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export default function windingLine(
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x0: number, y0: number, x1: number, y1: number, x: number, y: number
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): number {
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if ((y > y0 && y > y1) || (y < y0 && y < y1)) {
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return 0;
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}
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// Ignore horizontal line
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if (y1 === y0) {
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return 0;
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}
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const t = (y - y0) / (y1 - y0);
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let dir = y1 < y0 ? 1 : -1;
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// Avoid winding error when intersection point is the connect point of two line of polygon
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if (t === 1 || t === 0) {
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dir = y1 < y0 ? 0.5 : -0.5;
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}
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const x_ = t * (x1 - x0) + x0;
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// If (x, y) on the line, considered as "contain".
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return x_ === x ? Infinity : x_ > x ? dir : 0;
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}
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