module ThinkingSphinx
  class PostgreSQLAdapter < AbstractAdapter
    def setup
      create_array_accum_function
      create_crc32_function
    end

    def sphinx_identifier
      "pgsql"
    end

    def concatenate(clause, separator = ' ')
      if clause[/^COALESCE/]
        clause.split('), ').join(") || '#{separator}' || ")
      else
        clause.split(', ').collect { |field|
          "CAST(COALESCE(#{field}, '') as varchar)"
        }.join(" || '#{separator}' || ")
      end
    end

    def group_concatenate(clause, separator = ' ')
      "array_to_string(array_accum(COALESCE(#{clause}, '0')), '#{separator}')"
    end

    def cast_to_string(clause)
      clause
    end

    def cast_to_datetime(clause)
      if ThinkingSphinx::Configuration.instance.use_64_bit
        "cast(extract(epoch from #{clause}) as bigint)"
      else
        "cast(extract(epoch from #{clause}) as int)"
      end
    end

    def cast_to_unsigned(clause)
      clause
    end

    def cast_to_int(clause)
      "#{clause}::INT8"
    end

    def convert_nulls(clause, default = '')
      default = case default
      when String
        "'#{default}'"
      when NilClass
        'NULL'
      when Fixnum
        "#{default}::bigint"
      else
        default
      end

      "COALESCE(#{clause}, #{default})"
    end

    def boolean(value)
      value ? 'TRUE' : 'FALSE'
    end

    def crc(clause, blank_to_null = false)
      clause = "NULLIF(#{clause},'')" if blank_to_null
      "crc32(#{clause})"
    end

    def utf8_query_pre
      nil
    end

    def time_difference(diff)
      "current_timestamp - interval '#{diff} seconds'"
    end

    def utc_query_pre
      "SET TIME ZONE 'UTC'"
    end

    private

    def execute(command, output_error = false)
      if RUBY_PLATFORM == 'java'
        connection.transaction do
          execute_command command, output_error
        end
      else
        execute_command command, output_error
      end
    end

    def execute_command(command, output_error = false)
      connection.execute "begin"
      connection.execute "savepoint ts"
      begin
        connection.execute command
      rescue StandardError => err
        puts err if output_error
        connection.execute "rollback to savepoint ts"
      end
      connection.execute "release savepoint ts"
      connection.execute "commit"
    end

    def create_array_accum_function
      if connection.raw_connection.respond_to?(:server_version) && connection.raw_connection.server_version > 80200
        execute <<-SQL
          CREATE AGGREGATE array_accum (anyelement)
          (
              sfunc = array_append,
              stype = anyarray,
              initcond = '{}'
          );
        SQL
      else
        execute <<-SQL
          CREATE AGGREGATE array_accum
          (
              basetype = anyelement,
              sfunc = array_append,
              stype = anyarray,
              initcond = '{}'
          );
        SQL
      end
    end

    def create_crc32_function
      execute "CREATE LANGUAGE 'plpgsql';"
      function = <<-SQL
        CREATE OR REPLACE FUNCTION crc32(word text)
        RETURNS bigint AS $$
          DECLARE tmp bigint;
          DECLARE i int;
          DECLARE j int;
          DECLARE byte_length int;
          DECLARE word_array bytea;
          BEGIN
            IF COALESCE(word, '') = '' THEN
              return 0;
            END IF;

            i = 0;
            tmp = 4294967295;
            byte_length = bit_length(word) / 8;
            word_array = decode(replace(word, E'\\\\', E'\\\\\\\\'), 'escape');
            LOOP
              tmp = (tmp # get_byte(word_array, i))::bigint;
              i = i + 1;
              j = 0;
              LOOP
                tmp = ((tmp >> 1) # (3988292384 * (tmp & 1)))::bigint;
                j = j + 1;
                IF j >= 8 THEN
                  EXIT;
                END IF;
              END LOOP;
              IF i >= byte_length THEN
                EXIT;
              END IF;
            END LOOP;
            return (tmp # 4294967295);
          END
        $$ IMMUTABLE LANGUAGE plpgsql;
      SQL
      execute function, true
    end
  end
end