/**
   * @fileoverview Rule to flag use of implied eval via setTimeout and setInterval
   * @author James Allardice
   * @copyright 2015 Mathias Schreck. All rights reserved.
   * @copyright 2013 James Allardice. All rights reserved.
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = function(context) {
      var CALLEE_RE = /set(?:Timeout|Interval)|execScript/;
  
      // Figures out if we should inspect a given binary expression. Is a stack of
      // stacks, where the first element in each substack is a CallExpression.
      var impliedEvalAncestorsStack = [];
  
      //--------------------------------------------------------------------------
      // Helpers
      //--------------------------------------------------------------------------
  
      /**
       * Get the last element of an array, without modifying arr, like pop(), but non-destructive.
       * @param {array} arr What to inspect
       * @returns {*} The last element of arr
       * @private
       */
      function last(arr) {
          return arr ? arr[arr.length - 1] : null;
      }
  
      /**
       * Checks if the given MemberExpression node is a potentially implied eval identifier on window.
       * @param {ASTNode} node The MemberExpression node to check.
       * @returns {boolean} Whether or not the given node is potentially an implied eval.
       * @private
       */
      function isImpliedEvalMemberExpression(node) {
          var object = node.object,
              property = node.property,
              hasImpliedEvalName = CALLEE_RE.test(property.name) || CALLEE_RE.test(property.value);
  
          return object.name === "window" && hasImpliedEvalName;
      }
  
      /**
       * Determines if a node represents a call to a potentially implied eval.
       *
       * This checks the callee name and that there's an argument, but not the type of the argument.
       *
       * @param {ASTNode} node The CallExpression to check.
       * @returns {boolean} True if the node matches, false if not.
       * @private
       */
      function isImpliedEvalCallExpression(node) {
          var isMemberExpression = (node.callee.type === "MemberExpression"),
              isIdentifier = (node.callee.type === "Identifier"),
              isImpliedEvalCallee =
                  (isIdentifier && CALLEE_RE.test(node.callee.name)) ||
                  (isMemberExpression && isImpliedEvalMemberExpression(node.callee));
  
          return isImpliedEvalCallee && node.arguments.length;
      }
  
      /**
       * Checks that the parent is a direct descendent of an potential implied eval CallExpression, and if the parent is a CallExpression, that we're the first argument.
       * @param {ASTNode} node The node to inspect the parent of.
       * @returns {boolean} Was the parent a direct descendent, and is the child therefore potentially part of a dangerous argument?
       * @private
       */
      function hasImpliedEvalParent(node) {
          // make sure our parent is marked
          return node.parent === last(last(impliedEvalAncestorsStack)) &&
              // if our parent is a CallExpression, make sure we're the first argument
              (node.parent.type !== "CallExpression" || node === node.parent.arguments[0]);
      }
  
      /**
       * Checks if our parent is marked as part of an implied eval argument. If
       * so, collapses the top of impliedEvalAncestorsStack and reports on the
       * original CallExpression.
       * @param {ASTNode} node The CallExpression to check.
       * @returns {boolean} True if the node matches, false if not.
       * @private
       */
      function checkString(node) {
          if (hasImpliedEvalParent(node)) {
              // remove the entire substack, to avoid duplicate reports
              var substack = impliedEvalAncestorsStack.pop();
              context.report(substack[0], "Implied eval. Consider passing a function instead of a string.");
          }
      }
  
      //--------------------------------------------------------------------------
      // Public
      //--------------------------------------------------------------------------
  
      return {
          "CallExpression": function(node) {
              if (isImpliedEvalCallExpression(node)) {
                  // call expressions create a new substack
                  impliedEvalAncestorsStack.push([node]);
              }
          },
  
          "CallExpression:exit": function(node) {
              if (node === last(last(impliedEvalAncestorsStack))) {
                  // destroys the entire sub-stack, rather than just using
                  // last(impliedEvalAncestorsStack).pop(), as a CallExpression is
                  // always the bottom of a impliedEvalAncestorsStack substack.
                  impliedEvalAncestorsStack.pop();
              }
          },
  
          "BinaryExpression": function(node) {
              if (node.operator === "+" && hasImpliedEvalParent(node)) {
                  last(impliedEvalAncestorsStack).push(node);
              }
          },
  
          "BinaryExpression:exit": function(node) {
              if (node === last(last(impliedEvalAncestorsStack))) {
                  last(impliedEvalAncestorsStack).pop();
              }
          },
  
          "Literal": function(node) {
              if (typeof node.value === "string") {
                  checkString(node);
              }
          },
  
          "TemplateLiteral": function(node) {
              checkString(node);
          }
      };
  
  };
  
  module.exports.schema = [];