// Adater module exposing all `fs` methods with promises instead of callbacks.

"use strict";

const fs = require("fs");
const promisify = require("./promisify");

const isCallbackMethod = key => {
  return [
    typeof fs[key] === "function",
    !key.match(/Sync$/),
    !key.match(/^[A-Z]/),
    !key.match(/^create/),
    !key.match(/^(un)?watch/)
  ].every(Boolean);
};

const adaptMethod = name => {
  const original = fs[name];
  return promisify(original);
};

const adaptAllMethods = () => {
  const adapted = {};

  Object.keys(fs).forEach(key => {
    if (isCallbackMethod(key)) {
      if (key === "exists") {
        // fs.exists() does not follow standard
        // Node callback conventions, and has
        // no error object in the callback
        adapted.exists = () => {
          throw new Error("fs.exists() is deprecated");
        };
      } else {
        adapted[key] = adaptMethod(key);
      }
    } else {
      adapted[key] = fs[key];
    }
  });

  return adapted;
};

module.exports = adaptAllMethods();