const isWindows = /^win/.test(process.platform);
const forwardSlashPattern = /\//g;
const protocolPattern = /^(\w{2,}):\/\//i;
const url = module.exports;
const jsonPointerSlash = /~1/g;
const jsonPointerTilde = /~0/g;

/* eslint-disable prettier/prettier */
// RegExp patterns to URL-encode special characters in local filesystem paths
const urlEncodePatterns = [
  /\?/g, '%3F',
  /#/g, '%23',
];

// RegExp patterns to URL-decode special characters for local filesystem paths
const urlDecodePatterns = [
  /%23/g, '#',
  /%24/g, '$',
  /%26/g, '&',
  /%2C/g, ',',
  /%40/g, '@',
];
/* eslint-enable prettier/prettier */

exports.parse = require('url').parse;
exports.resolve = require('url').resolve;

/**
 * Returns the current working directory (in Node) or the current page URL (in browsers).
 *
 * @returns {string}
 */
exports.cwd = function cwd() {
  if (process.browser) {
    // eslint-disable-next-line no-restricted-globals
    return location.href;
  }

  const path = process.cwd();

  const lastChar = path.slice(-1);
  if (lastChar === '/' || lastChar === '\\') {
    return path;
  }

  return `${path}/`;
};

/**
 * Returns the protocol of the given URL, or `undefined` if it has no protocol.
 *
 * @param   {string} path
 * @returns {?string}
 */
exports.getProtocol = function getProtocol(path) {
  const match = protocolPattern.exec(path);
  if (match) {
    return match[1].toLowerCase();
  }
};

/**
 * Returns the lowercased file extension of the given URL,
 * or an empty string if it has no extension.
 *
 * @param   {string} path
 * @returns {string}
 */
exports.getExtension = function getExtension(path) {
  const lastDot = path.lastIndexOf('.');
  if (lastDot >= 0) {
    return url.stripQuery(path.substr(lastDot).toLowerCase());
  }
  return '';
};

/**
 * Removes the query, if any, from the given path.
 *
 * @param   {string} path
 * @returns {string}
 */
exports.stripQuery = function stripQuery(path) {
  const queryIndex = path.indexOf('?');
  if (queryIndex >= 0) {
    // eslint-disable-next-line no-param-reassign
    path = path.substr(0, queryIndex);
  }
  return path;
};

/**
 * Returns the hash (URL fragment), of the given path.
 * If there is no hash, then the root hash ("#") is returned.
 *
 * @param   {string} path
 * @returns {string}
 */
exports.getHash = function getHash(path) {
  const hashIndex = path.indexOf('#');
  if (hashIndex >= 0) {
    return path.substr(hashIndex);
  }
  return '#';
};

/**
 * Removes the hash (URL fragment), if any, from the given path.
 *
 * @param   {string} path
 * @returns {string}
 */
exports.stripHash = function stripHash(path) {
  const hashIndex = path.indexOf('#');
  if (hashIndex >= 0) {
    return path.substr(0, hashIndex);
  }
  return path;
};

/**
 * Determines whether the given path is an HTTP(S) URL.
 *
 * @param   {string} path
 * @returns {boolean}
 */
exports.isHttp = function isHttp(path) {
  const protocol = url.getProtocol(path);
  if (protocol === 'http' || protocol === 'https') {
    return true;
  } else if (protocol === undefined) {
    // There is no protocol.  If we're running in a browser, then assume it's HTTP.
    return process.browser;
  }

  // It's some other protocol, such as "ftp://", "mongodb://", etc.
  return false;
};

/**
 * Determines whether the given path is a filesystem path.
 * This includes "file://" URLs.
 *
 * @param   {string} path
 * @returns {boolean}
 */
exports.isFileSystemPath = function isFileSystemPath(path) {
  if (process.browser) {
    // We're running in a browser, so assume that all paths are URLs.
    // This way, even relative paths will be treated as URLs rather than as filesystem paths
    return false;
  }

  const protocol = url.getProtocol(path);
  return protocol === undefined || protocol === 'file';
};

/**
 * Converts a filesystem path to a properly-encoded URL.
 *
 * This is intended to handle situations where JSON Schema $Ref Parser is called
 * with a filesystem path that contains characters which are not allowed in URLs.
 *
 * @example
 * The following filesystem paths would be converted to the following URLs:
 *
 *    <"!@#$%^&*+=?'>.json              ==>   %3C%22!@%23$%25%5E&*+=%3F\'%3E.json
 *    C:\\My Documents\\File (1).json   ==>   C:/My%20Documents/File%20(1).json
 *    file://Project #42/file.json      ==>   file://Project%20%2342/file.json
 *
 * @param {string} path
 * @returns {string}
 */
/* eslint-disable no-param-reassign */
exports.fromFileSystemPath = function fromFileSystemPath(path) {
  // Step 1: On Windows, replace backslashes with forward slashes,
  // rather than encoding them as "%5C"
  if (isWindows) {
    path = path.replace(/\\/g, '/');
  }

  // Step 2: `encodeURI` will take care of MOST characters
  path = encodeURI(path);

  // Step 3: Manually encode characters that are not encoded by `encodeURI`.
  // This includes characters such as "#" and "?", which have special meaning in URLs,
  // but are just normal characters in a filesystem path.
  for (let i = 0; i < urlEncodePatterns.length; i += 2) {
    path = path.replace(urlEncodePatterns[i], urlEncodePatterns[i + 1]);
  }

  return path;
};
/* eslint-enable no-param-reassign */

/**
 * Converts a URL to a local filesystem path.
 *
 * @param {string}  path
 * @param {boolean} [keepFileProtocol] - If true, then "file://" will NOT be stripped
 * @returns {string}
 */
/* eslint-disable no-param-reassign */
exports.toFileSystemPath = function toFileSystemPath(path, keepFileProtocol) {
  // Step 1: `decodeURI` will decode characters such as Cyrillic characters, spaces, etc.
  path = decodeURI(path);

  // Step 2: Manually decode characters that are not decoded by `decodeURI`.
  // This includes characters such as "#" and "?", which have special meaning in URLs,
  // but are just normal characters in a filesystem path.
  for (let i = 0; i < urlDecodePatterns.length; i += 2) {
    path = path.replace(urlDecodePatterns[i], urlDecodePatterns[i + 1]);
  }

  // Step 3: If it's a "file://" URL, then format it consistently
  // or convert it to a local filesystem path
  let isFileUrl = path.substr(0, 7).toLowerCase() === 'file://';
  if (isFileUrl) {
    // Strip-off the protocol, and the initial "/", if there is one
    path = path[7] === '/' ? path.substr(8) : path.substr(7);

    // insert a colon (":") after the drive letter on Windows
    if (isWindows && path[1] === '/') {
      path = `${path[0]}:${path.substr(1)}`;
    }

    if (keepFileProtocol) {
      // Return the consistently-formatted "file://" URL
      path = `file:///${path}`;
    } else {
      // Convert the "file://" URL to a local filesystem path.
      // On Windows, it will start with something like "C:/".
      // On Posix, it will start with "/"
      isFileUrl = false;
      path = isWindows ? path : `/${path}`;
    }
  }

  // Step 4: Normalize Windows paths (unless it's a "file://" URL)
  if (isWindows && !isFileUrl) {
    // Replace forward slashes with backslashes
    path = path.replace(forwardSlashPattern, '\\');

    // Capitalize the drive letter
    if (path.substr(1, 2) === ':\\') {
      path = path[0].toUpperCase() + path.substr(1);
    }
  }

  return path;
};
/* eslint-enable no-param-reassign */

/**
 * Converts a $ref pointer to a valid JSON Path.
 *
 * @param {string}  pointer
 * @returns {Array<number | string>}
 */
exports.safePointerToPath = function safePointerToPath(pointer) {
  if (pointer.length <= 1 || pointer[0] !== '#' || pointer[1] !== '/') {
    return [];
  }

  return pointer
    .slice(2)
    .split('/')
    .map(value => {
      return decodeURIComponent(value).replace(jsonPointerSlash, '/').replace(jsonPointerTilde, '~');
    });
};