/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

(function(global) {

  /*
   * Return true if both of these return true:
   * - LENIENT_PRED applied to CODE
   * - STRICT_PRED applied to CODE with a use strict directive added to the front
   *
   * Run STRICT_PRED first, for testing code that affects the global environment
   * in loose mode, but fails in strict mode.
   */
  global.testLenientAndStrict = function testLenientAndStrict(code, lenient_pred, strict_pred) {
    return (strict_pred("'use strict'; " + code) && 
            lenient_pred(code));
  }

  /*
   * parsesSuccessfully(CODE) returns true if CODE parses as function
   * code without an error.
   */
  global.parsesSuccessfully = function parsesSuccessfully(code) {
    try {
      Function(code);
      return true;
    } catch (exception) {
      return false;
    }
  };

  /*
   * parseRaisesException(EXCEPTION)(CODE) returns true if parsing CODE
   * as function code raises EXCEPTION.
   */
  global.parseRaisesException = function parseRaisesException(exception) {
    return function (code) {
      try {
        Function(code);
        return false;
      } catch (actual) {
        return exception.prototype.isPrototypeOf(actual);
      }
    };
  };

  /*
   * returns(VALUE)(CODE) returns true if evaluating CODE (as eval code)
   * completes normally (rather than throwing an exception), yielding a value
   * strictly equal to VALUE.
   */
  global.returns = function returns(value) {
    return function(code) {
      try {
        return eval(code) === value;
      } catch (exception) {
        return false;
      }
    }
  }

})(this);