use rune::*;

#[test]
fn peek_works()
{
   let mut it = vec![1, 2, 3].into_iter().lookahead();
   assert_eq!(it.peek(0), Some(&1));
   assert_eq!(it.peek(1), Some(&2));
   assert_eq!(it.peek(2), Some(&3));
   assert_eq!(it.peek(3), None);
}

#[test]
fn peek_mut_modifies_item()
{
   let mut it = vec![10, 20, 30].into_iter().lookahead();
   if let Some(x) = it.peek_mut(1)
   {
      *x += 100;
   }
   assert_eq!(it.next(), Some(10));
   assert_eq!(it.next(), Some(120));
}

#[test]
fn iterates_correctly()
{
   let mut it = vec![1, 2, 3].into_iter().lookahead();
   assert_eq!(it.next(), Some(1));
   assert_eq!(it.next(), Some(2));
   assert_eq!(it.next(), Some(3));
   assert_eq!(it.next(), None);
}

#[test]
fn size_hint_accounts_for_buffer()
{
   let mut it = vec![1, 2, 3, 4].into_iter().lookahead();
   it.peek(2);
   let (low, high) = it.size_hint();
   assert!(low >= 4);
   assert_eq!(high, Some(4));
}