module Neo4j
  module Server
    # The CypherTransaction object lifecycle is as follows:
    # * It is initialized with the transactional endpoint URL and the connection object to use for communication. It does not communicate with the server to create this.
    # * The first query within the transaction sets the commit and execution addresses, :commit_url and :query_url.
    # * At any time, `failure` can be called to mark a transaction failed and trigger a rollback upon closure.
    # * `close` is called to end the transaction. It calls `commit` or `delete`.
    #
    # If a transaction is created and then closed without performing any queries, an OpenStruct is returned that behaves like a successfully closed query.
    class CypherTransaction < Neo4j::Transaction::Base
      include Resource

      attr_reader :commit_url, :query_url

      def connection
        @session.connection
      end

      def base_url
        require 'uri'
        URI(@session.instance_variable_get('@resource_url')).tap do |uri|
          uri.path = ''
        end.to_s
      end

      ROW_REST = %w(row REST)
      def _query(cypher_query, params = nil)
        fail 'Transaction expired, unable to perform query' if expired?
        statement = {statement: cypher_query, parameters: params, resultDataContents: ROW_REST}
        body = {statements: [statement]}

        response = @query_url ? query(body) : start(body)

        create_cypher_response(response)
      end

      def start(body)
        request(:post, start_url, 201, body).tap do |response|
          @commit_url = response.body[:commit]
          @query_url = response.headers[:Location]

          fail "NO ENDPOINT URL #{connection} : HEAD: #{response.headers.inspect}" if !@query_url || @query_url.empty?

          init_resource_data(response.body, base_url)
        end
      end

      def start_url
        @session.resource_data.fetch(:transaction) || base_url
      end

      def query(body)
        request(:post, @query_url, 200, body)
      end

      EMPTY_RESPONSE = OpenStruct.new(status: 200, body: '')

      def delete
        return EMPTY_RESPONSE if !@commit_url || expired?

        request(:delete, @query_url, 200, nil, resource_headers)
      end

      def commit
        return EMPTY_RESPONSE if !@commit_url || expired?

        request(:post, @commit_url, 200, nil, resource_headers)
      end

      private

      def request(action, endpoint_url, expected_code = 200, body = nil, headers = {})
        connection.send(action, endpoint_url, body, headers).tap do |response|
          expect_response_code!(response, expected_code)
        end
      end

      def create_cypher_response(response)
        CypherResponse.new(response, true).tap do |cypher_response|
          if response.body[:errors].empty?
            cypher_response.set_data(response.body[:results][0])
          else
            first_error = response.body[:errors].first
            tx_cleanup!(first_error)
            cypher_response.set_error(first_error)
          end
        end
      end

      def tx_cleanup!(first_error)
        autoclosed!
        mark_expired if first_error[:message] =~ /Unrecognized transaction id/
      end

      def empty_response
        OpenStruct.new(status: 200, body: '')
      end
    end
  end
end