/**
   * @fileoverview Rule to enforce a particular function style
   * @author Nicholas C. Zakas
   * @copyright 2013 Nicholas C. Zakas. All rights reserved.
   */
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = function(context) {
  
      var style = context.options[0],
          allowArrowFunctions = context.options[1] && context.options[1].allowArrowFunctions === true,
          enforceDeclarations = (style === "declaration"),
          stack = [];
  
      var nodesToCheck = {
          "Program": function() {
              stack = [];
          },
  
          "FunctionDeclaration": function(node) {
              stack.push(false);
  
              if (!enforceDeclarations) {
                  context.report(node, "Expected a function expression.");
              }
          },
          "FunctionDeclaration:exit": function() {
              stack.pop();
          },
  
          "FunctionExpression": function(node) {
              stack.push(false);
  
              if (enforceDeclarations && node.parent.type === "VariableDeclarator") {
                  context.report(node.parent, "Expected a function declaration.");
              }
          },
          "FunctionExpression:exit": function() {
              stack.pop();
          },
  
          "ThisExpression": function() {
              if (stack.length > 0) {
                  stack[stack.length - 1] = true;
              }
          }
      };
  
      if (!allowArrowFunctions) {
          nodesToCheck.ArrowFunctionExpression = function() {
              stack.push(false);
          };
  
          nodesToCheck["ArrowFunctionExpression:exit"] = function(node) {
              var hasThisExpr = stack.pop();
  
              if (enforceDeclarations && !hasThisExpr && node.parent.type === "VariableDeclarator") {
                  context.report(node.parent, "Expected a function declaration.");
              }
          };
      }
  
      return nodesToCheck;
  
  };
  
  module.exports.schema = [
      {
          "enum": ["declaration", "expression"]
      },
      {
          "type": "object",
          "properties": {
              "allowArrowFunctions": {
                  "type": "boolean"
              }
          },
          "additionalProperties": false
      }
  ];