Implement event for role changes

src/main/java/com/massivecraft/factions/event/FPlayerRoleChangeEvent.java

@@ -0,0 +1,50 @@
+package com.massivecraft.factions.event;
+
+import com.massivecraft.factions.FPlayer;
+import com.massivecraft.factions.Faction;
+import com.massivecraft.factions.struct.Role;
+import org.bukkit.event.Cancellable;
+
+/**
+ * Represents {@link Role} change of a factions player
+ * @see FPlayer#getRole()
+ */
+public class FPlayerRoleChangeEvent extends FactionPlayerEvent implements Cancellable {
+
+    private boolean cancelled;
+    private final Role from;
+    private Role to;
+
+    public FPlayerRoleChangeEvent(Faction faction, FPlayer fPlayer, Role from, Role to) {
+        super(faction, fPlayer);
+        this.from = from;
+        this.to = to;
+    }
+
+    public FPlayerRoleChangeEvent(Faction faction, FPlayer fPlayer, Role to) {
+        this(faction, fPlayer, fPlayer.getRole(), to);
+    }
+
+    @Override
+    public boolean isCancelled() {
+        return false;
+    }
+
+    @Override
+    public void setCancelled(boolean cancelled) {
+        this.cancelled = cancelled;
+    }
+
+    public Role getFrom() {
+        return from;
+    }
+
+    public Role getTo() {
+        return to;
+    }
+
+    public void setTo(Role to) {
+        this.to = to;
+    }
+
+}

src/main/java/com/massivecraft/factions/zcore/persist/MemoryFPlayer.java

@@ -241,7 +241,18 @@ public abstract class MemoryFPlayer implements FPlayer {
         return this.role;
     }
 
-    public void setRole(Role role) { this.role = role; }
+    public void setRole(Role role) {
+        if (this.role == role) {
+            return;
+        }
+
+        FPlayerRoleChangeEvent event = new FPlayerRoleChangeEvent(getFaction(), this, role);
+        Bukkit.getPluginManager().callEvent(event);
+
+        if (!event.isCancelled()) {
+            this.role = event.getTo();
+        }
+    }
 
     public double getPowerBoost() {
         return this.powerBoost;