use std::fmt;

pub trait FlatJoinStrsExt: Sized
{
    /// Join an iterator of iterators of strings  with a seperator `str`
    fn flat_join(self, with: &str) -> String;
}
pub trait JoinStrsExt: Sized
{
    /// Join an iterator of strings with a seperator `str`.
    fn join(self, with: &str) -> String;
}

impl<T,I> JoinStrsExt for I
where I: IntoIterator<Item=T>,
      T: fmt::Display
{
    /// Join an iterator of `str` with a seperator
    fn join(self, with: &str) -> String
    {
	let mut output = String::new();
	let mut first=true;
	for string in self.into_iter()
	{
	    if !first {
		output.push_str(with);
	    }
	    let string = string.to_string();
	    output.push_str(&string[..]);
	    first=false;
	}
	output
    }
}

impl<I, I2, T> FlatJoinStrsExt for I
where I: IntoIterator<Item = I2>,
      I2: IntoIterator<Item = T>,
      T: fmt::Display
{
    fn flat_join(self, with: &str) -> String
    {
	let mut output = String::new();
	let mut first=true;
	for string in self.into_iter()
	{
	    if !first {
		output.push_str(with);
	    }
	    let string: String = string.into_iter().map(|x| x.to_string()).collect();
	    output.push_str(&string[..]);
	    first=false;
	}
	output
    }
}