// Use the github public api to navigate to the
// last commit of a GitHub repository

(function openFirstCommit(args) {
  // args[1] is the `orgname/repo` url fragment
  // args[2] is the optional branch or hash

  return fetch('https://api.github.com/repos/' + args[1] + '/commits?sha=' + (args[2] || ''))

    // the link header has additional urls for paging
    // parse the original JSON for the case where no other pages exist
    .then(res => Promise.all([res.headers.get('link'), res.json()]))
    
    // get last page of commits
    .then(results => {
      // results[0] is the link
      // results[1] is the first page of commits

      if (results[0]) {
        // the link contains two urls in the form 
        // <https://github.com/...>; rel=blah, <https://github.com/...>; rel=thelastpage
        // split the url out of the string
        var pageurl = results[0].split(',')[1].split(';')[0].slice(2, -1);
        // fetch the last page
        return fetch(pageurl).then(res => res.json());
      }
    
      // if no link, we know we're on the only page
      return results[1];
    })
  
    // get the last commit and extract the url
    .then(commits => commits.pop().html_url)
  
    // navigate there
    .then(url => window.location = url);
})(window.location.pathname.match(/\/([^\/]+\/[^\/]+)(?:\/tree\/([^\/]+))?/));
void(0)