function getMC(p) {
    var m = (p[1][1] - p[0][1]) / (p[1][0] - p[0][0]);
    var c1 = p[0][1]-m*p[0][0];
    var c2 = p[1][1]-m*p[1][0];
    //console.log("Slop", m, "C1", c1, "C2", c2)
    if(Math.round(c1)!==Math.round(c2))
      throw new Error("Something is not right");
    return [m,c1];
}

function getIntersectionPoint(points){
   var line1 = getMC([points[0],points[1]]);
   var line2 = getMC([points[2],points[3]]);
   
   if(line1[0]===line2[0] && line1[1]===line2[1]){
   	console.log("same line");
   	return ("same line");
   }
   else if(line1[0]===line2[0]){
   	console.log("parallel line");
   	return ("parallel line");
   }
   else {
	   var x=((line2[1]-line1[1])/(line1[0]-line2[0]));
	   var iX = Math.round(x);
	   var y1=(line1[0]*x + line1[1]);
	   var y2=(line2[0]*x + line2[1]);
	   //console.log("Intersection point", "X", Math.round(x), "y1", Math.round(y1), "y2", Math.round(y2));
	   if(Math.round(y1)!==Math.round(y2))
	      throw new Error("Something is not right");
	   var iY=Math.round(y1);
	   var l1Status="";
	   var l2Status="";
	   if(iX>=points[0][0]){
	   	if(iX<=points[1][0]){
	   		l1Status="on L1 line segment";
	   	}
	   	else{
	   		l1Status="on L1 line forward side";
	   	}
	   } else {
	   	l1Status="on L1 line back side";
	   }
	   if(iX>=points[2][0]){
	   	if(iX<=points[3][0]){
	   		l2Status="on L2 line segment";
	   	}
	   	else{
	   		l2Status="on L2 line forward side";
	   	}
	   } else {
	   	l2Status="on L2 line back side";
	   }
	   console.log("Intersection point ("+ iX+", "+ iY+") is "+l1Status+" and "+l2Status);
	   return ("Intersection point ("+ iX+", "+ iY+") is "+l1Status+" and "+l2Status);
   }
}

/*
var points = [[15,10],[49,25],[29,5],[32,32]]; // intersacting
getIntersectionPoint(points);

var points = [[30,15],[50,25],[30,10],[50,20]] // parallel line
getIntersectionPoint(points);

var points = [[20,10],[30,15],[40,20],[50,25]] // same line
getIntersectionPoint(points);

var points = [[21,-4],[27,8],[40,20],[50,25]] // intersacting
getIntersectionPoint(points);

var points = [[21,-4],[31,8],[40,20],[50,25]] // intersacting
getIntersectionPoint(points);
*/