"use strict";
  
  const idlUtils = require("../generated/utils.js");
  const { setAttributeValue, removeAttributeByName } = require("../attributes");
  const validateName = require("../helpers/validate-names").name;
  const DOMException = require("domexception/webidl2js-wrapper");
  
  const dataAttrRe = /^data-([^A-Z]*)$/;
  
  function attrCamelCase(name) {
    return name.replace(/-([a-z])/g, (match, alpha) => alpha.toUpperCase());
  }
  
  function attrSnakeCase(name) {
    return name.replace(/[A-Z]/g, match => `-${match.toLowerCase()}`);
  }
  
  exports.implementation = class DOMStringMapImpl {
    constructor(globalObject, args, privateData) {
      this._globalObject = globalObject;
      this._element = privateData.element;
    }
    get [idlUtils.supportedPropertyNames]() {
      const result = new Set();
      const { attributes } = this._element;
      for (let i = 0; i < attributes.length; i++) {
        const attr = attributes.item(i);
        const matches = dataAttrRe.exec(attr.localName);
        if (matches) {
          result.add(attrCamelCase(matches[1]));
        }
      }
      return result;
    }
    [idlUtils.namedGet](name) {
      const { attributes } = this._element;
      for (let i = 0; i < attributes.length; i++) {
        const attr = attributes.item(i);
        const matches = dataAttrRe.exec(attr.localName);
        if (matches && attrCamelCase(matches[1]) === name) {
          return attr.value;
        }
      }
      return undefined;
    }
    [idlUtils.namedSetNew](name, value) {
      if (/-[a-z]/.test(name)) {
        throw DOMException.create(this._globalObject, [
          `'${name}' is not a valid property name`,
          "SyntaxError"
        ]);
      }
      name = `data-${attrSnakeCase(name)}`;
      validateName(this._globalObject, name);
      setAttributeValue(this._element, name, value);
    }
    [idlUtils.namedSetExisting](name, value) {
      this[idlUtils.namedSetNew](name, value);
    }
    [idlUtils.namedDelete](name) {
      name = `data-${attrSnakeCase(name)}`;
      removeAttributeByName(this._element, name);
    }
  };