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stitch.js
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stitch.js
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export default function(topology, arcs) {
var stitchedArcs = {},
fragmentByStart = {},
fragmentByEnd = {},
fragments = [],
emptyIndex = -1;
// Stitch empty arcs first, since they may be subsumed by other arcs.
arcs.forEach(function(i, j) {
var arc = topology.arcs[i < 0 ? ~i : i], t;
if (arc.length < 3 && !arc[1][0] && !arc[1][1]) {
t = arcs[++emptyIndex], arcs[emptyIndex] = i, arcs[j] = t;
}
});
arcs.forEach(function(i) {
var e = ends(i),
start = e[0],
end = e[1],
f, g;
if (f = fragmentByEnd[start]) {
delete fragmentByEnd[f.end];
f.push(i);
f.end = end;
if (g = fragmentByStart[end]) {
delete fragmentByStart[g.start];
var fg = g === f ? f : f.concat(g);
fragmentByStart[fg.start = f.start] = fragmentByEnd[fg.end = g.end] = fg;
} else {
fragmentByStart[f.start] = fragmentByEnd[f.end] = f;
}
} else if (f = fragmentByStart[end]) {
delete fragmentByStart[f.start];
f.unshift(i);
f.start = start;
if (g = fragmentByEnd[start]) {
delete fragmentByEnd[g.end];
var gf = g === f ? f : g.concat(f);
fragmentByStart[gf.start = g.start] = fragmentByEnd[gf.end = f.end] = gf;
} else {
fragmentByStart[f.start] = fragmentByEnd[f.end] = f;
}
} else {
f = [i];
fragmentByStart[f.start = start] = fragmentByEnd[f.end = end] = f;
}
});
function ends(i) {
var arc = topology.arcs[i < 0 ? ~i : i], p0 = arc[0], p1;
if (topology.transform) p1 = [0, 0], arc.forEach(function(dp) { p1[0] += dp[0], p1[1] += dp[1]; });
else p1 = arc[arc.length - 1];
return i < 0 ? [p1, p0] : [p0, p1];
}
function flush(fragmentByEnd, fragmentByStart) {
for (var k in fragmentByEnd) {
var f = fragmentByEnd[k];
delete fragmentByStart[f.start];
delete f.start;
delete f.end;
f.forEach(function(i) { stitchedArcs[i < 0 ? ~i : i] = 1; });
fragments.push(f);
}
}
flush(fragmentByEnd, fragmentByStart);
flush(fragmentByStart, fragmentByEnd);
arcs.forEach(function(i) { if (!stitchedArcs[i < 0 ? ~i : i]) fragments.push([i]); });
return fragments;
}