package ch.zhaw.hexboard;

import java.awt.Point;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

/***
 * <p>
 * This class represents a simple generic hexagonal game board.
 * </p>
 * <p>The game board uses a fixed coordinate system which is structured as follows:</p>
 * 
 * <pre>
 *         0    1    2    3    4    5    6    7    8 
 *         |    |    |    |    |    |    |    |    |   ...
 * 
 *  0----  C         C         C         C         C
 *            \   /     \   /     \   /     \   /     \ 
 *  1----       C         C         C         C         C
 *  
 *  2----  F    |    F    |    F    |    F    |    F    |   ...
 *  
 *  3----       C         C         C         C         C
 *           /     \   /     \   /     \   /     \   / 
 *  4----  C         C         C         C         C    
 *              
 *  5----  |    F    |    F    |    F    |    F    |    F   ...
 *              
 *  6----  C         C         C         C         C    
 *           \     /   \     /   \     /   \     /   \     
 *  7----       C         C         C         C         C    
 *   
 *    ...
 * </pre>
 *
 * <p>
 * Fields <strong>F</strong> and corners <strong>C</strong> can be retrieved
 * using their coordinates ({@link java.awt.Point}) on the board. Edges can be
 * retrieved using the coordinates of the two corners they connect.
 * </p>
 * 
 * <p>
 * When created, the board is empty (no fields added). To add fields, the
 * #{@link #addField(Point, Object)} function can be used. Edges and corners are
 * automatically created when adding a field. They cannot be created/removed
 * individually. When adding a field, edges and corners that were already
 * created, e.g., because adding an adjacent field already created them, are
 * left untouched.
 * </p>
 * 
 * <p>
 * Fields, edges and corners can store an object of the type of the
 * corresponding type parameter each.
 * </p>
 * 
 * <p>
 * Furthermore, the hexagonal game board can store six additional objects, so
 * called annotations, for each field. These objects are identified by the
 * coordinates of the field and the corner. Hence, they can be thought of being
 * located between the center and the respective corner. Or in other words,
 * their positions correspond to the positions N, NW, SW, NE, NW, SE and NE in
 * the below visualization of a field.
 * </p>
 * 
 * <pre>
 *       SW (C) SE
 *    /      N      \
 *  (C) NW       NE (C)
 *   |       F       |
 *   |               |
 *  (C) SW       SE (C)
 *    \      S      /
 *       NW (C) NE
 * </pre>
 * 
 * @param <F> Data type for the field data objects
 * @param <C> Data type for the corner data objects
 * @param <E> Data type for the edge data objects
 * @param <A> Data type for the annotation data objects
 * 
 * @author tebe
 *
 */
public class HexBoard<F, C, E, A> {
  private int maxCoordinateX = 0;
  private int maxCoordinateY = 0;
  private final Map<Point, F> field;
  private final Map<Point, C> corner;
  private final Map<Edge, E> edge;
  private final Map<FieldAnnotationPosition, A> annotation;

  /**
   * Constructs an empty hexagonal board.
   */
  public HexBoard() {
    field = new HashMap<>();
    corner = new HashMap<>();
    edge = new HashMap<>();
    annotation = new HashMap<>();
  }

  /**
   * Adds a field to the board and creates the surrounding (empty) corners and
   * edges if they do not yet exist Note: Corners and edges of a field might
   * already have been created while creating adjacent fields.
   * 
   * @param center  Coordinate of the center of a field on the unit grid
   * @param element Data element to be stored for this field
   * 
   * @throws IllegalArgumentException if center is not the center of a field, the
   *                                  field already exists or data is null
   */
  public void addField(Point center, F element) {
    if (isFieldCoordinate(center) && !field.containsKey(center)) {
      field.put(center, element);
      maxCoordinateX = Math.max(center.x + 1, maxCoordinateX);
      maxCoordinateY = Math.max(center.y + 2, maxCoordinateY);
      // add (empty) edge, if they do not yet exist
      for (Edge e : constructEdgesOfField(center)) {
        if (!edge.containsKey(e)) {
          edge.put(e, null);
        }
      }
      // add (empty) corners, if they do not yet exist
      for (Point p : getCornerCoordinatesOfField(center)) {
        if (!corner.containsKey(p)) {
          corner.put(p, null);
        }
      }
    } else {
      throw new IllegalArgumentException(
          "Coordinates are not the center of a field, the field already exists or data is null - ("
              + center.x + ", " + center.y + ")");
    }
  }

  /**
   * Add an annotation for the specified field and corner.
   * 
   * @param center the center of the field
   * @param corner the corner of the field
   * @param data   the annotation
   * @throws IllegalArgumentException if the field does not exists or when the
   *                                  annotation already exists
   */
  public void addFieldAnnotation(Point center, Point corner, A data) {
    FieldAnnotationPosition annotationPosition = new FieldAnnotationPosition(center, corner);
    if (!annotation.containsKey(annotationPosition)) {
      annotation.put(annotationPosition, data);
    } else {
      throw new IllegalArgumentException("Annotation: " + annotation + " already exists for field "
          + center + " and position " + corner);
    }
  }

  /**
   * Get an annotation for the specified field and corner.
   * 
   * @param center the center of the field
   * @param corner the corner of the field
   * @return the annotation
   * @throws IllegalArgumentException if coordinates are not a field and
   *                                  corresponding corner coordinate
   */
  public A getFieldAnnotation(Point center, Point corner) {
    return annotation.get(new FieldAnnotationPosition(center, corner));
  }

  /**
   * Get field annotation whose position information includes the specified corner.
   *  
   * @param corner the corner
   * @return a list with the annotations that are not null
   * @throws IllegalArgumentException if corner is not a corner
   */
  public List<A> getFieldAnnotationsForCorner(Point corner) {
    List<A> list = new LinkedList<>();
    for (Entry<FieldAnnotationPosition, A> entry : annotation.entrySet()) {
      if (entry.getKey().isCorner(corner) && entry.getValue() != null) {
        list.add(entry.getValue());
      }
    }
    return list;
  }

  /**
   * Get all field annotation of the specified field.
   * 
   * @param center the field
   * @return a list with the annotations that are not null
   * @throws IllegalArgumentException if center is not a field
   */
  public List<A> getFieldAnnotationsForField(Point center) {
    List<A> list = new LinkedList<>();
    for (Entry<FieldAnnotationPosition, A> entry : annotation.entrySet()) {
      if (entry.getKey().isField(center) && entry.getValue() != null) {
        list.add(entry.getValue());
      }
    }
    return list;
  }

  /**
   * Determines whether the field at the specified position exists.
   * 
   * @param center the field
   * @return false, if the field does not exist or the position is not a field
   */
  public boolean hasField(Point center) {
    if (!HexBoard.isFieldCoordinate(center)) {
      return false;
    }
    return field.containsKey(center);
  }

  static boolean isFieldCoordinate(Point position) {
    boolean isYFieldCoordinateEven = (position.y - 2) % 6 == 0;
    boolean isYFieldCoordinateOdd = (position.y - 5) % 6 == 0;
    boolean isXFieldCoordinateEven = position.x % 2 == 0;
    boolean isXFieldCoordinateOdd = (position.x - 1) % 2 == 0;

    return (position.y >= 2 && position.x >= 1)
        && (isYFieldCoordinateEven && isXFieldCoordinateEven)
        || (isYFieldCoordinateOdd && isXFieldCoordinateOdd);
  }

  static boolean isCornerCoordinate(Point p) {
    // On the horizontal center lines, no edge points exist
    boolean isOnFieldCenterLineHorizontal = (p.y - 2) % 3 == 0;

    // On the vertical center lines, edge points exist
    boolean isOnFieldCenterLineVerticalOdd = (p.x - 1) % 3 == 0 && p.x % 2 == 0;
    boolean isOnFieldCenterLineVerticalEven = (p.x - 1) % 3 == 0 && (p.x - 1) % 2 == 0;
    boolean isNotAnEdgePointOnFieldCentralVerticalLine = isOnFieldCenterLineVerticalOdd
        && !(p.y % 6 == 0 || (p.y + 2) % 6 == 0)
        || isOnFieldCenterLineVerticalEven && !((p.y + 5) % 6 == 0 || (p.y + 3) % 6 == 0);

    return !(isOnFieldCenterLineHorizontal || isNotAnEdgePointOnFieldCentralVerticalLine);
  }

  private List<Edge> constructEdgesOfField(Point position) {
    Edge[] e = new Edge[6];
    e[0] = new Edge(new Point(position.x, position.y - 2),
        new Point(position.x + 1, position.y - 1));
    e[1] = new Edge(new Point(position.x + 1, position.y - 1),
        new Point(position.x + 1, position.y + 1));
    e[2] = new Edge(new Point(position.x + 1, position.y + 1),
        new Point(position.x, position.y + 2));
    e[3] = new Edge(new Point(position.x, position.y + 2),
        new Point(position.x - 1, position.y + 1));
    e[4] = new Edge(new Point(position.x - 1, position.y + 1),
        new Point(position.x - 1, position.y - 1));
    e[5] = new Edge(new Point(position.x - 1, position.y - 1),
        new Point(position.x, position.y - 2));
    return Arrays.asList(e);
  }

  private static List<Point> getCornerCoordinatesOfField(Point position) {
    Point[] corner = new Point[6];
    corner[0] = new Point(position.x, position.y - 2);
    corner[1] = new Point(position.x + 1, position.y - 1);
    corner[2] = new Point(position.x + 1, position.y + 1);
    corner[3] = new Point(position.x, position.y + 2);
    corner[4] = new Point(position.x - 1, position.y - 1);
    corner[5] = new Point(position.x - 1, position.y + 1);
    return Collections.unmodifiableList(Arrays.asList(corner));
  }

  protected static List<Point> getAdjacentCorners(Point position) {
    Point[] corner = new Point[3];
    if (position.y % 3 == 0) {
      corner[0] = new Point(position.x, position.y - 2);
      corner[1] = new Point(position.x + 1, position.y + 1);
      corner[2] = new Point(position.x - 1, position.y + 1);
    } else {
      corner[0] = new Point(position.x, position.y + 2);
      corner[1] = new Point(position.x + 1, position.y - 1);
      corner[2] = new Point(position.x - 1, position.y - 1);
    }
    return Collections.unmodifiableList(Arrays.asList(corner));
  }

  /**
   * Returns all non-null corner data elements.
   * 
   * @return the non-null corner data elements
   */
  public List<C> getCorners() {
    List<C> result = new LinkedList<>();
    for (C c : this.corner.values()) {
      if (c != null) {
        result.add(c);
      }
    }
    return Collections.unmodifiableList(result);
  }

  protected Set<Point> getCornerCoordinates() {
    return Collections.unmodifiableSet(this.corner.keySet());
  }

  private static List<Point> getAdjacentFields(Point corner) {
    Point[] field = new Point[3];
    if (corner.y % 3 == 0) {
      field[0] = new Point(corner.x, corner.y + 2);
      field[1] = new Point(corner.x + 1, corner.y - 1);
      field[2] = new Point(corner.x - 1, corner.y - 1);
    } else {
      field[0] = new Point(corner.x, corner.y - 2);
      field[1] = new Point(corner.x + 1, corner.y + 1);
      field[2] = new Point(corner.x - 1, corner.y + 1);
    }
    return Collections.unmodifiableList(Arrays.asList(field));
  }

  /**
   * Returns the data for the field denoted by the point.
   * 
   * @param center the location of the field
   * @return the stored data (or null)
   * @throws IllegalArgumentException if the requested field does not exist
   */
  public F getField(Point center) {
    if (field.containsKey(center)) {
      return field.get(center);
    } else {
      throw new IllegalArgumentException("No field exists at these coordinates: " + center);
    }
  }

  /**
   * Returns the fields with non-null data elements.
   * 
   * @return the list with the (non-null) field data
   */
  public List<Point> getFields() {
    List<Point> result = new LinkedList<>();
    for (Entry<Point, F> e : field.entrySet()) {
      if (e.getValue() != null) {
        result.add(e.getKey());
      }
    }
    return Collections.unmodifiableList(result);
  }

  /**
   * Returns the field data of the fields that touch this corner.
   * <p>
   * If the specified corner is not a corner or none of the fields that touch this
   * corner have a non-null data element, an empty list is returned.
   * </p>
   * @param corner the location of the corner
   * @return the list with the (non-null) field data
   */
  public List<F> getFields(Point corner) {
    List<F> result = new LinkedList<>();
    if (isCornerCoordinate(corner)) {
      for (Point f : getAdjacentFields(corner)) {
        if (field.get(f) != null) {
          result.add(field.get(f));
        }
      }
    }
    return Collections.unmodifiableList(result);
  }

  /**
   * Returns the data for the edge denoted by the two points.
   * 
   * @param p1 first point
   * @param p2 second point
   * @return the stored data (or null)
   */
  public E getEdge(Point p1, Point p2) {
    Edge e = new Edge(p1, p2);
    if (edge.containsKey(e)) {
      return edge.get(e);
    } else {
      return null;
    }
  }

  /**
   * Stores the data for the edge denoted by the two points.
   * 
   * @param p1   first point
   * @param p2   second point
   * @param data the data to be stored
   * @throws IllegalArgumentException if the two points do not identify an
   *                                  EXISTING edge of the field
   */
  public void setEdge(Point p1, Point p2, E data) {
    Edge e = new Edge(p1, p2);
    if (edge.containsKey(e)) {
      edge.put(e, data);
    } else {
      throw new IllegalArgumentException("Edge does not exist => no data can be stored: " + e);
    }
  }

  /**
   * Returns the data for the corner denoted by the point.
   * 
   * @param location the location of the corner
   * @return the data stored for this node (or null)
   * @throws IllegalArgumentException if the requested corner does not exist
   */
  public C getCorner(Point location) {
    if (corner.containsKey(location)) {
      return corner.get(location);
    } else {
      throw new IllegalArgumentException("No corner exists at the coordinates: " + location);
    }
  }

  /**
   * Stores the data for the edge denoted by the two points.
   * 
   * @param location the location of the corner
   * @param data     the data to be stored
   * @return the old data entry (or null)
   * @throws IllegalArgumentException if there is no corner at this location
   */
  public C setCorner(Point location, C data) {
    C old = corner.get(location);
    if (corner.containsKey(location)) {
      corner.put(location, data);
      return old;
    } else {
      throw new IllegalArgumentException(
          "Corner does not exist => no data can be stored: " + location);
    }
  }

  /**
   * Returns the (non-null) corner data elements of the corners that are direct
   * neighbors of the specified corner.
   * <p>
   * Each corner has three direct neighbors, except corners that are located at
   * the border of the game board.
   * </p>
   * @param center the location of the corner for which to return the direct
   *               neighbors
   * @return list with non-null corner data elements
   */
  public List<C> getNeighboursOfCorner(Point center) {
    List<C> result = new LinkedList<>();
    for (Point c : HexBoard.getAdjacentCorners(center)) {
      C temp = corner.get(c);
      if (temp != null) {
        result.add(temp);
      }
    }
    return result;
  }

  /**
   * Returns the (non-null) edge data elements of the edges that directly connect
   * to that corner.
   * <p>
   * Each corner has three edges connecting to it, except edges that are located
   * at the border of the game board.
   * </p>
   * @param corner corner for which to get the edges
   * @return list with non-null edge data elements of edges connecting to the
   *         specified edge
   */
  public List<E> getAdjacentEdges(Point corner) {
    List<E> result = new LinkedList<>();
    for (Entry<Edge, E> e : this.edge.entrySet()) {
      if (e.getKey().isEdgePoint(corner)  
          && e.getValue() != null) {
        result.add(e.getValue());
      }
    }
    return result;
  }

  /**
   * Returns the (non-null) data elements of the corners of the specified field.
   * 
   * @param center the location of the field
   * @return list with non-null corner data elements
   */
  public List<C> getCornersOfField(Point center) {
    List<C> result = new LinkedList<>();
    for (Point c : getCornerCoordinatesOfField(center)) {
      C temp = getCorner(c);
      if (temp != null) {
        result.add(temp);
      }
    }
    return result;
  }

  int getMaxCoordinateX() {
    return maxCoordinateX;
  }

  int getMaxCoordinateY() {
    return maxCoordinateY;
  }

  /**
   * Checks whether there is a corner at that specified location.
   * @param location the location to check
   * @return true, if there is a corner at this location 
   */
  public boolean hasCorner(Point location) {
    if (!HexBoard.isCornerCoordinate(location)) {
      return false;
    }
    return corner.containsKey(location);
  }

  /**
   * Checks whether there is an edge between the two points.
   * @param p1 first point
   * @param p2 second point
   * @return true, if there is an edge between the two points
   */
  public boolean hasEdge(Point p1, Point p2) {
    if (Edge.isEdge(p1, p2)) {
      return edge.containsKey(new Edge(p1, p2));
    } else {
      return false;
    }
  }

  static boolean isCorner(Point field, Point corner) {
    return HexBoard.isFieldCoordinate(field)
        && HexBoard.getCornerCoordinatesOfField(field).contains(corner);
  }

}