
/*!
 * Module dependencies.
 */

var utils = require('./utils');

/*!
 * StateMachine represents a minimal `interface` for the
 * constructors it builds via StateMachine.ctor(...).
 *
 * @api private
 */

var StateMachine = module.exports = exports = function StateMachine () {
  this.paths = {};
  this.states = {};
}

/*!
 * StateMachine.ctor('state1', 'state2', ...)
 * A factory method for subclassing StateMachine.
 * The arguments are a list of states. For each state,
 * the constructor's prototype gets state transition
 * methods named after each state. These transition methods
 * place their path argument into the given state.
 *
 * @param {String} state
 * @param {String} [state]
 * @return {Function} subclass constructor
 * @private
 */

StateMachine.ctor = function () {
  var states = utils.args(arguments);

  var ctor = function () {
    StateMachine.apply(this, arguments);
    this.stateNames = states;

    var i = states.length
      , state;

    while (i--) {
      state = states[i];
      this.states[state] = {};
    }
  };

  ctor.prototype.__proto__ = StateMachine.prototype;

  states.forEach(function (state) {
    // Changes the `path`'s state to `state`.
    ctor.prototype[state] = function (path) {
      this._changeState(path, state);
    }
  });

  return ctor;
};

/*!
 * This function is wrapped by the state change functions:
 *
 * - `require(path)`
 * - `modify(path)`
 * - `init(path)`
 *
 * @api private
 */

StateMachine.prototype._changeState = function _changeState (path, nextState) {
  var prevBucket = this.states[this.paths[path]];
  if (prevBucket) delete prevBucket[path];

  this.paths[path] = nextState;
  this.states[nextState][path] = true;
}

/*!
 * ignore
 */

StateMachine.prototype.clear = function clear (state) {
  var keys = Object.keys(this.states[state])
    , i = keys.length
    , path

  while (i--) {
    path = keys[i];
    delete this.states[state][path];
    delete this.paths[path];
  }
}

/*!
 * Checks to see if at least one path is in the states passed in via `arguments`
 * e.g., this.some('required', 'inited')
 *
 * @param {String} state that we want to check for.
 * @private
 */

StateMachine.prototype.some = function some () {
  var self = this;
  var what = arguments.length ? arguments : this.stateNames;
  return Array.prototype.some.call(what, function (state) {
    return Object.keys(self.states[state]).length;
  });
}

/*!
 * This function builds the functions that get assigned to `forEach` and `map`,
 * since both of those methods share a lot of the same logic.
 *
 * @param {String} iterMethod is either 'forEach' or 'map'
 * @return {Function}
 * @api private
 */

StateMachine.prototype._iter = function _iter (iterMethod) {
  return function () {
    var numArgs = arguments.length
      , states = utils.args(arguments, 0, numArgs-1)
      , callback = arguments[numArgs-1];

    if (!states.length) states = this.stateNames;

    var self = this;

    var paths = states.reduce(function (paths, state) {
      return paths.concat(Object.keys(self.states[state]));
    }, []);

    return paths[iterMethod](function (path, i, paths) {
      return callback(path, i, paths);
    });
  };
}

/*!
 * Iterates over the paths that belong to one of the parameter states.
 *
 * The function profile can look like:
 * this.forEach(state1, fn);         // iterates over all paths in state1
 * this.forEach(state1, state2, fn); // iterates over all paths in state1 or state2
 * this.forEach(fn);                 // iterates over all paths in all states
 *
 * @param {String} [state]
 * @param {String} [state]
 * @param {Function} callback
 * @private
 */

StateMachine.prototype.forEach = function forEach () {
  this.forEach = this._iter('forEach');
  return this.forEach.apply(this, arguments);
}

/*!
 * Maps over the paths that belong to one of the parameter states.
 *
 * The function profile can look like:
 * this.forEach(state1, fn);         // iterates over all paths in state1
 * this.forEach(state1, state2, fn); // iterates over all paths in state1 or state2
 * this.forEach(fn);                 // iterates over all paths in all states
 *
 * @param {String} [state]
 * @param {String} [state]
 * @param {Function} callback
 * @return {Array}
 * @private
 */

StateMachine.prototype.map = function map () {
  this.map = this._iter('map');
  return this.map.apply(this, arguments);
}

