implemented summoning of heads

src/main/java/org/kapelle/hardcore_revive/HardcoreRevive.java

@@ -4,11 +4,13 @@ import org.bukkit.plugin.java.JavaPlugin;
 
 public class HardcoreRevive extends JavaPlugin {
     DropHead dropHead;
+    SummonHead summonHead;
 
     @Override
     public void onEnable() {
         this.getLogger().info("hardcore-revive plugin enabled");
 
         dropHead = new DropHead(this);
+        summonHead = new SummonHead(this);
     }
 }

src/main/java/org/kapelle/hardcore_revive/SummonHead.java

@@ -0,0 +1,111 @@
+package org.kapelle.hardcore_revive;
+
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.Particle;
+import org.bukkit.block.Block;
+import org.bukkit.block.Sign;
+import org.bukkit.block.Skull;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.block.BlockPlaceEvent;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.SkullMeta;
+import org.bukkit.plugin.java.JavaPlugin;
+import org.bukkit.util.Vector;
+
+public class SummonHead implements Listener {
+    private final JavaPlugin plugin;
+
+    public SummonHead(JavaPlugin plugin){
+        this.plugin = plugin;
+        plugin.getServer().getPluginManager().registerEvents(this, plugin);
+    }
+
+    @EventHandler
+    public void onBlockPlace(BlockPlaceEvent event){
+        if(event.getBlockPlaced().getType() == Material.SOUL_CAMPFIRE && !event.isCancelled()){
+            if (isValidMultiblock(event.getBlockPlaced().getLocation())){
+                summonHead(event.getBlockPlaced().getLocation());
+            }
+        }
+    }
+
+    /**
+     * Checks if a block type is a sign that is standing (not mounted on a wall)
+     * @param block
+     * @return
+     */
+    private boolean isStandingSign(Material block){
+        return block == Material.SPRUCE_SIGN
+                || block == Material.ACACIA_SIGN
+                || block == Material.BIRCH_SIGN
+                || block == Material.CRIMSON_SIGN
+                || block == Material.DARK_OAK_SIGN
+                || block == Material.JUNGLE_SIGN
+                || block == Material.OAK_SIGN
+                || block == Material.WARPED_SIGN;
+    }
+
+    /**
+     * Checks if the last placed block is a valid multiblock.
+     * The valid structure is from top to bottom: Standing sign, soul sand, soul campfire, soul sand
+     * @param lastBlockLocation Exprected to be the soul campfire
+     * @return if the structure is valid
+     */
+    private boolean isValidMultiblock(Location lastBlockLocation){
+        return lastBlockLocation.clone().add(new Vector(0,-1,0)).getBlock().getType() == Material.SOUL_SAND
+                && lastBlockLocation.clone().add(new Vector(0,1,0)).getBlock().getType() == Material.SOUL_SAND
+                && isStandingSign(lastBlockLocation.clone().add(new Vector(0,2,0)).getBlock().getType());
+
+    }
+
+    /**
+     * Perform the head summoning ritual.
+     * @param lastBlockLocation The location of the core block of the multiblock structure. In this case
+     *                          the soul campfire.
+     */
+    private void summonHead(Location lastBlockLocation){
+        Block topBlock = lastBlockLocation.clone().add(new Vector(0,2,0)).getBlock();
+
+        String spiritName = getSignText((Sign) topBlock.getState());
+        Player spirit = plugin.getServer().getPlayerExact(spiritName);
+
+        if (spirit == null) {
+            // TODO: inform player about spirit not readchable (must be online)
+            return;
+        }
+
+        // Remove sign
+        topBlock.setType(Material.AIR);
+
+        // Spawn particle at sign
+        topBlock.getWorld().spawnParticle(Particle.SPELL_WITCH,topBlock.getLocation(),20);
+
+        // Prepare head to be spawned
+        ItemStack head = new ItemStack(Material.PLAYER_HEAD);
+        SkullMeta headMeta = (SkullMeta) head.getItemMeta();
+        assert headMeta != null;
+        headMeta.setOwningPlayer(spirit);
+        head.setItemMeta(headMeta);
+
+        // Spawn head at the position of the sign
+        lastBlockLocation.getWorld().dropItem(topBlock.getLocation(),head);
+
+        // Remove soul campfire
+        // FIXME: removing the campfire raises an execption somewhere else. But i think its fine. Maybe removing a tile entity works different
+        lastBlockLocation.getBlock().setType(Material.AIR);
+    }
+
+    /**
+     * Joins all lines from a sign. That way usernames that are too long for a single line can fit.
+     * @param sign
+     * @return
+     */
+    private String getSignText(Sign sign){
+        return String.join("",sign.getLines());
+    }
+
+}