Be a little more untrusting of values we get from outside. Fixes #175

src/main/java/com/minelittlepony/client/model/armour/DefaultArmourTextureResolver.java

@@ -12,6 +12,7 @@ import com.google.common.base.Strings;
 import com.minelittlepony.model.armour.ArmourLayer;
 import com.minelittlepony.model.armour.ArmourVariant;
 import com.minelittlepony.model.armour.IArmourTextureResolver;
+import com.minelittlepony.util.ResourceUtil;
 
 import javax.annotation.Nullable;
 
@@ -40,10 +41,10 @@ public class DefaultArmourTextureResolver<T extends LivingEntity> implements IAr
             texture = texture.substring(idx + 1);
         }
 
-        String customType = type.isEmpty() ? "" : String.format("_%s", type);
+        String customType = type.isEmpty() ? "" : "_" + type;
 
-        String res = String.format("%s:textures/models/armor/%s_layer_%s%s.png", domain, texture, layer.name().toLowerCase(), customType);
+        String res = ResourceUtil.format("%s:textures/models/armor/%s_layer_%s%s.png", domain, texture, layer, customType);
-        String oldRes = String.format("%s:textures/models/armor/%s_layer_%d%s.png", domain, texture, layer == ArmourLayer.INNER ? 2 : 1, customType);
+        String oldRes = ResourceUtil.format("%s:textures/models/armor/%s_layer_%d%s.png", domain, texture, layer.getLegacyId(), customType);
 
         Identifier human = getArmorTexture(res, type);
         Identifier pony = ponifyResource(human);

src/main/java/com/minelittlepony/client/render/entity/npc/PonyTextures.java

@@ -10,6 +10,7 @@ import net.minecraft.village.VillagerProfession;
 import net.minecraft.village.VillagerType;
 
 import com.minelittlepony.client.MineLittlePony;
+import com.minelittlepony.util.ResourceUtil;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -62,7 +63,7 @@ public class PonyTextures<T extends LivingEntity & VillagerDataContainer> implem
             return fallback;
         }
 
-        String key = String.format("pony/%s/%s", type, profession);
+        String key = ResourceUtil.format("pony/%s/%s", type, profession);
 
         if (cache.containsKey(key)) {
             return cache.get(key); // People often complain that villagers cause lag,

src/main/java/com/minelittlepony/model/armour/ArmourLayer.java

@@ -4,12 +4,16 @@ package com.minelittlepony.model.armour;
  * The layer used to render a given armour piece.
  */
 public enum ArmourLayer {
-    /**
-     * Fits snugly to the player's model.
-     */
-    INNER,
     /**
      * Hanging loose and sagging free
      */
-    OUTER
+    OUTER,
+    /**
+     * Fits snugly to the player's model.
+     */
+    INNER;
+
+    public int getLegacyId() {
+        return ordinal() + 1;
+    }
 }

src/main/java/com/minelittlepony/util/ResourceUtil.java

@@ -0,0 +1,17 @@
+package com.minelittlepony.util;
+
+public final class ResourceUtil {
+
+    public static String format(String template, Object... args) {
+        for (int i = 0; i < args.length; i++) {
+            if (!(args[i] instanceof Number)) {
+                args[i] = toPathComponent(args[i]);
+            }
+        }
+        return String.format(template, args);
+    }
+
+    private static String toPathComponent(Object value) {
+        return value.toString().toLowerCase().replaceAll("[^a-z0-9_.-]", "_");
+    }
+}