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use std::{fmt};
use std::hash::{Hash, Hasher};
use std::iter::FromIterator;
use {List, Node};

/// Drop the list in O(n).
impl<T> Drop for List<T> {
    fn drop(&mut self) { self.clear(); }
}

/// A default empty list.
impl<T> Default for List<T> {
    fn default() -> List<T> { List::new() }
}

/// A debug formatter.
impl<T: fmt::Debug> fmt::Debug for List<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.iter().fold(f.debug_list(), |mut b, e| {
            b.entry(e);
            b
        }).finish()
    }
}

/// Clone a list in O(n).
///
/// `clone_from()` will reuse as many nodes from `self` as possible to avoid
/// reallocation.
impl<T: Clone> Clone for List<T> {
    fn clone(&self) -> List<T> {
        self.iter().cloned().collect()
    }

    fn clone_from(&mut self, source: &Self) {
        let mut src_iter = source.iter().cloned();
        let mut dst_iter = self.iter_mut();
        let mut src_exhausted = false;
        for dst_v in &mut dst_iter {
            if let Some(v) = src_iter.next() {
                *dst_v = v;
            } else {
                src_exhausted = true;
                break;
            }
        }
        if src_exhausted {
            dst_iter.truncate_next();
        } else {
            for src_v in src_iter {
                dst_iter.insert_next(src_v);
            }
        }
    }
}

/// Construct a list from the content of the iterator `iter` in O(n).
impl<T> FromIterator<T> for List<T> {
    fn from_iter<I: IntoIterator<Item=T>>(iter: I) -> List<T> {
        let mut r = List::new();
        r.extend(iter);
        r
    }
}

/// Extend the list from the content of `iter` in O(n).
impl<T> Extend<T> for List<T> {
    fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item=T> {
        let mut tail_link: *mut _ = self.last_link();
        unsafe {
            for v in iter {
                let mut node = Node::new_boxed(v, None);
                let next_link: *mut _ = &mut node.next;
                *tail_link = Some(node);
                self.len += 1;
                tail_link = &mut *next_link;
            }
        }
    }
}

impl<T: Hash> Hash for List<T> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.len().hash(state);
        for v in self {
            v.hash(state);
        }
    }
}