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