//! Where the tree reads its nodes from.

use std::collections::HashMap;
use std::hash::BuildHasher;

use crate::cid::Cid;

/// A (small) store of MST blocks from a partial CAR
///
/// (small because we're talking about firehose commits.)
pub trait Blocks {
    fn get(&self, cid: &Cid) -> Option<&[u8]>;
}

impl<B: AsRef<[u8]>, S: BuildHasher> Blocks for HashMap<Cid, B, S> {
    fn get(&self, cid: &Cid) -> Option<&[u8]> {
        HashMap::get(self, cid).map(AsRef::as_ref)
    }
}

impl<T: Blocks + ?Sized> Blocks for &T {
    fn get(&self, cid: &Cid) -> Option<&[u8]> {
        (**self).get(cid)
    }
}