/* Copyright 2013-2019 CS Systèmes d'Information
    * Licensed to CS Systèmes d'Information (CS) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS 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.orekit.rugged.raster;
  
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.orekit.bodies.GeodeticPoint;
  import org.orekit.rugged.utils.NormalizedGeodeticPoint;
  
  /** Interface representing a raster tile.
   * <p>
   * The elevations are considered to be at the <em>center</em> of each cells.
   * The minimum latitude and longitude hence correspond to the <em>center</em>
   * of the most South-West cell, and the maximum latitude and longitude
   * correspond to the <em>center</em> of the most North-East cell.
   * </p>
   * @author Luc Maisonobe
   * @author Guylaine Prat
   */
  public interface Tile extends UpdatableTile {
  
      /** Enumerate for point location with respect to the interpolation grid of a tile.
       * <p>
       * Elevations in a tile are interpolated using the four neighboring points
       * in a grid: (i, j), (i+1, j), (i, j+1), (i+1), (j+1). This implies that a point
       * can be interpolated only if the elevation for these four points is available
       * in the tile. A consequence is that a point in the northernmost row (resp.
       * easternmost column) miss neighboring points at row j+1 (resp. neighboring points
       * at column i+1) and therefore cannot be interpolated.
       * </p>
       * <p>
       * This enumerate represent the position of a point taking this off-by-one property
       * into account, the value {@link #HAS_INTERPOLATION_NEIGHBORS} correspond to points that
       * do have the necessary four neightbors, whereas the other values correspond to points
       * that are either completely outside of the tile or within the tile but in either the
       * northernmost row or easternmost column.
       * </p>
       */
      enum Location {
  
          /** Location for points out of tile interpolation grid, in the South-West corner direction. */
          SOUTH_WEST,
  
          /** Location for points out of tile interpolation grid, in the West edge direction. */
          WEST,
  
          /** Location for points out of tile interpolation grid, in the North-West corner direction.
           * <p>
           * The point may still be in the tile, but in the northernmost row thus missing required
           * interpolation points.
           * </p>
           */
          NORTH_WEST,
  
          /** Location for points out of tile interpolation grid, in the North edge direction.
           * <p>
           * The point may still be in the tile, but in the northernmost row thus missing required
           * interpolation points.
           * </p>
           */
          NORTH,
  
          /** Location for points out of tile interpolation grid, in the North-East corner direction.
           * <p>
           * The point may still be in the tile, but either in the northernmost row or in the
           * easternmost column thus missing required interpolation points.
           * </p>
           */
          NORTH_EAST,
  
          /** Location for points out of tile interpolation grid, in the East edge direction.
           * <p>
           * The point may still be in the tile, but in the easternmost column thus missing required
           * interpolation points.
           * </p>
           */
          EAST,
  
          /** Location for points out of tile interpolation grid, in the South-East corner direction.
           * <p>
           * The point may still be in the tile, but in the easternmost column thus missing required
           * interpolation points.
           * </p>
           */
          SOUTH_EAST,
  
         /** Location for points out of tile interpolation grid, in the South edge direction. */
         SOUTH,
 
         /** Location for points that do have interpolation neighbors.
          * <p>
          * The value corresponds to points that can be interpolated using their four
          * neighboring points in the grid at indices (i, j), (i+1, j), (i, j+1), (i+1),
          * (j+1). This implies that these points are neither in the northernmost latitude
          * row nor in the easternmost longitude column.
          * </p>
          */
         HAS_INTERPOLATION_NEIGHBORS
 
     }
 
     /** Hook called at the end of tile update completion.
      */
     void tileUpdateCompleted();
 
     /** Get minimum latitude of grid interpolation points.
      * @return minimum latitude of grid interpolation points (rad)
      * (latitude of the center of the cells of South row)
      */
     double getMinimumLatitude();
 
     /** Get the latitude at some index.
      * @param latitudeIndex latitude index
      * @return latitude at the specified index (rad)
      * (latitude of the center of the cells of specified row)
      */
     double getLatitudeAtIndex(int latitudeIndex);
 
     /** Get maximum latitude.
      * <p>
      * Beware that as a point at maximum latitude is the northernmost
      * one of the grid, it doesn't have a northwards neighbor and
      * therefore calling {@link #getLocation(double, double) getLocation}
      * on such a latitude will return either {@link Location#NORTH_WEST},
      * {@link Location#NORTH} or {@link Location#NORTH_EAST}, but can
      * <em>never</em> return {@link Location#HAS_INTERPOLATION_NEIGHBORS}!
      * </p>
      * @return maximum latitude (rad)
      * (latitude of the center of the cells of North row)
      */
     double getMaximumLatitude();
 
     /** Get minimum longitude.
      * @return minimum longitude (rad)
      * (longitude of the center of the cells of West column)
      */
     double getMinimumLongitude();
 
     /** Get the longitude at some index.
      * @param longitudeIndex longitude index
      * @return longitude at the specified index (rad)
      * (longitude of the center of the cells of specified column)
      */
     double getLongitudeAtIndex(int longitudeIndex);
 
     /** Get maximum longitude.
      * <p>
      * Beware that as a point at maximum longitude is the easternmost
      * one of the grid, it doesn't have an eastwards neighbor and
      * therefore calling {@link #getLocation(double, double) getLocation}
      * on such a longitude will return either {@link Location#SOUTH_EAST},
      * {@link Location#EAST} or {@link Location#NORTH_EAST}, but can
      * <em>never</em> return {@link Location#HAS_INTERPOLATION_NEIGHBORS}!
      * </p>
      * @return maximum longitude (rad)
      * (longitude of the center of the cells of East column)
      */
     double getMaximumLongitude();
 
     /** Get step in latitude (size of one raster element).
      * @return step in latitude (rad)
      */
     double getLatitudeStep();
 
     /** Get step in longitude (size of one raster element).
      * @return step in longitude (rad)
      */
     double getLongitudeStep();
 
     /** Get number of latitude rows.
      * @return number of latitude rows
      */
     int getLatitudeRows();
 
     /** Get number of longitude columns.
      * @return number of longitude columns
      */
     int getLongitudeColumns();
 
     /** Get the floor latitude index of a point.
      * <p>
      * The specified latitude is always between index and index+1.
      * </p>
      * @param latitude geodetic latitude
      * @return floor latitude index (it may lie outside of the tile!)
      */
     int getFloorLatitudeIndex(double latitude);
 
     /** Get the floor longitude index of a point.
      * <p>
      * The specified longitude is always between index and index+1.
      * </p>
      * @param longitude geodetic longitude
      * @return floor longitude index (it may lie outside of the tile!)
      */
     int getFloorLongitudeIndex(double longitude);
 
     /** Get the minimum elevation in the tile.
      * @return minimum elevation in the tile (m)
      */
     double getMinElevation();
 
     /** Get the latitude index of min elevation.
      * @return latitude index of min elevation*/
     int getMinElevationLatitudeIndex();
 
     /** Get the longitude index of min elevation.
      * @return longitude index of min elevation*/
     int getMinElevationLongitudeIndex();
 
    /** Get the maximum elevation in the tile.
      * @return maximum elevation in the tile (m)
      */
     double getMaxElevation();
 
     /** Get the latitude index of max elevation.
      * @return latitude index of max elevation*/
     int getMaxElevationLatitudeIndex();
 
     /** Get the longitude index of max elevation.
      * @return longitude index of max elevation*/
     int getMaxElevationLongitudeIndex();
 
     /** Get the elevation of an exact grid point.
      * @param latitudeIndex grid point index along latitude
      * @param longitudeIndex grid point index along longitude
      * @return elevation at grid point (m)
      */
     double getElevationAtIndices(int latitudeIndex, int longitudeIndex);
 
     /** Interpolate elevation.
      * <p>
      * In order to cope with numerical accuracy issues when computing
      * points at tile boundary, a slight tolerance (typically 1/8 cell)
      * around the tile is allowed. Elevation can therefore be interpolated
      * (really extrapolated in this case) even for points slightly overshooting
      * tile boundaries, using the closest tile cell. Attempting to interpolate
      * too far from the tile will trigger an exception.
      * </p>
      * @param latitude ground point latitude
      * @param longitude ground point longitude
      * @return interpolated elevation (m)
      */
     double interpolateElevation(double latitude, double longitude);
 
     /** Find the intersection of a line-of-sight and a Digital Elevation Model cell.
      * @param p point on the line
      * @param los line-of-sight, in the topocentric frame (East, North, Zenith) of the point,
      * scaled to match radians in the horizontal plane and meters along the vertical axis
      * @param latitudeIndex latitude index of the Digital Elevation Model cell
      * @param longitudeIndex longitude index of the Digital Elevation Model cell
      * @return point corresponding to line-of-sight crossing the Digital Elevation Model surface
      * if it lies within the cell, null otherwise
      */
     NormalizedGeodeticPoint cellIntersection(GeodeticPoint p, Vector3D los,
                                               int latitudeIndex, int longitudeIndex);
 
     /** Check if a tile covers a ground point.
      * @param latitude ground point latitude
      * @param longitude ground point longitude
      * @return location of the ground point with respect to tile
      */
     Location getLocation(double latitude, double longitude);
 
 }