define(["datetime"], function (datetime) {
    "use strict";

    function humaneDate(date_str) {
        var format;
        var time_formats = [
            [90, "a minute"],
            [3600, "minutes", 60],
            [5400, "an hour"],
            [86400, "hours", 3600],
            [129600, "a day"],
            [604800, "days", 86400],
            [907200, "a week"],
            [2628e3, "weeks", 604800],
            [3942e3, "a month"],
            [31536e3, "months", 2628e3],
            [47304e3, "a year"],
            [31536e5, "years", 31536e3]
        ];
        var dt = new Date();
        var date = datetime.parseISO8601Date(date_str, true);
        var seconds = (dt - date) / 1000.0;
        var i = 0;

        if (seconds < 0) {
            seconds = Math.abs(seconds);
        }
        // eslint-disable-next-line no-cond-assign
        for (; format = time_formats[i++];) {
            if (seconds < format[0]) {
                if (2 == format.length) {
                    return format[1] + " ago";
                }

                return Math.round(seconds / format[2]) + " " + format[1] + " ago";
            }
        }

        if (seconds > 47304e5) {
            return Math.round(seconds / 47304e5) + " centuries ago";
        }

        return date_str;
    }

    function humaneElapsed(firstDateStr, secondDateStr) {
        // TODO replace this whole script with a library or something
        var dateOne = new Date(firstDateStr);
        var dateTwo = new Date(secondDateStr);
        var delta = (dateTwo.getTime() - dateOne.getTime()) / 1e3;
        var days = Math.floor(delta % 31536e3 / 86400);
        var hours = Math.floor(delta % 31536e3 % 86400 / 3600);
        var minutes = Math.floor(delta % 31536e3 % 86400 % 3600 / 60);
        var seconds = Math.round(delta % 31536e3 % 86400 % 3600 % 60);
        var elapsed = "";
        elapsed += 1 == days ? days + " day " : "";
        elapsed += days > 1 ? days + " days " : "";
        elapsed += 1 == hours ? hours + " hour " : "";
        elapsed += hours > 1 ? hours + " hours " : "";
        elapsed += 1 == minutes ? minutes + " minute " : "";
        elapsed += minutes > 1 ? minutes + " minutes " : "";
        elapsed += elapsed.length > 0 ? "and " : "";
        elapsed += 1 == seconds ? seconds + " second" : "";
        elapsed += 0 == seconds || seconds > 1 ? seconds + " seconds" : "";
        return elapsed;
    }

    window.humaneDate = humaneDate;
    window.humaneElapsed = humaneElapsed;
    return {
        humaneDate: humaneDate,
        humaneElapsed: humaneElapsed
    };
});