Joining an Hypothesis group

join_hypothesis_group.rb

#!/usr/bin/env ruby
#
# Joining an Hypothesis group is done through the web, and there is no API method to do so.
# Sometimes this is useful. Here is an implementation that logs into Hypothesis, and joins a group.
#
# Set the environment variables:
#   HYPOTHESIS_USERNAME
#   HYPOTHESIS_PASSWORD
# Then call the script with argument the Hypothesis group id.
#   ruby join_hypothesis_group.rb abcd12345
#
# https://hypothes.is/
#
require 'faraday'

def web_join_group(id)
  conn = web_connection
  cookies = {}
  # get csrf token for login
  res = conn.get("login")
  csrf_token = web_csrf_token res
  return false unless csrf_token
  cookies.merge! cookie_header_to_hash(res.headers["Set-Cookie"])
  # login
  res = conn.post("login", csrf_token:, username: ENV["HYPOTHESIS_USERNAME"], password: ENV["HYPOTHESIS_PASSWORD"]) do |req|
    req.headers["Cookie"] = cookies.map { |k, v| [ k, v ].join("=") }.join("; ")
  end
  cookies.merge! cookie_header_to_hash(res.headers["Set-Cookie"])
  # join group
  conn.post("groups/#{id}/", group_join: "") do |req|
    req.headers["Cookie"] = cookies.map { |k, v| [ k, v ].join("=") }.join("; ")
  end
  true
end

def web_connection
  Faraday.new(url: "https://hypothesis.is/") do |builder|
    builder.request :url_encoded
    builder.response :raise_error
  end
end

def web_csrf_token(response)
  response.body.match(/"csrfToken"\s*:\s*"([^"]+)"/)&.captures&.first
end

# Somehow the existing cookie jar implementations didn't work when parsing multiple cookies.
def cookie_header_to_hash(cookies)
  cookies&.split(/,\s*(?=[^ ,;=]+=)/)&.map { |c| c.split(";").first.split("=") }&.to_h
end

web_join_group(ARGV.argv[0])