planetiler/flatmap-core/src/test/java/com/onthegomap/flatmap/geo/DouglasPeuckerSimplifierTest.java

package com.onthegomap.flatmap.geo;

import static com.onthegomap.flatmap.TestUtils.assertSameNormalizedFeature;
import static com.onthegomap.flatmap.TestUtils.newLineString;
import static com.onthegomap.flatmap.TestUtils.newPolygon;
import static com.onthegomap.flatmap.TestUtils.rectangle;

import org.junit.jupiter.api.Test;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.util.AffineTransformation;

public class DouglasPeuckerSimplifierTest {

  int[] rotations = new int[]{0, 45, 90, 180, 270};

  private void testSimplify(Geometry in, Geometry expected, double amount) {
    for (int rotation : rotations) {
      var rotate = AffineTransformation.rotationInstance(Math.PI * rotation / 180);
      assertSameNormalizedFeature(
        rotate.transform(expected),
        DouglasPeuckerSimplifier.simplify(rotate.transform(in), amount)
      );
    }
  }

  @Test
  public void testSimplify2Points() {
    testSimplify(newLineString(
      0, 0,
      10, 10
    ), newLineString(
      0, 0,
      10, 10
    ), 1);
  }

  @Test
  public void testRemoveAPoint() {
    testSimplify(newLineString(
      0, 0,
      5, 0.9,
      10, 0
    ), newLineString(
      0, 0,
      10, 0
    ), 1);
  }

  @Test
  public void testKeepAPoint() {
    testSimplify(newLineString(
      0, 0,
      5, 1.1,
      10, 0
    ), newLineString(
      0, 0,
      5, 1.1,
      10, 0
    ), 1);
  }

  @Test
  public void testPolygonLeaveAPoint() {
    testSimplify(
      rectangle(0, 10),
      newPolygon(
        0, 0,
        10, 10,
        10, 0,
        0, 0
      ),
      20
    );
  }
}