content: /*
   * Copyright (C) 2014 The Guava Authors
   *
   * 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.fernandocejas.frodo.core.objects;
  
  import com.fernandocejas.frodo.core.optional.Optional;
  import java.util.Arrays;
  import org.jetbrains.annotations.Nullable;
  
  import static com.fernandocejas.frodo.core.checks.Preconditions.checkNotNull;
  
  /**
   * Helper functions that operate on any {@code Object}, and are not already provided in
   * {@link java.util.Objects}.
   *
   * <p>See the Guava User Guide on <a
   * href="http://code.google.com/p/guava-libraries/wiki/CommonObjectUtilitiesExplained">writing
   * {@code Object} methods with {@code Objects}</a>.
   *
   * @author Laurence Gonsalves
   * @since 18.0 (since 2.0 as {@code Objects})
   *
   * <p><b>This class contains code derived from <a href="https://github.com/google/guava">Google
   * Guava</a></b>
   */
  public final class MoreObjects {
  
    /**
     * Determines whether two possibly-null objects are equal. Returns:
     *
     * <ul>
     * <li>{@code true} if {@code a} and {@code b} are both null.
     * <li>{@code true} if {@code a} and {@code b} are both non-null and they are
     * equal according to {@link Object#equals(Object)}.
     * <li>{@code false} in all other situations.
     * </ul>
     *
     * <p>This assumes that any non-null objects passed to this function conform
     * to the {@code equals()} contract.
     *
     * <p><b>Note for Java 7 and later:</b> This method should be treated as
     * deprecated; use {@link java.util.Objects#equals} instead.
     */
    public static boolean equal(@Nullable Object a, @Nullable Object b) {
      return a == b || a != null && a.equals(b);
    }
  
    /**
     * Generates a hash code for multiple values. The hash code is generated by
     * calling {@link Arrays#hashCode(Object[])}. Note that array arguments to
     * this method, with the exception of a single Object array, do not get any
     * special handling; their hash codes are based on identity and not contents.
     *
     * <p>This is useful for implementing {@link Object#hashCode()}. For example,
     * in an object that has three properties, {@code x}, {@code y}, and
     * {@code z}, one could write:
     * <pre>   {@code
     *   public int hashCode() {
     *     return Objects.hashCode(getX(), getY(), getZ());
     *   }}</pre>
     *
     * <p><b>Warning:</b> When a single object is supplied, the returned hash code
     * does not equal the hash code of that object.
     *
     * <p><b>Note for Java 7 and later:</b> This method should be treated as
     * deprecated; use {@link java.util.Objects#hash} instead.
     */
    public static int hashCode(@Nullable Object... objects) {
      return Arrays.hashCode(objects);
    }
  
    /**
     * Returns the first of two given parameters that is not {@code null}, if either is, or otherwise
     * throws a {@link NullPointerException}.
     *
     * <p><b>Note:</b> if {@code first} is represented as an {@link Optional}, this can be
     * accomplished with {@link Optional#or(Object) first.or(second)}.
     *
     * @return {@code first} if it is non-null; otherwise {@code second} if it is non-null
     * @throws NullPointerException if both {@code first} and {@code second} are null
     * @since 18.0 (since 3.0 as {@code Objects.firstNonNull()}.
     */
    public static <T> T firstNonNull(@Nullable T first, @Nullable T second) {
      return first != null ? first : checkNotNull(second);
    }
  
    /**
     * Creates an instance of {@link ToStringHelper}.
     *
     * <p>This is helpful for implementing {@link Object#toString()}.
     * Specification by example: <pre>   {@code
     *   // Returns "ClassName{}"
     *   MoreObjects.toStringHelper(this)
     *       .toString();
     *
     *   // Returns "ClassName{x=1}"
     *   MoreObjects.toStringHelper(this)
     *       .add("x", 1)
     *       .toString();
     *
     *   // Returns "MyObject{x=1}"
     *   MoreObjects.toStringHelper("MyObject")
     *       .add("x", 1)
     *       .toString();
     *
     *   // Returns "ClassName{x=1, y=foo}"
     *   MoreObjects.toStringHelper(this)
     *       .add("x", 1)
     *       .add("y", "foo")
     *       .toString();
     *
     *   // Returns "ClassName{x=1}"
     *   MoreObjects.toStringHelper(this)
     *       .omitNullValues()
     *       .add("x", 1)
     *       .add("y", null)
     *       .toString();
     *   }}</pre>
     *
     * <p>Note that in GWT, class names are often obfuscated.
     *
     * @param self the object to generate the string for (typically {@code this}), used only for its
     * class name
     * @since 18.0 (since 2.0 as {@code Objects.toStringHelper()}.
     */
    public static ToStringHelper toStringHelper(Object self) {
      return new ToStringHelper(simpleName(self.getClass()));
    }
  
    /**
     * Creates an instance of {@link ToStringHelper} in the same manner as {@link
     * #toStringHelper(Object)}, but using the simple name of {@code clazz} instead of using an
     * instance's {@link Object#getClass()}.
     *
     * <p>Note that in GWT, class names are often obfuscated.
     *
     * @param clazz the {@link Class} of the instance
     * @since 18.0 (since 7.0 as {@code Objects.toStringHelper()}.
     */
    public static ToStringHelper toStringHelper(Class<?> clazz) {
      return new ToStringHelper(simpleName(clazz));
    }
  
    /**
     * Creates an instance of {@link ToStringHelper} in the same manner as {@link
     * #toStringHelper(Object)}, but using {@code className} instead of using an instance's {@link
     * Object#getClass()}.
     *
     * @param className the name of the instance type
     * @since 18.0 (since 7.0 as {@code Objects.toStringHelper()}.
     */
    public static ToStringHelper toStringHelper(String className) {
      return new ToStringHelper(className);
    }
  
    /**
     * {@link Class#getSimpleName()} is not GWT compatible yet, so we
     * provide our own implementation.
     */
    // Package-private so Objects can call it.
    static String simpleName(Class<?> clazz) {
      String name = clazz.getName();
  
      // the nth anonymous class has a class name ending in "Outer$n"
      // and local inner classes have names ending in "Outer.$1Inner"
      name = name.replaceAll("\\$[0-9]+", "\\$");
  
      // we want the name of the inner class all by its lonesome
      int start = name.lastIndexOf('$');
  
      // if this isn't an inner class, just find the start of the
      // top level class name.
      if (start == -1) {
        start = name.lastIndexOf('.');
      }
      return name.substring(start + 1);
    }
  
    /**
     * Support class for {@link MoreObjects#toStringHelper}.
     *
     * @author Jason Lee
     * @since 18.0 (since 2.0 as {@code Objects.ToStringHelper}.
     */
    public static final class ToStringHelper {
      private final String className;
      private final ValueHolder holderHead = new ValueHolder();
      private ValueHolder holderTail = holderHead;
      private boolean omitNullValues;
  
      /**
       * Use {@link MoreObjects#toStringHelper(Object)} to create an instance.
       */
      ToStringHelper(String className) {
        this.className = checkNotNull(className);
      }
  
      /**
       * Configures the {@link ToStringHelper} so {@link #toString()} will ignore
       * properties with null value. The order of calling this method, relative
       * to the {@code add()}/{@code addValue()} methods, is not significant.
       *
       * @since 18.0 (since 12.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper omitNullValues() {
        omitNullValues = true;
        return this;
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format. If {@code value} is {@code null}, the string {@code "null"}
       * is used, unless {@link #omitNullValues()} is called, in which case this
       * name/value pair will not be added.
       */
      public ToStringHelper add(String name, @Nullable Object value) {
        return addHolder(name, value);
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper add(String name, boolean value) {
        return addHolder(name, String.valueOf(value));
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper add(String name, char value) {
        return addHolder(name, String.valueOf(value));
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper add(String name, double value) {
        return addHolder(name, String.valueOf(value));
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper add(String name, float value) {
        return addHolder(name, String.valueOf(value));
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper add(String name, int value) {
        return addHolder(name, String.valueOf(value));
      }
  
      /**
       * Adds a name/value pair to the formatted output in {@code name=value}
       * format.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper add(String name, long value) {
        return addHolder(name, String.valueOf(value));
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * <p>It is strongly encouraged to use {@link #add(String, Object)} instead
       * and give value a readable name.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(@Nullable Object value) {
        return addHolder(value);
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(boolean value) {
        return addHolder(String.valueOf(value));
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * <p>It is strongly encouraged to use {@link #add(String, char)} instead
       * and give value a readable name.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(char value) {
        return addHolder(String.valueOf(value));
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * <p>It is strongly encouraged to use {@link #add(String, double)} instead
       * and give value a readable name.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(double value) {
        return addHolder(String.valueOf(value));
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * <p>It is strongly encouraged to use {@link #add(String, float)} instead
       * and give value a readable name.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(float value) {
        return addHolder(String.valueOf(value));
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * <p>It is strongly encouraged to use {@link #add(String, int)} instead
       * and give value a readable name.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(int value) {
        return addHolder(String.valueOf(value));
      }
  
      /**
       * Adds an unnamed value to the formatted output.
       *
       * <p>It is strongly encouraged to use {@link #add(String, long)} instead
       * and give value a readable name.
       *
       * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.omitNullValues()}.
       */
      public ToStringHelper addValue(long value) {
        return addHolder(String.valueOf(value));
      }
  
      /**
       * Returns a string in the format specified by
       * {@link MoreObjects#toStringHelper(Object)}.
       *
       * <p>After calling this method, you can keep adding more properties to later
       * call toString() again and get a more complete representation of the
       * same object; but properties cannot be removed, so this only allows
       * limited reuse of the helper instance. The helper allows duplication of
       * properties (multiple name/value pairs with the same name can be added).
       */
      @Override
      public String toString() {
        // create a copy to keep it consistent in case value changes
        boolean omitNullValuesSnapshot = omitNullValues;
        String nextSeparator = "";
        StringBuilder builder = new StringBuilder(32).append(className)
            .append('{');
        for (ValueHolder valueHolder = holderHead.next; valueHolder != null;
            valueHolder = valueHolder.next) {
          if (!omitNullValuesSnapshot || valueHolder.value != null) {
            builder.append(nextSeparator);
            nextSeparator = ", ";
  
            if (valueHolder.name != null) {
              builder.append(valueHolder.name).append('=');
            }
            builder.append(valueHolder.value);
          }
        }
        return builder.append('}').toString();
      }
  
      private ValueHolder addHolder() {
        ValueHolder valueHolder = new ValueHolder();
        holderTail = holderTail.next = valueHolder;
        return valueHolder;
      }
  
      private ToStringHelper addHolder(@Nullable Object value) {
        ValueHolder valueHolder = addHolder();
        valueHolder.value = value;
        return this;
      }
  
      private ToStringHelper addHolder(String name, @Nullable Object value) {
        ValueHolder valueHolder = addHolder();
        valueHolder.value = value;
        valueHolder.name = checkNotNull(name);
        return this;
      }
  
      private static final class ValueHolder {
        String name;
        Object value;
        ValueHolder next;
      }
    }
  
    private MoreObjects() {
      // no instances
    }
  }
  