MoonData.js

"use strict";
/**
 * Returns Lunar Rise/Set times from USNO data
 */
var http = require('http');
var Q = require('q');

/**
 * Returns USNO data as a 3-deep nested JavaScript Array of [months][days][riseSetPair], [2][0][3] would be March 4, moon rise time
 * @todo add options for Eastern Hemisphere
 * @param year {Number} - 4 digit year
 * @param long_deg {Number} - Longitude in deg W
 * @param long_m {Number} - Longitude in minutes W
 * @param lat_deg {Number} - Latitude in deg
 * @param lat_m {Number} - Latitude in minutes
 * @param tz_offset {Number} - Western GMT offset, 5 = Eastern
 * @param name {String} - Friendly Name of data set
 * @returns {*|promise}
 */

function getData(year, long_deg, long_m, lat_deg, lat_m, tz_offset, name) {
    var deferred = Q.defer();
    var url = 'http://aa.usno.navy.mil/cgi-bin/aa_rstablew.pl?FFX=2&xxy=2015&type=0&place=' + name + '&xx0=-1&xx1=' + long_deg + '&xx2='+ long_m +'&yy0=1&yy1=' + lat_deg + '&yy2=' + lat_m + '&zz1=' + tz_offset + '&zz0=-1&ZZZ=END';

    http.get(url, function (response) {
        var str;

        response.on('data', function (chunk) {
            str += chunk;
        });

        response.on('end', function () {
            var dataTable = dataSetOnly(selectTable(str));
            var rows = splitIntoRows(dataTable);
            var months = dayMonths(rows);
            var cleaned = cleanup(months);
            var transformed = transform(cleaned, year);

            deferred.resolve(transformed);
        });
    }).on('error', function (e) {
        deferred.reject(e);
    });
    return deferred.promise;
}

/**
 * Selects the data table from the HTML document
 * Data is within a <pre> tag
 * @param str
 * @returns {String}
 */
function selectTable(str) {
    return str.match(/<pre>([\s\S]*?)<\/pre>/g).map(function (val) {
        return val.replace(/<\/?pre>/g, '');
    })[0];
}

/**
 * Select the data table only, regex starting at '01' and ending with two line breaks
 * Regex are dark magic, this could break if the format changes
 * @param str
 */
function dataSetOnly(str) {
    return str.match(/\s01([\s\S]*?)\n\n/).map(function (val) {
        return val.replace(/^\n/, '');
    })[0];
}

/**
 * Split each line into an array object (table -> rows) and remove the day index
 * @param str
 * @returns {Array}
 */
function splitIntoRows(str) {
    return str.split(/\r?\n/).map(function (val) {
        return val.replace(/^\d\d\ \ /g, '');
    });
}

/**
 * Push each rise/set tuple into an array for each month
 * @param rows
 * @returns {*[]}
 */
function dayMonths(rows) {
    var months = [[], [], [], [], [], [], [], [], [], [], [], []];
    rows.map(function (row) {
        months[0].push(row.substr(0, 9));
        months[1].push(row.substr(11, 9));
        months[2].push(row.substr(22, 9));
        months[3].push(row.substr(33, 9));
        months[4].push(row.substr(44, 9));
        months[5].push(row.substr(55, 9));
        months[6].push(row.substr(66, 9));
        months[7].push(row.substr(77, 9));
        months[8].push(row.substr(88, 9));
        months[9].push(row.substr(99, 9));
        months[10].push(row.substr(110, 9));
        months[11].push(row.substr(121, 9));
    });
    return months;
}

/**
 * Remove empty values and replace blank spaces with no rise/set time with null to normalize the input format
 * @param months
 * @returns {*}
 */
function cleanup(months) {
    for (var monthIdx in months) {
        months[monthIdx] = months[monthIdx].filter(function (i) {
            return i !== '' && i !== '         ';
        });
        months[monthIdx] = months[monthIdx].map(function (riseSetPairWithGap) {
            return riseSetPairWithGap.replace(/(^\ \ \ \ )|(\ \ \ \ $)/, null).split(' ');
        });
    }
    return months;
}

/**
 * Transform rise/set times into JavaScript Date objects
 * @param months
 * @returns {*}
 */
function transform(months, year) {
    for (var monthIdx = 0; monthIdx < 12; monthIdx++) {
        for (var dayIdx = 0; dayIdx < months[monthIdx].length; dayIdx++) {
            for (var riseSetIdx in months[monthIdx][dayIdx]) {
                if (months[monthIdx][dayIdx][riseSetIdx] !== 'null') {
                    var hour = months[monthIdx][dayIdx][riseSetIdx].substring(0, 2);
                    var minute = months[monthIdx][dayIdx][riseSetIdx].substring(2, 4);
                    months[monthIdx][dayIdx][riseSetIdx] = new Date(year, monthIdx, dayIdx + 1, hour, minute);
                }
            }
        }
    }
    return months;
}

module.exports = {
    getData: getData
};