refactor: correct FernFlowerDecompiler name typo

Author: AlexandrosAlexiou

server/src/main/kotlin/org/javacs/kt/externalsources/FernFlowerDecompiler.kt

@@ -0,0 +1,48 @@
+package org.javacs.kt.externalsources
+
+import java.nio.file.Files
+import java.nio.file.Path
+import org.javacs.kt.LOG
+import org.javacs.kt.util.KotlinLSException
+import org.javacs.kt.util.replaceExtensionWith
+import org.javacs.kt.util.withCustomStdout
+import org.jetbrains.java.decompiler.main.decompiler.ConsoleDecompiler
+
+class FernFlowerDecompiler : Decompiler {
+    private val outputDir: Path by lazy {
+        Files.createTempDirectory("fernflowerOut").also {
+            Runtime.getRuntime().addShutdownHook(Thread { it.toFile().deleteRecursively() })
+        }
+    }
+
+    private val decompilerOptions =
+        arrayOf(
+            "-iec=1", // Include entire classpath for better context
+            "-jpr=1", // Include parameter names in method signatures
+        )
+
+    override fun decompileClass(compiledClass: Path): Path {
+        return decompile(compiledClass, ".java")
+    }
+
+    override fun decompileJar(compiledJar: Path): Path {
+        return decompile(compiledJar, ".jar")
+    }
+
+    private fun decompile(input: Path, extension: String): Path {
+        LOG.info("Decompiling ${input.fileName} using FernFlower...")
+
+        val args = decompilerOptions + arrayOf(input.toString(), outputDir.toString())
+
+        withCustomStdout(LOG.outStream) { ConsoleDecompiler.main(args) }
+
+        val outName = input.fileName.replaceExtensionWith(extension)
+        val outPath = outputDir.resolve(outName)
+        if (!Files.exists(outPath)) {
+            throw KotlinLSException(
+                "Could not decompile ${input.fileName}: FernFlower did not generate sources at $outName"
+            )
+        }
+        return outPath
+    }
+}