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// Copyright 2024 Ulvetanna Inc.

use super::{
	error::Error,
	msetcheck::{reduce_msetcheck_claim, MsetcheckClaim, MsetcheckProof},
};
use crate::{oracle::MultilinearOracleSet, protocols::gkr_gpa::GrandProductClaim};
use binius_field::TowerField;
use binius_utils::bail;
use tracing::instrument;

/// Verify a multiset check instance reduction.
#[instrument(skip_all, name = "msetcheck::verify", level = "debug")]
pub fn verify<F: TowerField>(
	oracles: &mut MultilinearOracleSet<F>,
	claim: &MsetcheckClaim<F>,
	gamma: F,
	alpha: Option<F>,
	msetcheck_proof: MsetcheckProof<F>,
) -> Result<Vec<GrandProductClaim<F>>, Error> {
	let [t_product, u_product] = msetcheck_proof.grand_products[0..2]
		.try_into()
		.expect("must have a length of 2");

	if t_product != u_product {
		bail!(Error::ProductsDiffer);
	}

	let gpa_claim_oracle_ids = reduce_msetcheck_claim(oracles, claim, gamma, alpha)?;

	Ok(gpa_claim_oracle_ids
		.iter()
		.zip(msetcheck_proof.grand_products)
		.map(|(id, product)| GrandProductClaim {
			poly: oracles.oracle(*id),
			product,
		})
		.collect::<Vec<_>>())
}