/*
    * Copyright (C) 2011 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.collect;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.collect.BoundType.CLOSED;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Collection;
  
  import javax.annotation.Nullable;
  
  /**
   * An implementation of {@link ContiguousSet} that contains one or more elements.
   *
   * @author Gregory Kick
   */
  @GwtCompatible(emulated = true)
  @SuppressWarnings("unchecked") // allow ungenerified Comparable types
  final class RegularContiguousSet<C extends Comparable> extends ContiguousSet<C> {
    private final Range<C> range;
  
    RegularContiguousSet(Range<C> range, DiscreteDomain<C> domain) {
      super(domain);
      this.range = range;
    }
  
    private ContiguousSet<C> intersectionInCurrentDomain(Range<C> other) {
      return (range.isConnected(other))
          ? ContiguousSet.create(range.intersection(other), domain)
          : new EmptyContiguousSet<C>(domain);
    }
  
    @Override ContiguousSet<C> headSetImpl(C toElement, boolean inclusive) {
      return intersectionInCurrentDomain(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
    }
  
    @Override ContiguousSet<C> subSetImpl(C fromElement, boolean fromInclusive, C toElement,
        boolean toInclusive) {
      if (fromElement.compareTo(toElement) == 0 && !fromInclusive && !toInclusive) {
        // Range would reject our attempt to create (x, x).
        return new EmptyContiguousSet<C>(domain);
      }
      return intersectionInCurrentDomain(Range.range(
          fromElement, BoundType.forBoolean(fromInclusive),
          toElement, BoundType.forBoolean(toInclusive)));
    }
  
    @Override ContiguousSet<C> tailSetImpl(C fromElement, boolean inclusive) {
      return intersectionInCurrentDomain(Range.downTo(fromElement, BoundType.forBoolean(inclusive)));
    }
  
    @Override public UnmodifiableIterator<C> iterator() {
      return new AbstractSequentialIterator<C>(first()) {
        final C last = last();
  
        @Override
        protected C computeNext(C previous) {
          return equalsOrThrow(previous, last) ? null : domain.next(previous);
        }
      };
    }
  
    private static boolean equalsOrThrow(Comparable<?> left, @Nullable Comparable<?> right) {
      return right != null && Range.compareOrThrow(left, right) == 0;
    }
  
    @Override boolean isPartialView() {
      return false;
    }
  
    @Override public C first() {
      return range.lowerBound.leastValueAbove(domain);
    }
  
    @Override public C last() {
      return range.upperBound.greatestValueBelow(domain);
    }
  
    @Override public int size() {
      long distance = domain.distance(first(), last());
      return (distance >= Integer.MAX_VALUE) ? Integer.MAX_VALUE : (int) distance + 1;
    }
  
    @Override public boolean contains(@Nullable Object object) {
     if (object == null) {
       return false;
     }
     try {
       return range.contains((C) object);
     } catch (ClassCastException e) {
       return false;
     }
   }
 
   @Override public boolean containsAll(Collection<?> targets) {
     return Collections2.containsAllImpl(this, targets);
   }
 
   @Override public boolean isEmpty() {
     return false;
   }
 
   @Override public ContiguousSet<C> intersection(ContiguousSet<C> other) {
     checkNotNull(other);
     checkArgument(this.domain.equals(other.domain));
     if (other.isEmpty()) {
       return other;
     } else {
       C lowerEndpoint = Ordering.natural().max(this.first(), other.first());
       C upperEndpoint = Ordering.natural().min(this.last(), other.last());
       return (lowerEndpoint.compareTo(upperEndpoint) < 0)
           ? ContiguousSet.create(Range.closed(lowerEndpoint, upperEndpoint), domain)
           : new EmptyContiguousSet<C>(domain);
     }
   }
 
   @Override public Range<C> range() {
     return range(CLOSED, CLOSED);
   }
 
   @Override public Range<C> range(BoundType lowerBoundType, BoundType upperBoundType) {
     return Range.create(range.lowerBound.withLowerBoundType(lowerBoundType, domain),
         range.upperBound.withUpperBoundType(upperBoundType, domain));
   }
 
   @Override public boolean equals(@Nullable Object object) {
     if (object == this) {
       return true;
     } else if (object instanceof RegularContiguousSet) {
       RegularContiguousSet<?> that = (RegularContiguousSet<?>) object;
       if (this.domain.equals(that.domain)) {
         return this.first().equals(that.first())
             && this.last().equals(that.last());
       }
     }
     return super.equals(object);
   }
 
   // copied to make sure not to use the GWT-emulated version
   @Override public int hashCode() {
     return Sets.hashCodeImpl(this);
   }
 
   private static final long serialVersionUID = 0;
 }