/*!
 * chai
 * http://chaijs.com
 * Copyright(c) 2011-2013 Jake Luer <jake@alogicalparadox.com>
 * MIT Licensed
 */

module.exports = function (_chai, util) {
  /*!
   * Module dependencies.
   */

  var AssertionError = _chai.AssertionError
    , flag = util.flag;

  /*!
   * Module export.
   */

  _chai.Assertion = Assertion;

  /*!
   * Assertion Constructor
   *
   * Creates object for chaining.
   *
   * @api private
   */

  function Assertion (obj, msg, stack) {
    flag(this, 'ssfi', stack || arguments.callee);
    flag(this, 'object', obj);
    flag(this, 'message', msg);
  }

  /*!
    * ### Assertion.includeStack
    *
    * User configurable property, influences whether stack trace
    * is included in Assertion error message. Default of false
    * suppresses stack trace in the error message
    *
    *     Assertion.includeStack = true;  // enable stack on error
    *
    * @api public
    */

  Assertion.includeStack = false;

  /*!
   * ### Assertion.showDiff
   *
   * User configurable property, influences whether or not
   * the `showDiff` flag should be included in the thrown
   * AssertionErrors. `false` will always be `false`; `true`
   * will be true when the assertion has requested a diff
   * be shown.
   *
   * @api public
   */

  Assertion.showDiff = true;

  Assertion.addProperty = function (name, fn) {
    util.addProperty(this.prototype, name, fn);
  };

  Assertion.addMethod = function (name, fn) {
    util.addMethod(this.prototype, name, fn);
  };

  Assertion.addChainableMethod = function (name, fn, chainingBehavior) {
    util.addChainableMethod(this.prototype, name, fn, chainingBehavior);
  };

  Assertion.overwriteProperty = function (name, fn) {
    util.overwriteProperty(this.prototype, name, fn);
  };

  Assertion.overwriteMethod = function (name, fn) {
    util.overwriteMethod(this.prototype, name, fn);
  };

  /*!
   * ### .assert(expression, message, negateMessage, expected, actual)
   *
   * Executes an expression and check expectations. Throws AssertionError for reporting if test doesn't pass.
   *
   * @name assert
   * @param {Philosophical} expression to be tested
   * @param {String} message to display if fails
   * @param {String} negatedMessage to display if negated expression fails
   * @param {Mixed} expected value (remember to check for negation)
   * @param {Mixed} actual (optional) will default to `this.obj`
   * @api private
   */

  Assertion.prototype.assert = function (expr, msg, negateMsg, expected, _actual, showDiff) {
    var ok = util.test(this, arguments);
    if (true !== showDiff) showDiff = false;
    if (true !== Assertion.showDiff) showDiff = false;

    if (!ok) {
      var msg = util.getMessage(this, arguments)
        , actual = util.getActual(this, arguments);
      throw new AssertionError(msg, {
          actual: actual
        , expected: expected
        , showDiff: showDiff
      }, (Assertion.includeStack) ? this.assert : flag(this, 'ssfi'));
    }
  };

  /*!
   * ### ._obj
   *
   * Quick reference to stored `actual` value for plugin developers.
   *
   * @api private
   */

  Object.defineProperty(Assertion.prototype, '_obj',
    { get: function () {
        return flag(this, 'object');
      }
    , set: function (val) {
        flag(this, 'object', val);
      }
  });
};