index.js

/**
 * Dependencies
 */
var Emitter = require('emitter');

/**
 * Expose
 */
module.exports = functionSignatures;


/**
 * Constructor
 */
function functionSignatures(_signatures) {
  if (arguments.length !== 1)
    throw new Error('You must pass exactly one object');

  if (arguments.length === 1)
    for (var signature in _signatures)
      if (_signatures.hasOwnProperty(signature))
        if (typeof _signatures[signature] !== 'function')
          throw new Error("Property `" + signature + "` is not a function");

  this._signatures = _signatures;
}

/**
 * Prototype
 */
functionSignatures.prototype.normalize = function normalize(args) {
  var signatures = this._signatures;

  args = Array.prototype.slice.call(args, 0);

  for (var name in signatures) {
    if (signatures.hasOwnProperty(name)) {
      var signature = signatures[name];

      if (signature.length === 0 || signature.length === args.length) {
        if (signature.apply(this, args)) {
          return this.emit.apply(this, [name].concat(args));
        }
      }
    }
  }

  throw new Error("Invalid signature for: " + normalize.caller.toString());
};

/**
 * Mixin
 */
Emitter(functionSignatures.prototype);