import path from "path-browserify";

// https://github.com/gatsbyjs/gatsby/blob/5250a02/packages/gatsby/src/utils/page-data.ts#L20
export function fixedPagePath(pagePath: string): string {
  return pagePath === `/` ? `index` : pagePath;
}

export function joinWithSlash(start: string, end: string): string {
  if (start.length == 0) {
    return end;
  }
  if (end.length == 0) {
    return start;
  }
  let slashes = 0;
  if (start.endsWith("/")) {
    slashes++;
  }
  if (end.startsWith("/")) {
    slashes++;
  }
  if (slashes == 2) {
    return start + end.substring(1);
  }
  if (slashes == 1) {
    return start + end;
  }
  return start + "/" + end;
}

// https://github.com/gatsbyjs/gatsby/blob/5250a02/packages/gatsby/src/utils/page-data.ts#L24
export function getFilePath(publicDir: string, pagePath: string): string {
  return path.join(
    publicDir,
    `page-data`,
    fixedPagePath(pagePath),
    `page-data.json`,
  );
}

export const fixRelativeUrls = (href: string): string => {
  let linkUrl = href;
  if (linkUrl && linkUrl?.startsWith("./")) {
    linkUrl = new URL(linkUrl, document.baseURI).pathname;
  }
  return linkUrl;
};

export const linkUrlPageData = (linkUrl: string): string => {
  return getFilePath("/", fixRelativeUrls(linkUrl));
};

export const linkUrlCustom = (linkUrl: string): string => {
  return `/asyncData${fixRelativeUrls(linkUrl)}.json`;
};

export type FormattedFetchResponse<
  Response = { [name: string]: unknown },
  FormattedResponse = { [name: string]: unknown },
> = (data: Response) => FormattedResponse;

export const formatResponseFromPageData: FormattedFetchResponse<{
  result: { pageContext: unknown };
}> = (data) => data.result.pageContext as { [name: string]: unknown };

export const fetchPageData = (
  href: string,
): Promise<{ [name: string]: unknown }> =>
  fetch(linkUrlPageData(href))
    .then((res) => res.json())
    .then((data) => formatResponseFromPageData(data));