Add meta-value-selection config setting (#2167)

api/src/main/java/net/luckperms/api/query/meta/MetaValueSelector.java

@@ -0,0 +1,59 @@
+/*
+ * This file is part of LuckPerms, licensed under the MIT License.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) contributors
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy
+ *  of this software and associated documentation files (the "Software"), to deal
+ *  in the Software without restriction, including without limitation the rights
+ *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *  copies of the Software, and to permit persons to whom the Software is
+ *  furnished to do so, subject to the following conditions:
+ *
+ *  The above copyright notice and this permission notice shall be included in all
+ *  copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *  SOFTWARE.
+ */
+
+package net.luckperms.api.query.meta;
+
+import net.luckperms.api.node.types.MetaNode;
+import net.luckperms.api.query.OptionKey;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+import java.util.List;
+
+/**
+ * A function that selects the {@link MetaNode#getMetaValue() meta value} to be used in queries
+ * against a given {@link MetaNode#getMetaKey() meta key}.
+ *
+ * @since 5.1
+ */
+public interface MetaValueSelector {
+
+    /**
+     * The {@link OptionKey} for {@link MetaValueSelector}.
+     */
+    OptionKey<MetaValueSelector> KEY = OptionKey.of("metavalueselector", MetaValueSelector.class);
+
+    /**
+     * Selects the meta value to map to the given key.
+     *
+     * <p>The {@code values} list is guaranteed to contain at least 1 element.</p>
+     *
+     * @param key the key
+     * @param values the values, in the order in which they were accumulated.
+     * @return the selected value
+     */
+    @NonNull String selectValue(@NonNull String key, @NonNull List<String> values);
+
+}