }
    }
}

pub struct Moved<Iter>( pub(crate) Iter );

impl<'a,T,Iter> Iterator for Moved<Iter>
    where Iter : Iterator<Item=Visit<&'a T>>
        , T    : 'a
{
    type Item = Visit<T>;

    fn next( &mut self ) -> Option<Visit<T>> {
        self.0.next().map( |item| Visit {
            data : unsafe{ ptr::read( item.data )},
            size : item.size,
        })
    }
}