001    /*
002     * Created on Sep 8, 2010
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
005     * the License. You may obtain a copy of the License at
006     *
007     * http://www.apache.org/licenses/LICENSE-2.0
008     *
009     * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
010     * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
011     * specific language governing permissions and limitations under the License.
012     *
013     * Copyright @2010-2011 the original author or authors.
014     */
015    package org.fest.assertions.error;
016    
017    import static org.fest.util.ToString.toStringOf;
018    
019    import java.awt.image.BufferedImage;
020    
021    import org.fest.assertions.description.Description;
022    import org.fest.util.*;
023    
024    /**
025     * Formats the messages to be included in assertion errors.
026     *
027     * @author Alex Ruiz
028     */
029    public class MessageFormatter {
030    
031      private static final MessageFormatter INSTANCE = new MessageFormatter();
032    
033      /**
034       * Returns the singleton instance of this class.
035       * @return the singleton instance of this class.
036       */
037      public static MessageFormatter instance() {
038        return INSTANCE;
039      }
040    
041      @VisibleForTesting DescriptionFormatter descriptionFormatter = DescriptionFormatter.instance();
042    
043      @VisibleForTesting MessageFormatter() {}
044    
045      /**
046       * Interprets a printf-style format {@code String} for failed assertion messages. It is similar to
047       * <code>{@link String#format(String, Object...)}</code>, except for:
048       * <ol>
049       * <li>the value of the given <code>{@link Description}</code> is used as the first argument referenced in the format
050       * string</li>
051       * <li>each of the arguments in the given array is converted to a {@code String} by invoking
052       * <code>{@link ToString#toStringOf(Object)}</code>.
053       * </ol>
054       * @param d the description of the failed assertion, may be {@code null}.
055       * @param format the format string.
056       * @param args arguments referenced by the format specifiers in the format string.
057       * @throws NullPointerException if the format string is {@code null}.
058       * @return A formatted {@code String}.
059       */
060      public String format(Description d, String format, Object... args) {
061        if (format == null) throw new NullPointerException("The format string should not be null");
062        if (args == null) throw new NullPointerException("The array of arguments should not be null");
063        return descriptionFormatter.format(d) + String.format(format, format(args));
064      }
065    
066      private Object[] format(Object[] args) {
067        int argCount = args.length;
068        String[] formatted = new String[argCount];
069        for (int i = 0; i < argCount; i++)
070          formatted[i] = asText(args[i]);
071        return formatted;
072      }
073    
074      private String asText(Object o) {
075        if (o instanceof BufferedImage) return "image";
076        if (o instanceof ComparatorBasedComparisonStrategy) return " according to " + o + " comparator";
077        if (o instanceof StandardComparisonStrategy) return "";
078        return toStringOf(o);
079      }
080    }