/**
  * 已知三点坐标，求其中一点到另两点的垂线距离
  * （如果在垂足不在线段内，最短距离为到其中一点的直线距离）
  * Created by wzq on 17-11-2.
  */
object Point2lineDistance {
  def main(args: Array[String]) {
    val v: Double = pointToLine(-3, 0, 3, 0, 0, 3)
    System.out.println(v)
  }

  def pointToLine(x1: Int, y1: Int, x2: Int, y2: Int, x0: Int, y0: Int): Double = {
    var space: Double = 0
    var a: Double = .0
    var b: Double = .0
    var c: Double = .0
    a = lineSpace(x1, y1, x2, y2) // 线段的长度
    b = lineSpace(x1, y1, x0, y0) // (x1,y1)到点的距离
    c = lineSpace(x2, y2, x0, y0) // (x2,y2)到点的距离
    if (c <= 0.000001 || b <= 0.000001) {
      space = 0
      return space
    }
    if (a <= 0.000001) {
      space = b
      return space
    }
    //钝角三角形的最小边长
    if (c * c >= a * a + b * b) {
      space = b
      return space
    }
    if (b * b >= a * a + c * c) {
      space = c
      return space
    }
    val p: Double = (a + b + c) / 2 // 半周长
    val s: Double = Math.sqrt(p * (p - a) * (p - b) * (p - c)) // 海伦公式求面积
    space = 2 * s / a // 返回点到线的距离（利用三角形面积公式求高）
    space
  }

  // 计算两点之间的距离
  private def lineSpace(x1: Int, y1: Int, x2: Int, y2: Int): Double = {
    var lineLength: Double = 0
    lineLength = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))
    lineLength
  }
}