var traverse = require("../../traverse");
var t        = require("../../types");
var _        = require("lodash");

exports.Program =
exports.BlockStatement =
exports.ForInStatement =
exports.ForOfStatement =
exports.ForStatement = function (node, parent, file) {
  var constants = {};

  var check = function (node, names, parent) {
    _.each(names, function (name) {
      if (!_.has(constants, name)) return;
      if (parent && t.isBlockStatement(parent) && parent !== constants[name]) return;

      throw file.errorWithNode(node, name + " is read-only");
    });
  };

  var getIds = function (node) {
    return t.getIds(node, false, ["MemberExpression"]);
  };

  _.each(node.body, function (child, parent) {
    if (child && t.isVariableDeclaration(child, { kind: "const" })) {
      _.each(child.declarations, function (declar) {
        _.each(getIds(declar), function (name) {
          check(declar, [name], parent);
          constants[name] = parent;
        });

        declar._ignoreConstant = true;
      });

      child._ignoreConstant = true;
      child.kind = "let";
    }
  });

  if (_.isEmpty(constants)) return;

  traverse(node, function (child, parent) {
    if (child._ignoreConstant) return;

    if (t.isDeclaration(child) || t.isAssignmentExpression(child)) {
      check(child, getIds(child), parent);
    }
  });
};