"use strict";

// Returns "Type(value) is Object" in ES terminology.
function isObject(value) {
  return typeof value === "object" && value !== null || typeof value === "function";
}

const hasOwn = Function.prototype.call.bind(Object.prototype.hasOwnProperty);

const wrapperSymbol = Symbol("wrapper");
const implSymbol = Symbol("impl");
const sameObjectCaches = Symbol("SameObject caches");
const ctorRegistrySymbol = Symbol.for("[webidl2js]  constructor registry");

function getSameObject(wrapper, prop, creator) {
  if (!wrapper[sameObjectCaches]) {
    wrapper[sameObjectCaches] = Object.create(null);
  }

  if (prop in wrapper[sameObjectCaches]) {
    return wrapper[sameObjectCaches][prop];
  }

  wrapper[sameObjectCaches][prop] = creator();
  return wrapper[sameObjectCaches][prop];
}

function wrapperForImpl(impl) {
  return impl ? impl[wrapperSymbol] : null;
}

function implForWrapper(wrapper) {
  return wrapper ? wrapper[implSymbol] : null;
}

function tryWrapperForImpl(impl) {
  const wrapper = wrapperForImpl(impl);
  return wrapper ? wrapper : impl;
}

function tryImplForWrapper(wrapper) {
  const impl = implForWrapper(wrapper);
  return impl ? impl : wrapper;
}

const iterInternalSymbol = Symbol("internal");
const IteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf([][Symbol.iterator]()));
const AsyncIteratorPrototype = Object.getPrototypeOf(Object.getPrototypeOf(async function* () {}).prototype);

function isArrayIndexPropName(P) {
  if (typeof P !== "string") {
    return false;
  }
  const i = P >>> 0;
  if (i === Math.pow(2, 32) - 1) {
    return false;
  }
  const s = `${i}`;
  if (P !== s) {
    return false;
  }
  return true;
}

const byteLengthGetter =
    Object.getOwnPropertyDescriptor(ArrayBuffer.prototype, "byteLength").get;
function isArrayBuffer(value) {
  try {
    byteLengthGetter.call(value);
    return true;
  } catch (e) {
    return false;
  }
}

function iteratorResult([key, value], kind) {
  let result;
  switch (kind) {
    case "key":
      result = key;
      break;
    case "value":
      result = value;
      break;
    case "key+value":
      result = [key, value];
      break;
  }
  return { value: result, done: false };
}

const supportsPropertyIndex = Symbol("supports property index");
const supportedPropertyIndices = Symbol("supported property indices");
const supportsPropertyName = Symbol("supports property name");
const supportedPropertyNames = Symbol("supported property names");
const indexedGet = Symbol("indexed property get");
const indexedSetNew = Symbol("indexed property set new");
const indexedSetExisting = Symbol("indexed property set existing");
const namedGet = Symbol("named property get");
const namedSetNew = Symbol("named property set new");
const namedSetExisting = Symbol("named property set existing");
const namedDelete = Symbol("named property delete");

const asyncIteratorNext = Symbol("async iterator get the next iteration result");
const asyncIteratorReturn = Symbol("async iterator return steps");
const asyncIteratorInit = Symbol("async iterator initialization steps");
const asyncIteratorEOI = Symbol("async iterator end of iteration");

module.exports = exports = {
  isObject,
  hasOwn,
  wrapperSymbol,
  implSymbol,
  getSameObject,
  ctorRegistrySymbol,
  wrapperForImpl,
  implForWrapper,
  tryWrapperForImpl,
  tryImplForWrapper,
  iterInternalSymbol,
  IteratorPrototype,
  AsyncIteratorPrototype,
  isArrayBuffer,
  isArrayIndexPropName,
  supportsPropertyIndex,
  supportedPropertyIndices,
  supportsPropertyName,
  supportedPropertyNames,
  indexedGet,
  indexedSetNew,
  indexedSetExisting,
  namedGet,
  namedSetNew,
  namedSetExisting,
  namedDelete,
  asyncIteratorNext,
  asyncIteratorReturn,
  asyncIteratorInit,
  asyncIteratorEOI,
  iteratorResult
};