| 1 | export default function windingLine(x0, y0, x1, y1, x, y) {
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| 2 | if ((y > y0 && y > y1) || (y < y0 && y < y1)) {
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| 3 | return 0;
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| 4 | }
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| 5 | if (y1 === y0) {
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| 6 | return 0;
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| 7 | }
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| 8 | var t = (y - y0) / (y1 - y0);
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| 9 | var dir = y1 < y0 ? 1 : -1;
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| 10 | if (t === 1 || t === 0) {
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| 11 | dir = y1 < y0 ? 0.5 : -0.5;
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| 12 | }
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| 13 | var x_ = t * (x1 - x0) + x0;
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| 14 | return x_ === x ? Infinity : x_ > x ? dir : 0;
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| 15 | }
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