/**
   * @fileoverview Ensure handling of errors when we know they exist.
   * @author Jamund Ferguson
   * @copyright 2015 Mathias Schreck.
   * @copyright 2014 Jamund Ferguson. All rights reserved.
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = function(context) {
  
      var errorArgument = context.options[0] || "err";
  
      /**
       * Checks if the given argument should be interpreted as a regexp pattern.
       * @param {string} stringToCheck The string which should be checked.
       * @returns {boolean} Whether or not the string should be interpreted as a pattern.
       */
      function isPattern(stringToCheck) {
          var firstChar = stringToCheck[0];
          return firstChar === "^";
      }
  
      /**
       * Checks if the given name matches the configured error argument.
       * @param {string} name The name which should be compared.
       * @returns {boolean} Whether or not the given name matches the configured error variable name.
       */
      function matchesConfiguredErrorName(name) {
          if (isPattern(errorArgument)) {
              var regexp = new RegExp(errorArgument);
              return regexp.test(name);
          }
          return name === errorArgument;
      }
  
      /**
       * Get the parameters of a given function scope.
       * @param {object} scope The function scope.
       * @returns {array} All parameters of the given scope.
       */
      function getParameters(scope) {
          return scope.variables.filter(function(variable) {
              return variable.defs[0] && variable.defs[0].type === "Parameter";
          });
      }
  
      /**
       * Check to see if we're handling the error object properly.
       * @param {ASTNode} node The AST node to check.
       * @returns {void}
       */
      function checkForError(node) {
          var scope = context.getScope(),
              parameters = getParameters(scope),
              firstParameter = parameters[0];
  
          if (firstParameter && matchesConfiguredErrorName(firstParameter.name)) {
              if (firstParameter.references.length === 0) {
                  context.report(node, "Expected error to be handled.");
              }
          }
      }
  
      return {
          "FunctionDeclaration": checkForError,
          "FunctionExpression": checkForError,
          "ArrowFunctionExpression": checkForError
      };
  
  };
  
  module.exports.schema = [
      {
          "type": "string"
      }
  ];