/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

export function normalizeUrl(rawUrls: string[]): string {
  const urls = [...rawUrls];
  const resultArray = [];

  let hasStartingSlash = false;
  let hasEndingSlash = false;

  // If the first part is a plain protocol, we combine it with the next part.
  if (urls[0].match(/^[^/:]+:\/*$/) && urls.length > 1) {
    const first = urls.shift();
    urls[0] = first + urls[0];
  }

  // There must be two or three slashes in the file protocol,
  // two slashes in anything else.
  const replacement = urls[0].match(/^file:\/\/\//) ? '$1:///' : '$1://';
  urls[0] = urls[0].replace(/^([^/:]+):\/*/, replacement);

  // eslint-disable-next-line
  for (let i = 0; i < urls.length; i++) {
    let component = urls[i];

    if (typeof component !== 'string') {
      throw new TypeError(`Url must be a string. Received ${typeof component}`);
    }

    if (component === '') {
      if (i === urls.length - 1 && hasEndingSlash) {
        resultArray.push('/');
      }
      // eslint-disable-next-line
      continue;
    }

    if (component !== '/') {
      if (i > 0) {
        // Removing the starting slashes for each component but the first.
        component = component.replace(
          /^[/]+/,
          // Special case where the first element of rawUrls is empty ["", "/hello"] => /hello
          component[0] === '/' && !hasStartingSlash ? '/' : '',
        );
      }

      hasEndingSlash = component[component.length - 1] === '/';
      // Removing the ending slashes for each component but the last.
      // For the last component we will combine multiple slashes to a single one.
      component = component.replace(/[/]+$/, i < urls.length - 1 ? '' : '/');
    }

    hasStartingSlash = true;
    resultArray.push(component);
  }

  let str = resultArray.join('/');
  // Each input component is now separated by a single slash
  // except the possible first plain protocol part.

  // Remove trailing slash before parameters or hash.
  str = str.replace(/\/(\?|&|#[^!])/g, '$1');

  // Replace ? in parameters with &.
  const parts = str.split('?');
  str = parts.shift() + (parts.length > 0 ? '?' : '') + parts.join('&');

  // Dedupe forward slashes in the entire path, avoiding protocol slashes.
  str = str.replace(/([^:]\/)\/+/g, '$1');

  // Dedupe forward slashes at the beginning of the path.
  str = str.replace(/^\/+/g, '/');

  return str;
}