use crate::CollectedSubstring;
use crate::pos::Pos;

pub trait Predicate<C: Copy> {
    fn check(&mut self, chr: C) -> bool;
}

pub trait SourceStream<'source, 'pos> {
    type C: Copy;
    type P: Pos<'pos>;
    type CS: CollectedSubstring<'source, C = Self::C>;

    fn skipNext(&mut self, predicate: &mut impl Predicate<Self::C>) -> Option<Self::C>;

    fn skipCurrent(
        &mut self,
        current: Self::C,
        predicate: &mut impl Predicate<Self::C>,
    ) -> Option<Self::C> {
        if !predicate.check(current) {
            return Some(current);
        }

        return self.skipNext(predicate);
    }

    /**
     * Returns reference to a slice of the source which can be used for comparations
     * and exporting (not standardized).
     * Also returns char that failed predicate check for further
     * interpretation or 'None' if the stream is ended.
     *
     * Predicate applied to char starting with next after current, assuming that current char
     * already checked (you don't call this method in the blind, aren't you).
     *
     * Calling this method on ended stream (previous `nextChar` returned `None`)
     * is undefined behavior.
     */
    fn collect(&mut self, predicate: &mut impl Predicate<Self::C>) -> (Self::CS, Option<Self::C>);

    fn pos(&self) -> Self::P;

    fn nextChar(&mut self) -> Option<Self::C>;
}