Roll20 Wearynator for The One Ring

wearynator.js

/*
    The One Ring weary-state setter for Roll20 API
    By Michael Heilemann (michael.heilemann@me.com)

    Checks to see if a character's endurance drops below her fatigue, and
    automatically sets the `weary` attribute to `weary` or `normal`, depending.
    This is very useful particularly if you're using the TOR roll tables, as you
    can then read the weary attribute of the selected token in a macro and roll
    on the appropriate success die table automatically:

        /r 1t[feat] + @{travel}t[@{weary}]

    It requires that the character have `endurance`, `travel_fatigue`,
    `encumbrance_fatigue` and `weary` attributes.

    For information on how to setup rollable tables for The One Ring:
    https://wiki.roll20.net/The_One_Ring

    For more of my The One Ring shenanigans:
    https://ringen.squarespace.com/loremasters-journal/
 */
on('ready', function() {
    var characters = findObjs({
        _type: 'character'
    });

    characters.forEach(checkWeary, this);
});

on('change:attribute', function(obj, prev) {
    var characterid = obj.get('_characterid');
    var character = getObj("character", characterid);

    checkWeary(character);
});

var checkWeary = function (character) {
    var characterid = character.get('_id');
    var encumbrance_fatigue = findObjs({
        _characterid: characterid,
        _type: 'attribute',
        name: 'encumbrance_fatigue'
    })[0];
    var travel_fatigue = findObjs({
        _characterid: characterid,
        _type: 'attribute',
        name: 'travel_fatigue'
    })[0];
    var endurance = findObjs({
        _characterid: characterid,
        _type: 'attribute',
        name: 'endurance'
    })[0];
    var weary = findObjs({
        _characterid: characterid,
        _type: 'attribute',
        name: 'weary'
    })[0];
    var tokens = findObjs({
        _type: 'graphic',
        represents: characterid
    });

    if (!travel_fatigue || !encumbrance_fatigue || !endurance || !weary) {
        return;
    }

    var fatigue = encumbrance_fatigue.get('current') + travel_fatigue.get('current');

    if (endurance.get('current') < fatigue) {
        weary.set('current', 'weary');
        tokens.forEach(function(token) {
            token.set('status_yellow', '');
        }, this);

    } else {
        weary.set('current', 'normal');
        tokens.forEach(function(token) {
            token.set('status_yellow', false);
        }, this);
    }
};