Feature/issue 97/enhance lock file mechanism (#99)

* fixes #97

* fixes #97

vripper-core/src/main/kotlin/me/mnlr/vripper/listeners/AppLock.kt

@@ -0,0 +1,44 @@
+package me.mnlr.vripper.listeners
+
+import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent
+import org.springframework.context.ApplicationListener
+import java.io.RandomAccessFile
+import java.nio.file.Files
+import kotlin.io.path.Path
+import kotlin.io.path.pathString
+import kotlin.system.exitProcess
+
+class AppLock : ApplicationListener<ApplicationEnvironmentPreparedEvent> {
+    override fun onApplicationEvent(event: ApplicationEnvironmentPreparedEvent) {
+        val baseDir = event.environment.getProperty("base.dir")
+        val appDirName = event.environment.getProperty("base.dir.name")
+        if (baseDir == null || appDirName == null) {
+            if (baseDir == null) {
+                System.err.println("Property base.dir is undefined")
+            }
+            if (appDirName == null) {
+                System.err.println("Property base.dir.name is undefined")
+            }
+            System.err.println("Misconfiguration detected, quitting...")
+            exitProcess(-1)
+        }
+        val lock = Path(baseDir).resolve(appDirName).resolve("lock")
+        try {
+            val randomFile = RandomAccessFile(lock.pathString, "rw")
+            val channel = randomFile.channel
+            val fileLock = channel.tryLock()
+            if (fileLock == null) {
+                System.err.println("Another instance is already running in ${lock.parent.pathString}")
+                exitProcess(-1)
+            } else {
+                Runtime.getRuntime().addShutdownHook(Thread {
+                    fileLock.release()
+                    channel.close()
+                    Files.deleteIfExists(lock)
+                })
+            }
+        } catch (e: Exception) {
+            println(e.toString())
+        }
+    }
+}

vripper-gui/src/main/kotlin/me/mnlr/vripper/VripperGuiApplication.kt

@@ -6,7 +6,7 @@ import javafx.stage.Stage
 import javafx.stage.WindowEvent
 import me.mnlr.vripper.event.ApplicationInitialized
 import me.mnlr.vripper.gui.Styles
-import me.mnlr.vripper.listeners.AppListener
+import me.mnlr.vripper.listeners.AppLock
 import me.mnlr.vripper.view.LoadingView
 import org.springframework.boot.autoconfigure.SpringBootApplication
 import org.springframework.boot.builder.SpringApplicationBuilder
@@ -44,7 +44,7 @@ class VripperGuiApplication : App(
         }
         stage.addEventFilter(WindowEvent.WINDOW_SHOWN) {
             val contextInitThread = Thread {
-                context = SpringApplicationBuilder(this.javaClass).listeners(AppListener())
+                context = SpringApplicationBuilder(this.javaClass).listeners(AppLock())
                     .run() //We start the application context and let Spring Boot to initialize itself
                 context.autowireCapableBeanFactory.autowireBean(this) //We ask the context to inject all needed dependencies into the current instence (if needed)
 

vripper-web/src/main/kotlin/me/mnlr/vripper/VripperWebApplication.kt

@@ -1,12 +1,12 @@
 package me.mnlr.vripper
 
-import me.mnlr.vripper.listeners.AppListener
+import me.mnlr.vripper.listeners.AppLock
 import org.springframework.boot.autoconfigure.SpringBootApplication
 import org.springframework.boot.builder.SpringApplicationBuilder
 
 @SpringBootApplication
 class VripperWebApplication
 
 fun main(args: Array<String>) {
-    SpringApplicationBuilder(VripperWebApplication::class.java).listeners(AppListener()).run(*args)
+    SpringApplicationBuilder(VripperWebApplication::class.java).listeners(AppLock()).run(*args)
 }