/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package dev.metaschema.core.metapath.function.library;
   
   import java.util.List;
   
  import dev.metaschema.core.metapath.DynamicContext;
  import dev.metaschema.core.metapath.MetapathConstants;
  import dev.metaschema.core.metapath.function.FunctionUtils;
  import dev.metaschema.core.metapath.function.IArgument;
  import dev.metaschema.core.metapath.function.IFunction;
  import dev.metaschema.core.metapath.item.ICollectionValue;
  import dev.metaschema.core.metapath.item.IItem;
  import dev.metaschema.core.metapath.item.ISequence;
  import dev.metaschema.core.metapath.item.atomic.IAnyAtomicItem;
  import dev.metaschema.core.metapath.item.function.IMapItem;
  import dev.metaschema.core.util.ObjectUtils;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  /**
   * Implements the XPath 3.1
   * <a href= "https://www.w3.org/TR/xpath-functions-31/#func-map-get">map:get</a>
   * function.
   */
  public final class MapGet {
    private static final String NAME = "get";
    @NonNull
    static final IFunction SIGNATURE = IFunction.builder()
        .name(NAME)
        .namespace(MetapathConstants.NS_METAPATH_FUNCTIONS_MAP)
        .deterministic()
        .contextIndependent()
        .focusIndependent()
        .argument(IArgument.builder()
            .name("map")
            .type(IMapItem.type())
            .one()
            .build())
        .argument(IArgument.builder()
            .name("key")
            .type(IAnyAtomicItem.type())
            .one()
            .build())
        .returnType(IItem.type())
        .returnZeroOrOne()
        .functionHandler(MapGet::execute)
        .build();
  
    private MapGet() {
      // disable construction
    }
  
    @SuppressWarnings("unused")
    @NonNull
    private static ISequence<?> execute(@NonNull IFunction function,
        @NonNull List<ISequence<?>> arguments,
        @NonNull DynamicContext dynamicContext,
        IItem focus) {
      IMapItem<?> map = FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(0).getFirstItem(true)));
      IAnyAtomicItem key = FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(1).getFirstItem(true)));
  
      ICollectionValue value = get(map, key);
      return value == null ? ISequence.empty() : value.toSequence();
    }
  
    /**
     * An implementation of XPath 3.1 <a href=
     * "https://www.w3.org/TR/xpath-functions-31/#func-map-get">map:get</a>.
     *
     * @param <V>
     *          the type of items in the given Metapath map
     * @param map
     *          the map of Metapath items that is the target of retrieval
     * @param key
     *          the key for the item to retrieve
     * @return the retrieved item
     */
    @Nullable
    public static <V extends ICollectionValue> V get(
        @NonNull IMapItem<V> map,
        @NonNull IAnyAtomicItem key) {
      return map.get(key.asMapKey());
    }
  }