require 'bizzieLibrary'

$eqEpsilon = 0.0000000000001

def approxEq(a, b)
	return (abs(a - b) < $eqEpsilon)
end

# source: http://geometryalgorithms.com/Archive/algorithm_0104/algorithm_0104B.htm
def intersectionPoint(lineA, lineB)
	v = lineA.vect
	vPerp = lineA.vect.perp
	u = lineB.vect
	uPerp = lineB.vect.perp
	
	dpA = vPerp.dotProduct(u)
	
	if (!approxEq(dpA, 0.0))
		w = lineB.p1 - lineA.p1
		s1 = -1.0 * (vPerp.dotProduct(w)) / dpA
		t1 = -1.0 * (uPerp.dotProduct(w)) /  dpA
		if 0.0 <= s1 && s1 <= 1.0 && 0.0 <= t1 && t1 <= 1.0
			return lineB.doPathPoint(s1)
		else
			return nil
		end
	else
		return nil
	end
	
end

def allIntersections(lines)
	intersections = []
	linePairs = getGroups(lines)
	
	linePairs.each do |linePair|
		intersection = intersectionPoint(linePair[0], linePair[1])
		if (intersection != nil)
			intersections << intersection
			#puts intersection.x.to_s + ", " + intersection.y.to_s
		end
	end
	
	return intersections
end

def lineContainsPoint?(line, point)
	dx = line.p2.x - line.p1.x
	
	if dx != 0.0
		s = (point.x - line.p1.x)/dx
		if 0.0 <= s && s <= 1.0
			return approxEq(point.y, line.p1.y + (line.p2.y - line.p1.y) * s)
		else
			return false
		end
	else
		if !approxEq(line.p1.x, point.x)
			return false
		else
			return inInterval?(point.y, line.p1.y, line.p2.y)
		end
	end
end

# returns true if lineA contains lineB
def lineContainsLine?(lineA, lineB)
	return lineContainsPoint?(lineA, lineB.p1) && lineContainsPoint?(lineA, lineB.p2)
end

=begin
# either takes a line object or a 

ptA1 = Point2d.new(0.0, 0.0)
ptA2 = Point2d.new(1.0, 0.0)
ptB1 = Point2d.new(0.5, 0.5)
ptB2 = Point2d.new(0.5, -0.5)
ptC1 = Point2d.new(0.1, 0.0)
ptC2 = Point2d.new(0.9, 0.0)
lineA = Line2d.new(ptA1, ptA2)
lineB = Line2d.new(ptB1, ptB2)
lineC = Line2d.new(ptC1, ptC2)
lineD = Line2d.new(ptA1, ptC2)
lineE = Line2d.new(ptC1, ptA2)
lineF = Line2d.new(ptA2, ptA1)
lineG = Line2d.new(ptC2, ptC1)
lineH = Line2d.new(ptC2, ptB1)


puts intersectionPoint(lineA, lineB)

puts lineContainsLine?(lineA, lineA)
puts lineContainsLine?(lineA, lineB)
puts lineContainsLine?(lineA, lineC)
puts lineContainsLine?(lineA, lineD)
puts lineContainsLine?(lineA, lineE)
puts lineContainsLine?(lineA, lineF)
puts lineContainsLine?(lineA, lineG)
puts lineContainsLine?(lineA, lineH)
=end