pdlug/stardog-ruby

# encoding: utf-8

module Stardog
  class TransactionConflict < StandardError; end

  class Transaction
    attr_accessor :id, :database

    def initialize(database)
      @database = database
      @state = :created
    end

    # Start a transaction on the server and store the ID.
    # @yield [Transaction]
    # @return [Transaction]
    def start(&block)
      res = database.execute_request(
        :post,
        '/transaction/begin',
        headers: { content_type: 'text/plain' }
      ).body
      self.id = res
      @state = :started
      instance_eval(&block) if block_given?
      self
    end

    # Commit this transaction
    # @raise [TransactionConflict] if the transaction has not been started yet
    # or was already committed
    # @return [true,false]
    def commit
      unless started?
        fail TransactionConflict,
             'Unable to commit, transaction not started yet'
      end

      database.execute_request(
        :post,
        "/transaction/commit/#{id}",
        headers: { content_type: 'text/plain' }
      )
      @state = :committed

      true
    rescue Errors::Conflict
      raise TransactionConflict, 'Conflict - Transaction already committed'
    end

    # Rollback this transaction
    # @raise [TransactionConflict] if the transaction has not been started yet
    #                              or was already rolled back
    # @return [true,false]
    def rollback
      unless started?
        fail TransactionConflict,
             'Unable to rollback, transaction not started yet'
      end

      database.execute_request(
        :post,
        "/transaction/rollback/#{id}",
        headers: { content_type: 'text/plain' }
      )
      @state = :rolledback

      true
    rescue Errors::Conflict
      raise TransactionConflict, 'Conflict - Transaction already rolled back'
    end

    # Add statements to the database.
    # @param data [String]
    # @param format [Format]
    # @param graph_uri [String]
    # @return [true,false]
    def add(data, format = Format::RDF_XML, graph_uri = nil)
      req_params = {
        payload: data,
        headers: { content_type: format }
      }
      req_params[:params] = { 'graph-uri' => graph_uri } if graph_uri

      database.execute_request(:post, "/#{id}/add", req_params)

      true
    end

    # Remove statements from the database.
    # @param data [String]
    # @param format [Format]
    # @param graph_uri [String]
    # @return [true,false]
    def remove(data, format = Format::RDF_XML, graph_uri = nil)
      req_params = {
        payload: data,
        headers: { content_type: format }
      }
      req_params[:params] = { 'graph-uri' => graph_uri } if graph_uri

      database.execute_request(:post, "/#{id}/remove", req_params)

      true
    end

    # Clear all data out of the database (or just the data specified by the
    # named graph URI).
    # @param graph_uri [String]
    # @return [true,false]
    def clear(graph_uri = nil)
      req_params = {}
      req_params[:params] = { 'graph-uri' => graph_uri } if graph_uri

      database.execute_request(:post, "/#{id}/clear", req_params)

      true
    end

    # Whether or not this transaction has been started (has an ID and ready
    # to accept operations)
    # @return [true,false]
    def started?
      @state != :created
    end

    # Whether or not this transaction has been committed
    # @return [true,false]
    def committed?
      @state == :committed
    end
  end
end