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/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.squareup.javapoet;

import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import javax.lang.model.SourceVersion;

import static com.squareup.javapoet.Util.checkNotNull;

/**
 * Assigns Java identifier names to avoid collisions, keywords, and invalid characters. To use,
 * first create an instance and allocate all of the names that you need. Typically this is a
 * mix of user-supplied names and constants: 
   {@code
 *
 *   NameAllocator nameAllocator = new NameAllocator();
 *   for (MyProperty property : properties) {
 *     nameAllocator.newName(property.name(), property);
 *   }
 *   nameAllocator.newName("sb", "string builder");
 * }
* * Pass a unique tag object to each allocation. The tag scopes the name, and can be used to look up * the allocated name later. Typically the tag is the object that is being named. In the above * example we use {@code property} for the user-supplied property names, and {@code "string * builder"} for our constant string builder. * *

Once we've allocated names we can use them when generating code:

   {@code
 *
 *   MethodSpec.Builder builder = MethodSpec.methodBuilder("toString")
 *       .addAnnotation(Override.class)
 *       .addModifiers(Modifier.PUBLIC)
 *       .returns(String.class);
 *
 *   builder.addStatement("$1T $2N = new $1T()",
 *       StringBuilder.class, nameAllocator.get("string builder"));
 *   for (MyProperty property : properties) {
 *     builder.addStatement("$N.append($N)",
 *         nameAllocator.get("string builder"), nameAllocator.get(property));
 *   }
 *   builder.addStatement("return $N", nameAllocator.get("string builder"));
 *   return builder.build();
 * }
* * The above code generates unique names if presented with conflicts. Given user-supplied properties * with names {@code ab} and {@code sb} this generates the following:
   {@code
 *
 *   @Override
 *   public String toString() {
 *     StringBuilder sb_ = new StringBuilder();
 *     sb_.append(ab);
 *     sb_.append(sb);
 *     return sb_.toString();
 *   }
 * }
* * The underscore is appended to {@code sb} to avoid conflicting with the user-supplied {@code sb} * property. Underscores are also prefixed for names that start with a digit, and used to replace * name-unsafe characters like space or dash. * *

When dealing with multiple independent inner scopes, use a {@link #clone()} of the * NameAllocator used for the outer scope to further refine name allocation for a specific inner * scope. */ public final class NameAllocator implements Cloneable { private final Set allocatedNames; private final Map tagToName; public NameAllocator() { this(new LinkedHashSet(), new LinkedHashMap()); } private NameAllocator(LinkedHashSet allocatedNames, LinkedHashMap tagToName) { this.allocatedNames = allocatedNames; this.tagToName = tagToName; } /** * Return a new name using {@code suggestion} that will not be a Java identifier or clash with * other names. */ public String newName(String suggestion) { return newName(suggestion, UUID.randomUUID().toString()); } /** * Return a new name using {@code suggestion} that will not be a Java identifier or clash with * other names. The returned value can be queried multiple times by passing {@code tag} to * {@link #get(Object)}. */ public String newName(String suggestion, Object tag) { checkNotNull(suggestion, "suggestion"); checkNotNull(tag, "tag"); suggestion = toJavaIdentifier(suggestion); while (SourceVersion.isKeyword(suggestion) || !allocatedNames.add(suggestion)) { suggestion = suggestion + "_"; } String replaced = tagToName.put(tag, suggestion); if (replaced != null) { tagToName.put(tag, replaced); // Put things back as they were! throw new IllegalArgumentException("tag " + tag + " cannot be used for both '" + replaced + "' and '" + suggestion + "'"); } return suggestion; } public static String toJavaIdentifier(String suggestion) { StringBuilder result = new StringBuilder(); for (int i = 0; i < suggestion.length(); ) { int codePoint = suggestion.codePointAt(i); if (i == 0 && !Character.isJavaIdentifierStart(codePoint) && Character.isJavaIdentifierPart(codePoint)) { result.append("_"); } int validCodePoint = Character.isJavaIdentifierPart(codePoint) ? codePoint : '_'; result.appendCodePoint(validCodePoint); i += Character.charCount(codePoint); } return result.toString(); } /** Retrieve a name created with {@link #newName(String, Object)}. */ public String get(Object tag) { String result = tagToName.get(tag); if (result == null) { throw new IllegalArgumentException("unknown tag: " + tag); } return result; } /** * Create a deep copy of this NameAllocator. Useful to create multiple independent refinements * of a NameAllocator to be used in the respective definition of multiples, independently-scoped, * inner code blocks. * * @return A deep copy of this NameAllocator. */ @Override public NameAllocator clone() { return new NameAllocator( new LinkedHashSet<>(this.allocatedNames), new LinkedHashMap<>(this.tagToName)); } }





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