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src/olHelpers/SortedFeatures.js

/**
 * Created by gavorhes on 12/23/2015.
 */
import provide from '../util/provide';
let nm = provide('olHelpers');

/**
 * take an array of features and sort by a given property name
 */
class SortedFeatures {

    /**
     *
     * @param {Array<ol.Feature>} features array of ol features
     * @param {string} propertyName - the property name to use for lookup
     */
    constructor(features, propertyName) {
        this.sortedFeatures = features;
        this.propertyName = propertyName;

        if (this.sortedFeatures.length > 0) {
            this._propertyType = typeof this.sortedFeatures[0].getProperties()[this.propertyName];

            let _this = this;
            this.sortedFeatures.sort(function (a, b) {
                if (_this._propertyType == 'number'){
                    return (a['getProperties']()[_this.propertyName] - b['getProperties']()[_this.propertyName]);
                } else if (_this._propertyType == 'string'){
                    return (a['getProperties']()[_this.propertyName] > b['getProperties']()[_this.propertyName]);
                }
            });
        }
    }

    /**
     * recursive search to find the value
     * @param {number|string} propertyValue - the property value to search for
     * @param {boolean} [exactMatch=false] if only an exact match should be returned
     * @param {Array} [sortedFeatures=this.sortedFeatures] - the candidate features
     * @returns {ol.Feature|undefined} the feature matching the lookup
     */
    getFeature(propertyValue, exactMatch, sortedFeatures) {
        if (typeof sortedFeatures == 'undefined'){
            sortedFeatures = this.sortedFeatures;
        }

        if (typeof exactMatch !== 'boolean'){
            exactMatch = false;
        }

        if (sortedFeatures.length == 0){
            return undefined;
        }

        if (sortedFeatures.length == 1){
            if (exactMatch){
                if (sortedFeatures[0].getProperties()[this.propertyName] == propertyValue){
                    return sortedFeatures[0];
                } else {
                    return undefined;
                }
            } else {
                return sortedFeatures[0];
            }
        }

        let lowProp = sortedFeatures[0].getProperties()[this.propertyName];
        let highProp = sortedFeatures[sortedFeatures.length - 1].getProperties()[this.propertyName];

        if (exactMatch){
            if (lowProp == propertyValue){
                return sortedFeatures[0];
            } else if (propertyValue < lowProp){
                return undefined;
            } else if (highProp == propertyValue){
                return sortedFeatures[sortedFeatures.length - 1];
            } else if (propertyValue >  highProp){
                return undefined;
            }
        } else {
            if (propertyValue <= lowProp){
                return sortedFeatures[0];
            } else if (propertyValue >= highProp){
                return sortedFeatures[sortedFeatures.length - 1];
            }
        }

        let midIndex = Math.floor(sortedFeatures.length / 2);
        let midFeature = sortedFeatures[midIndex];
        let midProperty = midFeature.getProperties()[this.propertyName];

        if (midProperty ===  propertyValue){
            return midFeature;
        }

        if (propertyValue < midProperty){
            return this.getFeature(propertyValue, exactMatch, sortedFeatures.slice(0, midIndex));
        } else {
            return this.getFeature(propertyValue, exactMatch, sortedFeatures.slice(midIndex));
        }
    }
}

nm.SortedFeatures = SortedFeatures;
export default SortedFeatures;