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// (c) Copyright 2016, Sean Connelly (@voidqk), http://syntheti.cc
// MIT License
// Project Home: https://github.com/voidqk/polybooljs
//
// converts a list of segments into a list of regions, while also removing unnecessary verticies
//
function SegmentChainer(segments, eps, buildLog){
var chains = [];
var regions = [];
segments.forEach(function(seg){
var pt1 = seg.start;
var pt2 = seg.end;
if (eps.pointsSame(pt1, pt2)){
console.warn('PolyBool: Warning: Zero-length segment detected; your epsilon is ' +
'probably too small or too large');
return;
}
if (buildLog)
buildLog.chainStart(seg);
// search for two chains that this segment matches
var first_match = {
index: 0,
matches_head: false,
matches_pt1: false
};
var second_match = {
index: 0,
matches_head: false,
matches_pt1: false
};
var next_match = first_match;
function setMatch(index, matches_head, matches_pt1){
// return true if we've matched twice
next_match.index = index;
next_match.matches_head = matches_head;
next_match.matches_pt1 = matches_pt1;
if (next_match === first_match){
next_match = second_match;
return false;
}
next_match = null;
return true; // we've matched twice, we're done here
}
for (var i = 0; i < chains.length; i++){
var chain = chains[i];
var head = chain[0];
var head2 = chain[1];
var tail = chain[chain.length - 1];
var tail2 = chain[chain.length - 2];
if (eps.pointsSame(head, pt1)){
if (setMatch(i, true, true))
break;
}
else if (eps.pointsSame(head, pt2)){
if (setMatch(i, true, false))
break;
}
else if (eps.pointsSame(tail, pt1)){
if (setMatch(i, false, true))
break;
}
else if (eps.pointsSame(tail, pt2)){
if (setMatch(i, false, false))
break;
}
}
if (next_match === first_match){
// we didn't match anything, so create a new chain
chains.push([ pt1, pt2 ]);
if (buildLog)
buildLog.chainNew(pt1, pt2);
return;
}
if (next_match === second_match){
// we matched a single chain
if (buildLog)
buildLog.chainMatch(first_match.index);
// add the other point to the apporpriate end, and check to see if we've closed the
// chain into a loop
var index = first_match.index;
var pt = first_match.matches_pt1 ? pt2 : pt1; // if we matched pt1, then we add pt2, etc
var addToHead = first_match.matches_head; // if we matched at head, then add to the head
var chain = chains[index];
var grow = addToHead ? chain[0] : chain[chain.length - 1];
var grow2 = addToHead ? chain[1] : chain[chain.length - 2];
var oppo = addToHead ? chain[chain.length - 1] : chain[0];
var oppo2 = addToHead ? chain[chain.length - 2] : chain[1];
if (eps.pointsCollinear(grow2, grow, pt)){
// grow isn't needed because it's directly between grow2 and pt:
// grow2 ---grow---> pt
if (addToHead){
if (buildLog)
buildLog.chainRemoveHead(first_match.index, pt);
chain.shift();
}
else{
if (buildLog)
buildLog.chainRemoveTail(first_match.index, pt);
chain.pop();
}
grow = grow2; // old grow is gone... new grow is what grow2 was
}
if (eps.pointsSame(oppo, pt)){
// we're closing the loop, so remove chain from chains
chains.splice(index, 1);
if (eps.pointsCollinear(oppo2, oppo, grow)){
// oppo isn't needed because it's directly between oppo2 and grow:
// oppo2 ---oppo--->grow
if (addToHead){
if (buildLog)
buildLog.chainRemoveTail(first_match.index, grow);
chain.pop();
}
else{
if (buildLog)
buildLog.chainRemoveHead(first_match.index, grow);
chain.shift();
}
}
if (buildLog)
buildLog.chainClose(first_match.index);
// we have a closed chain!
regions.push(chain);
return;
}
// not closing a loop, so just add it to the apporpriate side
if (addToHead){
if (buildLog)
buildLog.chainAddHead(first_match.index, pt);
chain.unshift(pt);
}
else{
if (buildLog)
buildLog.chainAddTail(first_match.index, pt);
chain.push(pt);
}
return;
}
// otherwise, we matched two chains, so we need to combine those chains together
function reverseChain(index){
if (buildLog)
buildLog.chainReverse(index);
chains[index].reverse(); // gee, that's easy
}
function appendChain(index1, index2){
// index1 gets index2 appended to it, and index2 is removed
var chain1 = chains[index1];
var chain2 = chains[index2];
var tail = chain1[chain1.length - 1];
var tail2 = chain1[chain1.length - 2];
var head = chain2[0];
var head2 = chain2[1];
if (eps.pointsCollinear(tail2, tail, head)){
// tail isn't needed because it's directly between tail2 and head
// tail2 ---tail---> head
if (buildLog)
buildLog.chainRemoveTail(index1, tail);
chain1.pop();
tail = tail2; // old tail is gone... new tail is what tail2 was
}
if (eps.pointsCollinear(tail, head, head2)){
// head isn't needed because it's directly between tail and head2
// tail ---head---> head2
if (buildLog)
buildLog.chainRemoveHead(index2, head);
chain2.shift();
}
if (buildLog)
buildLog.chainJoin(index1, index2);
chains[index1] = chain1.concat(chain2);
chains.splice(index2, 1);
}
var F = first_match.index;
var S = second_match.index;
if (buildLog)
buildLog.chainConnect(F, S);
var reverseF = chains[F].length < chains[S].length; // reverse the shorter chain, if needed
if (first_match.matches_head){
if (second_match.matches_head){
if (reverseF){
// <<<< F <<<< --- >>>> S >>>>
reverseChain(F);
// >>>> F >>>> --- >>>> S >>>>
appendChain(F, S);
}
else{
// <<<< F <<<< --- >>>> S >>>>
reverseChain(S);
// <<<< F <<<< --- <<<< S <<<< logically same as:
// >>>> S >>>> --- >>>> F >>>>
appendChain(S, F);
}
}
else{
// <<<< F <<<< --- <<<< S <<<< logically same as:
// >>>> S >>>> --- >>>> F >>>>
appendChain(S, F);
}
}
else{
if (second_match.matches_head){
// >>>> F >>>> --- >>>> S >>>>
appendChain(F, S);
}
else{
if (reverseF){
// >>>> F >>>> --- <<<< S <<<<
reverseChain(F);
// <<<< F <<<< --- <<<< S <<<< logically same as:
// >>>> S >>>> --- >>>> F >>>>
appendChain(S, F);
}
else{
// >>>> F >>>> --- <<<< S <<<<
reverseChain(S);
// >>>> F >>>> --- >>>> S >>>>
appendChain(F, S);
}
}
}
});
return regions;
}
module.exports = SegmentChainer;
