//! Delimiters for the lexer.
use std::collections::HashSet;
use std::iter::FromIterator;

pub trait Inner {
    fn new_with_inner(v: HashSet<char>) -> Self;
    fn inner(&self) -> &HashSet<char>;
}
/// The interface of [DiscardDelimiters] and
/// [KeepDelimiters].
pub trait Delimiters: Inner + Sized {
    /// Construct a new set of delimiters from
    /// a list of characters.
    fn new(vec: Vec<char>) -> Self {
        Self::new_with_inner(
            HashSet::from_iter(vec.iter().cloned())
        )
    }
    
    /// Check if the set of delimiters contains a
    /// particular delimiter character.
    fn contains(&self, ch: char) -> bool {
        self.inner().contains(&ch)
    }
}

/// Set of all delimiter characters that will not
/// become tokens through [Tokens::new](crate::lexer::Tokens::new).
pub struct DiscardDelimiters(HashSet<char>);
impl Inner for DiscardDelimiters {
    fn new_with_inner(v: HashSet<char>) -> Self {
        Self(v)
    }
    fn inner(&self) -> &HashSet<char> {
        &self.0
    }
}
impl Delimiters for DiscardDelimiters {}

/// Set of all delimiter characters that will
/// also become tokens through [Tokens::new](crate::lexer::Tokens::new).
pub struct KeepDelimiters(HashSet<char>);
impl Delimiters for KeepDelimiters {}
impl Inner for KeepDelimiters {
    fn new_with_inner(v: HashSet<char>) -> Self {
        Self(v)
    }
    fn inner(&self) -> &HashSet<char> {
        &self.0
    }
}

/// Group the two delimiter sets.
pub struct DelimitersParam {
    /// The set of delimiters to keep.
    pub keep: KeepDelimiters,
    /// The set of delimiters to discard.
    pub discard: DiscardDelimiters
}