/**
   * @fileoverview Rule to flag when re-assigning native objects
   * @author Ilya Volodin
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = function(context) {
  
      var config = context.options[0];
      var exceptions = (config && config.exceptions) || [];
  
      /**
       * Gets the names of writeable built-in variables.
       * @param {escope.Scope} scope - A scope to get.
       * @returns {object} A map that its key is variable names.
       */
      function getBuiltinGlobals(scope) {
          return scope.variables.reduce(function(retv, variable) {
              if (variable.writeable === false && variable.name !== "__proto__") {
                  retv[variable.name] = true;
              }
              return retv;
          }, Object.create(null));
      }
  
      /**
       * Reports if a given reference's name is same as native object's.
       * @param {object} builtins - A map that its key is a variable name.
       * @param {Reference} reference - A reference to check.
       * @param {int} index - The index of the reference in the references.
       * @param {Reference[]} references - The array that the reference belongs to.
       * @returns {void}
       */
      function checkThroughReference(builtins, reference, index, references) {
          var identifier = reference.identifier;
  
          if (identifier &&
              builtins[identifier.name] &&
              exceptions.indexOf(identifier.name) === -1 &&
              reference.init === false &&
              reference.isWrite() &&
              // Destructuring assignments can have multiple default value,
              // so possibly there are multiple writeable references for the same identifier.
              (index === 0 || references[index - 1].identifier !== identifier)
          ) {
              context.report(
                  identifier,
                  "{{name}} is a read-only native object.",
                  {name: identifier.name});
          }
      }
  
      return {
          // Checks assignments of global variables.
          // References to implicit global variables are not resolved,
          // so those are in the `through` of the global scope.
          "Program": function() {
              var globalScope = context.getScope();
              var builtins = getBuiltinGlobals(globalScope);
              globalScope.through.forEach(checkThroughReference.bind(null, builtins));
          }
      };
  
  };
  
  module.exports.schema = [
      {
          "type": "object",
          "properties": {
              "exceptions": {
                  "type": "array",
                  "items": {"type": "string"},
                  "uniqueItems": true
              }
          },
          "additionalProperties": false
      }
  ];