/*
    * Copyright (C) 2007 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 java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.List;
  
  import javax.annotation.Nullable;
  
  /**
   * Static utility methods pertaining to {@code Predicate} instances.
   *
   * <p>All methods returns serializable predicates as long as they're given
   * serializable parameters.
   *
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/FunctionalExplained">the
   * use of {@code Predicate}</a>.
   *
   * @author Kevin Bourrillion
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible(emulated = true)
  public final class Predicates {
    private Predicates() {}
  
    // TODO(kevinb): considering having these implement a VisitablePredicate
    // interface which specifies an accept(PredicateVisitor) method.
  
    /**
     * Returns a predicate that always evaluates to {@code true}.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> alwaysTrue() {
      return ObjectPredicate.ALWAYS_TRUE.withNarrowedType();
    }
  
    /**
     * Returns a predicate that always evaluates to {@code false}.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> alwaysFalse() {
      return ObjectPredicate.ALWAYS_FALSE.withNarrowedType();
    }
  
    /**
     * Returns a predicate that evaluates to {@code true} if the object reference
     * being tested is null.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> isNull() {
      return ObjectPredicate.IS_NULL.withNarrowedType();
    }
  
    /**
     * Returns a predicate that evaluates to {@code true} if the object reference
     * being tested is not null.
     */
    @GwtCompatible(serializable = true)
    public static <T> Predicate<T> notNull() {
      return ObjectPredicate.NOT_NULL.withNarrowedType();
    }
  
    /**
     * Returns a predicate that evaluates to {@code true} if the given predicate
     * evaluates to {@code false}.
     */
    public static <T> Predicate<T> not(Predicate<T> predicate) {
      return new NotPredicate<T>(predicate);
    }
  
    /**
     * Returns a predicate that evaluates to {@code true} if each of its
     * components evaluates to {@code true}. The components are evaluated in
     * order, and evaluation will be "short-circuited" as soon as a false
     * predicate is found. It defensively copies the iterable passed in, so future
     * changes to it won't alter the behavior of this predicate. If {@code
     * components} is empty, the returned predicate will always evaluate to {@code
    * true}.
    */
   public static <T> Predicate<T> and(
       Iterable<? extends Predicate<? super T>> components) {
     return new AndPredicate<T>(defensiveCopy(components));
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if each of its
    * components evaluates to {@code true}. The components are evaluated in
    * order, and evaluation will be "short-circuited" as soon as a false
    * predicate is found. It defensively copies the array passed in, so future
    * changes to it won't alter the behavior of this predicate. If {@code
    * components} is empty, the returned predicate will always evaluate to {@code
    * true}.
    */
   public static <T> Predicate<T> and(Predicate<? super T>... components) {
     return new AndPredicate<T>(defensiveCopy(components));
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if both of its
    * components evaluate to {@code true}. The components are evaluated in
    * order, and evaluation will be "short-circuited" as soon as a false
    * predicate is found.
    */
   public static <T> Predicate<T> and(Predicate<? super T> first,
       Predicate<? super T> second) {
     return new AndPredicate<T>(Predicates.<T>asList(
         checkNotNull(first), checkNotNull(second)));
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if any one of its
    * components evaluates to {@code true}. The components are evaluated in
    * order, and evaluation will be "short-circuited" as soon as a
    * true predicate is found. It defensively copies the iterable passed in, so
    * future changes to it won't alter the behavior of this predicate. If {@code
    * components} is empty, the returned predicate will always evaluate to {@code
    * false}.
    */
   public static <T> Predicate<T> or(
       Iterable<? extends Predicate<? super T>> components) {
     return new OrPredicate<T>(defensiveCopy(components));
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if any one of its
    * components evaluates to {@code true}. The components are evaluated in
    * order, and evaluation will be "short-circuited" as soon as a
    * true predicate is found. It defensively copies the array passed in, so
    * future changes to it won't alter the behavior of this predicate. If {@code
    * components} is empty, the returned predicate will always evaluate to {@code
    * false}.
    */
   public static <T> Predicate<T> or(Predicate<? super T>... components) {
     return new OrPredicate<T>(defensiveCopy(components));
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if either of its
    * components evaluates to {@code true}. The components are evaluated in
    * order, and evaluation will be "short-circuited" as soon as a
    * true predicate is found.
    */
   public static <T> Predicate<T> or(
       Predicate<? super T> first, Predicate<? super T> second) {
     return new OrPredicate<T>(Predicates.<T>asList(
         checkNotNull(first), checkNotNull(second)));
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if the object being
    * tested {@code equals()} the given target or both are null.
    */
   public static <T> Predicate<T> equalTo(@Nullable T target) {
     return (target == null)
         ? Predicates.<T>isNull()
         : new IsEqualToPredicate<T>(target);
   }
 
   /**
    * Returns a predicate that evaluates to {@code true} if the object reference
    * being tested is a member of the given collection. It does not defensively
    * copy the collection passed in, so future changes to it will alter the
    * behavior of the predicate.
    *
    * <p>This method can technically accept any {@code Collection<?>}, but using
    * a typed collection helps prevent bugs. This approach doesn't block any
    * potential users since it is always possible to use {@code
    * Predicates.<Object>in()}.
    *
    * @param target the collection that may contain the function input
    */
   public static <T> Predicate<T> in(Collection<? extends T> target) {
     return new InPredicate<T>(target);
   }
 
   /**
    * Returns the composition of a function and a predicate. For every {@code x},
    * the generated predicate returns {@code predicate(function(x))}.
    *
    * @return the composition of the provided function and predicate
    */
   public static <A, B> Predicate<A> compose(
       Predicate<B> predicate, Function<A, ? extends B> function) {
     return new CompositionPredicate<A, B>(predicate, function);
   }
 
   // End public API, begin private implementation classes.
 
   // Package private for GWT serialization.
   enum ObjectPredicate implements Predicate<Object> {
     /** @see Predicates#alwaysTrue() */
     ALWAYS_TRUE {
       @Override public boolean apply(@Nullable Object o) {
         return true;
       }
       @Override public String toString() {
         return "Predicates.alwaysTrue()";
       }
     },
     /** @see Predicates#alwaysFalse() */
     ALWAYS_FALSE {
       @Override public boolean apply(@Nullable Object o) {
         return false;
       }
       @Override public String toString() {
         return "Predicates.alwaysFalse()";
       }
     },
     /** @see Predicates#isNull() */
     IS_NULL {
       @Override public boolean apply(@Nullable Object o) {
         return o == null;
       }
       @Override public String toString() {
         return "Predicates.isNull()";
       }
     },
     /** @see Predicates#notNull() */
     NOT_NULL {
       @Override public boolean apply(@Nullable Object o) {
         return o != null;
       }
       @Override public String toString() {
         return "Predicates.notNull()";
       }
     };
 
     @SuppressWarnings("unchecked") // safe contravariant cast
     <T> Predicate<T> withNarrowedType() {
       return (Predicate<T>) this;
     }
   }
 
   /** @see Predicates#not(Predicate) */
   private static class NotPredicate<T> implements Predicate<T>, Serializable {
     final Predicate<T> predicate;
 
     NotPredicate(Predicate<T> predicate) {
       this.predicate = checkNotNull(predicate);
     }
     @Override
     public boolean apply(@Nullable T t) {
       return !predicate.apply(t);
     }
     @Override public int hashCode() {
       return ~predicate.hashCode();
     }
     @Override public boolean equals(@Nullable Object obj) {
       if (obj instanceof NotPredicate) {
         NotPredicate<?> that = (NotPredicate<?>) obj;
         return predicate.equals(that.predicate);
       }
       return false;
     }
     @Override public String toString() {
       return "Predicates.not(" + predicate.toString() + ")";
     }
     private static final long serialVersionUID = 0;
   }
 
   private static final Joiner COMMA_JOINER = Joiner.on(',');
 
   /** @see Predicates#and(Iterable) */
   private static class AndPredicate<T> implements Predicate<T>, Serializable {
     private final List<? extends Predicate<? super T>> components;
 
     private AndPredicate(List<? extends Predicate<? super T>> components) {
       this.components = components;
     }
     @Override
     public boolean apply(@Nullable T t) {
       // Avoid using the Iterator to avoid generating garbage (issue 820).
       for (int i = 0; i < components.size(); i++) {
         if (!components.get(i).apply(t)) {
           return false;
         }
       }
       return true;
     }
     @Override public int hashCode() {
       // add a random number to avoid collisions with OrPredicate
       return components.hashCode() + 0x12472c2c;
     }
     @Override public boolean equals(@Nullable Object obj) {
       if (obj instanceof AndPredicate) {
         AndPredicate<?> that = (AndPredicate<?>) obj;
         return components.equals(that.components);
       }
       return false;
     }
     @Override public String toString() {
       return "Predicates.and(" + COMMA_JOINER.join(components) + ")";
     }
     private static final long serialVersionUID = 0;
   }
 
   /** @see Predicates#or(Iterable) */
   private static class OrPredicate<T> implements Predicate<T>, Serializable {
     private final List<? extends Predicate<? super T>> components;
 
     private OrPredicate(List<? extends Predicate<? super T>> components) {
       this.components = components;
     }
     @Override
     public boolean apply(@Nullable T t) {
       // Avoid using the Iterator to avoid generating garbage (issue 820).
       for (int i = 0; i < components.size(); i++) {
         if (components.get(i).apply(t)) {
           return true;
         }
       }
       return false;
     }
     @Override public int hashCode() {
       // add a random number to avoid collisions with AndPredicate
       return components.hashCode() + 0x053c91cf;
     }
     @Override public boolean equals(@Nullable Object obj) {
       if (obj instanceof OrPredicate) {
         OrPredicate<?> that = (OrPredicate<?>) obj;
         return components.equals(that.components);
       }
       return false;
     }
     @Override public String toString() {
       return "Predicates.or(" + COMMA_JOINER.join(components) + ")";
     }
     private static final long serialVersionUID = 0;
   }
 
   /** @see Predicates#equalTo(Object) */
   private static class IsEqualToPredicate<T>
       implements Predicate<T>, Serializable {
     private final T target;
 
     private IsEqualToPredicate(T target) {
       this.target = target;
     }
     @Override
     public boolean apply(T t) {
       return target.equals(t);
     }
     @Override public int hashCode() {
       return target.hashCode();
     }
     @Override public boolean equals(@Nullable Object obj) {
       if (obj instanceof IsEqualToPredicate) {
         IsEqualToPredicate<?> that = (IsEqualToPredicate<?>) obj;
         return target.equals(that.target);
       }
       return false;
     }
     @Override public String toString() {
       return "Predicates.equalTo(" + target + ")";
     }
     private static final long serialVersionUID = 0;
   }
 
   /** @see Predicates#in(Collection) */
   private static class InPredicate<T> implements Predicate<T>, Serializable {
     private final Collection<?> target;
 
     private InPredicate(Collection<?> target) {
       this.target = checkNotNull(target);
     }
 
     @Override
     public boolean apply(@Nullable T t) {
       try {
         return target.contains(t);
       } catch (NullPointerException e) {
         return false;
       } catch (ClassCastException e) {
         return false;
       }
     }
 
     @Override public boolean equals(@Nullable Object obj) {
       if (obj instanceof InPredicate) {
         InPredicate<?> that = (InPredicate<?>) obj;
         return target.equals(that.target);
       }
       return false;
     }
 
     @Override public int hashCode() {
       return target.hashCode();
     }
 
     @Override public String toString() {
       return "Predicates.in(" + target + ")";
     }
     private static final long serialVersionUID = 0;
   }
 
   /** @see Predicates#compose(Predicate, Function) */
   private static class CompositionPredicate<A, B>
       implements Predicate<A>, Serializable {
     final Predicate<B> p;
     final Function<A, ? extends B> f;
 
     private CompositionPredicate(Predicate<B> p, Function<A, ? extends B> f) {
       this.p = checkNotNull(p);
       this.f = checkNotNull(f);
     }
 
     @Override
     public boolean apply(@Nullable A a) {
       return p.apply(f.apply(a));
     }
 
     @Override public boolean equals(@Nullable Object obj) {
       if (obj instanceof CompositionPredicate) {
         CompositionPredicate<?, ?> that = (CompositionPredicate<?, ?>) obj;
         return f.equals(that.f) && p.equals(that.p);
       }
       return false;
     }
 
     @Override public int hashCode() {
       return f.hashCode() ^ p.hashCode();
     }
 
     @Override public String toString() {
       return p.toString() + "(" + f.toString() + ")";
     }
 
     private static final long serialVersionUID = 0;
   }
 
   private static <T> List<Predicate<? super T>> asList(
       Predicate<? super T> first, Predicate<? super T> second) {
     // TODO(kevinb): understand why we still get a warning despite @SafeVarargs!
     return Arrays.<Predicate<? super T>>asList(first, second);
   }
 
   private static <T> List<T> defensiveCopy(T... array) {
     return defensiveCopy(Arrays.asList(array));
   }
 
   static <T> List<T> defensiveCopy(Iterable<T> iterable) {
     ArrayList<T> list = new ArrayList<T>();
     for (T element : iterable) {
       list.add(checkNotNull(element));
     }
     return list;
   }
 }