chore: removes the usage of the merkletree package (#126)

## Overview

Inline with #125.
For more context, please see the following
[comment](#125 (comment)).

## Checklist


- [x] New and updated code has appropriate documentation
- [x] New and updated code has new and/or updated testing
- [x] Required CI checks are passing
- [x] Visual proof for any user facing features like CLI or
documentation updates
- [x] Linked issues closed with keywords

README.md

@@ -95,8 +95,7 @@ Where `nid_0 = nid_1 = 0` and `nid_2 = nid_3 = 1` and `data_i = "leaf_i"` for `i
 
 ## Related
 
-This implementation (currently) uses NebulousLabs' [merkletree][NebulousLabs'] implementation
-and was heavily inspired by the initial implementation in the celestiaorg [prototype].
+This implementation was heavily inspired by the initial implementation in the celestiaorg [prototype].
 
 <!--- TODO references --->
 [academic paper]: https://arxiv.org/abs/1905.09274

go.mod

@@ -3,7 +3,6 @@ module github.com/celestiaorg/nmt
 go 1.18
 
 require (
-	github.com/celestiaorg/merkletree v0.0.0-20210714075610-a84dc3ddbbe4
 	github.com/google/gofuzz v1.2.0
 	github.com/stretchr/testify v1.8.1
 )

go.sum

@@ -1,5 +1,3 @@
-github.com/celestiaorg/merkletree v0.0.0-20210714075610-a84dc3ddbbe4 h1:CJdIpo8n5MFP2MwK0gSRcOVlDlFdQJO1p+FqdxYzmvc=
-github.com/celestiaorg/merkletree v0.0.0-20210714075610-a84dc3ddbbe4/go.mod h1:fzuHnhzj1pUygGz+1ZkB3uQbEUL4htqCGJ4Qs2LwMZA=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -14,18 +12,6 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-gitlab.com/NebulousLabs/errors v0.0.0-20171229012116-7ead97ef90b8 h1:gZfMjx7Jr6N8b7iJO4eUjDsn6xJqoyXg8D+ogdoAfKY=
-gitlab.com/NebulousLabs/errors v0.0.0-20171229012116-7ead97ef90b8/go.mod h1:ZkMZ0dpQyWwlENaeZVBiQRjhMEZvk6VTXquzl3FOFP8=
-gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40 h1:dizWJqTWjwyD8KGcMOwgrkqu1JIkofYgKkmDeNE7oAs=
-gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40/go.mod h1:rOnSnoRyxMI3fe/7KIbVcsHRGxe30OONv8dEgo+vCfA=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20200109152110-61a87790db17 h1:nVJ3guKA9qdkEQ3TUdXI9QSINo2CUPM/cySEvw2w8I0=
-golang.org/x/crypto v0.0.0-20200109152110-61a87790db17/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

proof_test.go

@@ -3,58 +3,11 @@ package nmt
 import (
 	"bytes"
 	"crypto/sha256"
-	"io"
 	"testing"
 
-	"github.com/celestiaorg/merkletree"
 	"github.com/celestiaorg/nmt/namespace"
 )
 
-type treeHasher interface {
-	merkletree.TreeHasher
-	Size() int
-}
-
-// CachedSubtreeHasher implements SubtreeHasher using a set of precomputed
-// leaf hashes.
-type cachedSubtreeHasher struct {
-	leafHashes [][]byte
-	treeHasher
-}
-
-// NextSubtreeRoot implements SubtreeHasher.
-func (csh *cachedSubtreeHasher) NextSubtreeRoot(subtreeSize int) ([]byte, error) {
-	if len(csh.leafHashes) == 0 {
-		return nil, io.EOF
-	}
-	tree := merkletree.NewFromTreehasher(csh.treeHasher)
-	for i := 0; i < subtreeSize && len(csh.leafHashes) > 0; i++ {
-		if err := tree.PushSubTree(0, csh.leafHashes[0]); err != nil {
-			return nil, err
-		}
-		csh.leafHashes = csh.leafHashes[1:]
-	}
-	return tree.Root(), nil
-}
-
-// Skip implements SubtreeHasher.
-func (csh *cachedSubtreeHasher) Skip(n int) error {
-	if n > len(csh.leafHashes) {
-		return io.ErrUnexpectedEOF
-	}
-	csh.leafHashes = csh.leafHashes[n:]
-	return nil
-}
-
-// newCachedSubtreeHasher creates a CachedSubtreeHasher using the specified
-// leaf hashes and hash function.
-func newCachedSubtreeHasher(leafHashes [][]byte, h treeHasher) *cachedSubtreeHasher {
-	return &cachedSubtreeHasher{
-		leafHashes: leafHashes,
-		treeHasher: h,
-	}
-}
-
 func TestProof_VerifyNamespace_False(t *testing.T) {
 	const testNidLen = 3
 
@@ -75,7 +28,7 @@ func TestProof_VerifyNamespace_False(t *testing.T) {
 	if err != nil {
 		t.Fatalf("invalid test setup: error on ProveNamespace(): %v", err)
 	}
-	incompleteFirstNs := NewInclusionProof(0, 1, rangeProof(t, n, 0, 1), false)
+	incompleteFirstNs := NewInclusionProof(0, 1, n.buildRangeProof(0, 1), false)
 	type args struct {
 		nID  namespace.ID
 		data [][]byte
@@ -86,7 +39,7 @@ func TestProof_VerifyNamespace_False(t *testing.T) {
 
 	// an invalid absence proof for an existing namespace ID (2) in the constructed tree
 	leafIndex := 3
-	inclusionProofOfLeafIndex := rangeProof(t, n, leafIndex, leafIndex+1)
+	inclusionProofOfLeafIndex := n.buildRangeProof(leafIndex, leafIndex+1)
 	n.computeLeafHashesIfNecessary()
 	leafHash := n.leafHashes[leafIndex] // the only data item with namespace ID = 2 in the constructed tree is at index 3
 	invalidAbsenceProof := NewAbsenceProof(leafIndex, leafIndex+1, inclusionProofOfLeafIndex, leafHash, false)
@@ -133,7 +86,7 @@ func TestProof_VerifyNamespace_False(t *testing.T) {
 			false,
 		},
 		{
-			"incomplete namespace proof (left)", NewInclusionProof(10, 11, rangeProof(t, n, 10, 11), false),
+			"incomplete namespace proof (left)", NewInclusionProof(10, 11, n.buildRangeProof(10, 11), false),
 			args{[]byte{0, 0, 8}, pushedLastNs[1:], n.Root()},
 			false,
 		},
@@ -172,16 +125,6 @@ func TestProof_VerifyNamespace_False(t *testing.T) {
 	}
 }
 
-func rangeProof(t *testing.T, n *NamespacedMerkleTree, start, end int) [][]byte {
-	n.computeLeafHashesIfNecessary()
-	subTreeHasher := newCachedSubtreeHasher(n.leafHashes, n.treeHasher)
-	incompleteRange, err := merkletree.BuildRangeProof(start, end, subTreeHasher)
-	if err != nil {
-		t.Fatalf("Could not create range proof: %v", err)
-	}
-	return incompleteRange
-}
-
 func TestProof_MultipleLeaves(t *testing.T) {
 	n := New(sha256.New())
 	ns := []byte{1, 2, 3, 4, 5, 6, 7, 8}