terriajs/lib/Core/combineFilters.js

Geospatial data visualization platform.

'use strict';

var defined = require('terriajs-cesium/Source/Core/defined');

/**
 * Combines a number of functions that return a boolean into a single function that executes all of them and returns
 * true only if all them do. Maintains an set of filter functions, so if the same function is combined
 * more than once, it is only executed one time. This means that it is also safe to call combineFilter on its own result
 * to combine the result with another filter - the set of filters from the previous result will simply
 * be merged into that of the new result so that only individual filter functions are executed.
 *
 * @param {Array} filters A number of functions to combine into one logical function.
 * @returns {Function} The resulting function.
 */
function combineFilters(filters) {
    var allFilters, returnFn;

    allFilters = filters
        .filter(function(filter) {
            return defined(filter);
        })
        .reduce(function(filtersSoFar, thisFilter) {
            if (thisFilter._filterIndex) {
                // If a filter is an instance of this function just pull that filter's index into this one's.
                thisFilter._filterIndex.forEach(addToListUnique.bind(undefined, filtersSoFar));
            } else {
                // Otherwise add it.
                addToListUnique(filtersSoFar, thisFilter);
            }

            return filtersSoFar;
        }, []);

    returnFn = function() {
        var outerArgs = arguments;

        return !allFilters.some(function(filter) {
            return !filter.apply(this, outerArgs);
        }, this);
    };
    returnFn._filterIndex = allFilters;

    return returnFn;
}

function addToListUnique(list, filter) {
    if (list.indexOf(filter) === -1) {
        list.push(filter);
    }
}

module.exports = combineFilters;