module ActiveRecord
  module ConnectionAdapters
    module PostgreSQL
      module DatabaseStatements
        def explain(arel, binds = [])
          sql = "EXPLAIN #{to_sql(arel, binds)}"
          PostgreSQL::ExplainPrettyPrinter.new.pp(exec_query(sql, "EXPLAIN", binds))
        end

        # The internal PostgreSQL identifier of the money data type.
        MONEY_COLUMN_TYPE_OID = 790 #:nodoc:
        # The internal PostgreSQL identifier of the BYTEA data type.
        BYTEA_COLUMN_TYPE_OID = 17 #:nodoc:

        # create a 2D array representing the result set
        def result_as_array(res) #:nodoc:
          # check if we have any binary column and if they need escaping
          ftypes = Array.new(res.nfields) do |i|
            [i, res.ftype(i)]
          end

          rows = res.values
          return rows unless ftypes.any? { |_, x|
            x == BYTEA_COLUMN_TYPE_OID || x == MONEY_COLUMN_TYPE_OID
          }

          typehash = ftypes.group_by { |_, type| type }
          binaries = typehash[BYTEA_COLUMN_TYPE_OID] || []
          monies   = typehash[MONEY_COLUMN_TYPE_OID] || []

          rows.each do |row|
            # unescape string passed BYTEA field (OID == 17)
            binaries.each do |index, _|
              row[index] = unescape_bytea(row[index])
            end

            # If this is a money type column and there are any currency symbols,
            # then strip them off. Indeed it would be prettier to do this in
            # PostgreSQLColumn.string_to_decimal but would break form input
            # fields that call value_before_type_cast.
            monies.each do |index, _|
              data = row[index]
              # Because money output is formatted according to the locale, there are two
              # cases to consider (note the decimal separators):
              #  (1) $12,345,678.12
              #  (2) $12.345.678,12
              case data
              when /^-?\D+[\d,]+\.\d{2}$/  # (1)
                data.gsub!(/[^-\d.]/, "")
              when /^-?\D+[\d.]+,\d{2}$/  # (2)
                data.gsub!(/[^-\d,]/, "").sub!(/,/, ".")
              end
            end
          end
        end

        # Queries the database and returns the results in an Array-like object
        def query(sql, name = nil) #:nodoc:
          log(sql, name) do
            ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
              result_as_array @connection.async_exec(sql)
            end
          end
        end

        # Executes an SQL statement, returning a PG::Result object on success
        # or raising a PG::Error exception otherwise.
        # Note: the PG::Result object is manually memory managed; if you don't
        # need it specifically, you may want consider the <tt>exec_query</tt> wrapper.
        def execute(sql, name = nil)
          log(sql, name) do
            ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
              @connection.async_exec(sql)
            end
          end
        end

        def exec_query(sql, name = "SQL", binds = [], prepare: false)
          execute_and_clear(sql, name, binds, prepare: prepare) do |result|
            types = {}
            fields = result.fields
            fields.each_with_index do |fname, i|
              ftype = result.ftype i
              fmod  = result.fmod i
              types[fname] = get_oid_type(ftype, fmod, fname)
            end
            ActiveRecord::Result.new(fields, result.values, types)
          end
        end

        def exec_delete(sql, name = nil, binds = [])
          execute_and_clear(sql, name, binds) { |result| result.cmd_tuples }
        end
        alias :exec_update :exec_delete

        def sql_for_insert(sql, pk, id_value, sequence_name, binds) # :nodoc:
          if pk.nil?
            # Extract the table from the insert sql. Yuck.
            table_ref = extract_table_ref_from_insert_sql(sql)
            pk = primary_key(table_ref) if table_ref
          end

          if pk = suppress_composite_primary_key(pk)
            sql = "#{sql} RETURNING #{quote_column_name(pk)}"
          end

          super
        end
        private :sql_for_insert

        def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil)
          if use_insert_returning? || pk == false
            super
          else
            result = exec_query(sql, name, binds)
            unless sequence_name
              table_ref = extract_table_ref_from_insert_sql(sql)
              if table_ref
                pk = primary_key(table_ref) if pk.nil?
                pk = suppress_composite_primary_key(pk)
                sequence_name = default_sequence_name(table_ref, pk)
              end
              return result unless sequence_name
            end
            last_insert_id_result(sequence_name)
          end
        end

        # Begins a transaction.
        def begin_db_transaction
          execute "BEGIN"
        end

        def begin_isolated_db_transaction(isolation)
          begin_db_transaction
          execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
        end

        # Commits a transaction.
        def commit_db_transaction
          execute "COMMIT"
        end

        # Aborts a transaction.
        def exec_rollback_db_transaction
          execute "ROLLBACK"
        end

        private
          # Returns the current ID of a table's sequence.
          def last_insert_id_result(sequence_name)
            exec_query("SELECT currval(#{quote(sequence_name)})", "SQL")
          end

          def suppress_composite_primary_key(pk)
            pk unless pk.is_a?(Array)
          end
      end
    end
  end
end