Improves button and material customization

Allows specifying a comma-separated list of materials and tags for a portal's button, open-material, closed-material and border blocks. A random value is used if more than one material is available.0
Uses the supplied button if any, instead of enforcing the specified button material.
Always protects the button against block breaking.
Fixes an incorrect permission result in the previous commit, which caused players stargate access to be inverted.

src/main/java/net/knarcraft/stargate/utility/MaterialHelper.java

@@ -1,8 +1,19 @@
 package net.knarcraft.stargate.utility;
 
+import net.knarcraft.stargate.config.material.BukkitMaterialSpecifier;
+import net.knarcraft.stargate.config.material.BukkitTagSpecifier;
+import net.knarcraft.stargate.config.material.MaterialSpecifier;
+import org.bukkit.Bukkit;
 import org.bukkit.Material;
+import org.bukkit.NamespacedKey;
 import org.bukkit.Tag;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
 
 /**
  * This class helps decide properties of materials not already present in the Spigot API
@@ -50,4 +61,80 @@ public final class MaterialHelper {
         return Tag.BUTTONS.isTagged(material) || isWallCoral(material) || isContainer(material);
     }
 
+    @NotNull
+    public static String specifiersToString(@NotNull List<MaterialSpecifier> specifiers) {
+        List<String> names = new ArrayList<>();
+        for (MaterialSpecifier specifier : specifiers) {
+            names.add(specifier.asString());
+        }
+        return String.join(",", names);
+    }
+
+    /**
+     * Converts a list of material specifiers to a set of materials
+     *
+     * @param specifiers <p>The material specifiers to convert</p>
+     * @return <p>The materials the specifiers represent</p>
+     */
+    @NotNull
+    public static Set<Material> specifiersToMaterials(@NotNull List<MaterialSpecifier> specifiers) {
+        Set<Material> output = new HashSet<>();
+
+        for (MaterialSpecifier specifier : specifiers) {
+            output.addAll(specifier.asMaterials());
+        }
+
+        return output;
+    }
+
+    /**
+     * Parses all materials and material tags found in the input string
+     *
+     * @param input <p>The input string to parse</p>
+     * @return <p>All material specifiers found</p>
+     */
+    @NotNull
+    public static List<MaterialSpecifier> parseTagsAndMaterials(@NotNull String input) {
+        List<MaterialSpecifier> specifiers = new ArrayList<>();
+
+        // Nothing to parse
+        if (input.isBlank()) {
+            return specifiers;
+        }
+
+        String[] parts;
+        if (input.contains(",")) {
+            parts = input.split(",");
+        } else {
+            parts = new String[]{input};
+        }
+
+        for (String part : parts) {
+            MaterialSpecifier materialSpecifier = parseTagOrMaterial(part.trim());
+            if (materialSpecifier != null) {
+                specifiers.add(materialSpecifier);
+            }
+        }
+
+        return specifiers;
+    }
+
+    @Nullable
+    private static MaterialSpecifier parseTagOrMaterial(@NotNull String input) {
+        if (input.startsWith("#")) {
+            String tagString = input.replaceFirst("#", "").toLowerCase();
+            Tag<Material> tag = Bukkit.getTag(Tag.REGISTRY_BLOCKS, NamespacedKey.minecraft(tagString), Material.class);
+            if (tag != null) {
+                return new BukkitTagSpecifier(tag);
+            }
+        } else {
+            Material material = Material.matchMaterial(input);
+            if (material != null) {
+                return new BukkitMaterialSpecifier(material);
+            }
+        }
+
+        return null;
+    }
+
 }