module Sources
  
  # Raised when a Couch source is instantiated without a file.
  #
  # Example:
  #   Sources::Couch.new(:column1, :column2) # without file option
  #
  class NoCouchDBGiven < StandardError; end
  
  # A Couch database source.
  #
  # <b>IMPORTANT NOTE:
  #
  # Since Picky currently only handles integer ids (we're working on this),
  # and CouchDB uses hexadecimal ids, this source automatically
  # recalculates a couch id such as
  # fa3f2577a8dbc6a91d7f9989cdffd38e
  # into
  # 332634873577882511228481564366832915342
  # using String#hex.
  #
  # When using the integer ids in a webapp to get your
  # objects from CouchDB, please do a Integer#to_s(16) on the
  # ids you get from Picky before you use them to get your object from CouchDB.</b>
  # 
  #
  # Options:
  # * url
  # and all the options of a <tt>RestClient::Resource</tt>.
  # See http://github.com/archiloque/rest-client.
  #
  # Examples:
  #  Sources::Couch.new(:title, :author, :isbn, url:'localhost:5984')
  #  Sources::Couch.new(:title, :author, :isbn, url:'localhost:5984', user:'someuser', password:'somepassword')
  #
  class Couch < Base
    
    def initialize *category_names, options
      check_gem
      Hash === options && options[:url] || raise_no_db_given(category_names)
      @db = RestClient::Resource.new options.delete(:url), options
    end
    
    # Tries to require the rest_client gem.
    #
    def check_gem # :nodoc:
      require 'rest_client'
    rescue LoadError
      puts "Rest-client gem missing!\nTo use the CouchDB source, you need to:\n  1. Add the following line to Gemfile:\n     gem 'rest-client'\n  2. Then, run:\n     bundle update\n"
      exit 1
    end

    # Harvests the data to index.
    #
    # See important note, above.
    #
    def harvest type, category
      category_name = category.from.to_s
      get_data do |doc|
        yield doc['_id'].hex, doc[category_name] || next
      end
    end
    
    def get_data &block # :nodoc:
      resp = @db['_all_docs?include_docs=true'].get
      JSON.parse(resp)['rows'].
        map{|row| row['doc']}.
        each &block
    end
    
    def raise_no_db_given category_names # :nodoc:
      raise NoCouchDBGiven.new(category_names.join(', '))
    end
  end
end