/*
    * Portions of this software was developed by employees of the National Institute
    * of Standards and Technology (NIST), an agency of the Federal Government and is
    * being made available as a public service. Pursuant to title 17 United States
    * Code Section 105, works of NIST employees are not subject to copyright
    * protection in the United States. This software may be subject to foreign
    * copyright. Permission in the United States and in foreign countries, to the
    * extent that NIST may hold copyright, to use, copy, modify, create derivative
    * works, and distribute this software and its documentation without fee is hereby
   * granted on a non-exclusive basis, provided that this notice and disclaimer
   * of warranty appears in all copies.
   *
   * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
   * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
   * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
   * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
   * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
   * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
   * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
   * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
   * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
   * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
   * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
   */
  
  package gov.nist.secauto.metaschema.core.metapath.function;
  
  import gov.nist.secauto.metaschema.core.metapath.IExpression;
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.stream.Stream;
  
  import javax.xml.namespace.QName;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  public class FunctionLibrary implements IFunctionLibrary {
  
    @NonNull
    private final Map<QName, NamedFunctionSet> libraryByQName = new HashMap<>(); // NOPMD - intentional
    @NonNull
    private final Map<String, NamedFunctionSet> libraryByName = new HashMap<>(); // NOPMD - intentional
  
    /**
     * Register the provided function signature.
     *
     * @param function
     *          the function signature to register
     * @throws IllegalArgumentException
     *           if the provided function has the same arity as a previously
     *           registered function with the same name
     */
    public void registerFunction(@NonNull IFunction function) {
      registerFunctionByQName(function);
      registerFunctionByName(function);
    }
  
    protected void registerFunctionByQName(@NonNull IFunction function) {
      QName qname = function.getQName();
      IFunction duplicate;
      synchronized (this) {
        NamedFunctionSet functions = libraryByQName.get(qname);
        if (functions == null) {
          functions = new NamedFunctionSet();
          libraryByQName.put(qname, functions);
        }
        duplicate = functions.addFunction(function);
      }
      if (duplicate != null) {
        throw new IllegalArgumentException(String.format("Duplicate functions with same arity: %s shadows %s",
            duplicate.toSignature(), function.toSignature()));
      }
    }
  
    protected void registerFunctionByName(@NonNull IFunction function) {
      String name = function.getName();
      synchronized (this) {
        NamedFunctionSet functions = libraryByName.get(name);
        if (functions == null) {
          functions = new NamedFunctionSet();
          libraryByName.put(name, functions);
        }
        // replace duplicates
        functions.addFunction(function);
      }
    }
  
    @Override
    public Stream<IFunction> getFunctionsAsStream() {
      synchronized (this) {
        return ObjectUtils.notNull(
            libraryByQName.values().stream().flatMap(set -> {
              return set.getFunctionsAsStream();
            }));
     }
   }
 
   @Override
   public IFunction getFunction(@NonNull String name, @NonNull List<IExpression> args) {
     IFunction retval;
     synchronized (this) {
       NamedFunctionSet functions = libraryByName.get(name);
       retval = functions == null ? null : functions.getFunctionWithArity(args.size());
     }
     return retval;
   }
 
   @Override
   public IFunction getFunction(@NonNull QName name, @NonNull List<IExpression> args) {
     IFunction retval;
     synchronized (this) {
       NamedFunctionSet functions = libraryByQName.get(name);
       retval = functions == null ? null : functions.getFunctionWithArity(args.size());
     }
     return retval;
   }
 
   private static class NamedFunctionSet {
     private final Map<Integer, IFunction> arityToFunctionMap;
 
     public NamedFunctionSet() {
       this.arityToFunctionMap = new HashMap<>();
     }
 
     @SuppressWarnings("null")
     @NonNull
     public Stream<IFunction> getFunctionsAsStream() {
       return arityToFunctionMap.values().stream();
     }
 
     @Nullable
     public IFunction getFunctionWithArity(int arity) {
       return arityToFunctionMap.get(arity);
     }
 
     @Nullable
     public IFunction addFunction(@NonNull IFunction function) {
       return arityToFunctionMap.put(function.arity(), function);
     }
   }
 }