/*
    * 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 java.util.ArrayList;
  import java.util.List;
  
  import org.apache.commons.geometry.core.precision.DoublePrecisionContext;
  import org.apache.commons.geometry.core.precision.EpsilonDoublePrecisionContext;
  import org.junit.Assert;
  
  /** Helper class designed to assist with linecast test assertions in 2D.
   */
  public class LinecastChecker2D {
  
      private static final double TEST_EPS = 1e-10;
  
      private static final DoublePrecisionContext TEST_PRECISION =
              new EpsilonDoublePrecisionContext(TEST_EPS);
  
      /** The linecastable target. */
      private final Linecastable2D target;
  
      /** List of expected results from the line cast operation. */
      private final List<ExpectedResult> expectedResults = new ArrayList<>();
  
      /** Construct a new instance that performs linecast assertions against the
       * given target.
       * @param target
       */
      LinecastChecker2D(final Linecastable2D target) {
          this.target = target;
      }
  
      /** Configure the instance to expect no results (an empty list from linecast() and null from
       * linecastFirst()) from the next linecast operation performed by {@link #whenGiven(Line)}
       * or {@link #whenGiven(LineConvexSubset)}.
       * @return
       */
      public LinecastChecker2D expectNothing() {
          expectedResults.clear();
  
          return this;
      }
  
      /** Configure the instance to expect a linecast point with the given parameters on the next
       * linecast operation. Multiple calls to this method and/or {@link #and(Vector2D, Vector2D)}
       * create an internal ordered list of results.
       * @param point
       * @param normal
       * @return
       */
      public LinecastChecker2D expect(final Vector2D point, final Vector2D normal) {
          expectedResults.add(new ExpectedResult(point, normal));
  
          return this;
      }
  
      /** Fluent API alias for {@link #expect(Vector2D, Vector2D)}.
       * @param point
       * @param normal
       * @return
       */
      public LinecastChecker2D and(final Vector2D point, final Vector2D normal) {
          return expect(point, normal);
      }
  
      /** Perform {@link Linecastable2D#linecast(Line)} and {@link Linecastable2D#linecastFirst(Line)}
       * operations using the given line and assert that the results match the configured expected
       * values.
       * @param line
       */
      public void whenGiven(final Line line) {
          checkLinecastResults(target.linecast(line), line);
          checkLinecastFirstResult(target.linecastFirst(line), line);
      }
  
      /** Perform {@link Linecastable2D#linecast(LineConvexSubset)} and {@link Linecastable2D#linecastFirst(LineConvexSubset)}
       * operations using the given line segment and assert that the results match the configured
       * expected results.
       * @param segment
       */
      public void whenGiven(final LineConvexSubset segment) {
          final Line line = segment.getLine();
  
         checkLinecastResults(target.linecast(segment), line);
         checkLinecastFirstResult(target.linecastFirst(segment), line);
     }
 
     /** Check that the given set of linecast result points matches those expected.
      * @param results
      * @param line
      */
     private void checkLinecastResults(final List<LinecastPoint2D> results, final Line line) {
         Assert.assertNotNull("Linecast result list cannot be null", results);
         Assert.assertEquals("Unexpected result size for linecast", expectedResults.size(), results.size());
 
         for (int i = 0; i < expectedResults.size(); ++i) {
             final LinecastPoint2D expected = toLinecastPoint(expectedResults.get(i), line);
             final LinecastPoint2D actual = results.get(i);
 
             if (!eq(expected, actual)) {
                 Assert.fail("Unexpected linecast point at index " + i + " expected " + expected +
                         " but was " + actual);
             }
         }
     }
 
     /** Check that the given linecastFirst result matches that expected.
      * @param result
      * @param line
      */
     private void checkLinecastFirstResult(final LinecastPoint2D result, final Line line) {
         if (expectedResults.isEmpty()) {
             Assert.assertNull("Expected linecastFirst result to be null", result);
         } else {
             final LinecastPoint2D expected = toLinecastPoint(expectedResults.get(0), line);
 
             Assert.assertNotNull("Expected linecastFirst result to not be null", result);
 
             if (!eq(expected, result)) {
                 Assert.fail("Unexpected result from linecastFirst: expected " + expected +
                         " but was " + result);
             }
         }
     }
 
     /** Fluent API method for creating new instances.
      * @param src
      * @return
      */
     public static LinecastChecker2D with(final Linecastable2D src) {
         return new LinecastChecker2D(src);
     }
 
     /** Return true if the given linecast points are equivalent according to the test precision.
      * @param a
      * @param b
      * @return
      */
     private static boolean eq(final LinecastPoint2D a, final LinecastPoint2D b) {
         return a.getPoint().eq(b.getPoint(), TEST_PRECISION) &&
                 a.getNormal().eq(b.getNormal(), TEST_PRECISION) &&
                 a.getLine().equals(b.getLine()) &&
                 TEST_PRECISION.eq(a.getAbscissa(), b.getAbscissa());
     }
 
     /** Convert an {@link ExpectedResult} struct to a {@link LinecastPoint2D} instance
      * using the given line.
      * @param expected
      * @param line
      * @return
      */
     private static LinecastPoint2D toLinecastPoint(final ExpectedResult expected, final Line line) {
         return new LinecastPoint2D(expected.getPoint(), expected.getNormal(), line);
     }
 
     /** Class containing intermediate expected results for a linecast operation.
      */
     private static final class ExpectedResult {
         private final Vector2D point;
         private final Vector2D normal;
 
         ExpectedResult(final Vector2D point, final Vector2D normal) {
             this.point = point;
             this.normal = normal;
         }
 
         public Vector2D getPoint() {
             return point;
         }
 
         public Vector2D getNormal() {
             return normal;
         }
     }
 }