/*
    * 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.geometry.euclidean.twod;
  
  import org.apache.commons.geometry.core.RegionLocation;
  import org.apache.commons.geometry.core.Transform;
  import org.apache.commons.geometry.core.partitioning.Split;
  import org.apache.commons.numbers.core.Precision;
  
  /** Class representing a portion of a line in 2D Euclidean space that starts at infinity and
   * continues in the direction of the line up to a single end point. This is equivalent to taking a
   * {@link Ray} and reversing the line direction.
   *
   * <p>Instances of this class are guaranteed to be immutable.</p>
   * @see Ray
   * @see Lines
   */
  public final class ReverseRay extends LineConvexSubset {
  
      /** The end point of the reverse ray. */
      private final Vector2D endPoint;
  
      /** Construct a new instance from the given line and end point. Callers are responsible for ensuring that
       * the given end point lies on the line. No validation is performed.
       * @param line line for the instance
       * @param endPoint end point for the instance
       */
      ReverseRay(final Line line, final Vector2D endPoint) {
          super(line);
  
          this.endPoint = endPoint;
      }
  
      /** {@inheritDoc}
       *
       * <p>This method always returns {@code false}.</p>
       */
      @Override
      public boolean isFull() {
          return false;
      }
  
      /** {@inheritDoc}
       *
       * <p>This method always returns {@code true}.</p>
       */
      @Override
      public boolean isInfinite() {
          return true;
      }
  
      /** {@inheritDoc}
       *
       * <p>This method always returns {@code false}.</p>
       */
      @Override
      public boolean isFinite() {
          return false;
      }
  
      /** {@inheritDoc}
       *
       * <p>This method always returns {@link Double#POSITIVE_INFINITY}.</p>
       */
      @Override
      public double getSize() {
          return Double.POSITIVE_INFINITY;
      }
  
      /** {@inheritDoc}
       *
       * <p>This method always returns {@code null}.</p>
       */
      @Override
      public Vector2D getCentroid() {
          return null;
      }
  
      /** {@inheritDoc}
       *
       * <p>This method always returns {@code null}.</p>
       */
      @Override
      public Vector2D getStartPoint() {
          return null;
     }
 
     /** {@inheritDoc}
     *
     * <p>This method always returns {@link Double#NEGATIVE_INFINITY}.</p>
     */
     @Override
     public double getSubspaceStart() {
         return Double.NEGATIVE_INFINITY;
     }
 
     /** {@inheritDoc} */
     @Override
     public Vector2D getEndPoint() {
         return endPoint;
     }
 
     /** {@inheritDoc} */
     @Override
     public double getSubspaceEnd() {
         return getLine().abscissa(endPoint);
     }
 
     /** {@inheritDoc}
     *
     * <p>This method always returns {@code null}.</p>
     */
     @Override
     public Bounds2D getBounds() {
         return null; // infinite; no bounds
     }
 
     /** {@inheritDoc} */
     @Override
     public ReverseRay transform(final Transform<Vector2D> transform) {
         final Line tLine = getLine().transform(transform);
         final Vector2D tEnd = transform.apply(getEndPoint());
 
         return new ReverseRay(tLine, tEnd);
     }
 
     /** {@inheritDoc} */
     @Override
     public Ray reverse() {
         return new Ray(getLine().reverse(), endPoint);
     }
 
     /** {@inheritDoc} */
     @Override
     public String toString() {
         final StringBuilder sb = new StringBuilder();
         sb.append(getClass().getSimpleName())
             .append("[direction= ")
             .append(getLine().getDirection())
             .append(", endPoint= ")
             .append(getEndPoint())
             .append(']');
 
         return sb.toString();
     }
 
     /** {@inheritDoc} */
     @Override
     RegionLocation classifyAbscissa(final double abscissa) {
         final int cmp = getPrecision().compare(abscissa, getSubspaceEnd());
         if (cmp < 0) {
             return RegionLocation.INSIDE;
         } else if (cmp == 0) {
             return RegionLocation.BOUNDARY;
         }
 
         return RegionLocation.OUTSIDE;
     }
 
     /** {@inheritDoc} */
     @Override
     double closestAbscissa(final double abscissa) {
         return Math.min(getSubspaceEnd(), abscissa);
     }
 
     /** {@inheritDoc} */
     @Override
     protected Split<LineConvexSubset> splitOnIntersection(final Line splitter, final Vector2D intersection) {
         final Line line = getLine();
         final Precision.DoubleEquivalence splitterPrecision = splitter.getPrecision();
 
         final int endCmp = splitterPrecision.compare(splitter.offset(endPoint), 0.0);
         final boolean pointsTowardPlus = splitter.getOffsetDirection().dot(line.getDirection()) >= 0.0;
 
         if (pointsTowardPlus && endCmp < 1) {
             // entirely on minus side
             return new Split<>(this, null);
         } else if (!pointsTowardPlus && endCmp > -1) {
             // entirely on plus side
             return new Split<>(null, this);
         }
 
         // we're going to be split
         final Segment splitSeg = new Segment(line, intersection, endPoint);
         final ReverseRay splitRevRay = new ReverseRay(line, intersection);
 
         final LineConvexSubset minus = (endCmp > 0) ? splitRevRay : splitSeg;
         final LineConvexSubset plus = (endCmp > 0) ? splitSeg : splitRevRay;
 
         return new Split<>(minus, plus);
     }
 }