#[derive(Clone)]
pub struct Cursor<'a, T> {
    buf: &'a [T],
    index: usize,
}

impl<'a, T> Cursor<'a, T> {
    pub fn from(buf: &'a [T]) -> Self {
        Self { buf, index: 0 }
    }

    pub fn index(&mut self) -> usize {
        self.index
    }

    pub fn next(&mut self) -> Option<&T> {
        let next_index = self.index + 1;
        if next_index > self.buf.len() {
            None
        } else {
            let v = &self.buf[self.index];
            self.index = next_index;
            Some(v)
        }
    }

    pub fn seek(&mut self, location: usize) -> Result<(), ()> {
        if location > self.buf.len() {
            Err(())
        } else {
            self.index = location;
            Ok(())
        }
    }

    pub fn next_slice(&mut self, amount: usize) -> Option<&'a [T]> {
        let next_index = self.index + amount;
        if next_index > self.buf.len() {
            None
        } else {
            let slice = &self.buf[self.index..next_index];
            self.index = next_index;
            Some(slice)
        }
    }

    pub fn next_array<const N: usize>(&mut self) -> Option<[T; N]> where [T; N]: TryFrom<&'a [T]> {
        Some(self.next_slice(N)?.try_into().ok()?)
    }

    pub fn forward(&mut self, amount: usize) -> Result<(), ()> {
        let next_index = self.index + amount;
        if next_index > self.buf.len() {
            Err(())
        } else {
            self.index = next_index;
            Ok(())
        }
    }
}