health.js

'use strict';

var inherits = require('inherits');
var EventEmitter = require('events').EventEmitter;

module.exports = function(game, opts) {
  return new Health(game, opts);
};

module.exports.pluginInfo = {
  loadAfter: ['voxel-commands']
};

function Health(game, opts) {
  this.maxHealth = opts.maxHealth || 10;
  this.minHealth = opts.minHealth || 0;
  this.startHealth = opts.startHealth || this.maxHealth;

  this.value = this.startHealth;

  this.game = game;

  this.enable();
}

inherits(Health, EventEmitter);

Health.prototype.enable = function() {
  if (this.game.plugins && this.game.plugins.isEnabled('voxel-commands')) {
    this.game.plugins.get('voxel-commands').registerCommand('heal', this.onHeal = this.heal.bind(this, this.maxHealth), '', 'sets health to maximum');
  }
};

Health.prototype.disable = function() {
  if (this.game.plugins && this.game.plugins.isEnabled('voxel-commands')) {
    this.game.plugins.get('voxel-commands').unregisterCommand('heal', this.onHeal);
  }
};

Health.prototype.hurt = function(amount) {
  if (amount < 0) return this.heal(-amount);
  if (amount !== Infinity && !Number.isFinite(amount)) throw new Error('voxel-health hurt('+amount+') called with non-finite amount');
  
  var oldValue = this.value;
  this.value -= amount;
  if (this.value < this.minHealth) 
    this.value = this.minHealth;

  var effectiveAmount = this.value - oldValue;

  this.emit('health', this.value, oldValue);
  this.emit('hurt', effectiveAmount, amount, this.value, oldValue);

  if (this.value === this.minHealth) {
    this.emit('die');
  }

  return effectiveAmount;
};

Health.prototype.heal = function(amount) {
  if (amount < 0) return this.hurt(-amount);
  if (amount !== Infinity && !Number.isFinite(amount)) throw new Error('voxel-health heal('+amount+') called with non-finite amount');

  var oldValue = this.value;

  this.value += amount;
  if (this.value > this.maxHealth)
    this.value = this.maxHealth;

  var effectiveAmount = oldValue - this.value;

  this.emit('health', this.value, oldValue);
  this.emit('heal', effectiveAmount, amount, this.value, oldValue);

  return effectiveAmount;
};

Health.prototype.scaledValue = function() {
  return this.value / this.maxHealth;
};

Health.prototype.percentage = function() {
  return this.scaledValue() * 100.0;
};