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

pub struct EmptySourceStream<C: Copy, CS: CollectedSubstring<C = C>, PC: PosCounter<C>> {
    _pos: PC,
    __phantom: PhantomData<(C, CS)>
}

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

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

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

    fn collect(&mut self, _: &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;
    }
}