use std::fmt;
use super::DnsLabelRef;

/// Customize formatting of DNS labels
///
/// The default uses "." as separator and adds a trailing separator.
///
/// The `Debug` formatters just format as `Display` to a String and then
/// format that string as `Debug`.
#[derive(Clone,Copy,PartialEq,Eq,PartialOrd,Ord,Hash,Debug)]
pub struct DisplayLabelsOptions {
	/// separator to insert between (escaped) labels
	pub separator: &'static str,
	/// whether a trailing separator is added.
	///
	/// without a trailing separator the root zone is represented as
	/// empty string!
	pub trailing: bool,
}

impl Default for DisplayLabelsOptions {
	fn default() -> Self {
		DisplayLabelsOptions{
			separator: ".",
			trailing: true,
		}
	}
}

/// Wrap anything representing a collection of labels (`DnsLabelRef`) to
/// format using the given `options`.
///
/// As name you can pass any cloneable `(Into)Iterator` with
/// `DnsLabelRef` items, e.g:
///
/// * `&DnsName`
/// * `DnsNameIterator`
#[derive(Clone)]
pub struct DisplayLabels<'a, I>
where
	I: IntoIterator<Item=DnsLabelRef<'a>>+Clone
{
	/// Label collection to iterate over
	pub labels: I,
	/// Options
	pub options: DisplayLabelsOptions,
}

impl<'a, I> fmt::Debug for DisplayLabels<'a, I>
where
	I: IntoIterator<Item=DnsLabelRef<'a>>+Clone
{
	fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
		// just escape the display version1
		format!("{}", self).fmt(w)
	}
}

impl<'a, I> fmt::Display for DisplayLabels<'a, I>
where
	I: IntoIterator<Item=DnsLabelRef<'a>>+Clone
{
	fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
		let mut i = self.labels.clone().into_iter();
		if let Some(first_label) = i.next() {
			// first label
			fmt::Display::fmt(&first_label, w)?;
			// remaining labels
			while let Some(label) = i.next() {
				w.write_str(self.options.separator)?;
				fmt::Display::fmt(&label, w)?;
			}
		}
		if self.options.trailing {
			w.write_str(self.options.separator)?;
		}
		Ok(())
	}
}