/*
 * 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 javax.annotation.Nullable;

/**
 * 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.
   */
  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.
   */
  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.
   */
  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.
   */
  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.
   */
  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;
  @Nullable private final T lowerEndpoint;
  private final BoundType lowerBoundType;
  private final boolean hasUpperBound;
  @Nullable private final 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.
   */
  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 GeneralRange<T> reverse;

  /**
   * 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 new StringBuilder()
        .append(comparator)
        .append(":")
        .append(lowerBoundType == CLOSED ? '[' : '(')
        .append(hasLowerBound ? lowerEndpoint : "-\u221e")
        .append(',')
        .append(hasUpperBound ? upperEndpoint : "\u221e")
        .append(upperBoundType == CLOSED ? ']' : ')')
        .toString();
  }

  T getLowerEndpoint() {
    return lowerEndpoint;
  }

  BoundType getLowerBoundType() {
    return lowerBoundType;
  }

  T getUpperEndpoint() {
    return upperEndpoint;
  }

  BoundType getUpperBoundType() {
    return upperBoundType;
  }
}
