/*
 (c) 2013, Vladimir Agafonkin
 RBush, a JavaScript library for high-performance 2D spatial indexing of points and rectangles.
 https://github.com/mourner/rbush
*/

(function () { 'use strict';

function rbush(maxEntries, format) {

    // jshint newcap: false, validthis: true
    if (!(this instanceof rbush)) { return new rbush(maxEntries, format); }

    this._maxEntries = Math.max(4, maxEntries || 9);
    this._minEntries = Math.max(2, Math.ceil(this._maxEntries * 0.4));

    this._initFormat(format);

    this.clear();
}

rbush.prototype = {

    search: function (bbox) {

        var node = this.data,
            result = [];

        if (!this._intersects(bbox, node.bbox)) { return result; }

        var nodesToSearch = [],
            i, len, child, childBBox;

        while (node) {
            for (i = 0, len = node.children.length; i < len; i++) {
                child = node.children[i];
                childBBox = node.leaf ? this._toBBox(child) : child.bbox;

                if (this._intersects(bbox, childBBox)) {
                    (node.leaf ? result : nodesToSearch).push(child);
                }
            }

            node = nodesToSearch.pop();
        }

        return result;
    },

    load: function (data) {
        if (!(data && data.length)) { return this; }

        if (data.length < this._minEntries) {
            for (var i = 0, len = data.length; i < len; i++) {
                this.insert(data[i]);
            }
            return this;
        }

        // recursively build the tree with the given data from stratch using OMT algorithm
        var node = this._build(data.slice(), 0);
        this._calcBBoxes(node, true);

        if (!this.data.children.length) {
            // save as is if tree is empty
            this.data = node;

        } else if (this.data.height === node.height) {
            // split root if trees have the same height
            this._splitRoot(this.data, node);

        } else {
            if (this.data.height < node.height) {
                // swap trees if inserted one is bigger
                var tmpNode = this.data;
                this.data = node;
                node = tmpNode;
            }

            // insert the small tree into the large tree at appropriate level
            this._insert(node, this.data.height - node.height - 1, true);
        }

        return this;
    },

    insert: function (item) {
        if (item) {
            this._insert(item, this.data.height - 1);
        }
        return this;
    },

    clear: function () {
        this.data = {
            children: [],
            leaf: true,
            bbox: this._infinite(),
            height: 1
        };
        return this;
    },

    remove: function (item) {
        if (!item) { return this; }

        var node = this.data,
            bbox = this._toBBox(item),
            path = [],
            indexes = [],
            i, parent, index, goingUp;

        // depth-first iterative tree traversal
        while (node || path.length) {

            if (!node) { // go up
                node = path.pop();
                parent = path[path.length - 1];
                i = indexes.pop();
                goingUp = true;
            }

            if (node.leaf) { // check current node
                index = node.children.indexOf(item);

                if (index !== -1) {
                    // item found, remove the item and condense tree upwards
                    node.children.splice(index, 1);
                    path.push(node);
                    this._condense(path);
                    return this;
                }
            }

            if (!goingUp && !node.leaf && this._intersects(bbox, node.bbox)) { // go down
                path.push(node);
                indexes.push(i);
                i = 0;
                parent = node;
                node = node.children[0];

            } else if (parent) { // go right
                i++;
                node = parent.children[i];
                goingUp = false;

            } else { // nothing found
                node = null;
            }
        }

        return this;
    },

    toJSON: function () { return this.data; },

    fromJSON: function (data) {
        this.data = data;
        return this;
    },

    _build: function (items, level, height) {

        var N = items.length,
            M = this._maxEntries;

        if (N <= M) {
            return {
                children: items,
                leaf: true,
                height: 1
            };
        }

        if (!level) {
            // target height of the bulk-loaded tree
            height = Math.ceil(Math.log(N) / Math.log(M));

            // target number of root entries to maximize storage utilization
            M = Math.ceil(N / Math.pow(M, height - 1));

            items.sort(this._compareMinX);
        }

        // TODO eliminate recursion?

        var node = {
            children: [],
            height: height
        };

        var N1 = Math.ceil(N / M) * Math.ceil(Math.sqrt(M)),
            N2 = Math.ceil(N / M),
            compare = level % 2 === 1 ? this._compareMinX : this._compareMinY,
            i, j, slice, sliceLen, childNode;

        // split the items into M mostly square tiles
        for (i = 0; i < N; i += N1) {
            slice = items.slice(i, i + N1).sort(compare);

            for (j = 0, sliceLen = slice.length; j < sliceLen; j += N2) {
                // pack each entry recursively
                childNode = this._build(slice.slice(j, j + N2), level + 1, height - 1);
                node.children.push(childNode);
            }
        }

        return node;
    },

    _chooseSubtree: function (bbox, node, level, path) {

        var i, len, child, targetNode, area, enlargement, minArea, minEnlargement;

        while (true) {
            path.push(node);

            if (node.leaf || path.length - 1 === level) { break; }

            minArea = minEnlargement = Infinity;

            for (i = 0, len = node.children.length; i < len; i++) {
                child = node.children[i];
                area = this._area(child.bbox);
                enlargement = this._enlargedArea(bbox, child.bbox) - area;

                // choose entry with the least area enlargement
                if (enlargement < minEnlargement) {
                    minEnlargement = enlargement;
                    minArea = area < minArea ? area : minArea;
                    targetNode = child;

                } else if (enlargement === minEnlargement) {
                    // otherwise choose one with the smallest area
                    if (area < minArea) {
                        minArea = area;
                        targetNode = child;
                    }
                }
            }

            node = targetNode;
        }

        return node;
    },

    _insert: function (item, level, isNode, root) {

        var bbox = isNode ? item.bbox : this._toBBox(item),
            insertPath = [];

        // find the best node for accommodating the item, saving all nodes along the path too
        var node = this._chooseSubtree(bbox, root || this.data, level, insertPath),
            splitOccured;

        // put the item into the node
        node.children.push(item);
        this._extend(node.bbox, bbox);

        // split on node overflow; propagate upwards if necessary
        do {
            splitOccured = false;
            if (insertPath[level].children.length > this._maxEntries) {
                this._split(insertPath, level);
                splitOccured = true;
                level--;
            }
        } while (level >= 0 && splitOccured);

        // adjust bboxes along the insertion path
        this._adjustParentBBoxes(bbox, insertPath, level);
    },

    // split overflowed node into two
    _split: function (insertPath, level) {

        var node = insertPath[level],
            M = node.children.length,
            m = this._minEntries;

        this._chooseSplitAxis(node, m, M);

        var newNode = {
            children: node.children.splice(this._chooseSplitIndex(node, m, M)),
            height: node.height
        };

        if (node.leaf) {
            newNode.leaf = true;
        }

        this._calcBBoxes(node);
        this._calcBBoxes(newNode);

        if (level) {
            insertPath[level - 1].children.push(newNode);
        } else {
            this._splitRoot(node, newNode);
        }
    },

    _splitRoot: function (node, newNode) {
        // split root node
        this.data = {};
        this.data.children = [node, newNode];
        this.data.height = node.height + 1;
        this._calcBBoxes(this.data);
    },

    _chooseSplitIndex: function (node, m, M) {

        var i, bbox1, bbox2, overlap, area, minOverlap, minArea, index;

        minOverlap = minArea = Infinity;

        for (i = m; i <= M - m; i++) {
            bbox1 = this._distBBox(node, 0, i);
            bbox2 = this._distBBox(node, i, M);

            overlap = this._intersectionArea(bbox1, bbox2);
            area = this._area(bbox1) + this._area(bbox2);

            // choose distribution with minimum overlap
            if (overlap < minOverlap) {
                minOverlap = overlap;
                index = i;

                minArea = area < minArea ? area : minArea;

            } else if (overlap === minOverlap) {
                // otherwise choose distribution with minimum area
                if (area < minArea) {
                    minArea = area;
                    index = i;
                }
            }
        }

        return index;
    },

    // sorts node children by the best axis for split
    _chooseSplitAxis: function (node, m, M) {

        var compareMinX = node.leaf ? this._compareMinX : this._compareNodeMinX,
            compareMinY = node.leaf ? this._compareMinY : this._compareNodeMinY,
            xMargin = this._allDistMargin(node, m, M, compareMinX),
            yMargin = this._allDistMargin(node, m, M, compareMinY);

        // if total distributions margin value is minimal for x, sort by minX,
        // otherwise it's already sorted by minY

        if (xMargin < yMargin) {
            node.children.sort(compareMinX);
        }
    },

    // total margin of all possible split distributions where each node is at least m full
    _allDistMargin: function (node, m, M, compare) {

        node.children.sort(compare);

        var leftBBox = this._distBBox(node, 0, m),
            rightBBox = this._distBBox(node, M - m, M),
            margin = this._margin(leftBBox) + this._margin(rightBBox),
            i, child;

        for (i = m; i < M - m; i++) {
            child = node.children[i];
            this._extend(leftBBox, node.leaf ? this._toBBox(child) : child.bbox);
            margin += this._margin(leftBBox);
        }

        for (i = M - m - 1; i >= 0; i--) {
            child = node.children[i];
            this._extend(rightBBox, node.leaf ? this._toBBox(child) : child.bbox);
            margin += this._margin(rightBBox);
        }

        return margin;
    },

    // min bounding rectangle of node children from k to p-1
    _distBBox: function (node, k, p) {
        var bbox = this._infinite();

        for (var i = k, child; i < p; i++) {
            child = node.children[i];
            this._extend(bbox, node.leaf ? this._toBBox(child) : child.bbox);
        }

        return bbox;
    },

    _calcBBoxes: function (node, recursive) {
        // TODO eliminate recursion
        node.bbox = this._infinite();

        for (var i = 0, len = node.children.length, child; i < len; i++) {
            child = node.children[i];

            if (node.leaf) {
                this._extend(node.bbox, this._toBBox(child));
            } else {
                if (recursive) {
                    this._calcBBoxes(child, recursive);
                }
                this._extend(node.bbox, child.bbox);
            }
        }
    },

    _adjustParentBBoxes: function (bbox, path, level) {
        // adjust bboxes along the given tree path
        for (var i = level; i >= 0; i--) {
            this._extend(path[i].bbox, bbox);
        }
    },

    _condense: function (path) {
        // go through the path, removing empty nodes and updating bboxes
        for (var i = path.length - 1, parent; i >= 0; i--) {
            if (i > 0 && path[i].children.length === 0) {
                parent = path[i - 1].children;
                parent.splice(parent.indexOf(path[i]), 1);
            } else {
                this._calcBBoxes(path[i]);
            }
        }
    },

    _intersects: function (a, b) {
        return b[0] <= a[2] &&
               b[1] <= a[3] &&
               b[2] >= a[0] &&
               b[3] >= a[1];
    },

    _extend: function (a, b) {
        a[0] = Math.min(a[0], b[0]);
        a[1] = Math.min(a[1], b[1]);
        a[2] = Math.max(a[2], b[2]);
        a[3] = Math.max(a[3], b[3]);
        return a;
    },

    _area:   function (a) { return (a[2] - a[0]) * (a[3] - a[1]); },
    _margin: function (a) { return (a[2] - a[0]) + (a[3] - a[1]); },

    _enlargedArea: function (a, b) {
        return (Math.max(b[2], a[2]) - Math.min(b[0], a[0])) *
               (Math.max(b[3], a[3]) - Math.min(b[1], a[1]));
    },

    _intersectionArea: function (a, b) {
        var minX = Math.max(a[0], b[0]),
            minY = Math.max(a[1], b[1]),
            maxX = Math.min(a[2], b[2]),
            maxY = Math.min(a[3], b[3]);

        return Math.max(0, maxX - minX) *
               Math.max(0, maxY - minY);
    },

    _infinite: function () { return [Infinity, Infinity, -Infinity, -Infinity]; },

    _compareNodeMinX: function (a, b) { return a.bbox[0] - b.bbox[0]; },
    _compareNodeMinY: function (a, b) { return a.bbox[1] - b.bbox[1]; },

    _initFormat: function (format) {
        // data format (minX, minY, maxX, maxY accessors)
        format = format || ['[0]', '[1]', '[2]', '[3]'];

        // uses eval-type function compilation instead of just accepting a toBBox function
        // because the algorithms are very sensitive to sorting functions performance,
        // so they should be dead simple and without inner calls

        // jshint evil: true

        var compareArr = ['return a', ' - b', ';'];

        this._compareMinX = new Function('a', 'b', compareArr.join(format[0]));
        this._compareMinY = new Function('a', 'b', compareArr.join(format[1]));

        this._toBBox = new Function('a', 'return [a' + format.join(', a') + '];');
    }
};

if (typeof module !== 'undefined') {
    module.exports = rbush;
} else {
    window.rbush = rbush;
}

})();