test(kotlin-jvm): set custom logging via builder method

bindings/kotlin/ldk-node-jvm/lib/src/test/kotlin/org/lightningdevkit/ldknode/LibraryTest.kt

@@ -9,7 +9,8 @@ import java.net.http.HttpRequest
 import java.net.http.HttpResponse
 import kotlin.io.path.createTempDirectory
 import kotlin.test.assertEquals
-
+import kotlin.test.assertTrue
+~~~
 fun runCommandAndWait(vararg cmd: String): String {
     println("Running command \"${cmd.joinToString(" ")}\"")
 
@@ -92,6 +93,59 @@ fun waitForBlock(esploraEndpoint: String, blockHash: String) {
     }
 }
 
+class CustomLogWriter(private var currentLogLevel: LogLevel = LogLevel.INFO, noPointer: NoPointer = NoPointer) :
+    LogWriter(noPointer) {
+    enum class LogLevel {
+        ERROR, WARN, INFO, DEBUG, TRACE, GOSSIP
+    }
+
+    private val logMessages = mutableListOf<String>()
+
+    fun setLogLevel(level: LogLevel) {
+        currentLogLevel = level
+    }
+
+    fun getLogMessages(): List<String> {
+        return logMessages.toList()
+    }
+
+    override fun log(record: LogRecord) {
+        val recordLevel =
+            when (record.level.toString().lowercase()) {
+                "error" -> LogLevel.ERROR
+                "warn" -> LogLevel.WARN
+                "info" -> LogLevel.INFO
+                "debug" -> LogLevel.DEBUG
+                "trace" -> LogLevel.TRACE
+                "gossip" -> LogLevel.GOSSIP
+                else -> LogLevel.INFO
+            }
+
+        if (isLevelEnabled(recordLevel)) {
+            val logMessage = formatRecord(record)
+            logMessages.add(logMessage)
+        }
+    }
+
+    private fun formatRecord(record: LogRecord): String {
+        val timestamp =
+            java.time.LocalDateTime.now()
+                .format(java.time.format.DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"))
+        return String.format(
+            "%s %-5s [%s:%d] %s\n",
+            timestamp,
+            record.level,
+            record.modulePath,
+            record.line,
+            record.args
+        )
+    }
+
+    private fun isLevelEnabled(level: LogLevel): Boolean {
+        return level.ordinal <= currentLogLevel.ordinal
+    }
+}
+
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
 class LibraryTest {
 
@@ -106,6 +160,9 @@ class LibraryTest {
     }
 
     @Test fun fullCycle() {
+        val logWriter1 = CustomLogWriter(CustomLogWriter.LogLevel.GOSSIP)
+        val logWriter2 = CustomLogWriter(CustomLogWriter.LogLevel.GOSSIP)
+
         val tmpDir1 = createTempDirectory("ldk_node").toString()
         println("Random dir 1: $tmpDir1")
         val tmpDir2 = createTempDirectory("ldk_node").toString()
@@ -129,8 +186,11 @@ class LibraryTest {
 
         val builder1 = Builder.fromConfig(config1)
         builder1.setChainSourceEsplora(esploraEndpoint, null)
+        builder1.setCustomLogger(logWriter1)
+
         val builder2 = Builder.fromConfig(config2)
         builder2.setChainSourceEsplora(esploraEndpoint, null)
+        builder2.setCustomLogger(logWriter2)
 
         val node1 = builder1.build()
         val node2 = builder2.build()
@@ -262,6 +322,9 @@ class LibraryTest {
         assert(spendableBalance1AfterClose < 100000u)
         assertEquals(102500uL, spendableBalance2AfterClose)
 
+        assertTrue(logWriter1.getLogMessages().isNotEmpty())
+        assertTrue(logWriter2.getLogMessages().isNotEmpty())
+
         node1.stop()
         node2.stop()
     }