001/* 002 * Portions of this software was developed by employees of the National Institute 003 * of Standards and Technology (NIST), an agency of the Federal Government and is 004 * being made available as a public service. Pursuant to title 17 United States 005 * Code Section 105, works of NIST employees are not subject to copyright 006 * protection in the United States. This software may be subject to foreign 007 * copyright. Permission in the United States and in foreign countries, to the 008 * extent that NIST may hold copyright, to use, copy, modify, create derivative 009 * works, and distribute this software and its documentation without fee is hereby 010 * granted on a non-exclusive basis, provided that this notice and disclaimer 011 * of warranty appears in all copies. 012 * 013 * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER 014 * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY 015 * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF 016 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM 017 * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE 018 * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE. IN NO EVENT 019 * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT, 020 * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM, 021 * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY, 022 * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR 023 * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT 024 * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER. 025 */ 026 027package gov.nist.secauto.metaschema.core.metapath.function; 028 029import gov.nist.secauto.metaschema.core.metapath.IExpression; 030import gov.nist.secauto.metaschema.core.metapath.StaticMetapathException; 031import gov.nist.secauto.metaschema.core.util.ObjectUtils; 032 033import java.util.Arrays; 034import java.util.List; 035import java.util.ServiceLoader; 036import java.util.ServiceLoader.Provider; 037 038import edu.umd.cs.findbugs.annotations.NonNull; 039import nl.talsmasoftware.lazy4j.Lazy; 040 041public final class FunctionService { 042 private static final Lazy<FunctionService> INSTANCE = Lazy.lazy(() -> new FunctionService()); 043 @NonNull 044 private final ServiceLoader<IFunctionLibrary> loader; 045 @NonNull 046 private IFunctionLibrary library; 047 048 /** 049 * Get the singleton instance of the function service. 050 * 051 * @return the service instance 052 */ 053 public static FunctionService getInstance() { 054 return INSTANCE.get(); 055 } 056 057 /** 058 * Construct a new function service. 059 */ 060 @SuppressWarnings("null") 061 public FunctionService() { 062 this.loader = ServiceLoader.load(IFunctionLibrary.class); 063 this.library = load(); 064 } 065 066 /** 067 * Load all known functions registered with this function service. 068 * 069 * @return the function library 070 */ 071 @NonNull 072 public IFunctionLibrary load() { 073 ServiceLoader<IFunctionLibrary> loader = getLoader(); 074 075 FunctionLibrary functionLibrary = new FunctionLibrary(); 076 loader.stream() 077 .map(Provider<IFunctionLibrary>::get) 078 .flatMap(library -> { 079 return library.getFunctionsAsStream(); 080 }) 081 .forEachOrdered(function -> functionLibrary.registerFunction(ObjectUtils.requireNonNull(function))); 082 083 synchronized (this) { 084 this.library = functionLibrary; 085 } 086 return functionLibrary; 087 } 088 089 /** 090 * Get the function service loader instance. 091 * 092 * @return the service loader instance. 093 */ 094 @NonNull 095 private ServiceLoader<IFunctionLibrary> getLoader() { 096 return loader; 097 } 098 099 /** 100 * Retrieve the function with the provided name that supports the signature of 101 * the provided methods, if such a function exists. 102 * 103 * @param name 104 * the name of a group of functions 105 * @param arguments 106 * a list of argument expressions for use in determining an argument 107 * signature match 108 * @return the matching function or {@code null} if no match exists 109 * @throws StaticMetapathException 110 * if a matching function was not found 111 */ 112 @SuppressWarnings("null") 113 public IFunction getFunction(@NonNull String name, @NonNull IExpression... arguments) { 114 return getFunction(name, Arrays.asList(arguments)); 115 } 116 117 /** 118 * Retrieve the function with the provided name that supports the signature of 119 * the provided methods, if such a function exists. 120 * 121 * @param name 122 * the name of a group of functions 123 * @param arguments 124 * a list of argument expressions for use in determining an argument 125 * signature match 126 * @return the matching function 127 * @throws StaticMetapathException 128 * if a matching function was not found 129 */ 130 public IFunction getFunction(@NonNull String name, @NonNull List<IExpression> arguments) { 131 IFunction retval; 132 synchronized (this) { 133 retval = library.getFunction(name, arguments); 134 } 135 136 if (retval == null) { 137 throw new StaticMetapathException(StaticMetapathException.NO_FUNCTION_MATCH, 138 String.format("unable to find function with name '%s' having arity '%d'", name, arguments.size())); 139 } 140 return retval; 141 } 142}