From 4baae88a1c2f9da97be4ea0e772e057d758312db Mon Sep 17 00:00:00 2001
From: Daniel Sanchez Quiros <sanchez.quiros.daniel@gmail.com>
Date: Tue, 2 Apr 2024 17:35:25 +0200
Subject: [PATCH] Implement rs encode/decode

---
 nomos-da/kzgrs/src/common.rs |  2 --
 nomos-da/kzgrs/src/rs.rs     | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/nomos-da/kzgrs/src/common.rs b/nomos-da/kzgrs/src/common.rs
index bc23eaa1..9f6636d9 100644
--- a/nomos-da/kzgrs/src/common.rs
+++ b/nomos-da/kzgrs/src/common.rs
@@ -5,8 +5,6 @@ use ark_ff::{BigInteger256, PrimeField, Zero};
 use ark_poly::domain::general::GeneralEvaluationDomain;
 use ark_poly::evaluations::univariate::Evaluations;
 use ark_poly::univariate::DensePolynomial;
-use num_bigint;
-use num_traits::ops::bytes::FromBytes;
 use thiserror::Error;
 // internal
 
diff --git a/nomos-da/kzgrs/src/rs.rs b/nomos-da/kzgrs/src/rs.rs
index e69de29b..19f18e47 100644
--- a/nomos-da/kzgrs/src/rs.rs
+++ b/nomos-da/kzgrs/src/rs.rs
@@ -0,0 +1,34 @@
+use ark_bls12_381::Fr;
+use ark_poly::univariate::DensePolynomial;
+use ark_poly::{EvaluationDomain, Evaluations, GeneralEvaluationDomain, Polynomial};
+
+pub fn encode(
+    polynomial: &DensePolynomial<Fr>,
+    evaluations: &Evaluations<Fr>,
+    factor: usize,
+    domain: &GeneralEvaluationDomain<Fr>,
+) -> Evaluations<Fr> {
+    assert!(factor > 1);
+    Evaluations::from_vec_and_domain(
+        (0..evaluations.evals.len() * factor)
+            .map(|i| polynomial.evaluate(&domain.element(i)))
+            .collect(),
+        *domain,
+    )
+}
+
+pub fn decode(
+    original_chunks_len: usize,
+    points: &[Fr],
+    domain: &GeneralEvaluationDomain<Fr>,
+) -> Evaluations<Fr> {
+    let evals = Evaluations::<Fr>::from_vec_and_domain(points.to_vec(), *domain);
+    let coeffs = evals.interpolate();
+
+    Evaluations::from_vec_and_domain(
+        (0..original_chunks_len)
+            .map(|i| coeffs.evaluate(&domain.element(i)))
+            .collect(),
+        *domain,
+    )
+}