Add driver stub

.golangci.yml

@@ -213,8 +213,8 @@ linters-settings:
     no-mixed-args: true
     kv-only: false
     attr-only: true
-    context-only: true
-    static-msg: true
+    context-only: false # https://github.com/go-simpler/sloglint/issues/29
+    static-msg: false # TODO https://github.com/FerretDB/FerretDB/issues/3421
     no-raw-keys: false # TODO https://github.com/FerretDB/FerretDB/issues/3421
     key-naming-case: snake
     args-on-sep-lines: false

internal/driver/driver.go

@@ -0,0 +1,171 @@
+// 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 driver provides low-level wire protocol driver for testing.
+package driver
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"log/slog"
+	"net"
+	"net/url"
+
+	"github.com/FerretDB/FerretDB/internal/util/lazyerrors"
+	"github.com/FerretDB/FerretDB/internal/wire"
+)
+
+// Conn represents a single connection.
+//
+// It is not safe for concurrent use.
+//
+// Logger is used only with debug level.
+type Conn struct {
+	c net.Conn
+	r *bufio.Reader
+	w *bufio.Writer
+	l *slog.Logger
+}
+
+// Connect creates a new connection for the given MongoDB URI and logger.
+//
+// Context can be used to cancel the connection attempt.
+// Canceling the context after the connection is established has no effect.
+func Connect(ctx context.Context, uri string, l *slog.Logger) (*Conn, error) {
+	u, err := url.Parse(uri)
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	if u.Scheme != "mongodb" {
+		return nil, lazyerrors.Errorf("invalid scheme %q", u.Scheme)
+	}
+
+	if u.Opaque != "" {
+		return nil, lazyerrors.Errorf("invalid URI %q", uri)
+	}
+
+	if _, _, err = net.SplitHostPort(u.Host); err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	if u.User != nil {
+		return nil, lazyerrors.Errorf("authentication is not supported")
+	}
+
+	if u.Path != "/" {
+		return nil, lazyerrors.Errorf("path %q is not supported", u.Path)
+	}
+
+	for k := range u.Query() {
+		switch k {
+		default:
+			return nil, lazyerrors.Errorf("query parameter %q is not supported", k)
+		}
+	}
+
+	l.DebugContext(ctx, "Connecting...", slog.String("uri", uri))
+
+	d := net.Dialer{}
+
+	c, err := d.DialContext(ctx, "tcp", u.Host)
+	if err != nil {
+		return nil, lazyerrors.Error(err)
+	}
+
+	return &Conn{
+		c: c,
+		r: bufio.NewReader(c),
+		w: bufio.NewWriter(c),
+		l: l,
+	}, nil
+}
+
+// Close closes the connection.
+func (c *Conn) Close() error {
+	var err error
+
+	c.l.Debug("Closing...")
+
+	if e := c.w.Flush(); e != nil {
+		err = lazyerrors.Error(e)
+	}
+
+	if e := c.c.Close(); e != nil && err == nil {
+		err = lazyerrors.Error(e)
+	}
+
+	return err
+}
+
+// Read reads the next message from the connection.
+func (c *Conn) Read() (*wire.MsgHeader, wire.MsgBody, error) {
+	header, body, err := wire.ReadMessage(c.r)
+	if err != nil {
+		return nil, nil, lazyerrors.Error(err)
+	}
+
+	c.l.Debug(
+		fmt.Sprintf("<<<\n%s", body.String()),
+		slog.Int("length", int(header.MessageLength)),
+		slog.Int("id", int(header.ResponseTo)),
+		slog.Int("response_to", int(header.ResponseTo)),
+		slog.String("opcode", header.OpCode.String()),
+	)
+
+	return header, body, nil
+}
+
+// Write writes the given message to the connection.
+func (c *Conn) Write(header *wire.MsgHeader, body wire.MsgBody) error {
+	c.l.Debug(
+		fmt.Sprintf(">>>\n%s", body.String()),
+		slog.Int("length", int(header.MessageLength)),
+		slog.Int("id", int(header.ResponseTo)),
+		slog.Int("response_to", int(header.ResponseTo)),
+		slog.String("opcode", header.OpCode.String()),
+	)
+
+	if err := wire.WriteMessage(c.w, header, body); err != nil {
+		return lazyerrors.Error(err)
+	}
+
+	if err := c.w.Flush(); err != nil {
+		return lazyerrors.Error(err)
+	}
+
+	return nil
+}
+
+// WriteRaw writes the given raw bytes to the connection.
+func (c *Conn) WriteRaw(b []byte) error {
+	c.l.Debug(fmt.Sprintf(">>> %d raw bytes", len(b)))
+
+	if _, err := c.w.Write(b); err != nil {
+		return lazyerrors.Error(err)
+	}
+
+	if err := c.w.Flush(); err != nil {
+		return lazyerrors.Error(err)
+	}
+
+	return nil
+}
+
+// Request sends the given request to the connection and returns the response.
+func (c *Conn) Request(ctx context.Context, header *wire.MsgHeader, body wire.MsgBody) (*wire.MsgHeader, wire.MsgBody, error) {
+	// TODO https://github.com/FerretDB/FerretDB/issues/4146
+	panic("not implemented")
+}

internal/driver/driver_test.go

@@ -0,0 +1,38 @@
+// 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 driver
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/FerretDB/FerretDB/internal/util/testutil"
+)
+
+func TestDriver(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+
+	ctx := testutil.Ctx(t)
+
+	c, err := Connect(ctx, "mongodb://127.0.0.1:47017/", testutil.SLogger(t))
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, c.Close()) })
+
+	// TODO https://github.com/FerretDB/FerretDB/issues/4146
+	_ = c
+}