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distribution.js
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distribution.js
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/**
* Execute all Gremlins randomly following a distribution, separated by a 10ms
* delay, for 100 times
*
* This is the default attack strategy, so selecting no strategy is equivalent to
*
* var distributionStrategy = gremlins.strategies.distribution();
* horde.strategy(distributionStrategy);
*
* The attack duration is roughly equivalent to delay * nb, although setTimeout
* may make it longer when delay is small.
*
* By default, this strategy uses a uniform distribution, i.e. all gremlins
* have an equal chance to be selected for the next action.
*
* The distribution strategy can be customized as follows:
*
* distributionStrategy.distribution([0.25, 0.25, 0.25, 0.25]); // chances for each gremlin to be selected ; total must equal 1
* distributionStrategy.delay(10); // delay in milliseconds between each wave
* distributionStrategy.nb(100); // number of waves to execute (can be overridden in params)
* distributionStrategy.randomizer(randomizerObject); // inject a randomizer
*
* Example usage:
*
* horde.strategy(gremlins.strategies.distribution()
* .delay(50)
* .distribution([
* 0.3, // first gremlin
* 0.3, // second gremlin
* 0.3, // third gremlin
* 0.1, // fourth gremlin
* ])
* )
*/
define(function(require) {
"use strict";
var executeInSeries = require('../utils/executeInSeries');
var configurable = require('../utils/configurable');
var Chance = require('../vendor/chance');
return function() {
/**
* @mixin
*/
var config = {
distribution: [], // percentage of each gremlin species ; the sum of all values should equal to 1
delay: 10, // delay in milliseconds between each wave
nb: 1000, // number of waves to execute (can be overridden in params)
randomizer: new Chance()
};
var stopped;
var doneCallback;
/**
* @mixes config
*/
function distributionStrategy(gremlins, params, done) {
var nb = params && params.nb ? params.nb : config.nb,
gremlins = gremlins.slice(0), // clone the array to avoid modifying the original
distribution = config.distribution.length === 0 ? getUniformDistribution(gremlins) : config.distribution,
horde = this;
if (nb === 0) return done();
stopped = false;
doneCallback = done; // done can also be called by stop()
function executeNext(gremlin, i, callback) {
if (stopped) return;
if (i >= nb) return callDone();
executeInSeries([gremlin], [], horde, function() {
setTimeout(function() {
executeNext(pickGremlin(gremlins, distribution), ++i, callback);
}, config.delay);
});
}
executeNext(pickGremlin(gremlins, distribution), 0, executeNext);
}
function getUniformDistribution(gremlins) {
var len = gremlins.length;
if (len === 0) return [];
var distribution = [];
var value = 1 / len;
for (var i = 0; i < len ; i++) {
distribution.push(value);
}
return distribution;
}
function pickGremlin(gremlins, distribution) {
var chance = 0;
var random = config.randomizer.floating({ min: 0, max: 1 });
for (var i = 0, count = gremlins.length; i < count; i++) {
chance += distribution[i];
if (random <= chance) return gremlins[i];
}
// no gremlin - probably error in the distribution
return function() {};
}
distributionStrategy.stop = function() {
stopped = true;
setTimeout(callDone, 4);
};
function callDone() {
if (typeof doneCallback === 'function') {
doneCallback();
}
doneCallback = null;
}
configurable(distributionStrategy, config);
return distributionStrategy;
};
});