nested-set/lib/nested-set.js

Fast nested set model helpers. Conversion flatten <-> nested

/**
 * Created by jacek on 07.01.17.
 */

const nestedSetContextFactory = ( options = {} ) => {

    const defaultContext = {
        left: 'lft',
        right: 'rgt',
        children: 'children'
    };

    const context = Object.assign({},defaultContext,options);

    const allocateNode = (hier, node, hMap) => {

        const hNode = hMap.has(node) ? hMap.get(node ) : {l:node[context.left],r:node[context.right]};

        delete node[context.left];
        delete node[context.right];

        hMap.set(node,hNode);

        if (!hier.length ) {
            hier.push([]);
        }

        let last = hier[hier.length-1];

        //if root level
        if (!hMap.has(last)) {

            last.push(node);
            hier.push(node);
        }
        else if (hMap.get(last).r > hMap.get(node).r ) {

            if(!last[context.children]) {
                last[context.children] = [];
            }
            last[context.children].push(node);
            hier.push(node);
        }
        else {
            hier.pop();
            return allocateNode(hier,node,hMap);
        }

        return hier;
    };

    const nest = ( table, treeMap = [], hMap ) => {

        let set = table;

        if (treeMap.length === 0) {
            hMap = new WeakMap();
            set = [...set];
        }

        let currentNode = Object.assign({},set.shift());

        treeMap = allocateNode(treeMap, currentNode, hMap);

        if (!set.length) {

            return treeMap[0];

        } else {

            return nest(set, treeMap, hMap);
        }
    };

    const flat = ( nested, pointer = {i:0}, flatten = [] ) => {

        for(var i in nested ) {
            let node = nested[i];
            let row = Object.assign({},node);
            flatten.push(row);
            row[context.left] = ++pointer.i;
            delete row[context.children];
            if(node[context.children]) {
                flat(node[context.children],pointer,flatten);
            }
            row[context.right] = ++pointer.i;
        }

        return flatten;
    };

    return {
        nest,
        flat
    }
};

module.exports = nestedSetContextFactory;