/*
 * 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 static com.google.common.collect.BoundType.OPEN;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import java.io.Serializable;
import java.util.Comparator;
import org.checkerframework.checker.nullness.qual.Nullable;

A generalized interval on any ordering, for internal use. Supports null. Unlike Range, this allows the use of an arbitrary comparator. This is designed for use in the implementation of subcollections of sorted collection types. 
Whenever possible, use Range instead, which is better supported. 
Author:
Louis Wasserman/**
 * A generalized interval on any ordering, for internal use. Supports {@code null}. Unlike {@link
 * Range}, this allows the use of an arbitrary comparator. This is designed for use in the
 * implementation of subcollections of sorted collection types.
 *
 * <p>Whenever possible, use {@code Range} instead, which is better supported.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true)
final class GeneralRange<T> implements Serializable {
  
Converts a Range to a GeneralRange. /** Converts a Range to a GeneralRange. */
  static <T extends Comparable> GeneralRange<T> from(Range<T> range) {
    @Nullable T lowerEndpoint = range.hasLowerBound() ? range.lowerEndpoint() : null;
    BoundType lowerBoundType = range.hasLowerBound() ? range.lowerBoundType() : OPEN;

    @Nullable T upperEndpoint = range.hasUpperBound() ? range.upperEndpoint() : null;
    BoundType upperBoundType = range.hasUpperBound() ? range.upperBoundType() : OPEN;
    return new GeneralRange<T>(
        Ordering.natural(),
        range.hasLowerBound(),
        lowerEndpoint,
        lowerBoundType,
        range.hasUpperBound(),
        upperEndpoint,
        upperBoundType);
  }

  
Returns the whole range relative to the specified comparator. /** Returns the whole range relative to the specified comparator. */
  static <T> GeneralRange<T> all(Comparator<? super T> comparator) {
    return new GeneralRange<T>(comparator, false, null, OPEN, false, null, OPEN);
  }

  
Returns everything above the endpoint relative to the specified comparator, with the specified
endpoint behavior.
/**
   * Returns everything above the endpoint relative to the specified comparator, with the specified
   * endpoint behavior.
   */
  static <T> GeneralRange<T> downTo(
      Comparator<? super T> comparator, @Nullable T endpoint, BoundType boundType) {
    return new GeneralRange<T>(comparator, true, endpoint, boundType, false, null, OPEN);
  }

  
Returns everything below the endpoint relative to the specified comparator, with the specified
endpoint behavior.
/**
   * Returns everything below the endpoint relative to the specified comparator, with the specified
   * endpoint behavior.
   */
  static <T> GeneralRange<T> upTo(
      Comparator<? super T> comparator, @Nullable T endpoint, BoundType boundType) {
    return new GeneralRange<T>(comparator, false, null, OPEN, true, endpoint, boundType);
  }

  
Returns everything between the endpoints relative to the specified comparator, with the
specified endpoint behavior.
/**
   * Returns everything between the endpoints relative to the specified comparator, with the
   * specified endpoint behavior.
   */
  static <T> GeneralRange<T> range(
      Comparator<? super T> comparator,
      @Nullable T lower,
      BoundType lowerType,
      @Nullable T upper,
      BoundType upperType) {
    return new GeneralRange<T>(comparator, true, lower, lowerType, true, upper, upperType);
  }

  private final Comparator<? super T> comparator;
  private final boolean hasLowerBound;
  private final @Nullable T lowerEndpoint;
  private final BoundType lowerBoundType;
  private final boolean hasUpperBound;
  private final @Nullable T upperEndpoint;
  private final BoundType upperBoundType;

  private GeneralRange(
      Comparator<? super T> comparator,
      boolean hasLowerBound,
      @Nullable T lowerEndpoint,
      BoundType lowerBoundType,
      boolean hasUpperBound,
      @Nullable T upperEndpoint,
      BoundType upperBoundType) {
    this.comparator = checkNotNull(comparator);
    this.hasLowerBound = hasLowerBound;
    this.hasUpperBound = hasUpperBound;
    this.lowerEndpoint = lowerEndpoint;
    this.lowerBoundType = checkNotNull(lowerBoundType);
    this.upperEndpoint = upperEndpoint;
    this.upperBoundType = checkNotNull(upperBoundType);

    if (hasLowerBound) {
      comparator.compare(lowerEndpoint, lowerEndpoint);
    }
    if (hasUpperBound) {
      comparator.compare(upperEndpoint, upperEndpoint);
    }
    if (hasLowerBound && hasUpperBound) {
      int cmp = comparator.compare(lowerEndpoint, upperEndpoint);
      // be consistent with Range
      checkArgument(
          cmp <= 0, "lowerEndpoint (%s) > upperEndpoint (%s)", lowerEndpoint, upperEndpoint);
      if (cmp == 0) {
        checkArgument(lowerBoundType != OPEN | upperBoundType != OPEN);
      }
    }
  }

  Comparator<? super T> comparator() {
    return comparator;
  }

  boolean hasLowerBound() {
    return hasLowerBound;
  }

  boolean hasUpperBound() {
    return hasUpperBound;
  }

  boolean isEmpty() {
    return (hasUpperBound() && tooLow(getUpperEndpoint()))
        || (hasLowerBound() && tooHigh(getLowerEndpoint()));
  }

  boolean tooLow(@Nullable T t) {
    if (!hasLowerBound()) {
      return false;
    }
    T lbound = getLowerEndpoint();
    int cmp = comparator.compare(t, lbound);
    return cmp < 0 | (cmp == 0 & getLowerBoundType() == OPEN);
  }

  boolean tooHigh(@Nullable T t) {
    if (!hasUpperBound()) {
      return false;
    }
    T ubound = getUpperEndpoint();
    int cmp = comparator.compare(t, ubound);
    return cmp > 0 | (cmp == 0 & getUpperBoundType() == OPEN);
  }

  boolean contains(@Nullable T t) {
    return !tooLow(t) && !tooHigh(t);
  }

  
Returns the intersection of the two ranges, or an empty range if their intersection is empty.
/**
   * Returns the intersection of the two ranges, or an empty range if their intersection is empty.
   */
  GeneralRange<T> intersect(GeneralRange<T> other) {
    checkNotNull(other);
    checkArgument(comparator.equals(other.comparator));

    boolean hasLowBound = this.hasLowerBound;
    @Nullable T lowEnd = getLowerEndpoint();
    BoundType lowType = getLowerBoundType();
    if (!hasLowerBound()) {
      hasLowBound = other.hasLowerBound;
      lowEnd = other.getLowerEndpoint();
      lowType = other.getLowerBoundType();
    } else if (other.hasLowerBound()) {
      int cmp = comparator.compare(getLowerEndpoint(), other.getLowerEndpoint());
      if (cmp < 0 || (cmp == 0 && other.getLowerBoundType() == OPEN)) {
        lowEnd = other.getLowerEndpoint();
        lowType = other.getLowerBoundType();
      }
    }

    boolean hasUpBound = this.hasUpperBound;
    @Nullable T upEnd = getUpperEndpoint();
    BoundType upType = getUpperBoundType();
    if (!hasUpperBound()) {
      hasUpBound = other.hasUpperBound;
      upEnd = other.getUpperEndpoint();
      upType = other.getUpperBoundType();
    } else if (other.hasUpperBound()) {
      int cmp = comparator.compare(getUpperEndpoint(), other.getUpperEndpoint());
      if (cmp > 0 || (cmp == 0 && other.getUpperBoundType() == OPEN)) {
        upEnd = other.getUpperEndpoint();
        upType = other.getUpperBoundType();
      }
    }

    if (hasLowBound && hasUpBound) {
      int cmp = comparator.compare(lowEnd, upEnd);
      if (cmp > 0 || (cmp == 0 && lowType == OPEN && upType == OPEN)) {
        // force allowed empty range
        lowEnd = upEnd;
        lowType = OPEN;
        upType = CLOSED;
      }
    }

    return new GeneralRange<T>(comparator, hasLowBound, lowEnd, lowType, hasUpBound, upEnd, upType);
  }

  @Override
  public boolean equals(@Nullable Object obj) {
    if (obj instanceof GeneralRange) {
      GeneralRange<?> r = (GeneralRange<?>) obj;
      return comparator.equals(r.comparator)
          && hasLowerBound == r.hasLowerBound
          && hasUpperBound == r.hasUpperBound
          && getLowerBoundType().equals(r.getLowerBoundType())
          && getUpperBoundType().equals(r.getUpperBoundType())
          && Objects.equal(getLowerEndpoint(), r.getLowerEndpoint())
          && Objects.equal(getUpperEndpoint(), r.getUpperEndpoint());
    }
    return false;
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(
        comparator,
        getLowerEndpoint(),
        getLowerBoundType(),
        getUpperEndpoint(),
        getUpperBoundType());
  }

  private transient @Nullable GeneralRange<T> reverse;

  
Returns the same range relative to the reversed comparator. /** Returns the same range relative to the reversed comparator. */
  GeneralRange<T> reverse() {
    GeneralRange<T> result = reverse;
    if (result == null) {
      result =
          new GeneralRange<T>(
              Ordering.from(comparator).reverse(),
              hasUpperBound,
              getUpperEndpoint(),
              getUpperBoundType(),
              hasLowerBound,
              getLowerEndpoint(),
              getLowerBoundType());
      result.reverse = this;
      return this.reverse = result;
    }
    return result;
  }

  @Override
  public String toString() {
    return comparator
        + ":"
        + (lowerBoundType == CLOSED ? '[' : '(')
        + (hasLowerBound ? lowerEndpoint : "-\u221e")
        + ','
        + (hasUpperBound ? upperEndpoint : "\u221e")
        + (upperBoundType == CLOSED ? ']' : ')');
  }

  T getLowerEndpoint() {
    return lowerEndpoint;
  }

  BoundType getLowerBoundType() {
    return lowerBoundType;
  }

  T getUpperEndpoint() {
    return upperEndpoint;
  }

  BoundType getUpperBoundType() {
    return upperBoundType;
  }
}