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use clvmr::{
    allocator::{NodePtr, SExp},
    Allocator,
};

use crate::FromClvmError;

pub trait ClvmDecoder {
    type Node: Clone;

    fn decode_atom(&self, node: &Self::Node) -> Result<&[u8], FromClvmError>;
    fn decode_pair(&self, node: &Self::Node) -> Result<(Self::Node, Self::Node), FromClvmError>;

    /// This is a helper function that just calls `clone` on the node.
    /// It's required only because the compiler can't infer that `N` is `Clone`,
    /// since there's no `Clone` bound on the `FromClvm` trait.
    fn clone_node(&self, node: &Self::Node) -> Self::Node {
        node.clone()
    }
}

impl ClvmDecoder for Allocator {
    type Node = NodePtr;

    fn decode_atom(&self, node: &Self::Node) -> Result<&[u8], FromClvmError> {
        if let SExp::Atom = self.sexp(*node) {
            Ok(self.atom(*node))
        } else {
            Err(FromClvmError::ExpectedAtom)
        }
    }

    fn decode_pair(&self, node: &Self::Node) -> Result<(Self::Node, Self::Node), FromClvmError> {
        if let SExp::Pair(first, rest) = self.sexp(*node) {
            Ok((first, rest))
        } else {
            Err(FromClvmError::ExpectedPair)
        }
    }
}