function generateAPI(baseUrl, defaults = {}, scope = []) {
  const callable = () => {}
  callable.url = baseUrl
  return new Proxy(callable, {
    get({ url }, propKey) {
      const method = propKey.toUpperCase()
      const path = scope.concat(propKey)
      if (['GET', 'POST', 'PUT', 'DELETE', 'PATCH'].includes(method)) {
        return (data, overrides = {}) => {
          const payload = { method, ...overrides }
          switch (method) {
            case 'GET': {
              if (data) url = `${url}?${new URLSearchParams(data)}`
              break
            }
            case 'POST':
            case 'PUT':
            case 'PATCH': {
              payload.body = JSON.stringify(data)
            }
          }
          console.log(`Calling: ${url}${path.slice(0, -1).join('/')}`)
          console.log('payload', payload)
          return fetch(url, payload).then((d) => d.json())
        }
      }
      return generateAPI(`${url}/${propKey}`, defaults, path)
    },
    apply({ url }, thisArg, [arg] = []) {
      const path = url.split('/')
      return generateAPI(arg ? `${url}/${arg}` : url, defaults, path)
    }
  })
}

function githubClient(token) {
  return generateAPI('https://api.github.com', {
    headers: {
      'User-Agent': 'required field',
      'Authorization': `bearer ${token}`
    }
  })
}

const token = 'tokenxyz'
const client = generateAPI('https://api.github.com', {
  headers: {
    'User-Agent': 'required field',
    'Authorization': `bearer ${token}`
  }
})

async function getRepo() {
  // GET /repos/{owner}/{repo}
  return client.repos.davidwells.analytics.get()
}

getRepo().then((r) => {
  console.log('repo, r)
})