import npmurl from 'url'

function loadJSON(url: string, defaultValue: any, cb: (...args: any[]) => void) {
  fetch(url, {
    mode: 'cors',
    credentials: "same-origin"
  })
    .then((response) => {
      if (!response.ok) {
        throw new Error('Failed to load metadata for ' + url);
      }
      return response.json();
    })
    .then((body) => {
      cb(body)
    })
    .catch(() => {
      console.warn('Can not load metadata for ' + url + ', using default value ' + defaultValue);
      cb(defaultValue)
    })
}

export function downloadGlyphsMetadata(urlTemplate: string, cb: (...args: any[]) => void) {
  if(!urlTemplate) return cb([])

  // Special handling because Tileserver GL serves the fontstacks metadata differently
  // https://github.com/klokantech/tileserver-gl/pull/104#issuecomment-274444087
  const urlObj = npmurl.parse(urlTemplate);
  const normPathPart = '/%7Bfontstack%7D/%7Brange%7D.pbf';
  if(urlObj.pathname === normPathPart) {
    urlObj.pathname = '/fontstacks.json';
  } else {
    urlObj.pathname = urlObj.pathname!.replace(normPathPart, '.json');
  }
  const url = npmurl.format(urlObj);

  loadJSON(url, [], cb)
}

export function downloadSpriteMetadata(baseUrl: string, cb: (...args: any[]) => void) {
  if(!baseUrl) return cb([])
  const url = baseUrl + '.json'
  loadJSON(url, {}, glyphs => cb(Object.keys(glyphs)))
}