The start of a couchdb library

require 'rest_client'
require 'json'

class Couch
  def initialize(url)
    @db = url.gsub(/\/$/, '')
  end

  # Updates the given doc by yielding the current state of the doc
  # and trying to update update_limit times. Returns the new doc
  # if the doc was successfully updated without hitting the limit
  def update_doc(doc_id, update_limit=20)
    url = @db + '/' + doc_id
    resp = {'ok' => false}
    new_doc = nil
    
    until resp['ok'] or update_limit == 0
      doc = JSON.parse(RestClient.get(url)) # grab the doc
      new_doc = yield doc                   # give it to the caller to be updated
      begin
        resp = JSON.parse(RestClient.put(url, JSON.generate(new_doc))) # try to PUT the updated doc into the db
      rescue RestClient::RequestFailed => e
        if e.http_code == 409 # Update collision
          update_limit -= 1
        else # some other error
          raise e
        end
      end
    end
    
    raise RestClient::RequestFailed.new unless resp['ok']
    new_doc
  end
end