Sound detector

gistfile1.js

'use strict';

var playerModes = require('../../game/player').modes;

/**
 * This module exports a single function that checks a game state and
 * its latest diff for game sound triggers and plays the appropriate
 * sounds on the provided AudioPlayer object.
 */

var soundChecks = {
    'sound_throw': [projectileExistenceChanged(true, 'axe', true)],
    'sound_shoot': [projectileExistenceChanged(true, 'laser', true)],
    'sound_hit':   [somePlayerStateChanged('alive', true, false)],
    'sound_jump':  [somePlayerStateChanged('mode', playerModes.STANDING, playerModes.JUMPING)],
    'sound_slam':  [somePlayerStateChanged('mode', playerModes.DROPKICK, null)],
    'sound_dash':  [somePlayerStateChanged('mode', null, playerModes.DROPKICK)],
    'sound_die':   [thisPlayerStateChanged('alive', true, false)],
    'sound_rekt':  [{after:100, event:thisPlayerStateChanged('alive', true, false)}]
};


module.exports = function(audioPlayer, state0, state1, playerId) {
    for (var k in soundChecks) {
        for (var i = 0; i < soundChecks[k].length; ++i) {
            var checker = soundChecks[k][i];
            if (typeof checker === 'function') {
                if (checker(state0, state1, playerId)) {
                    audioPlayer.playSound(k);
                }
            }
            else if (checker.event(state0, state1, playerId)) {
                setTimeout(audioPlayer.playSound.bind(audioPlayer, k), checker.after);
            }
        }
    }
}


// If `created` is true then check for a matching newly created projectile, otherwise
// check for a projectile which has just been destroyed.
function projectileExistenceChanged(created, type, owned) {
    return function(state0, state1, playerId) {
        var filter = {type: type};
        if (owned) filter.ownerId = playerId;

        var ids = _.map([state0, state1], function(state) {
            return _.chain(state.projectiles)
                .filter(filter)
                .pluck('id')
                .value();
        });
        return _.difference(ids[created ? 1 : 0], ids[created ? 0 : 1]).length > 0;
    }
}

function somePlayerStateChanged(property, oldValue, newValue) {
    return function(state0, state1, playerId) {
        return _.chain(Object.keys(state1.players))
            .map(playerStateCheck.bind(null, property, oldValue, newValue, state0, state1))
            .any()
            .value();
    }
}

function thisPlayerStateChanged(property, oldValue, newValue) {
    return playerStateCheck.bind(null, property, oldValue, newValue);
}

function playerStateCheck(property, oldValue, newValue, state0, state1, playerId) {
    oldValue = oldValue !== null ? oldValue : state0.players[playerId][property];
    newValue = newValue !== null ? newValue : state1.players[playerId][property];

    return _.chain([state0.players[playerId], state1.players[playerId]])
        .pluck(property)
        .isEqual([oldValue, newValue])
        .value();
}