/**
   * @fileoverview Rule to disallow a negated condition
   * @author Alberto Rodríguez
   * @copyright 2015 Alberto Rodríguez. All rights reserved.
   * See LICENSE file in root directory for full license.
   */
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = function(context) {
  
      /**
       * Determines if a given node is an if-else without a condition on the else
       * @param {ASTNode} node The node to check.
       * @returns {boolean} True if the node has an else without an if.
       * @private
       */
      function hasElseWithoutCondition(node) {
          return node.alternate && node.alternate.type !== "IfStatement";
      }
  
      /**
       * Determines if a given node is a negated unary expression
       * @param {Object} test The test object to check.
       * @returns {boolean} True if the node is a negated unary expression.
       * @private
       */
      function isNegatedUnaryExpression(test) {
          return test.type === "UnaryExpression" && test.operator === "!";
      }
  
      /**
       * Determines if a given node is a negated binary expression
       * @param {Test} test The test to check.
       * @returns {boolean} True if the node is a negated binary expression.
       * @private
       */
      function isNegatedBinaryExpression(test) {
          return test.type === "BinaryExpression" &&
              (test.operator === "!=" || test.operator === "!==");
      }
  
      /**
       * Determines if a given node has a negated if expression
       * @param {ASTNode} node The node to check.
       * @returns {boolean} True if the node has a negated if expression.
       * @private
       */
      function isNegatedIf(node) {
          return isNegatedUnaryExpression(node.test) || isNegatedBinaryExpression(node.test);
      }
  
      return {
          "IfStatement": function(node) {
              if (!hasElseWithoutCondition(node)) {
                  return;
              }
  
              if (isNegatedIf(node)) {
                  context.report(node, "Unexpected negated condition.");
              }
          },
          "ConditionalExpression": function(node) {
              if (isNegatedIf(node)) {
                  context.report(node, "Unexpected negated condition.");
              }
          }
      };
  };
  
  module.exports.schema = [];