Convert MerkleTree timestamp from Long to java.time.Instant for better type safety

.github/workflows/build-test.yaml

@@ -30,7 +30,7 @@ jobs:
           sudo apt-get install -y sbt
 
       - name: Run tests
-        run: sbt -J--add-opens=java.base/sun.nio.ch=ALL-UNNAMED clean test
+        run: make test
 
       - name: Upload coverage reports to Codecov
         uses: codecov/codecov-action@v3

Makefile

@@ -13,5 +13,5 @@ format:
 	sbt scalafmt
 
 test:
-	sbt -J--add-opens=java.base/sun.nio.ch=ALL-UNNAMED test
+	sbt -J--add-opens=java.base/sun.nio.ch=ALL-UNNAMED coverage test coverageReport
 	@make clean

build.sbt

@@ -1,4 +1,4 @@
-ThisBuild / version := "1.5.0"
+ThisBuild / version := "1.6.0"
 
 ThisBuild / scalaVersion := "2.12.20"
 
@@ -24,7 +24,7 @@ libraryDependencies ++= Seq(
   "io.circe" %% "circe-yaml" % "1.15.0",
   "io.circe" %% "circe-core" % circeVersion,
   "io.circe" %% "circe-parser" % circeVersion,
-  "com.swoop" %% "spark-alchemy" % "1.2.1"
+  "com.swoop" %% "spark-alchemy" % "1.2.1",
 )
 
 dependencyOverrides += "org.scala-lang.modules" %% "scala-xml" % "2.4.0"

project/plugins.sbt

@@ -0,0 +1 @@
+addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.3.1")

src/main/scala/org/mitchelllisle/analysers/MerkleTree.scala

@@ -1,29 +1,28 @@
 package org.mitchelllisle.analysers
 
 import org.apache.spark.sql.{DataFrame, functions => F}
-import org.apache.spark.sql.types._
 import java.security.MessageDigest
+import java.time.Instant
 import scala.annotation.tailrec
 
+case class MerkleProof(
+                        rootHash: String,
+                        recordCount: Long,
+                        leafHashes: Seq[String],
+                        timestamp: Instant = Instant.now()
+                      )
+
+case class DeletionProof(
+                          beforeProof: MerkleProof,
+                          afterProof: MerkleProof,
+                          deletedRecordHashes: Seq[String],
+                          merklePathProofs: Seq[String]
+                        )
+
 /** MerkleTreeAnalyser provides cryptographic proof capabilities for data retention and deletion verification.
  * This complements the KHyperLogLogAnalyser by adding tamper-evident audit trails.
  */
 object MerkleTree {
-
-  case class MerkleProof(
-                          rootHash: String,
-                          recordCount: Long,
-                          leafHashes: Seq[String],
-                          timestamp: Long = System.currentTimeMillis()
-                        )
-
-  case class DeletionProof(
-                            beforeProof: MerkleProof,
-                            afterProof: MerkleProof,
-                            deletedRecordHashes: Seq[String],
-                            merklePathProofs: Seq[String]
-                          )
-
   /** Main entry point for creating a Merkle proof. This is the standard way to use MerkleTree.
    *
    * @param data The DataFrame to create proof for
@@ -98,7 +97,7 @@ object MerkleTree {
       rootHash = rootHash,
       recordCount = recordCount,
       leafHashes = leafHashes,
-      timestamp = System.currentTimeMillis()
+      timestamp = Instant.now()
     )
   }
 

src/test/scala/MerkleTreeTest.scala

@@ -1,6 +1,7 @@
 import org.apache.spark.sql.DataFrame
 import org.mitchelllisle.analysers.MerkleTree
 import org.scalatest.flatspec.AnyFlatSpec
+import java.time.Instant
 
 class MerkleTreeTest extends AnyFlatSpec with SparkFunSuite {
   import spark.implicits._
@@ -21,7 +22,8 @@ class MerkleTreeTest extends AnyFlatSpec with SparkFunSuite {
     assert(proof.rootHash.nonEmpty)
     assert(proof.recordCount == 4)
     assert(proof.leafHashes.length == 4)
-    assert(proof.timestamp > 0)
+    assert(proof.timestamp.isInstanceOf[Instant])
+    assert(proof.timestamp.isBefore(Instant.now().plusSeconds(1)))
   }
 
   "apply" should "produce same result as createMerkleProof" in {
@@ -183,4 +185,14 @@ class MerkleTreeTest extends AnyFlatSpec with SparkFunSuite {
 
     assert(hashes1.sameElements(hashes2))
   }
+
+  "timestamp" should "use proper Instant type and be recent" in {
+    val beforeTime = Instant.now().minusSeconds(1)
+    val proof = MerkleTree.createMerkleProof(testData, columns, idColumn)
+    val afterTime = Instant.now().plusSeconds(1)
+
+    assert(proof.timestamp.isInstanceOf[Instant])
+    assert(proof.timestamp.isAfter(beforeTime))
+    assert(proof.timestamp.isBefore(afterTime))
+  }
 }