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/*
 * 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.lucene.geo;

import org.apache.lucene.util.SloppyMath;

/** Draws shapes on the earth surface and renders using the very cool http://www.webglearth.org.
 *
 * Just instantiate this class, add the things you want plotted, and call {@link #finish} to get the
 * resulting HTML that you should save and load with a browser. */

public class EarthDebugger {
  final StringBuilder b = new StringBuilder();
  private int nextShape;
  private boolean finished;

  public EarthDebugger() {
    b.append("\n");
    b.append("\n");
    b.append("  \n");
    b.append("    \n");
    b.append("    \n");
    b.append("    \n");
    b.append("    \n");
    b.append("    WebGL Earth API: Hello World\n");
    b.append("  \n");
    b.append("  \n");
    b.append("    \n");
    b.append("  \n");
    b.append("\n");

    return b.toString();
  }

  private static void inverseHaversin(StringBuilder b, double centerLat, double centerLon, double radiusMeters) {
    double angle = 0;
    int steps = 100;

    newAngle:
    while (angle < 360) {
      double x = Math.cos(SloppyMath.toRadians(angle));
      double y = Math.sin(SloppyMath.toRadians(angle));
      double factor = 2.0;
      double step = 1.0;
      int last = 0;
      double lastDistanceMeters = 0.0;
      //System.out.println("angle " + angle + " slope=" + slope);
      while (true) {
        double lat = wrapLat(centerLat + y * factor);
        double lon = wrapLon(centerLon + x * factor);
        double distanceMeters = SloppyMath.haversinMeters(centerLat, centerLon, lat, lon);

        if (last == 1 && distanceMeters < lastDistanceMeters) {
          // For large enough circles, some angles are not possible:
          //System.out.println("  done: give up on angle " + angle);
          angle += 360./steps;
          continue newAngle;
        }
        if (last == -1 && distanceMeters > lastDistanceMeters) {
          // For large enough circles, some angles are not possible:
          //System.out.println("  done: give up on angle " + angle);
          angle += 360./steps;
          continue newAngle;
        }
        lastDistanceMeters = distanceMeters;

        //System.out.println("  iter lat=" + lat + " lon=" + lon + " distance=" + distanceMeters + " vs " + radiusMeters);
        if (Math.abs(distanceMeters - radiusMeters) < 0.1) {
          b.append("          [" + lat + ", " + lon + "],\n");
          break;
        }
        if (distanceMeters > radiusMeters) {
          // too big
          //System.out.println("    smaller");
          factor -= step;
          if (last == 1) {
            //System.out.println("      half-step");
            step /= 2.0;
          }
          last = -1;
        } else if (distanceMeters < radiusMeters) {
          // too small
          //System.out.println("    bigger");
          factor += step;
          if (last == -1) {
            //System.out.println("      half-step");
            step /= 2.0;
          }
          last = 1;
        }
      }
      angle += 360./steps;
    }
  }
  // craziness for plotting stuff :)

  private static double wrapLat(double lat) {
    //System.out.println("wrapLat " + lat);
    if (lat > 90) {
      //System.out.println("  " + (180 - lat));
      return 180 - lat;
    } else if (lat < -90) {
      //System.out.println("  " + (-180 - lat));
      return -180 - lat;
    } else {
      //System.out.println("  " + lat);
      return lat;
    }
  }

  private static double wrapLon(double lon) {
    //System.out.println("wrapLon " + lon);
    if (lon > 180) {
      //System.out.println("  " + (lon - 360));
      return lon - 360;
    } else if (lon < -180) {
      //System.out.println("  " + (lon + 360));
      return lon + 360;
    } else {
      //System.out.println("  " + lon);
      return lon;
    }
  }
}