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pub type Position = (usize, usize);
pub type PosRange = (Position, Position); // TODO RangeBound

pub struct RowColIterator<I> {
    iter: I,
    row: usize,
    col: usize,
}
impl<I> RowColIterator<I> {
    pub fn new(iter: I) -> Self {
        RowColIterator { iter, row: 0, col: 0 }
    }

    pub fn pos(&self) -> Position {
        (self.row, self.col)
    }
}
impl<I, E> Iterator for RowColIterator<I>
where
    I: Iterator<Item = Result<u8, E>>,
{
    type Item = (Position, I::Item);

    fn next(&mut self) -> Option<Self::Item> {
        self.iter.next().map(|r| {
            let pos = self.pos();
            let res = r.map(|c| {
                match c {
                    b'\n' => {
                        self.row += 1;
                        self.col = 0;
                    }
                    _ => self.col += 1,
                };
                c
            });
            (pos, res)
        })
    }
}

#[cfg(test)]
mod tests {
    use std::io::{BufReader, Read};

    use super::*;

    #[test]
    fn behavior_row_col_iterator() {
        // [
        //   "foo",
        //   "bar",
        //   "baz"
        // ]
        let target = ["[", r#"  "foo","#, r#"  "bar","#, r#"  "baz""#, "]"].join("\n");
        let reader = BufReader::new(target.as_bytes());
        let mut iter = RowColIterator::new(reader.bytes());

        assert!(matches!(iter.next(), Some(((0, 0), Ok(b'[')))));
        assert!(matches!(iter.next(), Some(((0, 1), Ok(b'\n')))));

        assert!(matches!(iter.next(), Some(((1, 0), Ok(b' ')))));
        assert!(matches!(iter.next(), Some(((1, 1), Ok(b' ')))));
        assert!(matches!(iter.next(), Some(((1, 2), Ok(b'"')))));
        assert!(matches!(iter.next(), Some(((1, 3), Ok(b'f')))));
        assert!(matches!(iter.next(), Some(((1, 4), Ok(b'o')))));
        assert!(matches!(iter.next(), Some(((1, 5), Ok(b'o')))));
        assert!(matches!(iter.next(), Some(((1, 6), Ok(b'"')))));
        assert!(matches!(iter.next(), Some(((1, 7), Ok(b',')))));
        assert!(matches!(iter.next(), Some(((1, 8), Ok(b'\n')))));

        assert!(matches!(iter.next(), Some(((2, 0), Ok(b' ')))));
        assert!(matches!(iter.next(), Some(((2, 1), Ok(b' ')))));
        assert!(matches!(iter.next(), Some(((2, 2), Ok(b'"')))));
        assert!(matches!(iter.next(), Some(((2, 3), Ok(b'b')))));
        assert!(matches!(iter.next(), Some(((2, 4), Ok(b'a')))));
        assert!(matches!(iter.next(), Some(((2, 5), Ok(b'r')))));
        assert!(matches!(iter.next(), Some(((2, 6), Ok(b'"')))));
        assert!(matches!(iter.next(), Some(((2, 7), Ok(b',')))));
        assert!(matches!(iter.next(), Some(((2, 8), Ok(b'\n')))));

        assert!(matches!(iter.next(), Some(((3, 0), Ok(b' ')))));
        assert!(matches!(iter.next(), Some(((3, 1), Ok(b' ')))));
        assert!(matches!(iter.next(), Some(((3, 2), Ok(b'"')))));
        assert!(matches!(iter.next(), Some(((3, 3), Ok(b'b')))));
        assert!(matches!(iter.next(), Some(((3, 4), Ok(b'a')))));
        assert!(matches!(iter.next(), Some(((3, 5), Ok(b'z')))));
        assert!(matches!(iter.next(), Some(((3, 6), Ok(b'"')))));
        assert!(matches!(iter.next(), Some(((3, 7), Ok(b'\n')))));

        assert!(matches!(iter.next(), Some(((4, 0), Ok(b']')))));
        assert!(matches!(iter.next(), None));
        assert!(matches!(iter.next(), None));
        assert!(matches!(iter.next(), None));
    }
}