op_msg_section.go

// Copyright 2021 FerretDB Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package wire

import (
	"github.com/FerretDB/wire/internal/util/lazyerrors"
	"github.com/FerretDB/wire/wirebson"
)

// OpMsgSection is one or more sections contained in an OpMsg.
type OpMsgSection struct {
	// The order of fields is weird to make the struct smaller due to alignment.
	// The wire order is: Kind, Identifier, documents.

	Identifier string
	documents  []wirebson.RawDocument
	Kind       byte
}

// Documents returns all documents of that section.
func (msg *OpMsgSection) Documents() []wirebson.RawDocument {
	return msg.documents
}

// checkSections checks given sections.
func checkSections(sections []OpMsgSection) error {
	if len(sections) == 0 {
		return lazyerrors.New("no sections")
	}

	var kind0Found bool

	for _, s := range sections {
		switch s.Kind {
		case 0:
			if kind0Found {
				return lazyerrors.New("multiple kind 0 sections")
			}
			kind0Found = true

			if s.Identifier != "" {
				return lazyerrors.New("kind 0 section has identifier")
			}

			if len(s.documents) != 1 {
				return lazyerrors.Errorf("kind 0 section has %d documents", len(s.documents))
			}

		case 1:
			if s.Identifier == "" {
				return lazyerrors.New("kind 1 section has no identifier")
			}

		default:
			return lazyerrors.Errorf("unknown kind %d", s.Kind)
		}
	}

	return nil
}