Add listener for BlockFormEvent

src/main/kotlin/io/dico/parcels2/Options.kt

@@ -34,6 +34,8 @@ class Options {
 data class WorldOptions(var gameMode: GameMode? = GameMode.CREATIVE,
                         var dayTime: Boolean = true,
                         var noWeather: Boolean = true,
+                        var preventWeatherBlockChanges: Boolean = true,
+                        var preventBlockSpread: Boolean = true, // TODO
                         var dropEntityItems: Boolean = true,
                         var doTileDrops: Boolean = false,
                         var disableExplosions: Boolean = true,

src/main/kotlin/io/dico/parcels2/ParcelsPlugin.kt

@@ -77,13 +77,15 @@ class ParcelsPlugin : JavaPlugin() {
         if (optionsFile.exists()) {
             yamlObjectMapper.readerForUpdating(options).readValue<Options>(optionsFile)
         } else if (optionsFile.tryCreate()) {
-            options.addWorld("plotworld", WorldOptions())
+            options.addWorld("parcels", WorldOptions())
             try {
                 yamlObjectMapper.writeValue(optionsFile, options)
             } catch (ex: Throwable) {
                 optionsFile.delete()
                 throw ex
             }
+            plogger.warn("Created options file with a world template. Please review it before next start.")
+            return false
         } else {
             plogger.error("Failed to save options file ${optionsFile.canonicalPath}")
             return false

src/main/kotlin/io/dico/parcels2/listener/ParcelListeners.kt

@@ -376,6 +376,40 @@ class ParcelListeners(val worlds: Worlds, val entityTracker: ParcelEntityTracker
         w.setGameRuleValue("doTileDrops", world.options.doTileDrops.toString())
     }
 
+    // TODO: BlockFormEvent, BlockSpreadEvent, BlockFadeEvent
+
+    /*
+     * Prevents natural blocks forming
+     */
+    @ListenerMarker(priority = NORMAL)
+    val onBlockFormEvent = RegistratorListener<BlockFormEvent> l@{ event ->
+        val block = event.block
+        val (wo, ppa) = getWoAndPPa(block) ?: return@l
+
+        // prevent any generation whatsoever on paths
+        if (ppa == null) {
+            event.isCancelled = true; return@l
+        }
+
+        val hasEntity = event is EntityBlockFormEvent
+        val player = (event as? EntityBlockFormEvent)?.entity as? Player
+
+        val cancel: Boolean = when (block.type) {
+
+            // prevent ice generation from Frost Walkers enchantment
+            ICE -> player != null && !ppa.canBuild(player)
+
+            // prevent snow generation from weather
+            SNOW -> !hasEntity && wo.options.preventWeatherBlockChanges
+
+            else -> false
+        }
+
+        if (cancel) {
+            event.isCancelled = true
+        }
+    }
+
     /*
      * Prevents mobs (living entities) from spawning if that is disabled for that world in the config.
      */