refactor: expose CreateShareToRowRootProofs for downstream use (backp…

…ort #3739) (#3740)

## Overview

Exposes that functionality so that we don't end up copy-pasting that
code in Celestia-node.<hr>This is an automatic backport of pull request
#3739 done by [Mergify](https://mergify.com).

---------

Co-authored-by: sweexordious <chamirachid1@gmail.com>

pkg/proof/proof.go

@@ -5,6 +5,9 @@ import (
 	"errors"
 	"fmt"
 
+	tmbytes "github.com/tendermint/tendermint/libs/bytes"
+	coretypes "github.com/tendermint/tendermint/proto/tendermint/types"
+
 	"github.com/celestiaorg/rsmt2d"
 
 	"github.com/celestiaorg/celestia-app/pkg/appconsts"
@@ -14,8 +17,6 @@ import (
 	"github.com/celestiaorg/celestia-app/pkg/square"
 	"github.com/celestiaorg/celestia-app/pkg/wrapper"
 	"github.com/tendermint/tendermint/crypto/merkle"
-	tmbytes "github.com/tendermint/tendermint/libs/bytes"
-	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
 	"github.com/tendermint/tendermint/types"
 )
 
@@ -98,9 +99,11 @@ func NewShareInclusionProofFromEDS(
 	_, allProofs := merkle.ProofsFromByteSlices(append(edsRowRoots, edsColRoots...))
 	rowProofs := make([]*merkle.Proof, endRow-startRow+1)
 	rowRoots := make([]tmbytes.HexBytes, endRow-startRow+1)
+	bzRowRoots := make([][]byte, endRow-startRow+1)
 	for i := startRow; i <= endRow; i++ {
 		rowProofs[i-startRow] = allProofs[i]
 		rowRoots[i-startRow] = edsRowRoots[i]
+		bzRowRoots[i-startRow] = edsRowRoots[i]
 	}
 
 	// get the extended rows containing the shares.
@@ -113,9 +116,30 @@ func NewShareInclusionProofFromEDS(
 		rows[i-startRow] = shares
 	}
 
-	var shareProofs []*tmproto.NMTProof //nolint:prealloc
+	shareProofs, rawShares, err := CreateShareToRowRootProofs(squareSize, rows, bzRowRoots, startLeaf, endLeaf)
+	if err != nil {
+		return types.ShareProof{}, err
+	}
+	return types.ShareProof{
+		RowProof: types.RowProof{
+			RowRoots: rowRoots,
+			Proofs:   rowProofs,
+			StartRow: uint32(startRow),
+			EndRow:   uint32(endRow),
+		},
+		Data:             rawShares,
+		ShareProofs:      shareProofs,
+		NamespaceID:      namespace.ID,
+		NamespaceVersion: uint32(namespace.Version),
+	}, nil
+}
+
+// CreateShareToRowRootProofs takes a set of shares and their corresponding row roots, and generates
+// an NMT inclusion proof of a set of shares, defined by startLeaf and endLeaf, to their corresponding row roots.
+func CreateShareToRowRootProofs(squareSize int, rowShares [][]shares.Share, rowRoots [][]byte, startLeaf, endLeaf int) ([]*coretypes.NMTProof, [][]byte, error) {
+	shareProofs := make([]*coretypes.NMTProof, 0, len(rowRoots))
 	var rawShares [][]byte
-	for i, row := range rows {
+	for i, row := range rowShares {
 		// create an nmt to generate a proof.
 		// we have to re-create the tree as the eds one is not accessible.
 		tree := wrapper.NewErasuredNamespacedMerkleTree(uint64(squareSize), uint(i))
@@ -124,17 +148,17 @@ func NewShareInclusionProofFromEDS(
 				share.ToBytes(),
 			)
 			if err != nil {
-				return types.ShareProof{}, err
+				return nil, nil, err
 			}
 		}
 
 		// make sure that the generated root is the same as the eds row root.
 		root, err := tree.Root()
 		if err != nil {
-			return types.ShareProof{}, err
+			return nil, nil, err
 		}
-		if !bytes.Equal(rowRoots[i].Bytes(), root) {
-			return types.ShareProof{}, errors.New("eds row root is different than tree root")
+		if !bytes.Equal(rowRoots[i], root) {
+			return nil, nil, errors.New("eds row root is different than tree root")
 		}
 
 		startLeafPos := startLeaf
@@ -145,34 +169,22 @@ func NewShareInclusionProofFromEDS(
 			startLeafPos = 0
 		}
 		// if this is not the last row, then select for the rest of the row
-		if i != (len(rows) - 1) {
+		if i != (len(rowShares) - 1) {
 			endLeafPos = squareSize - 1
 		}
 
 		rawShares = append(rawShares, shares.ToBytes(row[startLeafPos:endLeafPos+1])...)
-		proof, err := tree.ProveRange(int(startLeafPos), int(endLeafPos+1))
+		proof, err := tree.ProveRange(startLeafPos, endLeafPos+1)
 		if err != nil {
-			return types.ShareProof{}, err
+			return nil, nil, err
 		}
 
-		shareProofs = append(shareProofs, &tmproto.NMTProof{
+		shareProofs = append(shareProofs, &coretypes.NMTProof{
 			Start:    int32(proof.Start()),
 			End:      int32(proof.End()),
 			Nodes:    proof.Nodes(),
 			LeafHash: proof.LeafHash(),
 		})
 	}
-
-	return types.ShareProof{
-		RowProof: types.RowProof{
-			RowRoots: rowRoots,
-			Proofs:   rowProofs,
-			StartRow: uint32(startRow),
-			EndRow:   uint32(endRow),
-		},
-		Data:             rawShares,
-		ShareProofs:      shareProofs,
-		NamespaceID:      namespace.ID,
-		NamespaceVersion: uint32(namespace.Version),
-	}, nil
+	return shareProofs, rawShares, nil
 }