use itertools::{Itertools, MultiPeek};
use std::str::Chars;

pub(super) struct StringWalker<'a> {
    chars: MultiPeek<Chars<'a>>,
    pub(crate) real_position: usize,
    pub(crate) peek_position: usize,
}

impl<'a> StringWalker<'a> {
    pub fn create(s: &str) -> StringWalker {
        StringWalker {
            chars: s.chars().multipeek(),
            real_position: 0,
            peek_position: 0,
        }
    }

    pub fn peek(&mut self) -> Option<&char> {
        self.peek_position += 1;
        self.chars.peek()
    }

    pub fn next(&mut self) -> Option<char> {
        self.real_position += 1;
        self.peek_position = self.real_position;
        self.chars.next()
    }

    pub fn reset_peek(&mut self) {
        self.peek_position = self.real_position;
        self.chars.reset_peek()
    }

    pub fn take(&mut self, length: usize) -> String {
        self.real_position += length;
        self.peek_position = self.real_position;
        self.chars.by_ref().take(length).collect()
    }
}