stuff.

util/math.go

@@ -251,3 +251,17 @@ func (m mathUtil) RotateCoordinate(cx, cy, x, y int, thetaRadians float64) (rx,
 	ry = int(rotatedY) + cy
 	return
 }
+
+func (m mathUtil) LinesIntersect(l0x0, l0y0, l0x1, l0y1, l1x0, l1y0, l1x1, l1y1 float64) bool {
+	var s0x, s0y, s1x, s1y float64
+	s0x = l0x1 - l0x0
+	s0y = l0y1 - l0y0
+	s1x = l1x1 - l1x0
+	s1y = l1y1 - l1y0
+
+	var s, t float64
+	s = (-s0y*(l0x0-l1x0) + s0x*(l0y0-l1y0)) / (-s1x*s0y + s0x*s1y)
+	t = (s1x*(l0y0-l1y0) - s1y*(l0x0-l1x0)) / (-s1x*s0y + s0x*s1y)
+
+	return s >= 0 && s <= 1 && t >= 0 && t <= 1
+}

util/math_test.go

@@ -182,3 +182,27 @@ func TestRotateCoordinate45(t *testing.T) {
 	assert.Equal(7, rx)
 	assert.Equal(7, ry)
 }
+
+func TestLinesIntersect(t *testing.T) {
+	assert := assert.New(t)
+
+	p0x := 1.0
+	p0y := 1.0
+
+	p1x := 3.0
+	p1y := 1.0
+
+	p2x := 2.0
+	p2y := 2.0
+
+	p3x := 2.0
+	p3y := 0.0
+
+	p4x := 2.0
+	p4y := 2.0
+	p5x := 3.0
+	p5y := 2.0
+
+	assert.True(Math.LinesIntersect(p0x, p0y, p1x, p1y, p2x, p2y, p3x, p3y))
+	assert.False(Math.LinesIntersect(p0x, p0y, p1x, p1y, p4x, p4y, p5x, p5y))
+}