depot/go/nix/nixstore/remotestore.go

package nixstore

import (
	"bytes"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"path"
	"strings"
	"sync"

	"hg.lukegb.com/lukegb/depot/go/nix/nar"
	"hg.lukegb.com/lukegb/depot/go/nix/nar/narinfo"
	"hg.lukegb.com/lukegb/depot/go/nix/nixdrv"
	"hg.lukegb.com/lukegb/depot/go/nix/nixwire"
)

const (
	DaemonSock      = "/nix/var/nix/daemon-socket/socket"
	WorkerMagic1    = 0x6e697863
	WorkerMagic2    = 0x6478696f
	ProtocolVersion = 0x120 // 0x115

	WopAddMultipleToStore         = 44
	WopAddToStoreNar              = 39
	WopBuildDerivation            = 36
	WopEnsurePath                 = 10
	WopIsValidPath                = 1
	WopNarFromPath                = 38
	WopQueryPathInfo              = 26
	WopQuerySubstitutablePathInfo = 21
	WopQueryValidDerivers         = 33
	WopQueryValidPaths            = 31

	MaxBuf = 1024 * 1024 // 1 MB
)

type Daemon struct {
	name string

	conn io.Closer
	w    *nixwire.Serializer
	r    *nixwire.Deserializer
	mu   sync.Mutex
	err  error

	peerMinorVersion int
}

type PathNotValidError struct{ Path string }

func (err PathNotValidError) Error() string {
	return fmt.Sprintf("path %q is not valid", err.Path)
}

func (d *Daemon) Err() error {
	return d.err
}

func (d *Daemon) NARInfo(storePath string) (*narinfo.NarInfo, error) {
	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopQueryPathInfo); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing worker op WopQueryPathInfo: %w", err)
	}
	if _, err := d.w.WriteString(storePath); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing store path query %v: %w", storePath, err)
	}

	if err := d.processStderr(nil, nil, nil); err != nil {
		d.err = err
		return nil, fmt.Errorf("reading stderr from WopQueryPathInfo: %w", err)
	}

	validInt, err := d.r.ReadUint64()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading path validity: %w", err)
	}
	valid := validInt == uint64(1)
	if !valid {
		return nil, PathNotValidError{storePath}
	}

	ni := &narinfo.NarInfo{
		StorePath: storePath,
	}
	if ni.Deriver, err = d.r.ReadString(); err != nil {
		d.err = err
		return nil, fmt.Errorf("reading deriver: %w", err)
	}
	ni.Deriver = path.Base(ni.Deriver)
	if ni.Deriver == "." {
		ni.Deriver = ""
	}

	hashStr, err := d.r.ReadString()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading NAR hash: %w", err)
	}
	if ni.NarHash, err = narinfo.HashFromString("sha256:" + hashStr); err != nil {
		d.err = err
		return nil, fmt.Errorf("parsing NAR hash %q: %w", hashStr, err)
	}

	refs, err := d.r.ReadStrings()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading referrers: %w", err)
	}
	for n, ref := range refs {
		refs[n] = path.Base(ref)
	}
	ni.References = refs

	if _, err := d.r.ReadUint64(); err != nil {
		d.err = err
		return nil, fmt.Errorf("reading registration time: %w", err)
	}
	if ni.NarSize, err = d.r.ReadUint64(); err != nil {
		d.err = err
		return nil, fmt.Errorf("reading narsize: %w", err)
	}
	if _, err := d.r.ReadUint64(); err != nil {
		d.err = err
		return nil, fmt.Errorf("reading ultimate: %w", err)
	}
	sigs, err := d.r.ReadStrings()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading sigs: %w", err)
	}
	ni.CA, err = d.r.ReadString()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading CA: %w", err)
	}

	ni.Sig = make(map[string][]byte)
	for _, sigStr := range sigs {
		sigBits := strings.Split(sigStr, ":")
		sigHash, err := base64.StdEncoding.DecodeString(sigBits[1])
		if err != nil {
			return nil, fmt.Errorf("decoding signature %q: %w", sigStr, err)
		}
		ni.Sig[sigBits[0]] = sigHash
	}

	return ni, nil
}

func (d *Daemon) NARFromPath(storePath string) (io.ReadCloser, error) {
	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopNarFromPath); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing worker op WopNarFromPath: %w", err)
	}
	if _, err := d.w.WriteString(storePath); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing store path query %v: %w", storePath, err)
	}
	if err := d.processStderr(nil, nil, nil); err != nil {
		return nil, fmt.Errorf("waiting for NAR packing: %w", err)
	}

	pr, pw := io.Pipe()
	go func() {
		err := nar.Unpack(io.TeeReader(d.r.Reader, pw), nar.NullFS{}, "irrelevant")
		if err != nil {
			pw.CloseWithError(err)
		} else {
			pw.Close()
		}
	}()

	return io.NopCloser(pr), nil
}

func (d *Daemon) writeOp(op uint64) (int64, error) {
	return d.w.WriteUint64(op)
}

func (d *Daemon) ValidPaths(storePaths []string) ([]string, error) {
	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopQueryValidPaths); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing worker op WopQueryValidPaths: %w", err)
	}
	if _, err := d.w.WriteStrings(storePaths); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing store path query %v: %w", storePaths, err)
	}
	if d.peerMinorVersion >= 27 {
		// Substitute flag
		if _, err := d.w.WriteUint64(0); err != nil {
			d.err = err
			return nil, fmt.Errorf("writing substitute flag: %w", err)
		}
	}

	if err := d.processStderr(nil, nil, nil); err != nil {
		return nil, fmt.Errorf("reading stderr from WopQueryValidPaths: %w", err)
	}

	validPaths, err := d.r.ReadStrings()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading valid paths: %w", err)
	}
	return validPaths, nil
}

func (d *Daemon) Close() error {
	d.mu.Lock()
	defer d.mu.Unlock()

	return d.conn.Close()
}

func (d *Daemon) readFields() ([]any, error) {
	fieldsSz, err := d.r.ReadUint64()
	if err != nil {
		return nil, fmt.Errorf("reading fields count: %w", err)
	}
	var fields []any
	for n := 0; n < int(fieldsSz); n++ {
		fieldTyp, err := d.r.ReadUint64()
		if err != nil {
			return nil, fmt.Errorf("reading field %d type: %w", n, err)
		}
		switch fieldTyp {
		case 0: // tInt
			fieldVal, err := d.r.ReadUint64()
			if err != nil {
				return nil, fmt.Errorf("reading field %d int: %w", n, err)
			}
			fields = append(fields, fieldVal)
		case 1: // tString
			fieldVal, err := d.r.ReadString()
			if err != nil {
				return nil, fmt.Errorf("reading field %d str: %w", n, err)
			}
			fields = append(fields, fieldVal)
		default:
			return nil, fmt.Errorf("reading field %d: unsupported field type %x", n, fieldTyp)
		}
	}
	return fields, nil
}

type NixError struct {
	Code    uint64
	Message string
}

func (ne NixError) Error() string {
	return fmt.Sprintf("nix error %d: %v", ne.Code, ne.Message)
}

func (d *Daemon) processStderr(al *ActivityLogger, stdout io.Writer, stdin io.Reader) error {
	for {
		msg, err := d.r.ReadUint64()
		if err != nil {
			d.err = err
			return fmt.Errorf("read stderr msg code: %w", err)
		}
		switch msg {
		case 0x64617416: // STDERR_WRITE
			if stdout == nil {
				d.err = err
				return fmt.Errorf("STDERR_WRITE requested")
			}
			bs, err := d.r.ReadBytes()
			if err != nil {
				d.err = err
				return fmt.Errorf("read bytes: %w", err)
			}
			_, err = stdout.Write(bs)
			if err != nil {
				d.err = err
				return fmt.Errorf("write bytes into stdout: %w", err)
			}
		case 0x64617461: // STDERR_READ
			if stdin == nil {
				d.err = err
				return fmt.Errorf("STDERR_READ requested")
			}
			readSizeU64, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_READ reading uint64: %w", err)
			}
			readSize := int(readSizeU64)
			if readSize > MaxBuf {
				readSize = MaxBuf
			}
			buf := make([]byte, readSize)
			readSize, err = stdin.Read(buf)
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_READ reading from stdin: %w", err)
			}
			if _, err := d.w.WriteBytes(buf[:readSize]); err != nil {
				d.err = err
				return fmt.Errorf("STDERR_READ writing stdin to socket: %w", err)
			}
		case 0x63787470: // STDERR_ERROR
			if d.peerMinorVersion >= 26 {
				errStr, err := d.r.ReadString()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading 'Error' string: %w", err)
				}
				errLevel, err := d.r.ReadUint64()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading error level: %w", err)
				}
				errName, err := d.r.ReadString()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading error name: %w", err)
				}
				errMsg, err := d.r.ReadString()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading error message: %w", err)
				}
				errPos, err := d.r.ReadUint64()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading error position: %w", err)
				}
				log.Printf("error? Error=%s Level=%d Name=%s Msg=%s Pos=%d", errStr, errLevel, errName, errMsg, errPos)
				errTraceNum, err := d.r.ReadUint64()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading trace count: %w", err)
				}
				for n := 0; n < int(errTraceNum); n++ {
					tracePos, err := d.r.ReadUint64()
					if err != nil {
						d.err = err
						return fmt.Errorf("STDERR_ERROR reading trace position: %w", err)
					}
					traceHint, err := d.r.ReadString()
					if err != nil {
						d.err = err
						return fmt.Errorf("STDERR_ERROR reading trace hint: %w", err)
					}
					log.Printf("error? trace %d/%d: Pos=%d Hint=%s", n+1, errTraceNum, tracePos, traceHint)
				}
				return fmt.Errorf("nix Error=%s Level=%d Name=%s Msg=%s Pos=%d", errStr, errLevel, errName, errMsg, errPos)
			} else {
				errStr, err := d.r.ReadString()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading error string: %w", err)
				}
				status, err := d.r.ReadUint64()
				if err != nil {
					d.err = err
					return fmt.Errorf("STDERR_ERROR reading uint64: %w", err)
				}
				al.AddError(status, errStr)
				return NixError{status, errStr}
			}
		case 0x6f6c6d67: // STDERR_NEXT
			msg, err := d.r.ReadString()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_NEXT reading log string: %w", err)
			}
			al.AddLog(msg)
		case 0x53545254: // STDERR_START_ACTIVITY
			activity, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_START_ACTIVITY reading ActivityId: %w", err)
			}
			lvl, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_START_ACTIVITY reading level: %w", err)
			}
			actTypeU64, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_START_ACTIVITY reading activity type: %w", err)
			}
			actType := ActivityType(actTypeU64)
			s, err := d.r.ReadString()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_START_ACTIVITY reading s: %w", err)
			}
			fields, err := d.readFields()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_START_ACTIVITY fields: %w", err)
			}
			parentActivity, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_START_ACTIVITY reading parent activity: %w", err)
			}
			al.StartActivity(actType, ActivityMeta{
				ActivityID:       activity,
				Level:            lvl,
				String:           s,
				Fields:           fields,
				ParentActivityID: parentActivity,
			})
		case 0x53544f50: // STDERR_STOP_ACTIVITY
			activity, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_STOP_ACTIVITY reading ActivityId: %w", err)
			}
			al.EndActivity(al.Activity(activity))
		case 0x52534c54: // STDERR_RESULT
			activity, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_RESULT reading ActivityId: %w", err)
			}
			resultTypU64, err := d.r.ReadUint64()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_RESULT reading result: %w", err)
			}
			resultTyp := ResultType(resultTypU64)
			fields, err := d.readFields()
			if err != nil {
				d.err = err
				return fmt.Errorf("STDERR_RESULT fields: %w", err)
			}
			al.ActivityResult(al.Activity(activity), resultTyp, fields)
		case 0x616c7473: // STDERR_LAST
			return nil
		}
	}
}

func (d *Daemon) hello() error {
	_, err := d.w.WriteUint64(WorkerMagic1)
	if err != nil {
		d.err = err
		return fmt.Errorf("writing magic 1: %w", err)
	}

	magic2, err := d.r.ReadUint64()
	if err != nil {
		d.err = err
		return fmt.Errorf("reading magic 2: %w", err)
	}
	if magic2 != WorkerMagic2 {
		d.err = err
		return fmt.Errorf("magic 2 mismatch: got %x, wanted %x", magic2, WorkerMagic2)
	}

	daemonVersion, err := d.r.ReadUint64()
	if err != nil {
		d.err = err
		return fmt.Errorf("reading daemon version: %w", err)
	}
	majorVersion := int((daemonVersion >> 8) & 0xff)
	minorVersion := int(daemonVersion & 0xff)
	if majorVersion != 1 {
		d.err = err
		return fmt.Errorf("daemon major version mismatch: got %d, want 1", majorVersion)
	}
	if minorVersion < 21 {
		d.err = err
		return fmt.Errorf("daemon minor version too old: got %d, want at least 21", minorVersion)
	}
	d.peerMinorVersion = minorVersion

	if _, err := d.w.WriteUint64(ProtocolVersion); err != nil {
		d.err = err
		return fmt.Errorf("writing protocol version: %w", err)
	}

	if _, err := d.w.WriteUint64(0); err != nil {
		d.err = err
		return fmt.Errorf("writing obsolete CPU affinity: %w", err)
	}
	if _, err := d.w.WriteUint64(0); err != nil {
		d.err = err
		return fmt.Errorf("writing obsolete reserveSpace: %w", err)
	}

	return d.processStderr(nil, nil, nil)
}

func (d *Daemon) IsValidPath(at *ActivityTracker, storePath string) (bool, error) {
	al := at.StartAction(fmt.Sprintf("IsValidPath(%q)", storePath))
	defer al.Close()

	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopIsValidPath); err != nil {
		d.err = err
		return false, fmt.Errorf("writing worker op WopIsValidPath: %w", err)
	}
	if _, err := d.w.WriteString(storePath); err != nil {
		d.err = err
		return false, fmt.Errorf("writing store path %v: %w", storePath, err)
	}

	if err := d.processStderr(al, nil, nil); err != nil {
		return false, fmt.Errorf("reading stderr from WopIsValidPath: %w", err)
	}

	validInt, err := d.r.ReadUint64()
	if err != nil {
		d.err = err
		return false, fmt.Errorf("reading path validity: %w", err)
	}
	return validInt != 0, nil

}

func (d *Daemon) EnsurePath(at *ActivityTracker, storePath string) error {
	al := at.StartAction(fmt.Sprintf("EnsurePath(%q)", storePath))
	defer al.Close()

	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopEnsurePath); err != nil {
		d.err = err
		return fmt.Errorf("writing worker op WopEnsurePath: %w", err)
	}
	if _, err := d.w.WriteString(storePath); err != nil {
		d.err = err
		return fmt.Errorf("writing store path %v: %w", storePath, err)
	}

	if err := d.processStderr(al, nil, nil); err != nil {
		return fmt.Errorf("reading stderr from WopEnsurePath: %w", err)
	}

	validInt, err := d.r.ReadUint64()
	if err != nil {
		d.err = err
		return fmt.Errorf("reading path validity: %w", err)
	}
	if validInt != 1 {
		return PathNotValidError{storePath}
	}
	return nil
}

type BuildMode uint64

const (
	BMNormal BuildMode = iota
	BMRepair
	BMCheck
)

func (bm BuildMode) String() string {
	return map[BuildMode]string{
		BMNormal: "normal",
		BMRepair: "repair",
		BMCheck:  "check",
	}[bm]
}

type BuildResultStatus uint64

const (
	BRSBuilt BuildResultStatus = iota
	BRSSubstituted
	BRSAlreadyValid
	BRSPermanentFailure
	BRSInputRejected
	BRSOutputRejected
	BRSTransientFailure
	BRSTimedOut
	BRSMiscFailure
	BRSDependencyFailed
	BRSLogLimitExceeded
	BRSNotDeterministic
)

func (brs BuildResultStatus) String() string {
	return map[BuildResultStatus]string{
		BRSBuilt:            "built",
		BRSSubstituted:      "substituted",
		BRSAlreadyValid:     "already valid",
		BRSPermanentFailure: "permanent failure",
		BRSInputRejected:    "input rejected",
		BRSOutputRejected:   "output rejected",
		BRSTransientFailure: "transient failure",
		BRSTimedOut:         "timed out",
		BRSMiscFailure:      "misc failure",
		BRSDependencyFailed: "dependency failed",
		BRSLogLimitExceeded: "log limit exceeded",
		BRSNotDeterministic: "not deterministic",
	}[brs]
}

func (brs BuildResultStatus) IsSuccess() bool {
	switch brs {
	case BRSBuilt, BRSSubstituted, BRSAlreadyValid:
		return true
	default:
		return false
	}
}

func (d *Daemon) BuildDerivation(at *ActivityTracker, derivationPath string, derivation *nixdrv.BasicDerivation, buildMode BuildMode) (BuildResultStatus, error) {
	al := at.StartAction(fmt.Sprintf("BuildDerivation(%q, %q)", derivationPath, buildMode))
	defer al.Close()

	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopBuildDerivation); err != nil {
		d.err = err
		return BRSMiscFailure, fmt.Errorf("writing worker op WopBuildDerivation: %w", err)
	}
	if _, err := d.w.WriteString(derivationPath); err != nil {
		d.err = err
		return BRSMiscFailure, fmt.Errorf("writing derivation store path %v: %w", derivationPath, err)
	}
	if _, err := d.w.WriteDerivation(derivation); err != nil {
		d.err = err
		return BRSMiscFailure, fmt.Errorf("writing derivation content of %v: %w", derivationPath, err)
	}
	if _, err := d.w.WriteUint64(uint64(buildMode)); err != nil {
		d.err = err
		return BRSMiscFailure, fmt.Errorf("writing build mode %v: %w", buildMode, err)
	}

	if err := d.processStderr(al, nil, nil); err != nil {
		return BRSMiscFailure, fmt.Errorf("reading stderr from WopBuildDerivation: %w", err)
	}

	buildStatusU64, err := d.r.ReadUint64()
	if err != nil {
		d.err = err
		return BRSMiscFailure, fmt.Errorf("reading build status code: %w", err)
	}
	buildStatus := BuildResultStatus(buildStatusU64)
	buildErrorMsg, err := d.r.ReadString()
	if err != nil {
		d.err = err
		return BRSMiscFailure, fmt.Errorf("reading build error message: %w", err)
	}

	if !buildStatus.IsSuccess() {
		return buildStatus, fmt.Errorf("%s: %s", buildStatus, buildErrorMsg)
	}

	return buildStatus, nil
}

func (d *Daemon) writeNarInfo(ni *narinfo.NarInfo, w *nixwire.Serializer) error {

	storeRoot := path.Dir(ni.StorePath)

	if _, err := w.WriteString(ni.StorePath); err != nil {
		d.err = err
		return fmt.Errorf("writing store path: %w", err)
	}
	var deriverPath string
	if ni.Deriver != "" {
		deriverPath = path.Join(storeRoot, ni.Deriver)
	}
	if _, err := w.WriteString(deriverPath); err != nil {
		d.err = err
		return fmt.Errorf("writing deriver: %w", err)
	}
	if _, err := w.WriteString(hex.EncodeToString(ni.NarHash.Hash)); err != nil {
		d.err = err
		return fmt.Errorf("writing NAR hash: %w", err)
	}
	rootedRefs := make([]string, len(ni.References))
	for n, ref := range ni.References {
		rootedRefs[n] = path.Join(storeRoot, ref)
	}
	if _, err := w.WriteStrings(rootedRefs); err != nil {
		d.err = err
		return fmt.Errorf("writing references: %w", err)
	}
	if _, err := w.WriteUint64(0); err != nil {
		d.err = err
		return fmt.Errorf("writing dummy registration time: %w", err)
	}
	if _, err := w.WriteUint64(ni.NarSize); err != nil {
		d.err = err
		return fmt.Errorf("writing NAR size: %w", err)
	}
	if _, err := w.WriteUint64(1); err != nil {
		d.err = err
		return fmt.Errorf("writing ultimate (true): %w", err)
	}
	if _, err := w.WriteStrings(ni.Sigs()); err != nil {
		d.err = err
		return fmt.Errorf("writing signatures: %w", err)
	}
	if _, err := w.WriteString(ni.CA); err != nil {
		d.err = err
		return fmt.Errorf("writing content-addressable: %w", err)
	}
	return nil
}

type bufferingReader struct {
	r io.Reader
}

func (r *bufferingReader) Read(p []byte) (int, error) {
	pos := 0
	for {
		n, err := r.r.Read(p[pos:])
		pos += n
		if err != nil {
			if pos > 0 && errors.Is(err, io.EOF) {
				return pos, nil
			}
			return pos, err
		} else if pos >= len(p) {
			break
		}
	}
	return pos, nil
}

func (d *Daemon) AddToStoreNar(ni *narinfo.NarInfo, r io.Reader) error {
	d.mu.Lock()
	defer d.mu.Unlock()

	var preBuffer []byte

	if d.peerMinorVersion >= 32 {
		if _, err := d.writeOp(WopAddMultipleToStore); err != nil {
			d.err = err
			return fmt.Errorf("writing worker op WopAddMultipleToStore: %w", err)
		}
		if _, err := d.w.WriteUint64(0); err != nil {
			d.err = err
			return fmt.Errorf("writing repair (false): %w", err)
		}
		if _, err := d.w.WriteUint64(1); err != nil {
			d.err = err
			return fmt.Errorf("writing dont-check-sigs (true): %w", err)
		}
		buf := new(bytes.Buffer)
		bufs := &nixwire.Serializer{Writer: buf}
		if _, err := bufs.WriteUint64(1); err != nil {
			d.err = err
			return fmt.Errorf("writing count (1): %w", err)
		}
		if err := d.writeNarInfo(ni, bufs); err != nil {
			return fmt.Errorf("buffering NAR info: %w", err)
		}
		preBuffer = buf.Bytes()
	} else {
		if _, err := d.writeOp(WopAddToStoreNar); err != nil {
			d.err = err
			return fmt.Errorf("writing worker op WopAddToStoreNar: %w", err)
		}
		if err := d.writeNarInfo(ni, d.w); err != nil {
			return fmt.Errorf("writing NAR info: %w", err)
		}
		if _, err := d.w.WriteUint64(0); err != nil {
			d.err = err
			return fmt.Errorf("writing repair (false): %w", err)
		}
		if _, err := d.w.WriteUint64(1); err != nil {
			d.err = err
			return fmt.Errorf("writing dont-check-sigs (true): %w", err)
		}
	}

	if d.peerMinorVersion >= 23 {
		// FramedSink
		errCh := make(chan error)
		mr := &bufferingReader{io.MultiReader(bytes.NewReader(preBuffer), r)}
		w := &nixwire.Serializer{Writer: &hexDumpingWriter{enabled: false, w: d.w.Writer}}
		go func() {
			defer close(errCh)
			buf := make([]byte, MaxBuf)
			sofar := 0
			for {
				n, err := mr.Read(buf)
				sofar += n
				if errors.Is(err, io.EOF) {
					break
				} else if err != nil {
					err = fmt.Errorf("reading: %w", err)
					d.err = err
					errCh <- err
					return
				}
				if _, err := w.WriteBytes(buf[:n]); err != nil {
					err = fmt.Errorf("writing payload: %w", err)
					d.err = err
					errCh <- err
					return
				}
			}
			if _, err := w.WriteUint64(0); err != nil {
				err = fmt.Errorf("sending framed EOF: %w", err)
				d.err = err
				errCh <- err
				return
			}
		}()
		if err := d.processStderr(nil, nil, nil); err != nil {
			return fmt.Errorf("reading (framed) stderr from WopAddToStoreNar: %w", err)
		}
		return <-errCh
	} else {
		if err := d.processStderr(nil, nil, &bufferingReader{r}); err != nil {
			return fmt.Errorf("reading stderr from WopAddToStoreNar: %w", err)
		}
	}
	return nil
}

func (d *Daemon) QueryValidDerivers(path string) ([]string, error) {
	d.mu.Lock()
	defer d.mu.Unlock()

	if _, err := d.writeOp(WopQueryValidDerivers); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing worker op WopQueryValidDerivers: %w", err)
	}
	if _, err := d.w.WriteString(path); err != nil {
		d.err = err
		return nil, fmt.Errorf("writing store path: %w", err)
	}

	if err := d.processStderr(nil, nil, nil); err != nil {
		return nil, fmt.Errorf("reading stderr from WopQueryValidDerivers: %w", err)
	}

	drvPaths, err := d.r.ReadStrings()
	if err != nil {
		d.err = err
		return nil, fmt.Errorf("reading deriver paths: %w", err)
	}
	return drvPaths, nil
}

func OpenDaemon(path string) (*Daemon, error) {
	conn, err := net.Dial("unix", path)
	if err != nil {
		return nil, fmt.Errorf("dialing %v: %w", path, err)
	}

	return OpenDaemonWithIOs("unix://"+path, conn, conn, conn)
}

type hexDumpingWriter struct {
	w       io.Writer
	enabled bool
}

func (w *hexDumpingWriter) Write(p []byte) (int, error) {
	n, err := w.w.Write(p)
	if err != nil {
		return 0, err
	}
	if w.enabled {
		log.Printf(">>\n>> %s", strings.TrimSuffix(strings.ReplaceAll(hex.Dump(p), "\n", "\n>> "), "\n>> "))
	}
	return n, nil
}

func OpenDaemonWithIOs(name string, r io.Reader, w io.Writer, c io.Closer) (*Daemon, error) {
	d := &Daemon{
		name: name,
		conn: c,
		w:    &nixwire.Serializer{Writer: &hexDumpingWriter{w: w}},
		r:    &nixwire.Deserializer{Reader: r},
	}
	if err := d.hello(); err != nil {
		d.Close()
		return nil, fmt.Errorf("sending hello: %w", err)
	}

	return d, nil
}