/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.lang3;

import java.io.Serializable;
import java.util.Comparator;

import net.lax1dude.eaglercraft.v1_8.HString;

/**
 * <p>
 * An immutable range of objects from a minimum to maximum point inclusive.
 * </p>
 *
 * <p>
 * The objects need to either be implementations of {@code Comparable} or you
 * need to supply a {@code Comparator}.
 * </p>
 *
 * <p>
 * #ThreadSafe# if the objects and comparator are thread-safe
 * </p>
 *
 * @param <T> The type of range values.
 * @since 3.0
 */
public final class Range<T> implements Serializable {

	@SuppressWarnings({ "rawtypes", "unchecked" })
	private enum ComparableComparator implements Comparator {
		INSTANCE;

		/**
		 * Comparable based compare implementation.
		 *
		 * @param obj1 left hand side of comparison
		 * @param obj2 right hand side of comparison
		 * @return negative, 0, positive comparison value
		 */
		@Override
		public int compare(final Object obj1, final Object obj2) {
			return ((Comparable) obj1).compareTo(obj2);
		}
	}

	/**
	 * Serialization version.
	 * 
	 * @see java.io.Serializable
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * <p>
	 * Obtains a range with the specified minimum and maximum values (both
	 * inclusive).
	 * </p>
	 *
	 * <p>
	 * The range uses the natural ordering of the elements to determine where values
	 * lie in the range.
	 * </p>
	 *
	 * <p>
	 * The arguments may be passed in the order (min,max) or (max,min). The
	 * getMinimum and getMaximum methods will return the correct values.
	 * </p>
	 *
	 * @param <T>           the type of the elements in this range
	 * @param fromInclusive the first value that defines the edge of the range,
	 *                      inclusive
	 * @param toInclusive   the second value that defines the edge of the range,
	 *                      inclusive
	 * @return the range object, not null
	 * @throws IllegalArgumentException if either element is null
	 * @throws ClassCastException       if the elements are not {@code Comparable}
	 */
	public static <T extends Comparable<T>> Range<T> between(final T fromInclusive, final T toInclusive) {
		return between(fromInclusive, toInclusive, null);
	}

	/**
	 * <p>
	 * Obtains a range with the specified minimum and maximum values (both
	 * inclusive).
	 * </p>
	 *
	 * <p>
	 * The range uses the specified {@code Comparator} to determine where values lie
	 * in the range.
	 * </p>
	 *
	 * <p>
	 * The arguments may be passed in the order (min,max) or (max,min). The
	 * getMinimum and getMaximum methods will return the correct values.
	 * </p>
	 *
	 * @param <T>           the type of the elements in this range
	 * @param fromInclusive the first value that defines the edge of the range,
	 *                      inclusive
	 * @param toInclusive   the second value that defines the edge of the range,
	 *                      inclusive
	 * @param comparator    the comparator to be used, null for natural ordering
	 * @return the range object, not null
	 * @throws IllegalArgumentException if either element is null
	 * @throws ClassCastException       if using natural ordering and the elements
	 *                                  are not {@code Comparable}
	 */
	public static <T> Range<T> between(final T fromInclusive, final T toInclusive, final Comparator<T> comparator) {
		return new Range<>(fromInclusive, toInclusive, comparator);
	}

	/**
	 * <p>
	 * Obtains a range using the specified element as both the minimum and maximum
	 * in this range.
	 * </p>
	 *
	 * <p>
	 * The range uses the natural ordering of the elements to determine where values
	 * lie in the range.
	 * </p>
	 *
	 * @param <T>     the type of the elements in this range
	 * @param element the value to use for this range, not null
	 * @return the range object, not null
	 * @throws IllegalArgumentException if the element is null
	 * @throws ClassCastException       if the element is not {@code Comparable}
	 */
	public static <T extends Comparable<T>> Range<T> is(final T element) {
		return between(element, element, null);
	}

	/**
	 * <p>
	 * Obtains a range using the specified element as both the minimum and maximum
	 * in this range.
	 * </p>
	 *
	 * <p>
	 * The range uses the specified {@code Comparator} to determine where values lie
	 * in the range.
	 * </p>
	 *
	 * @param <T>        the type of the elements in this range
	 * @param element    the value to use for this range, must not be {@code null}
	 * @param comparator the comparator to be used, null for natural ordering
	 * @return the range object, not null
	 * @throws IllegalArgumentException if the element is null
	 * @throws ClassCastException       if using natural ordering and the elements
	 *                                  are not {@code Comparable}
	 */
	public static <T> Range<T> is(final T element, final Comparator<T> comparator) {
		return between(element, element, comparator);
	}

	/**
	 * The ordering scheme used in this range.
	 */
	private final Comparator<T> comparator;

	/**
	 * Cached output hashCode (class is immutable).
	 */
	private transient int hashCode;

	/**
	 * The maximum value in this range (inclusive).
	 */
	private final T maximum;

	/**
	 * The minimum value in this range (inclusive).
	 */
	private final T minimum;

	/**
	 * Cached output toString (class is immutable).
	 */
	private transient String toString;

	/**
	 * Creates an instance.
	 *
	 * @param element1 the first element, not null
	 * @param element2 the second element, not null
	 * @param comp     the comparator to be used, null for natural ordering
	 */
	@SuppressWarnings("unchecked")
	private Range(final T element1, final T element2, final Comparator<T> comp) {
		if (element1 == null || element2 == null) {
			throw new IllegalArgumentException(
					"Elements in a range must not be null: element1=" + element1 + ", element2=" + element2);
		}
		if (comp == null) {
			this.comparator = ComparableComparator.INSTANCE;
		} else {
			this.comparator = comp;
		}
		if (this.comparator.compare(element1, element2) < 1) {
			this.minimum = element1;
			this.maximum = element2;
		} else {
			this.minimum = element2;
			this.maximum = element1;
		}
	}

	/**
	 * <p>
	 * Checks whether the specified element occurs within this range.
	 * </p>
	 *
	 * @param element the element to check for, null returns false
	 * @return true if the specified element occurs within this range
	 */
	public boolean contains(final T element) {
		if (element == null) {
			return false;
		}
		return comparator.compare(element, minimum) > -1 && comparator.compare(element, maximum) < 1;
	}

	/**
	 * <p>
	 * Checks whether this range contains all the elements of the specified range.
	 * </p>
	 *
	 * <p>
	 * This method may fail if the ranges have two different comparators or element
	 * types.
	 * </p>
	 *
	 * @param otherRange the range to check, null returns false
	 * @return true if this range contains the specified range
	 * @throws RuntimeException if ranges cannot be compared
	 */
	public boolean containsRange(final Range<T> otherRange) {
		if (otherRange == null) {
			return false;
		}
		return contains(otherRange.minimum) && contains(otherRange.maximum);
	}

	/**
	 * <p>
	 * Checks where the specified element occurs relative to this range.
	 * </p>
	 *
	 * <p>
	 * The API is reminiscent of the Comparable interface returning {@code -1} if
	 * the element is before the range, {@code 0} if contained within the range and
	 * {@code 1} if the element is after the range.
	 * </p>
	 *
	 * @param element the element to check for, not null
	 * @return -1, 0 or +1 depending on the element's location relative to the range
	 */
	public int elementCompareTo(final T element) {
		// Comparable API says throw NPE on null
		Validate.notNull(element, "element");
		if (isAfter(element)) {
			return -1;
		} else if (isBefore(element)) {
			return 1;
		} else {
			return 0;
		}
	}

	// Element tests
	// --------------------------------------------------------------------

	/**
	 * <p>
	 * Compares this range to another object to test if they are equal.
	 * </p>
	 * .
	 *
	 * <p>
	 * To be equal, the minimum and maximum values must be equal, which ignores any
	 * differences in the comparator.
	 * </p>
	 *
	 * @param obj the reference object with which to compare
	 * @return true if this object is equal
	 */
	@Override
	public boolean equals(final Object obj) {
		if (obj == this) {
			return true;
		} else if (obj == null || obj.getClass() != getClass()) {
			return false;
		} else {
			@SuppressWarnings("unchecked") // OK because we checked the class above
			final Range<T> range = (Range<T>) obj;
			return minimum.equals(range.minimum) && maximum.equals(range.maximum);
		}
	}

	/**
	 * <p>
	 * Gets the comparator being used to determine if objects are within the range.
	 * </p>
	 *
	 * <p>
	 * Natural ordering uses an internal comparator implementation, thus this method
	 * never returns null. See {@link #isNaturalOrdering()}.
	 * </p>
	 *
	 * @return the comparator being used, not null
	 */
	public Comparator<T> getComparator() {
		return comparator;
	}

	/**
	 * <p>
	 * Gets the maximum value in this range.
	 * </p>
	 *
	 * @return the maximum value in this range, not null
	 */
	public T getMaximum() {
		return maximum;
	}

	/**
	 * <p>
	 * Gets the minimum value in this range.
	 * </p>
	 *
	 * @return the minimum value in this range, not null
	 */
	public T getMinimum() {
		return minimum;
	}

	/**
	 * <p>
	 * Gets a suitable hash code for the range.
	 * </p>
	 *
	 * @return a hash code value for this object
	 */
	@Override
	public int hashCode() {
		int result = hashCode;
		if (hashCode == 0) {
			result = 17;
			result = 37 * result + getClass().hashCode();
			result = 37 * result + minimum.hashCode();
			result = 37 * result + maximum.hashCode();
			hashCode = result;
		}
		return result;
	}

	/**
	 * Calculate the intersection of {@code this} and an overlapping Range.
	 * 
	 * @param other overlapping Range
	 * @return range representing the intersection of {@code this} and {@code other}
	 *         ({@code this} if equal)
	 * @throws IllegalArgumentException if {@code other} does not overlap
	 *                                  {@code this}
	 * @since 3.0.1
	 */
	public Range<T> intersectionWith(final Range<T> other) {
		if (!this.isOverlappedBy(other)) {
			throw new IllegalArgumentException(
					HString.format("Cannot calculate intersection with non-overlapping range %s", other));
		}
		if (this.equals(other)) {
			return this;
		}
		final T min = getComparator().compare(minimum, other.minimum) < 0 ? other.minimum : minimum;
		final T max = getComparator().compare(maximum, other.maximum) < 0 ? maximum : other.maximum;
		return between(min, max, getComparator());
	}

	/**
	 * <p>
	 * Checks whether this range is after the specified element.
	 * </p>
	 *
	 * @param element the element to check for, null returns false
	 * @return true if this range is entirely after the specified element
	 */
	public boolean isAfter(final T element) {
		if (element == null) {
			return false;
		}
		return comparator.compare(element, minimum) < 0;
	}

	/**
	 * <p>
	 * Checks whether this range is completely after the specified range.
	 * </p>
	 *
	 * <p>
	 * This method may fail if the ranges have two different comparators or element
	 * types.
	 * </p>
	 *
	 * @param otherRange the range to check, null returns false
	 * @return true if this range is completely after the specified range
	 * @throws RuntimeException if ranges cannot be compared
	 */
	public boolean isAfterRange(final Range<T> otherRange) {
		if (otherRange == null) {
			return false;
		}
		return isAfter(otherRange.maximum);
	}

	/**
	 * <p>
	 * Checks whether this range is before the specified element.
	 * </p>
	 *
	 * @param element the element to check for, null returns false
	 * @return true if this range is entirely before the specified element
	 */
	public boolean isBefore(final T element) {
		if (element == null) {
			return false;
		}
		return comparator.compare(element, maximum) > 0;
	}

	/**
	 * <p>
	 * Checks whether this range is completely before the specified range.
	 * </p>
	 *
	 * <p>
	 * This method may fail if the ranges have two different comparators or element
	 * types.
	 * </p>
	 *
	 * @param otherRange the range to check, null returns false
	 * @return true if this range is completely before the specified range
	 * @throws RuntimeException if ranges cannot be compared
	 */
	public boolean isBeforeRange(final Range<T> otherRange) {
		if (otherRange == null) {
			return false;
		}
		return isBefore(otherRange.minimum);
	}

	/**
	 * <p>
	 * Checks whether this range ends with the specified element.
	 * </p>
	 *
	 * @param element the element to check for, null returns false
	 * @return true if the specified element occurs within this range
	 */
	public boolean isEndedBy(final T element) {
		if (element == null) {
			return false;
		}
		return comparator.compare(element, maximum) == 0;
	}

	/**
	 * <p>
	 * Whether or not the Range is using the natural ordering of the elements.
	 * </p>
	 *
	 * <p>
	 * Natural ordering uses an internal comparator implementation, thus this method
	 * is the only way to check if a null comparator was specified.
	 * </p>
	 *
	 * @return true if using natural ordering
	 */
	public boolean isNaturalOrdering() {
		return comparator == ComparableComparator.INSTANCE;
	}

	/**
	 * <p>
	 * Checks whether this range is overlapped by the specified range.
	 * </p>
	 *
	 * <p>
	 * Two ranges overlap if there is at least one element in common.
	 * </p>
	 *
	 * <p>
	 * This method may fail if the ranges have two different comparators or element
	 * types.
	 * </p>
	 *
	 * @param otherRange the range to test, null returns false
	 * @return true if the specified range overlaps with this range; otherwise,
	 *         {@code false}
	 * @throws RuntimeException if ranges cannot be compared
	 */
	public boolean isOverlappedBy(final Range<T> otherRange) {
		if (otherRange == null) {
			return false;
		}
		return otherRange.contains(minimum) || otherRange.contains(maximum) || contains(otherRange.minimum);
	}

	/**
	 * <p>
	 * Checks whether this range starts with the specified element.
	 * </p>
	 *
	 * @param element the element to check for, null returns false
	 * @return true if the specified element occurs within this range
	 */
	public boolean isStartedBy(final T element) {
		if (element == null) {
			return false;
		}
		return comparator.compare(element, minimum) == 0;
	}

	/**
	 * <p>
	 * Fits the given element into this range by returning the given element or, if
	 * out of bounds, the range minimum if below, or the range maximum if above.
	 * </p>
	 * 
	 * <pre>
	 * Range&lt;Integer&gt; range = Range.between(16, 64);
	 * range.fit(-9) --&gt;  16
	 * range.fit(0)  --&gt;  16
	 * range.fit(15) --&gt;  16
	 * range.fit(16) --&gt;  16
	 * range.fit(17) --&gt;  17
	 * ...
	 * range.fit(63) --&gt;  63
	 * range.fit(64) --&gt;  64
	 * range.fit(99) --&gt;  64
	 * </pre>
	 * 
	 * @param element the element to check for, not null
	 * @return the minimum, the element, or the maximum depending on the element's
	 *         location relative to the range
	 * @since 3.10
	 */
	public T fit(final T element) {
		// Comparable API says throw NPE on null
		Validate.notNull(element, "element");
		if (isAfter(element)) {
			return minimum;
		} else if (isBefore(element)) {
			return maximum;
		} else {
			return element;
		}
	}

	/**
	 * <p>
	 * Gets the range as a {@code String}.
	 * </p>
	 *
	 * <p>
	 * The format of the String is '[<i>min</i>..<i>max</i>]'.
	 * </p>
	 *
	 * @return the {@code String} representation of this range
	 */
	@Override
	public String toString() {
		if (toString == null) {
			toString = "[" + minimum + ".." + maximum + "]";
		}
		return toString;
	}

	/**
	 * <p>
	 * Formats the receiver using the given format.
	 * </p>
	 *
	 * <p>
	 * This uses {@link java.util.Formattable} to perform the formatting. Three
	 * variables may be used to embed the minimum, maximum and comparator. Use
	 * {@code %1$s} for the minimum element, {@code %2$s} for the maximum element
	 * and {@code %3$s} for the comparator. The default format used by
	 * {@code toString()} is {@code [%1$s..%2$s]}.
	 * </p>
	 *
	 * @param format the format string, optionally containing {@code %1$s},
	 *               {@code %2$s} and {@code %3$s}, not null
	 * @return the formatted string, not null
	 */
	public String toString(final String format) {
		return HString.format(format, minimum, maximum, comparator);
	}

}