feat!: use a struct for namespace and rename namespaceID (#175)

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## Overview

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Closes #172
and #174


## Checklist

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

---------

Co-authored-by: Rootul P <rootulp@gmail.com>

src/lib/tree/Constants.sol

@@ -14,8 +14,10 @@ library Constants {
     /// @dev The prefixes of leaves and nodes
     bytes1 internal constant LEAF_PREFIX = 0x00;
     bytes1 internal constant NODE_PREFIX = 0x01;
+}
 
-    /// @dev Parity share namespace ID
-    NamespaceID internal constant PARITY_SHARE_NAMESPACE_ID =
-        NamespaceID.wrap(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
+/// @dev Parity share namespace.
+/// utility function to provide the parity share namespace as a Namespace struct.
+function PARITY_SHARE_NAMESPACE() pure returns (Namespace memory) {
+    return Namespace(0xFF, 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF);
 }

src/lib/tree/Types.sol

@@ -1,20 +1,37 @@
 // SPDX-License-Identifier: Apache-2.0
 pragma solidity ^0.8.19;
 
-type NamespaceID is bytes29;
+/// @notice A representation of the Celestia-app namespace ID and its version.
+/// See: https://celestiaorg.github.io/celestia-app/specs/namespace.html
+struct Namespace {
+    // The namespace version.
+    bytes1 version;
+    // The namespace ID.
+    bytes28 id;
+}
+
+using {equalTo, lessThan, greaterThan, toBytes} for Namespace global;
 
-using {equality as ==} for NamespaceID global;
-using {lessthan as <} for NamespaceID global;
-using {greaterthan as >} for NamespaceID global;
+function equalTo(Namespace memory l, Namespace memory r) pure returns (bool) {
+    return l.toBytes() == r.toBytes();
+}
+
+function lessThan(Namespace memory l, Namespace memory r) pure returns (bool) {
+    return l.toBytes() < r.toBytes();
+}
 
-function equality(NamespaceID l, NamespaceID r) pure returns (bool) {
-    return NamespaceID.unwrap(l) == NamespaceID.unwrap(r);
+function greaterThan(Namespace memory l, Namespace memory r) pure returns (bool) {
+    return l.toBytes() > r.toBytes();
 }
 
-function lessthan(NamespaceID l, NamespaceID r) pure returns (bool) {
-    return NamespaceID.unwrap(l) < NamespaceID.unwrap(r);
+function toBytes(Namespace memory n) pure returns (bytes29) {
+    return bytes29(abi.encodePacked(n.version, n.id));
 }
 
-function greaterthan(NamespaceID l, NamespaceID r) pure returns (bool) {
-    return NamespaceID.unwrap(l) > NamespaceID.unwrap(r);
+function toNamespace(bytes29 n) pure returns (Namespace memory) {
+    bytes memory id = new bytes(28);
+    for (uint256 i = 1; i < 29; i++) {
+        id[i - 1] = n[i];
+    }
+    return Namespace(n[0], bytes28(id));
 }

src/lib/tree/namespace/NamespaceMerkleTree.sol

@@ -14,18 +14,18 @@ library NamespaceMerkleTree {
     /// @notice Verify if element exists in Merkle tree, given data, proof, and root.
     /// @param root The root of the tree in which the given leaf is verified.
     /// @param proof Namespace Merkle proof for the leaf.
-    /// @param minmaxNID Namespace ID of the leaf.
+    /// @param namespace Namespace of the leaf.
     /// @param data The data of the leaf to verify.
     /// @return `true` if the proof is valid, `false` otherwise.
     /// @dev proof.numLeaves is necessary to determine height of subtree containing the data to prove.
     function verify(
         NamespaceNode memory root,
         NamespaceMerkleProof memory proof,
-        NamespaceID minmaxNID,
+        Namespace memory namespace,
         bytes memory data
     ) internal pure returns (bool) {
         // A sibling at height 1 is created by getting the leafDigest of the original data.
-        NamespaceNode memory node = leafDigest(minmaxNID, data);
+        NamespaceNode memory node = leafDigest(namespace, data);
 
         // Since we're verifying a leaf, height parameter is 1.
         return verifyInner(root, proof, node, 1);
@@ -137,19 +137,19 @@ library NamespaceMerkleTree {
     /// @notice Verify if contiguous elements exists in Merkle tree, given leaves, mutliproof, and root.
     /// @param root The root of the tree in which the given leaves are verified.
     /// @param proof Namespace Merkle multiproof for the leaves.
-    /// @param minmaxNID Namespace ID of the leaves. All leaves must have the same namespace ID.
-    /// @param data The leaves to verify. Note: leaf data must be the _entire_ share (including namespace ID prefixing).
+    /// @param namespace Namespace of the leaves. All leaves must have the same namespace.
+    /// @param data The leaves to verify. Note: leaf data must be the _entire_ share (including namespace prefixing).
     /// @return `true` if the proof is valid, `false` otherwise.
     function verifyMulti(
         NamespaceNode memory root,
         NamespaceMerkleMultiproof memory proof,
-        NamespaceID minmaxNID,
+        Namespace memory namespace,
         bytes[] memory data
     ) internal pure returns (bool) {
         // Hash all the leaves to get leaf nodes.
         NamespaceNode[] memory nodes = new NamespaceNode[](data.length);
         for (uint256 i = 0; i < data.length; ++i) {
-            nodes[i] = leafDigest(minmaxNID, data[i]);
+            nodes[i] = leafDigest(namespace, data[i]);
         }
 
         // Verify inclusion of leaf nodes.

src/lib/tree/namespace/NamespaceNode.sol

@@ -5,10 +5,10 @@ import "../Types.sol";
 
 /// @notice Namespace Merkle Tree node.
 struct NamespaceNode {
-    // Minimum namespace ID.
-    NamespaceID min;
-    // Maximum namespace ID.
-    NamespaceID max;
+    // Minimum namespace.
+    Namespace min;
+    // Maximum namespace.
+    Namespace max;
     // Node value.
     bytes32 digest;
 }
@@ -19,5 +19,5 @@ struct NamespaceNode {
 /// @return `true` is equal, `false otherwise.
 // solhint-disable-next-line func-visibility
 function namespaceNodeEquals(NamespaceNode memory first, NamespaceNode memory second) pure returns (bool) {
-    return (first.min == second.min) && (first.max == second.max) && (first.digest == second.digest);
+    return first.min.equalTo(second.min) && first.max.equalTo(second.max) && (first.digest == second.digest);
 }

src/lib/tree/namespace/TreeHasher.sol

@@ -7,8 +7,8 @@ import "./NamespaceNode.sol";
 
 /// @notice Get the minimum namespace.
 // solhint-disable-next-line func-visibility
-function namespaceMin(NamespaceID l, NamespaceID r) pure returns (NamespaceID) {
-    if (l < r) {
+function namespaceMin(Namespace memory l, Namespace memory r) pure returns (Namespace memory) {
+    if (l.lessThan(r)) {
         return l;
     } else {
         return r;
@@ -17,22 +17,22 @@ function namespaceMin(NamespaceID l, NamespaceID r) pure returns (NamespaceID) {
 
 /// @notice Get the maximum namespace.
 // solhint-disable-next-line func-visibility
-function namespaceMax(NamespaceID l, NamespaceID r) pure returns (NamespaceID) {
-    if (l > r) {
+function namespaceMax(Namespace memory l, Namespace memory r) pure returns (Namespace memory) {
+    if (l.greaterThan(r)) {
         return l;
     } else {
         return r;
     }
 }
 
 /// @notice Hash a leaf node.
-/// @param minmaxNID Namespace ID.
+/// @param namespace Namespace of the leaf.
 /// @param data Raw data of the leaf.
 /// @dev More details in https://github.com/celestiaorg/celestia-specs/blob/master/src/specs/data_structures.md#namespace-merkle-tree
 // solhint-disable-next-line func-visibility
-function leafDigest(NamespaceID minmaxNID, bytes memory data) pure returns (NamespaceNode memory) {
-    bytes32 digest = sha256(abi.encodePacked(Constants.LEAF_PREFIX, minmaxNID, data));
-    NamespaceNode memory node = NamespaceNode(minmaxNID, minmaxNID, digest);
+function leafDigest(Namespace memory namespace, bytes memory data) pure returns (NamespaceNode memory) {
+    bytes32 digest = sha256(abi.encodePacked(Constants.LEAF_PREFIX, namespace.toBytes(), data));
+    NamespaceNode memory node = NamespaceNode(namespace, namespace, digest);
     return node;
 }
 
@@ -42,17 +42,27 @@ function leafDigest(NamespaceID minmaxNID, bytes memory data) pure returns (Name
 /// @dev More details in https://github.com/celestiaorg/celestia-specs/blob/master/src/specs/data_structures.md#namespace-merkle-tree
 // solhint-disable-next-line func-visibility
 function nodeDigest(NamespaceNode memory l, NamespaceNode memory r) pure returns (NamespaceNode memory) {
-    NamespaceID min = namespaceMin(l.min, r.min);
-    NamespaceID max;
-    if (l.min == Constants.PARITY_SHARE_NAMESPACE_ID) {
-        max = Constants.PARITY_SHARE_NAMESPACE_ID;
-    } else if (r.min == Constants.PARITY_SHARE_NAMESPACE_ID) {
+    Namespace memory min = namespaceMin(l.min, r.min);
+    Namespace memory max;
+    if (l.min.equalTo(PARITY_SHARE_NAMESPACE())) {
+        max = PARITY_SHARE_NAMESPACE();
+    } else if (r.min.equalTo(PARITY_SHARE_NAMESPACE())) {
         max = l.max;
     } else {
         max = namespaceMax(l.max, r.max);
     }
 
-    bytes32 digest = sha256(abi.encodePacked(Constants.NODE_PREFIX, l.min, l.max, l.digest, r.min, r.max, r.digest));
+    bytes32 digest = sha256(
+        abi.encodePacked(
+            Constants.NODE_PREFIX,
+            l.min.toBytes(),
+            l.max.toBytes(),
+            l.digest,
+            r.min.toBytes(),
+            r.max.toBytes(),
+            r.digest
+        )
+    );
 
     NamespaceNode memory node = NamespaceNode(min, max, digest);
     return node;

src/lib/tree/namespace/test/NamespaceMerkleMultiproof.t.sol

@@ -11,7 +11,7 @@ import "../NamespaceMerkleTree.sol";
 /**
  * TEST VECTORS
  *
- * Data blocks: namespace id, data
+ * Data blocks: namespace, data
  * 0x0000000000000000000000000000000000000000000000000000000010 0x01
  * 0x0000000000000000000000000000000000000000000000000000000010 0x02
  * 0x0000000000000000000000000000000000000000000000000000000010 0x03
@@ -50,33 +50,33 @@ contract NamespaceMerkleMultiproofTest is DSTest {
     function setUp() external {}
 
     function assertEqNamespaceNode(NamespaceNode memory first, NamespaceNode memory second) internal {
-        assertEq(NamespaceID.unwrap(first.min), NamespaceID.unwrap(second.min));
-        assertEq(NamespaceID.unwrap(first.max), NamespaceID.unwrap(second.max));
+        assertTrue(first.min.equalTo(second.min));
+        assertTrue(first.max.equalTo(second.max));
         assertEq(first.digest, second.digest);
     }
 
     /// @notice Verify inclusion of leaves 0 and 1.
     function testVerifyMulti01() external {
-        NamespaceID nid = NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010);
+        Namespace memory nid = Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010);
         NamespaceNode memory root = NamespaceNode(
-            NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010),
-            NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010),
+            Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010),
+            Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010),
             0x5b3328b03a538d627db78668034089cb395f63d05b24fdf99558d36fe991d268
         );
         NamespaceNode[] memory sideNodes = new NamespaceNode[](3);
         sideNodes[0] = NamespaceNode(
-            NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010),
-            NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010),
+            Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010),
+            Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010),
             0xfdb4e3c872666aa9869a1d46c8a5a0e735becdf17c62b9c3ccf4258449475bda
         );
         sideNodes[1] = NamespaceNode(
-            NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010),
-            NamespaceID.wrap(0x0000000000000000000000000000000000000000000000000000000010),
+            Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010),
+            Namespace(0x00, 0x00000000000000000000000000000000000000000000000000000010),
             0xc350aeddd5ada629057034f15d4545065213a7a28f9f9b77bdc71c4225145920
         );
         sideNodes[2] = NamespaceNode(
-            Constants.PARITY_SHARE_NAMESPACE_ID,
-            Constants.PARITY_SHARE_NAMESPACE_ID,
+            PARITY_SHARE_NAMESPACE(),
+            PARITY_SHARE_NAMESPACE(),
             0x5aa3e7ea31995fdd38f41015275229b290a8ee4810521db766ad457b9a8373d6
         );