/*
 * 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.google.common.base;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Arrays;
import org.checkerframework.checker.nullness.qual.Nullable;

Helper functions that operate on any Object, and are not already provided in Objects. 
See the Guava User Guide on writing Object methods with MoreObjects.
Author:
Laurence Gonsalves
Since:
18.0 (since 2.0 as Objects)/**
 * 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="https://github.com/google/guava/wiki/CommonObjectUtilitiesExplained">writing {@code Object}
 * methods with {@code MoreObjects}</a>.
 *
 * @author Laurence Gonsalves
 * @since 18.0 (since 2.0 as {@code Objects})
 */
@GwtCompatible
public final class MoreObjects {
  
Returns the first of two given parameters that is not null, if either is, or otherwise throws a NullPointerException. 
To find the first non-null element in an iterable, use Iterables.find(iterable,
Predicates.notNull()). For varargs, use Iterables.find(Arrays.asList(a, b, c, ...),
Predicates.notNull()), static importing as necessary. 
Note: if first is represented as an Optional, this can be accomplished with first.or(second). That approach also allows for lazy evaluation of the fallback instance, using 
first.or(supplier). 
Throws:
NullPointerException – if both first and second are null
Returns:
first if it is non-null; otherwise second if it is non-null
Since:
18.0 (since 3.0 as Objects.firstNonNull())./**
   * Returns the first of two given parameters that is not {@code null}, if either is, or otherwise
   * throws a {@link NullPointerException}.
   *
   * <p>To find the first non-null element in an iterable, use {@code Iterables.find(iterable,
   * Predicates.notNull())}. For varargs, use {@code Iterables.find(Arrays.asList(a, b, c, ...),
   * Predicates.notNull())}, static importing as necessary.
   *
   * <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)}. That approach also allows for
   * lazy evaluation of the fallback instance, using {@link Optional#or(Supplier)
   * first.or(supplier)}.
   *
   * @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) {
    if (first != null) {
      return first;
    }
    if (second != null) {
      return second;
    }
    throw new NullPointerException("Both parameters are null");
  }

  
Creates an instance of ToStringHelper. 
This is helpful for implementing Object.toString(). Specification by example: 

// 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();

Note that in GWT, class names are often obfuscated.
Params:
self – the object to generate the string for (typically this), used only for its class name
Since:
18.0 (since 2.0 as Objects.toStringHelper())./**
   * 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(self.getClass().getSimpleName());
  }

  
Creates an instance of ToStringHelper in the same manner as toStringHelper(Object), but using the simple name of clazz instead of using an instance's Object.getClass(). 
Note that in GWT, class names are often obfuscated.
Params:
clazz – the Class of the instance
Since:
18.0 (since 7.0 as Objects.toStringHelper())./**
   * 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(clazz.getSimpleName());
  }

  
Creates an instance of ToStringHelper in the same manner as toStringHelper(Object), but using className instead of using an instance's Object.getClass(). 
Params:
className – the name of the instance type
Since:
18.0 (since 7.0 as Objects.toStringHelper())./**
   * 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);
  }

  
Support class for MoreObjects.toStringHelper. 
Author:
Jason Lee
Since:
18.0 (since 2.0 as Objects.ToStringHelper)./**
   * 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 = false;

    
Use MoreObjects.toStringHelper(Object) to create an instance. /** Use {@link MoreObjects#toStringHelper(Object)} to create an instance. */
    private ToStringHelper(String className) {
      this.className = checkNotNull(className);
    }

    
Configures the ToStringHelper so toString() will ignore properties with null value. The order of calling this method, relative to the add()/addValue() methods, is not significant. 
Since:
18.0 (since 12.0 as Objects.ToStringHelper.omitNullValues())./**
     * 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()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper omitNullValues() {
      omitNullValues = true;
      return this;
    }

    
Adds a name/value pair to the formatted output in name=value format. If value is null, the string "null" is used, unless omitNullValues() is called, in which case this name/value pair will not be added. /**
     * 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.
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, @Nullable Object value) {
      return addHolder(name, value);
    }

    
Adds a name/value pair to the formatted output in name=value format. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.add())./**
     * Adds a name/value pair to the formatted output in {@code name=value} format.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, boolean value) {
      return addHolder(name, String.valueOf(value));
    }

    
Adds a name/value pair to the formatted output in name=value format. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.add())./**
     * Adds a name/value pair to the formatted output in {@code name=value} format.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, char value) {
      return addHolder(name, String.valueOf(value));
    }

    
Adds a name/value pair to the formatted output in name=value format. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.add())./**
     * Adds a name/value pair to the formatted output in {@code name=value} format.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, double value) {
      return addHolder(name, String.valueOf(value));
    }

    
Adds a name/value pair to the formatted output in name=value format. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.add())./**
     * Adds a name/value pair to the formatted output in {@code name=value} format.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, float value) {
      return addHolder(name, String.valueOf(value));
    }

    
Adds a name/value pair to the formatted output in name=value format. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.add())./**
     * Adds a name/value pair to the formatted output in {@code name=value} format.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, int value) {
      return addHolder(name, String.valueOf(value));
    }

    
Adds a name/value pair to the formatted output in name=value format. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.add())./**
     * Adds a name/value pair to the formatted output in {@code name=value} format.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.add()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper add(String name, long value) {
      return addHolder(name, String.valueOf(value));
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, Object) instead and give value a readable name. /**
     * 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.
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(@Nullable Object value) {
      return addHolder(value);
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, boolean) instead and give value a readable name. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.addValue())./**
     * Adds an unnamed value to the formatted output.
     *
     * <p>It is strongly encouraged to use {@link #add(String, boolean)} instead and give value a
     * readable name.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(boolean value) {
      return addHolder(String.valueOf(value));
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, char) instead and give value a readable name. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.addValue())./**
     * 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.addValue()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(char value) {
      return addHolder(String.valueOf(value));
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, double) instead and give value a readable name. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.addValue())./**
     * 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.addValue()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(double value) {
      return addHolder(String.valueOf(value));
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, float) instead and give value a readable name. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.addValue())./**
     * 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.addValue()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(float value) {
      return addHolder(String.valueOf(value));
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, int) instead and give value a readable name. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.addValue())./**
     * 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.addValue()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(int value) {
      return addHolder(String.valueOf(value));
    }

    
Adds an unnamed value to the formatted output.
It is strongly encouraged to use add(String, long) instead and give value a readable name. 
Since:
18.0 (since 11.0 as Objects.ToStringHelper.addValue())./**
     * 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.addValue()}).
     */
    @CanIgnoreReturnValue
    public ToStringHelper addValue(long value) {
      return addHolder(String.valueOf(value));
    }

    
Returns a string in the format specified by MoreObjects.toStringHelper(Object). 
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).
/**
     * 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) {
        Object value = valueHolder.value;
        if (!omitNullValuesSnapshot || value != null) {
          builder.append(nextSeparator);
          nextSeparator = ", ";

          if (valueHolder.name != null) {
            builder.append(valueHolder.name).append('=');
          }
          if (value != null && value.getClass().isArray()) {
            Object[] objectArray = {value};
            String arrayString = Arrays.deepToString(objectArray);
            builder.append(arrayString, 1, arrayString.length() - 1);
          } else {
            builder.append(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 {
      @Nullable String name;
      @Nullable Object value;
      @Nullable ValueHolder next;
    }
  }

  private MoreObjects() {}
}