use std::marker::PhantomData;
use crate::{CollectedSubstring, Pos, Predicate, SourceStream};
use crate::pos::PosCounter;

pub struct EmptySourceStream<
    'source,
    'pos,
    C: Copy,
    P: Pos<'pos>,
    CS: CollectedSubstring<'source, C=C>,
    PC: PosCounter<'pos, C, P=P>,
> {
    _pos: PC,
    __phantom: PhantomData<(&'source (), &'pos (), P, CS)>,
}
impl<
    'source,
    'pos,
    C: Copy,
    P: Pos<'pos>,
    CS: CollectedSubstring<'source, C=C>,
    PC: PosCounter<'pos, C, P=P>,
> EmptySourceStream<'source, 'pos, C, P, CS, PC>
{
    pub fn start(pos: PC) -> (Self, Option<C>) {
        let stream = EmptySourceStream {
            _pos: pos,
            __phantom: PhantomData::default()
        };
        return (stream, None);
    }
}

impl<
    'source,
    'pos,
    C: Copy,
    P: Pos<'pos>,
    CS: CollectedSubstring<'source, C=C>,
    PC: PosCounter<'pos, C, P=P>,
> SourceStream<'source, 'pos> for EmptySourceStream<'source, 'pos, C, P, CS, PC>
{
    type C = C;
    type P = P;
    type CS = CS;

    fn skipNext(&mut self, predicate: &mut impl Predicate<Self::C>) -> Option<Self::C> {
        return None;
    }

    fn collect(&mut self, predicate: &mut impl Predicate<Self::C>) -> (Self::CS, Option<Self::C>) {
        panic!("How about to check first char of substring being collected first");
    }

    fn pos(&self) -> Self::P {
        return self._pos.export();
    }

    fn nextChar(&mut self) -> Option<Self::C> {
        return None;
    }
}