"use strict";

module.exports = earcut;
module.exports.default = earcut;


function earcut(data, holeIndices, dim) {
//    console.log("earcut " + data.length + "," + holeIndices + "," + dim);
    dim = dim || 2;

    var hasHoles = holeIndices && holeIndices.length,
        outerLen = hasHoles ? holeIndices[0] * dim : data.length,
        outerNode = linkedList(data, 0, outerLen, dim, true),
        triangles = [];

    if (!outerNode) return triangles;

    var minX, minY, maxX, maxY, x, y, invSize;

    if (hasHoles) outerNode = eliminateHoles(data, holeIndices, outerNode, dim);

    // if the shape is not too simple, we"ll use z-order curve hash later; calculate polygon bbox
    if (data.length > 80 * dim) {
        minX = maxX = data[0];
        minY = maxY = data[1];

        for (var i = dim; i < outerLen; i += dim) {
            x = data[i];
            y = data[i + 1];
            if (x < minX) minX = x;
            if (y < minY) minY = y;
            if (x > maxX) maxX = x;
            if (y > maxY) maxY = y;
        }

        // minX, minY and invSize are later used to transform coords into integers for z-order calculation
        invSize = Math.max(maxX - minX, maxY - minY);
        invSize = invSize !== 0 ? 1 / invSize : 0;
    }

    earcutLinked(outerNode, triangles, dim, minX, minY, invSize);

    return triangles;
}

// create a circular doubly linked list from polygon points in the specified winding order
function linkedList(data, start, end, dim, clockwise) {
//    console.log("llist" + data.length + "," + start.i + "," + end.i + "," + dim + "," + clockwise);
    var i, last;

    if (clockwise === (signedArea(data, start, end, dim) > 0)) {
        for (i = start; i < end; i += dim)
			last = insertNode(i, data[i], data[i + 1], last);
    } else {
        for (i = end - dim; i >= start; i -= dim)
			last = insertNode(i, data[i], data[i + 1], last);
    }

    if (last && equals(last, last.next)) {
        removeNode(last);
        last = last.next;
    }

    return last;
}

// eliminate colinear or duplicate points
function filterPoints(start, end) {
    if (!start) return start;
    if (!end) end = start;
//    console.log("filterpoints points " + start.i + "," + end.i);

    var p = start,
        again;
    do {
        again = false;

        if (!p.steiner && (equals(p, p.next) || area(p.prev, p, p.next) === 0)) {
            removeNode(p);
            p = end = p.prev;
            if (p === p.next) break;
            again = true;

        } else {
            p = p.next;
        }
    } while (again || p !== end);

//    console.log("filter points end", end.i);
    return end;
}

/* main ear slicing loop which triangulates a polygon (given as a linked list).
nodes are removed from the linked list as the triangles are added.
*/
function earcutLinked(ear, triangles, dim, minX, minY, invSize, pass) {
//    console.log("earcutlinked: ear.i:", ear.i, "pass:", pass);
    //",",dim,minX,minY,invSize,pass);
    if (!ear) return;

    // interlink polygon nodes in z-order
    if (!pass && invSize) indexCurve(ear, minX, minY, invSize);

    var stop = ear,
        prev, next;

    // iterate through ears, slicing them one by one
    while (ear.prev !== ear.next) {
        prev = ear.prev;
        next = ear.next;

        if (invSize ? isEarHashed(ear, minX, minY, invSize) : isEar(ear)) {
            // cut off the triangle
            triangles.push(prev.i / dim);
            triangles.push(ear.i / dim);
            triangles.push(next.i / dim);

            //			console.log("earcutlinked beg removeNode ear.i:",ear.i," cyclen:",cycle_len(ear));
            removeNode(ear);

            // skipping the next vertex leads to less sliver triangles
            ear = next.next;
            stop = next.next;

            //			console.log("earcutlinked end removeNode ear.i:",ear.i," cyclen:",cycle_len(ear));
            continue;
        }

        /*
4:earcutlinked beg remove_node ear.i 1454 cyclen 1339
4:earcutlinked end remove_node ear.i 1450 cyclen 1338
4:earcutlinked beg remove_node ear.i 1448 cyclen 1338 << vi 327,n328,nn1323
4:earcutlinked end remove_node ear.i 2674 cyclen 1337 <<<<< vi i p n vi:1323
4:earcutlinked beg remove_node ear.i 2674 cyclen 1337
4:earcutlinked end remove_node ear.i 2670 cyclen 1336
4:earcutlinked beg remove_node ear.i 2660 cyclen 1336
4:earcutlinked end remove_node ear.i 2656 cyclen 1335
4:earcutlinked beg remove_node ear.i 1446 cyclen 1335
4:earcutlinked end remove_node ear.i 1442 cyclen 1334
b 1454 1339 --
e 1450 1338 --
b 1448 1338 --
e 1444 1337 xx <<<<<<<<< s/b vi 329
b 2660 1337 xx
e 2656 1336 xx
b 1440 1336
e 1436 1335
b 1434 1335
e 1430 1334
		*/

        ear = next;

        // if we looped through the whole remaining polygon and can"t find any more ears
        if (ear === stop) {
            // try filtering points and slicing again
            if (!pass) {
                earcutLinked(filterPoints(ear), triangles, dim, minX, minY, invSize, 1);

                // if this didn"t work, try curing all small self-intersections locally
            } else if (pass === 1) {
                ear = cureLocalIntersections(ear, triangles, dim);
                earcutLinked(ear, triangles, dim, minX, minY, invSize, 2);

                // as a last resort, try splitting the remaining polygon into two
            } else if (pass === 2) {
                splitEarcut(ear, triangles, dim, minX, minY, invSize);
            }

            break;
        }
    }
}

// check whether a polygon node forms a valid ear with adjacent nodes
function isEar(ear) {
    //	console.log("isear"+ear);
    var a = ear.prev,
        b = ear,
        c = ear.next;

    if (area(a, b, c) >= 0) return false; // reflex, can"t be an ear

    // now make sure we don"t have other points inside the potential ear
    var p = ear.next.next;

    while (p !== ear.prev) {
        if (pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
            area(p.prev, p, p.next) >= 0) return false;
        p = p.next;
    }

    return true;
}

function isEarHashed(ear, minX, minY, invSize) {
    //console.log("isearhashed",ear.i,minX,minY,invSize);
    var a = ear.prev,
        b = ear,
        c = ear.next;

    if (area(a, b, c) >= 0) return false; // reflex, can"t be an ear

    // triangle bbox; min & max are calculated like this for speed
    var minTX = a.x < b.x ? (a.x < c.x ? a.x : c.x) : (b.x < c.x ? b.x : c.x),
        minTY = a.y < b.y ? (a.y < c.y ? a.y : c.y) : (b.y < c.y ? b.y : c.y),
        maxTX = a.x > b.x ? (a.x > c.x ? a.x : c.x) : (b.x > c.x ? b.x : c.x),
        maxTY = a.y > b.y ? (a.y > c.y ? a.y : c.y) : (b.y > c.y ? b.y : c.y);

    // z-order range for the current triangle bbox;
    var minZ = zOrder(minTX, minTY, minX, minY, invSize),
        maxZ = zOrder(maxTX, maxTY, minX, minY, invSize);

    var p = ear.prevZ,
        n = ear.nextZ;

    // look for points inside the triangle in both directions
    while (p && p.z >= minZ && n && n.z <= maxZ) {
        if (p !== ear.prev && p !== ear.next &&
            pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
            area(p.prev, p, p.next) >= 0) return false;
        p = p.prevZ;

        if (n !== ear.prev && n !== ear.next &&
            pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, n.x, n.y) &&
            area(n.prev, n, n.next) >= 0) return false;
        n = n.nextZ;
    }

    // look for remaining points in decreasing z-order
    while (p && p.z >= minZ) {
        if (p !== ear.prev && p !== ear.next &&
            pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) &&
            area(p.prev, p, p.next) >= 0) return false;
        p = p.prevZ;
    }

    // look for remaining points in increasing z-order
    while (n && n.z <= maxZ) {
        if (n !== ear.prev && n !== ear.next &&
            pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, n.x, n.y) &&
            area(n.prev, n, n.next) >= 0) return false;
        n = n.nextZ;
    }

    return true;
}

// go through all polygon nodes and cure small local self-intersections
function cureLocalIntersections(start, triangles, dim) {
    console.log("cure local intersections i" + start.i + "," + triangles + "," + dim);
    var p = start;
    do {
        var a = p.prev,
            b = p.next.next;

        if (!equals(a, b) && intersects(a, p, p.next, b) && locallyInside(a, b) && locallyInside(b, a)) {

            triangles.push(a.i / dim);
            triangles.push(p.i / dim);
            triangles.push(b.i / dim);

            // remove two nodes involved
            removeNode(p);
            removeNode(p.next);

            p = start = b;
        }
        p = p.next;
    } while (p !== start);

    return p;
}

// try splitting polygon into two and triangulate them independently
function splitEarcut(start, triangles, dim, minX, minY, invSize) {
//    console.log("split ear cut i:" + start.i);
    // look for a valid diagonal that divides the polygon into two
    var a = start;
    do {
        var b = a.next.next;
//        console.log("splitearcut loop is:", a.i, ",", b.i);
        while (b !== a.prev) {
  //          console.log("splitearcut mloop", a.i, b.i, isValidDiagonal(a, b));
            if (a.i !== b.i && isValidDiagonal(a, b)) {
//                console.log("splitear inner loop ai bi", a.i, b.i);
                // split the polygon in two by the diagonal
                var c = splitPolygon(a, b);

                // filter colinear points around the cuts
                a = filterPoints(a, a.next);
                c = filterPoints(c, c.next);

                // run earcut on each half
                earcutLinked(a, triangles, dim, minX, minY, invSize);
                earcutLinked(c, triangles, dim, minX, minY, invSize);
                return;
            }
            b = b.next;
        }
        a = a.next;
    } while (a !== start);
}

function cycle_len(node) {
    var start = node;
    var a = start;
    var count = 0;
    var s1 = a.i;
    var s2 = -1;
    do {
        count += 1;
        s2 = a.i;
        a = a.next;
    } while (a != start);
    return count;
}

// https://www.cs.hmc.edu/~geoff/classes/hmc.cs070.200101/homework10/hashfuncs.html
// https://stackoverflow.com/questions/1908492/unsigned-integer-in-javascript
function horsh(h,n) {
     var highorder = h>>>0 & 0xf8000000 >>>0  ;  // extract high-order 5 bits from h
//	console.log("horsh a",h>>>0," ",n>>>0);
                                   // 0xf8000000 is the hexadecimal representation
                                   //   for the 32-bit number with the first five 
                                   //   bits = 1 and the other bits = 0   
     h = h << 5               ; // shift h left by 5 bits
//	console.log("horsh b",h>>>0," ",n>>>0);
     h = h ^ ( highorder >>> 27)  ;  // move the highorder 5 bits to the low-order
                                   //   end and XOR into h
//	console.log("horsh c",h>>>0," ",n>>>0);
     h = h ^ n                ;  // XOR h and ki
//	console.log("horsh d",h>>>0," ",n>>>0);
    return h >>>0;
}

function llhorsh(node) {
    var start = node;
    var a = start;
    var count = 0;
    var s1 = a.i;
    var s2 = -1;
	var state = 0;
    do {
		state = horsh(state,a.i);
        count += 1;
        a = a.next;
    } while (a != start);
    return "horshcount:"+count+" horsh:"+state;
}

function dumpnodes(node) {
    var start = node;
    var a = start;
    var count = 0;
    var s1 = a.i;
    var s2 = -1;
	var state = 0;
    do {
		state = horsh(state,a.i);
//        console.log(count, a.i, a.prev.i, a.next.i, a.x, a.y, a.steiner);
        count += 1;
        a = a.next;
    } while (a != start);
//    console.log("ll dump end. horsh: ",state);
}

function dumplist(node) {
    var start = node;
    var a = start;
    var count = 0;
    var s1 = a.i;
    var s2 = -1;
    do {
        count += 1;
        s2 = a.i;
        a = a.next;
    } while (a != start);
//    console.log("ll count:", count, " 1sti:", s1, " lasti:", s2);
}

// link every hole into the outer loop, producing a single-ring polygon without holes
function eliminateHoles(data, holeIndices, outerNode, dim) {
//    console.log("eliminateHoles", data, holeIndices, outerNode, dim);
    var queue = [],
        i, len, start, end, list;

    for (i = 0, len = holeIndices.length; i < len; i++) {
        start = holeIndices[i] * dim;
        end = i < len - 1 ? holeIndices[i + 1] * dim : data.length;
        list = linkedList(data, start, end, dim, false);
        if (list === list.next) list.steiner = true;
        queue.push(getLeftmost(list));
    }

    queue.sort(compareX);

    // process holes from left to right
    for (i = 0; i < queue.length; i++) {
//        console.log("eliminating hole begin, " + i + " of " + queue.length, "outerNode.i", outerNode.i, " cyclelen", cycle_len(outerNode),llhorsh( outerNode) );
        eliminateHole(queue[i], outerNode);
//        console.log("eliminating hole end,   " + i + " of " + queue.length, "outerNode.i", outerNode.i, " cyclelen", cycle_len(outerNode), llhorsh( outerNode) );
        outerNode = filterPoints(outerNode, outerNode.next);
    }

    return outerNode;
}

function compareX(a, b) {
    return a.x - b.x;
}

// find a bridge between vertices that connects hole with an outer ring and and link it
function eliminateHole(hole, outerNode) {
//    console.log("eliminateHole", hole.i, outerNode.i);
    outerNode = findHoleBridge(hole, outerNode);
    if (outerNode) {
        var b = splitPolygon(outerNode, hole);
        filterPoints(b, b.next);
    }
}

// David Eberly"s algorithm for finding a bridge between hole and outer
// polygon
function findHoleBridge(hole, outerNode) {
//    console.log("findholebridge", hole.i, outerNode.i);
    var p = outerNode,
        hx = hole.x,
        hy = hole.y,
        qx = -Infinity,
        m;

    // find a segment intersected by a ray from the hole"s leftmost point to the left;
    // segment"s endpoint with lesser x will be potential connection point
    do {
        if (hy <= p.y &&
            hy >= p.next.y &&
            p.next.y !== p.y) {
            var x = p.x + (hy - p.y) * (p.next.x - p.x) / (p.next.y - p.y);
            if (x <= hx && x > qx) {
                qx = x;
                if (x === hx) {
                    if (hy === p.y) return p;
                    if (hy === p.next.y) return p.next;
                }
                m = p.x < p.next.x ? p : p.next;
            }
        }
        p = p.next;
    } while (p !== outerNode);

//	console.log("fhb p",p.i,"hx",hx,"hy",hy,"qx",qx,"m",m.i);

    if (!m) return null;

    if (hx === qx) return m.prev; // hole touches outer segment; pick lower endpoint

    // look for points inside the triangle of hole point, segment intersection and endpoint;
    // if there are no points found, we have a valid connection;
    // otherwise choose the point of the minimum angle with the ray as connection point

    var stop = m,
        mx = m.x,
        my = m.y,
        tanMin = Infinity,
        tan;

    p = m.next;


    while (p !== stop) {

        var x1 = hy < my ? hx : qx;
        var x2 = hy < my ? qx : hx;

        if (
            (hx >= p.x) &&
            (p.x >= mx) &&
            (hx !== p.x) &&
            pointInTriangle(
                x1,
                hy,
                mx,
                my,
                x2,
                hy,
                p.x,
                p.y)) {

            tan = Math.abs(hy - p.y) / (hx - p.x); // tangential
            if ((tan < tanMin || (tan === tanMin && p.x > m.x)) &&
                locallyInside(p, hole)) {
                m = p;
                tanMin = tan;
            }
        }

        p = p.next;
    }


    return m;
}

// interlink polygon nodes in z-order
function indexCurve(start, minX, minY, invSize) {
//    console.log("indexcurve", start, minX, minY, invSize);
    var p = start;
    do {
        if (p.z === null) p.z = zOrder(p.x, p.y, minX, minY, invSize);
        p.prevZ = p.prev;
        p.nextZ = p.next;
        p = p.next;
    } while (p !== start);

    p.prevZ.nextZ = null;
    p.prevZ = null;

    sortLinked(p);
}

// Simon Tatham"s linked list merge sort algorithm
// http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
function sortLinked(list) {
//    console.log("sortlinked", list);
    var i, p, q, e, tail, numMerges, pSize, qSize,
        inSize = 1;

    do {
        p = list;
        list = null;
        tail = null;
        numMerges = 0;

        while (p) {
            numMerges++;
            q = p;
            pSize = 0;
            for (i = 0; i < inSize; i++) {
                pSize++;
                q = q.nextZ;
                if (!q) break;
            }
            qSize = inSize;

            while (pSize > 0 || (qSize > 0 && q)) {

                if (pSize !== 0 && (qSize === 0 || !q || p.z <= q.z)) {
                    e = p;
                    p = p.nextZ;
                    pSize--;
                } else {
                    e = q;
                    q = q.nextZ;
                    qSize--;
                }

                if (tail) tail.nextZ = e;
                else list = e;

                e.prevZ = tail;
                tail = e;
            }

            p = q;
        }

        tail.nextZ = null;
        inSize *= 2;

    } while (numMerges > 1);

    return list;
}

// z-order of a point given coords and inverse of the longer side of data bbox
function zOrder(x, y, minX, minY, invSize) {
    //console.log("zorder",x,y);
    // coords are transformed into non-negative 15-bit integer range
    x = 32767 * (x - minX) * invSize;
    y = 32767 * (y - minY) * invSize;

    x = (x | (x << 8)) & 0x00FF00FF;
    x = (x | (x << 4)) & 0x0F0F0F0F;
    x = (x | (x << 2)) & 0x33333333;
    x = (x | (x << 1)) & 0x55555555;

    y = (y | (y << 8)) & 0x00FF00FF;
    y = (y | (y << 4)) & 0x0F0F0F0F;
    y = (y | (y << 2)) & 0x33333333;
    y = (y | (y << 1)) & 0x55555555;

    return x | (y << 1);
}

// find the leftmost node of a polygon ring
function getLeftmost(start) {
//    console.log("getleftmost ", start.i);
    var p = start,
        leftmost = start;
    do {
        if (p.x < leftmost.x) leftmost = p;
        p = p.next;
    } while (p !== start);

    return leftmost;
}

// check if a point lies within a convex triangle
function pointInTriangle(ax, ay, bx, by, cx, cy, px, py) {
    //console.log("point in tri",ax,ay,bx,by,cx,cy,px,py);
    return (cx - px) * (ay - py) - (ax - px) * (cy - py) >= 0 &&
        (ax - px) * (by - py) - (bx - px) * (ay - py) >= 0 &&
        (bx - px) * (cy - py) - (cx - px) * (by - py) >= 0;
}

// check if a diagonal between two polygon nodes is valid (lies in polygon interior)
function isValidDiagonal(a, b) {

//    console.log("is-valid-diagonal a.i b.i !ip li li mi ", a.i, b.i, !intersectsPolygon(a, b), locallyInside(a, b), locallyInside(b, a), middleInside(a, b));

    return a.next.i !== b.i &&
        a.prev.i !== b.i &&
        !intersectsPolygon(a, b) &&
        locallyInside(a, b) &&
        locallyInside(b, a) &&
        middleInside(a, b);
}

// signed area of a triangle
function area(p, q, r) {
    //	console.log("area",p,q,r);
    return (q.y - p.y) * (r.x - q.x) - (q.x - p.x) * (r.y - q.y);
}

// check if two points are equal
function equals(p1, p2) {
    return p1.x === p2.x && p1.y === p2.y;
}

// check if two segments intersect p1-q1  p2-q2
function intersects(p1, q1, p2, q2) {
    //	console.log("intersects",p1,q1,p2,q1);
    if ((equals(p1, p2) && equals(q1, q2)) ||
        (equals(p1, q2) && equals(q1, p2))) return true;
    return area(p1, q1, p2) > 0 !== area(p1, q1, q2) > 0 &&
        area(p2, q2, p1) > 0 !== area(p2, q2, q1) > 0;
}

// check if a polygon diagonal intersects any polygon segments
function intersectsPolygon(a, b) {
    //	console.log("intersectsPolygon",a,b);
    var p = a;
    do {
//        console.log("intersectsPolygon isect?", p.i, p.next.i, a.i, b.i, intersects(p, p.next, a, b));
        if (p.i !== a.i &&
            p.next.i !== a.i &&
            p.i !== b.i &&
            p.next.i !== b.i &&
            intersects(p, p.next, a, b)) {
            return true;
        }
        p = p.next;
    } while (p !== a);

    return false;
}

// check if a polygon diagonal is locally inside the polygon
function locallyInside(a, b) {
    //	console.log("locallyInside",a,b);
    return area(a.prev, a, a.next) < 0 ?
        area(a, b, a.next) >= 0 && area(a, a.prev, b) >= 0 :
        area(a, b, a.prev) < 0 || area(a, a.next, b) < 0;
}

// check if the middle point of a polygon diagonal is inside the polygon
function middleInside(a, b) {
    //	console.log("middleInside",a,b);
    var p = a,
        inside = false,
        px = (a.x + b.x) / 2,
        py = (a.y + b.y) / 2;
    do {
        if (((p.y > py) !== (p.next.y > py)) && p.next.y !== p.y &&
            (px < (p.next.x - p.x) * (py - p.y) / (p.next.y - p.y) + p.x))
            inside = !inside;
        p = p.next;
    } while (p !== a);

    return inside;
}

// link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits polygon into two;
// if one belongs to the outer ring and another to a hole, it merges it into a single ring
function splitPolygon(a, b) {
//    console.log("splitPolygon", a.i, b.i);
    var a2 = new Node(a.i, a.x, a.y),
        b2 = new Node(b.i, b.x, b.y),
        an = a.next,
        bp = b.prev;

    a.next = b;
    b.prev = a;

    a2.next = an;
    an.prev = a2;

    b2.next = a2;
    a2.prev = b2;

    bp.next = b2;
    b2.prev = bp;

    return b2;
}

// create a node and optionally link it with previous one (in a circular doubly linked list)
function insertNode(i, x, y, last) {
    var p = new Node(i, x, y);

    if (!last) {
        p.prev = p;
        p.next = p;

    } else {
        p.next = last.next;
        p.prev = last;
        last.next.prev = p;
        last.next = p;
    }
    return p;
}

function removeNode(p) {
    //	console.log("removeNode",p.i);
    p.next.prev = p.prev;
    p.prev.next = p.next;

    if (p.prevZ) p.prevZ.nextZ = p.nextZ;
    if (p.nextZ) p.nextZ.prevZ = p.prevZ;
}

function Node(i, x, y) {
    //	console.log("Node",i,x,y);
    // vertex index in coordinates array
    this.i = i;

    // vertex coordinates
    this.x = x;
    this.y = y;

    // previous and next vertex nodes in a polygon ring
    this.prev = null;
    this.next = null;

    // z-order curve value
    this.z = null;

    // previous and next nodes in z-order
    this.prevZ = null;
    this.nextZ = null;

    // indicates whether this is a steiner point
    this.steiner = false;
}

// return a percentage difference between the polygon area and its triangulation area;
// used to verify correctness of triangulation
earcut.deviation = function(data, holeIndices, dim, triangles) {
    var hasHoles = holeIndices && holeIndices.length;
    var outerLen = hasHoles ? holeIndices[0] * dim : data.length;

    var polygonArea = Math.abs(signedArea(data, 0, outerLen, dim));
    if (hasHoles) {
        for (var i = 0, len = holeIndices.length; i < len; i++) {
            var start = holeIndices[i] * dim;
            var end = i < len - 1 ? holeIndices[i + 1] * dim : data.length;
            polygonArea -= Math.abs(signedArea(data, start, end, dim));
        }
    }

    var trianglesArea = 0;
    for (i = 0; i < triangles.length; i += 3) {
        var a = triangles[i] * dim;
        var b = triangles[i + 1] * dim;
        var c = triangles[i + 2] * dim;
        trianglesArea += Math.abs(
            (data[a] - data[c]) * (data[b + 1] - data[a + 1]) -
            (data[a] - data[b]) * (data[c + 1] - data[a + 1]));
    }

    return polygonArea === 0 && trianglesArea === 0 ? 0 :
        Math.abs((trianglesArea - polygonArea) / polygonArea);
};

function signedArea(data, start, end, dim) {
    //console.log("signedarea",data,start,end,dim);
    var sum = 0;
    for (var i = start, j = end - dim; i < end; i += dim) {
        sum += (data[j] - data[i]) * (data[i + 1] + data[j + 1]);
        j = i;
    }
    return sum;
}

// turn a polygon in a multi-dimensional array form (e.g. as in GeoJSON) into a form Earcut accepts
earcut.flatten = function(data) {
    console.log("flatten", data);
    var dim = data[0][0].length,
        result = {
            vertices: [],
            holes: [],
            dimensions: dim
        },
        holeIndex = 0;

    for (var i = 0; i < data.length; i++) {
        for (var j = 0; j < data[i].length; j++) {
            for (var d = 0; d < dim; d++) result.vertices.push(data[i][j][d]);
        }
        if (i > 0) {
            holeIndex += data[i - 1].length;
            result.holes.push(holeIndex);
        }
    }
    return result;
};