package com.android.imooc.goo;
import android.graphics.PointF;
/**
 * 幾何圖形工具
 */
public class GeometryUtil {
  /**
   * As meaning of method name. 獲得兩點(diǎn)之間的距離
   *
   * @param p0
   * @param p1
   * @return
   */
  public static float getDistanceBetween2Points(PointF p0, PointF p1) {
    float distance = (float) Math.sqrt(Math.pow(p0.y - p1.y, 2) + Math.pow(p0.x - p1.x, 2));
    return distance;
  }
  /**
   * Get middle point between p1 and p2. 獲得兩點(diǎn)連線的中點(diǎn)
   *
   * @param p1
   * @param p2
   * @return
   */
  public static PointF getMiddlePoint(PointF p1, PointF p2) {
    return new PointF((p1.x + p2.x) / 2.0f, (p1.y + p2.y) / 2.0f);
  }
  /**
   * Get point between p1 and p2 by percent. 根據(jù)百分比獲取兩點(diǎn)之間的某個(gè)點(diǎn)坐標(biāo)
   *
   * @param p1
   * @param p2
   * @param percent
   * @return
   */
  public static PointF getPointByPercent(PointF p1, PointF p2, float percent) {
    return new PointF(evaluateValue(percent, p1.x, p2.x), evaluateValue(percent, p1.y, p2.y));
  }
  /**
   * 根據(jù)分度值，計(jì)算從start到end中，fraction位置的值。fraction范圍為0 -> 1
   *
   * @param fraction
   * @param start
   * @param end
   * @return
   */
  public static float evaluateValue(float fraction, Number start, Number end) {
    return start.floatValue() + (end.floatValue() - start.floatValue()) * fraction;
  }
  /**
   * Get the point of intersection between circle and line. 獲取
   * 通過指定圓心，斜率為lineK的直線與圓的交點(diǎn)。
   *
   * @param pMiddle
   *      The circle center point.
   * @param radius
   *      The circle radius.
   * @param lineK
   *      The slope of line which cross the pMiddle.
   * @return
   */
  public static PointF[] getIntersectionPoints(PointF pMiddle, float radius, Double lineK) {
    PointF[] points = new PointF[2];
    float radian, xOffset = 0, yOffset = 0;
    if (lineK != null) {
      radian = (float) Math.atan(lineK);
      xOffset = (float) (Math.sin(radian) * radius);
      yOffset = (float) (Math.cos(radian) * radius);
    } else {
      xOffset = radius;
      yOffset = 0;
    }
    points[0] = new PointF(pMiddle.x + xOffset, pMiddle.y - yOffset);
    points[1] = new PointF(pMiddle.x - xOffset, pMiddle.y + yOffset);
    return points;
  }
}