Roll20 API: A command wrapped version of the Darkness Closing In API sample script.

DarknessClosingIn.js

// GIST: https://gist.github.com/shdwjk/d67c07ba49e1a57a1c0f

var DarknessClosingIn = DarknessClosingIn || (function() {
    'use strict';

    var version = 0.1,
		schemaVersion = 0.1,

	checkInstall = function() {
        if( ! _.has(state,'DarknessClosingIn') || state.DarknessClosingIn.version !== schemaVersion) {
            log('DarknessClosingIn: Resetting state');
            state.DarknessClosingIn = {
				version: schemaVersion,
				gettingDarker: false
			};
		}
	},

	handleInput = function(msg) {
		var args;

		if (msg.type !== "api" || ! isGM(msg.playerid) ) {
			return;
		}

		args = msg.content.split(/\s+/);
		switch(args[0]) {
			case '!dci':
				state.DarknessClosingIn.gettingDarker = ! state.DarknessClosingIn.gettingDarker;
				sendChat('','/w gm ' + ( 
                        state.DarknessClosingIn.gettingDarker 
                        ? 'Darkness is now closing in.' 
                        : 'Darkness is no longer closing in.' 
                    ) 
                ); 
				break;
		}
    },
	
	gettingDarker = function(obj, prev) {
		if( state.DarknessClosingIn.gettingDarker
			&& ( 
				obj.get("left") !== prev.left
				|| obj.get("top") !== prev.top
			)
            && obj.get('light_radius')
		) {
			obj.set({
				light_radius: Math.floor(obj.get('light_radius') * 0.90)
			});
		}
	},


	registerEventHandlers = function() {
		on('chat:message', handleInput);
		on("change:token", gettingDarker);
	};

	return {
		CheckInstall: checkInstall,
		RegisterEventHandlers: registerEventHandlers
	};
    
}());

on('ready',function() {
	'use strict';

    if("undefined" !== typeof isGM && _.isFunction(isGM)) {
		DarknessClosingIn.CheckInstall();
		DarknessClosingIn.RegisterEventHandlers();
    } else {
        log('--------------------------------------------------------------');
        log('DarknessClosingIn requires the isGM module to work.');
        log('isGM GIST: https://gist.github.com/shdwjk/8d5bb062abab18463625');
        log('--------------------------------------------------------------');
    }
});