Polsl-Notes/!Załączniki/Excalidraw/Scripts/Downloaded/Concatenate lines.md

/* Connects two lines. Lines may be type of arrow or line. The resulting line will carry the style of the line higher in the drawing layers (bring to front the one you want to control the look and feel). Arrows are connected intelligently.

const lines = ea.getViewSelectedElements().filter(el=>el.type==="line" || el.type==="arrow");
if(lines.length !== 2) {
  new Notice ("Select two lines or arrows");
  return;
}

// https://math.stackexchange.com/questions/2204520/how-do-i-rotate-a-line-segment-in-a-specific-point-on-the-line
const rotate = (point, element) => {
  const [x1, y1] = point;
  const x2 = element.x + element.width/2;
  const y2 = element.y - element.height/2;
  const angle = element.angle;
  return [
    (x1 - x2) * Math.cos(angle) - (y1 - y2) * Math.sin(angle) + x2,
    (x1 - x2) * Math.sin(angle) + (y1 - y2) * Math.cos(angle) + y2,
  ];
}

const points = lines.map(
  el=>el.points.map(p=>rotate([p[0]+el.x, p[1]+el.y],el))
);

const last = (p) => p[p.length-1];
const first = (p) => p[0];
const distance = (p1,p2) => Math.sqrt((p1[0]-p2[0])**2+(p1[1]-p2[1])**2);

const distances = [
	distance(first(points[0]),first(points[1])),
	distance(first(points[0]),last (points[1])),
	distance(last (points[0]),first(points[1])),
	distance(last (points[0]),last (points[1]))
];

const connectDirection = distances.indexOf(Math.min(...distances));

let newPoints = [];
switch(connectDirection) {
	case 0: //first-first
	  newPoints = [...points[0].reverse(),...points[1].slice(1)];
	  break;
	case 1: //first-last
	  newPoints = [...points[0].reverse(),...points[1].reverse().slice(1)];
	  break;	
	case 2: //last-first
	  newPoints = [...points[0],...points[1].slice(1)];
	  break;
  case 3: //last-last
	  newPoints = [...points[0],...points[1].reverse().slice(1)];
	  break;
}

["strokeColor", "backgrounColor", "fillStyle", "roundness", "roughness", "strokeWidth", "strokeStyle", "opacity"].forEach(prop=>{
	ea.style[prop] = lines[1][prop];
})

ea.style.startArrowHead = null;
ea.style.endArrowHead = null;

ea.copyViewElementsToEAforEditing(lines);
ea.getElements().forEach(el=>{el.isDeleted = true});

const lineTypes = parseInt(lines.map(line => line.type === "line" ? '1' : '0').join(''),2);

switch (lineTypes) {
  case 0: //arrow - arrow
    ea.addArrow(
      newPoints,
		  connectDirection === 0 //first-first
		  ? { startArrowHead: lines[0].endArrowhead, endArrowHead: lines[1].endArrowhead }
		  : connectDirection === 1 //first-last
		    ? { startArrowHead: lines[0].endArrowhead, endArrowHead: lines[1].startArrowhead }
		    : connectDirection === 2 //last-first
		      ? { startArrowHead: lines[0].startArrowhead, endArrowHead: lines[1].endArrowhead }
		      //3: last-last
		      : { startArrowHead: lines[0].startArrowhead, endArrowHead: lines[1].startArrowhead }
	  );
    break;
  case 1: //arrow - line
    reverse = connectDirection === 0 || connectDirection === 1;
    ea.addArrow(newPoints,{
      startArrowHead: reverse ? lines[0].endArrowhead : lines[0].startArrowhead,
      endArrowHead: reverse ? lines[0].startArrowhead : lines[0].endArrowhead
    });
    break;
  case 2: //line - arrow
    reverse = connectDirection === 1 || connectDirection === 3;
    ea.addArrow(newPoints,{
      startArrowHead: reverse ? lines[1].endArrowhead : lines[1].startArrowhead,
      endArrowHead: reverse ? lines[1].startArrowhead : lines[1].endArrowhead
    });
    break;
  case 3: //line - line
    ea.addLine(newPoints);
    break;
}


ea.addElementsToView();