sweepline-intersections/dist/sweeplineIntersections.cjs

A module to check if a polygon self-intersects using a sweepline algorithm

(function (global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
    typeof define === 'function' && define.amd ? define(factory) :
    (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.sweeplineIntersections = factory());
})(this, (function () { 'use strict';

    var TinyQueue = function TinyQueue(data, compare) {
        if ( data === void 0 ) data = [];
        if ( compare === void 0 ) compare = defaultCompare;

        this.data = data;
        this.length = this.data.length;
        this.compare = compare;

        if (this.length > 0) {
            for (var i = (this.length >> 1) - 1; i >= 0; i--) { this._down(i); }
        }
    };

    TinyQueue.prototype.push = function push (item) {
        this.data.push(item);
        this.length++;
        this._up(this.length - 1);
    };

    TinyQueue.prototype.pop = function pop () {
        if (this.length === 0) { return undefined; }

        var top = this.data[0];
        var bottom = this.data.pop();
        this.length--;

        if (this.length > 0) {
            this.data[0] = bottom;
            this._down(0);
        }

        return top;
    };

    TinyQueue.prototype.peek = function peek () {
        return this.data[0];
    };

    TinyQueue.prototype._up = function _up (pos) {
        var ref = this;
            var data = ref.data;
            var compare = ref.compare;
        var item = data[pos];

        while (pos > 0) {
            var parent = (pos - 1) >> 1;
            var current = data[parent];
            if (compare(item, current) >= 0) { break; }
            data[pos] = current;
            pos = parent;
        }

        data[pos] = item;
    };

    TinyQueue.prototype._down = function _down (pos) {
        var ref = this;
            var data = ref.data;
            var compare = ref.compare;
        var halfLength = this.length >> 1;
        var item = data[pos];

        while (pos < halfLength) {
            var left = (pos << 1) + 1;
            var best = data[left];
            var right = left + 1;

            if (right < this.length && compare(data[right], best) < 0) {
                left = right;
                best = data[right];
            }
            if (compare(best, item) >= 0) { break; }

            data[pos] = best;
            pos = left;
        }

        data[pos] = item;
    };

    function defaultCompare(a, b) {
        return a < b ? -1 : a > b ? 1 : 0;
    }

    function checkWhichEventIsLeft (e1, e2) {
        if (e1.p.x > e2.p.x) { return 1 }
        if (e1.p.x < e2.p.x) { return -1 }

        if (e1.p.x === e2.p.x && (e1.featureId !== e2.featureId || e1.ringId !== e2.ringId)) {
            if (e1.isLeftEndpoint && !e2.isLeftEndpoint) { return -1 }
        }

        if (e1.p.y !== e2.p.y) { return e1.p.y > e2.p.y ? 1 : -1 }
        return 1
    }

    function checkWhichSegmentHasRightEndpointFirst (seg1, seg2) {
        if (seg1.rightSweepEvent.p.x > seg2.rightSweepEvent.p.x) { return 1 }
        if (seg1.rightSweepEvent.p.x < seg2.rightSweepEvent.p.x) { return -1 }

        if (seg1.rightSweepEvent.p.y !== seg2.rightSweepEvent.p.y) {
            return seg1.rightSweepEvent.p.y < seg2.rightSweepEvent.p.y ? 1 : -1
        }
        return 1
    }

    var Event = function Event (p, featureId, ringId, eventId) {
        this.p = {
            x: p[0],
            y: p[1]
        };
        this.featureId = featureId;
        this.ringId = ringId;
        this.eventId = eventId;

        this.otherEvent = null;
        this.isLeftEndpoint = null;
    };

    Event.prototype.isSamePoint = function isSamePoint (eventToCheck) {
        return this.p.x === eventToCheck.p.x && this.p.y === eventToCheck.p.y
    };

    Event.prototype.asNewXY = function asNewXY () {
        return [this.p.x, this.p.y]
    };

    function fillEventQueue (geojson, eventQueue) {
        if (geojson.type === 'FeatureCollection') {
            var features = geojson.features;
            for (var i = 0; i < features.length; i++) {
                processFeature(features[i], eventQueue);
            }
        } else {
            processFeature(geojson, eventQueue);
        }
    }

    var featureId = 0;
    var ringId = 0;
    var eventId = 0;
    function processFeature (featureOrGeometry, eventQueue) {
        var geom = featureOrGeometry.type === 'Feature' ? featureOrGeometry.geometry : featureOrGeometry;
        var coords = geom.coordinates;
        // standardise the input
        if (geom.type === 'Polygon' || geom.type === 'MultiLineString') { coords = [coords]; }
        if (geom.type === 'LineString') { coords = [[coords]]; }

        for (var i = 0; i < coords.length; i++) {
            for (var ii = 0; ii < coords[i].length; ii++) {
                var currentP = coords[i][ii][0];
                var nextP = null;
                ringId = ringId + 1;
                for (var iii = 0; iii < coords[i][ii].length - 1; iii++) {
                    nextP = coords[i][ii][iii + 1];

                    var e1 = new Event(currentP, featureId, ringId, eventId);
                    var e2 = new Event(nextP, featureId, ringId, eventId + 1);

                    e1.otherEvent = e2;
                    e2.otherEvent = e1;

                    if (checkWhichEventIsLeft(e1, e2) > 0) {
                        e2.isLeftEndpoint = true;
                        e1.isLeftEndpoint = false;
                    } else {
                        e1.isLeftEndpoint = true;
                        e2.isLeftEndpoint = false;
                    }
                    eventQueue.push(e1);
                    eventQueue.push(e2);

                    currentP = nextP;
                    eventId = eventId + 1;
                }
            }
        }
        featureId = featureId + 1;
    }

    var Segment = function Segment (event) {
        this.leftSweepEvent = event;
        this.rightSweepEvent = event.otherEvent;
    };

    var epsilon = 1.1102230246251565e-16;
    var splitter = 134217729;
    var resulterrbound = (3 + 8 * epsilon) * epsilon;

    // fast_expansion_sum_zeroelim routine from oritinal code
    function sum(elen, e, flen, f, h) {
        var Q, Qnew, hh, bvirt;
        var enow = e[0];
        var fnow = f[0];
        var eindex = 0;
        var findex = 0;
        if ((fnow > enow) === (fnow > -enow)) {
            Q = enow;
            enow = e[++eindex];
        } else {
            Q = fnow;
            fnow = f[++findex];
        }
        var hindex = 0;
        if (eindex < elen && findex < flen) {
            if ((fnow > enow) === (fnow > -enow)) {
                Qnew = enow + Q;
                hh = Q - (Qnew - enow);
                enow = e[++eindex];
            } else {
                Qnew = fnow + Q;
                hh = Q - (Qnew - fnow);
                fnow = f[++findex];
            }
            Q = Qnew;
            if (hh !== 0) {
                h[hindex++] = hh;
            }
            while (eindex < elen && findex < flen) {
                if ((fnow > enow) === (fnow > -enow)) {
                    Qnew = Q + enow;
                    bvirt = Qnew - Q;
                    hh = Q - (Qnew - bvirt) + (enow - bvirt);
                    enow = e[++eindex];
                } else {
                    Qnew = Q + fnow;
                    bvirt = Qnew - Q;
                    hh = Q - (Qnew - bvirt) + (fnow - bvirt);
                    fnow = f[++findex];
                }
                Q = Qnew;
                if (hh !== 0) {
                    h[hindex++] = hh;
                }
            }
        }
        while (eindex < elen) {
            Qnew = Q + enow;
            bvirt = Qnew - Q;
            hh = Q - (Qnew - bvirt) + (enow - bvirt);
            enow = e[++eindex];
            Q = Qnew;
            if (hh !== 0) {
                h[hindex++] = hh;
            }
        }
        while (findex < flen) {
            Qnew = Q + fnow;
            bvirt = Qnew - Q;
            hh = Q - (Qnew - bvirt) + (fnow - bvirt);
            fnow = f[++findex];
            Q = Qnew;
            if (hh !== 0) {
                h[hindex++] = hh;
            }
        }
        if (Q !== 0 || hindex === 0) {
            h[hindex++] = Q;
        }
        return hindex;
    }

    function estimate(elen, e) {
        var Q = e[0];
        for (var i = 1; i < elen; i++) { Q += e[i]; }
        return Q;
    }

    function vec(n) {
        return new Float64Array(n);
    }

    var ccwerrboundA = (3 + 16 * epsilon) * epsilon;
    var ccwerrboundB = (2 + 12 * epsilon) * epsilon;
    var ccwerrboundC = (9 + 64 * epsilon) * epsilon * epsilon;

    var B = vec(4);
    var C1 = vec(8);
    var C2 = vec(12);
    var D = vec(16);
    var u = vec(4);

    function orient2dadapt(ax, ay, bx, by, cx, cy, detsum) {
        var acxtail, acytail, bcxtail, bcytail;
        var bvirt, c, ahi, alo, bhi, blo, _i, _j, _0, s1, s0, t1, t0, u3;

        var acx = ax - cx;
        var bcx = bx - cx;
        var acy = ay - cy;
        var bcy = by - cy;

        s1 = acx * bcy;
        c = splitter * acx;
        ahi = c - (c - acx);
        alo = acx - ahi;
        c = splitter * bcy;
        bhi = c - (c - bcy);
        blo = bcy - bhi;
        s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
        t1 = acy * bcx;
        c = splitter * acy;
        ahi = c - (c - acy);
        alo = acy - ahi;
        c = splitter * bcx;
        bhi = c - (c - bcx);
        blo = bcx - bhi;
        t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
        _i = s0 - t0;
        bvirt = s0 - _i;
        B[0] = s0 - (_i + bvirt) + (bvirt - t0);
        _j = s1 + _i;
        bvirt = _j - s1;
        _0 = s1 - (_j - bvirt) + (_i - bvirt);
        _i = _0 - t1;
        bvirt = _0 - _i;
        B[1] = _0 - (_i + bvirt) + (bvirt - t1);
        u3 = _j + _i;
        bvirt = u3 - _j;
        B[2] = _j - (u3 - bvirt) + (_i - bvirt);
        B[3] = u3;

        var det = estimate(4, B);
        var errbound = ccwerrboundB * detsum;
        if (det >= errbound || -det >= errbound) {
            return det;
        }

        bvirt = ax - acx;
        acxtail = ax - (acx + bvirt) + (bvirt - cx);
        bvirt = bx - bcx;
        bcxtail = bx - (bcx + bvirt) + (bvirt - cx);
        bvirt = ay - acy;
        acytail = ay - (acy + bvirt) + (bvirt - cy);
        bvirt = by - bcy;
        bcytail = by - (bcy + bvirt) + (bvirt - cy);

        if (acxtail === 0 && acytail === 0 && bcxtail === 0 && bcytail === 0) {
            return det;
        }

        errbound = ccwerrboundC * detsum + resulterrbound * Math.abs(det);
        det += (acx * bcytail + bcy * acxtail) - (acy * bcxtail + bcx * acytail);
        if (det >= errbound || -det >= errbound) { return det; }

        s1 = acxtail * bcy;
        c = splitter * acxtail;
        ahi = c - (c - acxtail);
        alo = acxtail - ahi;
        c = splitter * bcy;
        bhi = c - (c - bcy);
        blo = bcy - bhi;
        s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
        t1 = acytail * bcx;
        c = splitter * acytail;
        ahi = c - (c - acytail);
        alo = acytail - ahi;
        c = splitter * bcx;
        bhi = c - (c - bcx);
        blo = bcx - bhi;
        t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
        _i = s0 - t0;
        bvirt = s0 - _i;
        u[0] = s0 - (_i + bvirt) + (bvirt - t0);
        _j = s1 + _i;
        bvirt = _j - s1;
        _0 = s1 - (_j - bvirt) + (_i - bvirt);
        _i = _0 - t1;
        bvirt = _0 - _i;
        u[1] = _0 - (_i + bvirt) + (bvirt - t1);
        u3 = _j + _i;
        bvirt = u3 - _j;
        u[2] = _j - (u3 - bvirt) + (_i - bvirt);
        u[3] = u3;
        var C1len = sum(4, B, 4, u, C1);

        s1 = acx * bcytail;
        c = splitter * acx;
        ahi = c - (c - acx);
        alo = acx - ahi;
        c = splitter * bcytail;
        bhi = c - (c - bcytail);
        blo = bcytail - bhi;
        s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
        t1 = acy * bcxtail;
        c = splitter * acy;
        ahi = c - (c - acy);
        alo = acy - ahi;
        c = splitter * bcxtail;
        bhi = c - (c - bcxtail);
        blo = bcxtail - bhi;
        t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
        _i = s0 - t0;
        bvirt = s0 - _i;
        u[0] = s0 - (_i + bvirt) + (bvirt - t0);
        _j = s1 + _i;
        bvirt = _j - s1;
        _0 = s1 - (_j - bvirt) + (_i - bvirt);
        _i = _0 - t1;
        bvirt = _0 - _i;
        u[1] = _0 - (_i + bvirt) + (bvirt - t1);
        u3 = _j + _i;
        bvirt = u3 - _j;
        u[2] = _j - (u3 - bvirt) + (_i - bvirt);
        u[3] = u3;
        var C2len = sum(C1len, C1, 4, u, C2);

        s1 = acxtail * bcytail;
        c = splitter * acxtail;
        ahi = c - (c - acxtail);
        alo = acxtail - ahi;
        c = splitter * bcytail;
        bhi = c - (c - bcytail);
        blo = bcytail - bhi;
        s0 = alo * blo - (s1 - ahi * bhi - alo * bhi - ahi * blo);
        t1 = acytail * bcxtail;
        c = splitter * acytail;
        ahi = c - (c - acytail);
        alo = acytail - ahi;
        c = splitter * bcxtail;
        bhi = c - (c - bcxtail);
        blo = bcxtail - bhi;
        t0 = alo * blo - (t1 - ahi * bhi - alo * bhi - ahi * blo);
        _i = s0 - t0;
        bvirt = s0 - _i;
        u[0] = s0 - (_i + bvirt) + (bvirt - t0);
        _j = s1 + _i;
        bvirt = _j - s1;
        _0 = s1 - (_j - bvirt) + (_i - bvirt);
        _i = _0 - t1;
        bvirt = _0 - _i;
        u[1] = _0 - (_i + bvirt) + (bvirt - t1);
        u3 = _j + _i;
        bvirt = u3 - _j;
        u[2] = _j - (u3 - bvirt) + (_i - bvirt);
        u[3] = u3;
        var Dlen = sum(C2len, C2, 4, u, D);

        return D[Dlen - 1];
    }

    function orient2d(ax, ay, bx, by, cx, cy) {
        var detleft = (ay - cy) * (bx - cx);
        var detright = (ax - cx) * (by - cy);
        var det = detleft - detright;

        if (detleft === 0 || detright === 0 || (detleft > 0) !== (detright > 0)) { return det; }

        var detsum = Math.abs(detleft + detright);
        if (Math.abs(det) >= ccwerrboundA * detsum) { return det; }

        return -orient2dadapt(ax, ay, bx, by, cx, cy, detsum);
    }

    function testSegmentIntersect (seg1, seg2) {
        if (seg1 === null || seg2 === null) { return false }

        var x1 = seg1.leftSweepEvent.p.x;
        var y1 = seg1.leftSweepEvent.p.y;
        var x2 = seg1.rightSweepEvent.p.x;
        var y2 = seg1.rightSweepEvent.p.y;
        var x3 = seg2.leftSweepEvent.p.x;
        var y3 = seg2.leftSweepEvent.p.y;
        var x4 = seg2.rightSweepEvent.p.x;
        var y4 = seg2.rightSweepEvent.p.y;

        var score1 = orient2d(x1, y1, x2, y2, x3, y3);
        var score2 = orient2d(x1, y1, x2, y2, x4, y4);

        if (score1 > 0 && score2 > 0) { return false }
        else if (score1 < 0 && score2 < 0) { return false }

        if (seg1.leftSweepEvent.ringId === seg2.leftSweepEvent.ringId) {
            if (
                seg1.rightSweepEvent.isSamePoint(seg2.leftSweepEvent) ||
                seg1.rightSweepEvent.isSamePoint(seg2.rightSweepEvent) ||
                seg1.leftSweepEvent.isSamePoint(seg2.leftSweepEvent) ||
                seg1.leftSweepEvent.isSamePoint(seg2.rightSweepEvent)
            ) { return false }
        } else {
            if (seg1.rightSweepEvent.isSamePoint(seg2.leftSweepEvent)) { return seg2.leftSweepEvent.asNewXY() }
            if (seg1.rightSweepEvent.isSamePoint(seg2.rightSweepEvent)) { return seg2.rightSweepEvent.asNewXY() }
            if (seg1.leftSweepEvent.isSamePoint(seg2.leftSweepEvent)) { return seg2.leftSweepEvent.asNewXY() }
            if (seg1.leftSweepEvent.isSamePoint(seg2.rightSweepEvent)) { return seg2.rightSweepEvent.asNewXY() }
        }


        var denom = ((y4 - y3) * (x2 - x1)) - ((x4 - x3) * (y2 - y1));
        var numeA = ((x4 - x3) * (y1 - y3)) - ((y4 - y3) * (x1 - x3));
        var numeB = ((x2 - x1) * (y1 - y3)) - ((y2 - y1) * (x1 - x3));

        if (denom === 0) {
            if (numeA === 0 && numeB === 0) { return false }
            return false
        }

        var uA = numeA / denom;
        var uB = numeB / denom;

        if (uA >= 0 && uA <= 1 && uB >= 0 && uB <= 1) {
            var x = x1 + (uA * (x2 - x1));
            var y = y1 + (uA * (y2 - y1));
            return [x, y]
        }
        return false
    }

    // import {debugEventAndSegments, debugRemovingSegment} from './debug'

    function runCheck (eventQueue, ignoreSelfIntersections) {
        ignoreSelfIntersections = ignoreSelfIntersections ? ignoreSelfIntersections : false;

        var intersectionPoints = [];
        var outQueue = new TinyQueue([], checkWhichSegmentHasRightEndpointFirst);

        while (eventQueue.length) {
            var event = eventQueue.pop();
            if (event.isLeftEndpoint) {
                // debugEventAndSegments(event.p, outQueue.data)
                var segment = new Segment(event);
                for (var i = 0; i < outQueue.data.length; i++) {
                    var otherSeg = outQueue.data[i];
                    if (ignoreSelfIntersections) {
                        if (otherSeg.leftSweepEvent.featureId === event.featureId) { continue }
                    }
                    var intersection = testSegmentIntersect(segment, otherSeg);
                    if (intersection !== false) { intersectionPoints.push(intersection); }
                }
                outQueue.push(segment);
            } else if (event.isLeftEndpoint === false) {
                outQueue.pop();
                // const seg = outQueue.pop()
                // debugRemovingSegment(event.p, seg)
            }
        }
        return intersectionPoints
    }

    function sweeplineIntersections (geojson, ignoreSelfIntersections) {
        var eventQueue = new TinyQueue([], checkWhichEventIsLeft);
        fillEventQueue(geojson, eventQueue);
        return runCheck(eventQueue, ignoreSelfIntersections)
    }

    return sweeplineIntersections;

}));