Changes to task cancelation and fix

- fixed generate command error on multiple tasks for one world
- changed check of task completion from polling to interrupt (via callback function)

src/main/kotlin/net/trivernis/chunkmaster/commands/CmdCancel.kt

@@ -21,9 +21,7 @@ class CmdCancel(private val chunkmaster: Chunkmaster): Subcommand {
         args: List<String>
     ): MutableList<String> {
         val genManager = chunkmaster.generationManager
-        val allTasks = HashSet<TaskEntry>()
-        allTasks.addAll(genManager.pausedTasks)
-        allTasks.addAll(genManager.tasks)
+        val allTasks = genManager.allTasks
         return allTasks.filter {it.id.toString().indexOf(args[0]) == 0}
             .map { it.id.toString() }.toMutableList()
     }

src/main/kotlin/net/trivernis/chunkmaster/commands/CmdGenerate.kt

@@ -59,17 +59,21 @@ class CmdGenerate(private val chunkmaster: Chunkmaster): Subcommand {
             }
         }
         val world = chunkmaster.server.getWorld(worldName)
-        return if (world != null) {
+        val allTasks = chunkmaster.generationManager.allTasks
+        return if (world != null && (allTasks.find { it.generationTask.world == world }) == null) {
             chunkmaster.generationManager.addTask(world, stopAfter)
             sender.spigot().sendMessage(*ComponentBuilder("Generation task for world ").color(ChatColor.BLUE)
                 .append(worldName).color(ChatColor.GREEN).append(" until ").color(ChatColor.BLUE)
                 .append(if (stopAfter > 0) "$stopAfter chunks" else "WorldBorder").color(ChatColor.GREEN)
                 .append(" successfully created").color(ChatColor.BLUE).create())
             true
-        } else {
+        } else if (world == null){
             sender.spigot().sendMessage(*ComponentBuilder("World ").color(ChatColor.RED)
                 .append(worldName).color(ChatColor.GREEN).append(" not found!").color(ChatColor.RED).create())
             false
+        } else {
+            sender.spigot().sendMessage(*ComponentBuilder("Task already exists!").color(ChatColor.RED).create())
+            return false
         }
     }
 }

src/main/kotlin/net/trivernis/chunkmaster/lib/generation/GenerationManager.kt

@@ -12,6 +12,13 @@ class GenerationManager(private val chunkmaster: Chunkmaster, private val server
 
     val tasks: HashSet<RunningTaskEntry> = HashSet()
     val pausedTasks: HashSet<PausedTaskEntry> = HashSet()
+    val allTasks: HashSet<TaskEntry>
+        get() {
+            val all = HashSet<TaskEntry>()
+            all.addAll(pausedTasks)
+            all.addAll(tasks)
+            return all
+        }
     var paused = false
         private set
 
@@ -19,6 +26,8 @@ class GenerationManager(private val chunkmaster: Chunkmaster, private val server
      * Adds a generation task
      */
     fun addTask(world: World, stopAfter: Int = -1): Int {
+        val foundTask = allTasks.find { it.generationTask.world == world }
+        if (foundTask == null) {
             val centerChunk = world.getChunkAt(world.spawnLocation)
             val generationTask = createGenerationTask(world, centerChunk, centerChunk, stopAfter)
 
@@ -45,6 +54,11 @@ class GenerationManager(private val chunkmaster: Chunkmaster, private val server
             insertStatement.close()
             getIdStatement.close()
 
+            generationTask.onEndReached {
+                server.consoleSender.sendMessage("Task #${id} finished after ${generationTask.count} chunks.")
+                removeTask(id)
+            }
+
             if (!paused) {
                 val task = server.scheduler.runTaskTimer(chunkmaster, generationTask, 10,
                     chunkmaster.config.getLong("generation.period"))
@@ -54,6 +68,9 @@ class GenerationManager(private val chunkmaster: Chunkmaster, private val server
             }
 
             return id
+        } else {
+            return foundTask.id
+        }
     }
 
     /**
@@ -66,6 +83,10 @@ class GenerationManager(private val chunkmaster: Chunkmaster, private val server
             val task = server.scheduler.runTaskTimer(chunkmaster, generationTask, 10,
                 chunkmaster.config.getLong("generation.period"))
             tasks.add(RunningTaskEntry(id, task, generationTask))
+            generationTask.onEndReached {
+                server.consoleSender.sendMessage("Task #${id} finished after ${generationTask.count} chunks.")
+                removeTask(id)
+            }
         }
     }
 
@@ -201,11 +222,6 @@ class GenerationManager(private val chunkmaster: Chunkmaster, private val server
                 updateStatement.setInt(3, task.id)
                 updateStatement.execute()
                 updateStatement.close()
-
-                if (genTask.endReached) {   // remove the task if it is finished after the progress has been saved
-                    server.consoleSender.sendMessage("Task #${task.id} finished after ${genTask.count} chunks.")
-                    removeTask(task.id)
-                }
             } catch (error: Exception) {
                 server.consoleSender.sendMessage("Exception when saving task progress ${error.message}")
             }

src/main/kotlin/net/trivernis/chunkmaster/lib/generation/GenerationTask.kt

@@ -23,6 +23,9 @@ abstract class GenerationTask(plugin: Chunkmaster, centerChunk: Chunk, startChun
     protected val msptThreshold = plugin.config.getLong("generation.mspt-pause-threshold")
     protected val maxLoadedChunks = plugin.config.getInt("generation.max-loaded-chunks")
 
+    protected var endReachedCallback: (() -> Unit)? = null
+        private set
+
     abstract override fun run()
     abstract fun cancel()
 
@@ -48,4 +51,11 @@ abstract class GenerationTask(plugin: Chunkmaster, centerChunk: Chunk, startChun
     protected fun borderReached(): Boolean {
         return !world.worldBorder.isInside(lastChunkCoords.getCenterLocation(world)) || (stopAfter in 1..count)
     }
+
+    /**
+     * Registers end reached callback
+     */
+    fun onEndReached(cb: () -> Unit) {
+        endReachedCallback = cb
+    }
 }

src/main/kotlin/net/trivernis/chunkmaster/lib/generation/GenerationTaskPaper.kt

@@ -38,6 +38,7 @@ class GenerationTaskPaper(
             } else if (pendingChunks.size < maxPendingChunks) {   // if more than 10 chunks are pending, wait.
                 if (borderReached()) {
                     endReached = true
+                    endReachedCallback?.invoke()
                     return
                 }
 

src/main/kotlin/net/trivernis/chunkmaster/lib/generation/GenerationTaskSpigot.kt

@@ -33,6 +33,7 @@ class GenerationTaskSpigot(
             } else {
                 if (borderReached()) {
                     endReached = true
+                    endReachedCallback?.invoke()
                     return
                 }