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use core::fmt;

use miden_crypto::{hash::rpo::RpoDigest, Felt};

use crate::OPCODE_DYN;

// DYN NODE
// ================================================================================================

/// A Dyn node specifies that the node to be executed next is defined dynamically via the stack.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct DynNode;

/// Constants
impl DynNode {
    /// The domain of the Dyn block (used for control block hashing).
    pub const DOMAIN: Felt = Felt::new(OPCODE_DYN as u64);
}

/// Public accessors
impl DynNode {
    /// Returns a commitment to a Dyn node.
    ///
    /// The commitment is computed by hashing two empty words ([ZERO; 4]) in the domain defined
    /// by [Self::DOMAIN], i.e.:
    ///
    /// ```
    /// # use miden_core::mast::DynNode;
    /// # use miden_crypto::{hash::rpo::{RpoDigest as Digest, Rpo256 as Hasher}};
    /// Hasher::merge_in_domain(&[Digest::default(), Digest::default()], DynNode::DOMAIN);
    /// ```
    pub fn digest(&self) -> RpoDigest {
        RpoDigest::new([
            Felt::new(8115106948140260551),
            Felt::new(13491227816952616836),
            Felt::new(15015806788322198710),
            Felt::new(16575543461540527115),
        ])
    }
}

// PRETTY PRINTING
// ================================================================================================

impl crate::prettier::PrettyPrint for DynNode {
    fn render(&self) -> crate::prettier::Document {
        use crate::prettier::*;
        const_text("dyn")
    }
}

impl fmt::Display for DynNode {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use miden_formatting::prettier::PrettyPrint;
        self.pretty_print(f)
    }
}

// TESTS
// ================================================================================================

#[cfg(test)]
mod tests {
    use miden_crypto::hash::rpo::Rpo256;

    use super::*;

    /// Ensures that the hash of `DynNode` is indeed the hash of 2 empty words, in the `DynNode`
    /// domain.
    #[test]
    pub fn test_dyn_node_digest() {
        assert_eq!(
            DynNode.digest(),
            Rpo256::merge_in_domain(&[RpoDigest::default(), RpoDigest::default()], DynNode::DOMAIN)
        );
    }
}