// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

// The pNFS layout layer: the wire codecs of LAYOUTGET, LAYOUTCOMMIT,
// LAYOUTRETURN and GETDEVICEINFO over the flexfiles layout of RFC 8435.
// The shapes follow the XDR of RFC 8881 sections 18.43 to 18.45 and RFC
// 8435 section 6.

package nfs4

import (
	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
)

// Layout types of the layouttype4 enum, the registry values of RFC 7863
// and RFC 8435: files, objects and block volume are the NFSv4.1 core,
// flexfiles is four, SCSI five.
const (
	LayoutTypeFiles     = 1
	LayoutTypeObjects   = 2
	LayoutTypeBlock     = 3
	LayoutTypeFlexfiles = 4
	LayoutTypeScsi      = 5
)

// Layout IO modes of the layoutiomode4 enum, RFC 7863.
const (
	IoModeRead = 1
	IoModeRW   = 2
	IoModeAny  = 3
)

// LAYOUTCOMMIT uses the newtime4 union for the modify time a client
// asserts.
type NewTime struct {
	Set      bool
	Seconds  int64
	Nseconds uint32
}

// AppendLayoutGetArgs encodes the whole LAYOUTGET argop: the signal flag,
// the layout type, the IO mode, the range, the stateid the layout hangs
// from and the response size budget.
func AppendLayoutGetArgs(b []byte, signalAvail bool, layoutType, iomode uint32, offset, length, minlength uint64, st Stateid, maxcount uint32) []byte {
	b = xdr.AppendUint32(b, OpLayoutGet)
	b = xdr.AppendBool(b, signalAvail)
	b = xdr.AppendUint32(b, layoutType)
	b = xdr.AppendUint32(b, iomode)
	b = xdr.AppendUint64(b, offset)
	b = xdr.AppendUint64(b, length)
	b = xdr.AppendUint64(b, minlength)
	b = st.Append(b)
	return xdr.AppendUint32(b, maxcount)
}

// A Layout4 is one segment of a granted layout: the byte range, the IO
// mode and the type specific body.
type Layout4 struct {
	Offset uint64
	Length uint64
	IoMode uint32
	Type   uint32
	Body   []byte
}

// AppendLayout4 encodes one layout4.
func AppendLayout4(b []byte, l Layout4) []byte {
	b = xdr.AppendUint64(b, l.Offset)
	b = xdr.AppendUint64(b, l.Length)
	b = xdr.AppendUint32(b, l.IoMode)
	b = xdr.AppendUint32(b, l.Type)
	return xdr.AppendVarOpaque(b, l.Body)
}

// AppendLayoutGetRes encodes a successful LAYOUTGET result: the layout
// stateid, the return-on-close flag and the layouts.
func AppendLayoutGetRes(b []byte, layoutSt Stateid, returnOnClose bool, layouts []Layout4) []byte {
	b = layoutSt.Append(b)
	b = xdr.AppendBool(b, returnOnClose)
	b = xdr.AppendUint32(b, uint32(len(layouts)))
	for _, l := range layouts {
		b = AppendLayout4(b, l)
	}
	return b
}

// AppendLayoutCommitArgs encodes the LAYOUTCOMMIT argop body: the range,
// the reclaim flag, the layout stateid, the last write offset, the modify
// time and the layout update record.
func AppendLayoutCommitArgs(b []byte, offset, length uint64, reclaim bool, layoutSt Stateid, lastWriteSet bool, lastWrite uint64, timeSet bool, seconds int64, nseconds uint32, updateType uint32, updateBody []byte) []byte {
	b = xdr.AppendUint32(b, OpLayoutCommit)
	b = xdr.AppendUint64(b, offset)
	b = xdr.AppendUint64(b, length)
	b = xdr.AppendBool(b, reclaim)
	b = layoutSt.Append(b)
	if lastWriteSet {
		b = xdr.AppendBool(b, true)
		b = xdr.AppendUint64(b, lastWrite)
	} else {
		b = xdr.AppendBool(b, false)
	}
	if timeSet {
		b = xdr.AppendBool(b, true)
		b = xdr.AppendInt64(b, seconds)
		b = xdr.AppendUint32(b, nseconds)
	} else {
		b = xdr.AppendBool(b, false)
	}
	b = xdr.AppendUint32(b, updateType)
	return xdr.AppendVarOpaque(b, updateBody)
}

// AppendLayoutCommitRes encodes a successful LAYOUTCOMMIT result: the
// newsize4 union with the size the layout commit leaves the file at.
func AppendLayoutCommitRes(b []byte, newSize uint64) []byte {
	b = xdr.AppendBool(b, true)
	return xdr.AppendUint64(b, newSize)
}

// AppendLayoutReturnArgs encodes the LAYOUTRETURN argop of the whole file
// system or the whole client: no layoutreturn_file4 body follows.
func AppendLayoutReturnArgs(b []byte, reclaim bool, layoutType, iomode, returnKind uint32) []byte {
	b = xdr.AppendUint32(b, OpLayoutReturn)
	b = xdr.AppendBool(b, reclaim)
	b = xdr.AppendUint32(b, layoutType)
	b = xdr.AppendUint32(b, iomode)
	return xdr.AppendUint32(b, returnKind)
}

// AppendLayoutReturnFileArgs encodes the LAYOUTRETURN argop of one file:
// the offset, the length and the layout stateid ride after the header,
// with the empty ffsid body of NFSv4.2.
func AppendLayoutReturnFileArgs(b []byte, reclaim bool, layoutType, iomode uint32, offset, length uint64, st Stateid) []byte {
	b = AppendLayoutReturnArgs(b, reclaim, layoutType, iomode, ReturnFile)
	b = xdr.AppendUint64(b, offset)
	b = xdr.AppendUint64(b, length)
	b = st.Append(b)
	return xdr.AppendUint32(b, 0) // ffsid_info_type: the empty default
}

// AppendLayoutReturnRes encodes a successful LAYOUTRETURN result: the
// layoutreturn_stateid4 union with the returned flag set and the stateid
// of the layout as returned.
func AppendLayoutReturnRes(b []byte, stateid Stateid) []byte {
	b = xdr.AppendBool(b, true)
	return stateid.Append(b)
}

// AppendGetDeviceInfoArgs encodes the GETDEVICEINFO argop: the device id,
// the layout type, the response size budget and the notification types.
func AppendGetDeviceInfoArgs(b []byte, deviceID [16]byte, layoutType, maxcount uint32, notifyTypes Bitmap) []byte {
	b = xdr.AppendUint32(b, OpGetDeviceInfo)
	b = append(b, deviceID[:]...)
	b = xdr.AppendUint32(b, layoutType)
	b = xdr.AppendUint32(b, maxcount)
	return notifyTypes.AppendTo(b)
}

// AppendGetDeviceInfoRes encodes a successful GETDEVICEINFO result: the
// device address of the flexfiles layout and the notification bitmap.
func AppendGetDeviceInfoRes(b []byte, addrBody []byte) []byte {
	b = xdr.AppendUint32(b, LayoutTypeFlexfiles)
	b = xdr.AppendVarOpaque(b, addrBody)
	return Bitmap{}.AppendTo(b)
}

// A LayoutCommitArgs is the structured form of the LAYOUTCOMMIT argop.
type LayoutCommitArgs struct {
	Offset       uint64
	Length       uint64
	Reclaim      bool
	LayoutSt     Stateid
	LastWriteSet bool
	LastWrite    uint64
	TimeSet      bool
	Seconds      int64
	Nseconds     uint32
	UpdateType   uint32
	UpdateBody   []byte
}

// Encode builds the whole LAYOUTCOMMIT argop.
func (a LayoutCommitArgs) Encode() []byte {
	return AppendLayoutCommitArgs(nil, a.Offset, a.Length, a.Reclaim, a.LayoutSt,
		a.LastWriteSet, a.LastWrite, a.TimeSet, a.Seconds, a.Nseconds, a.UpdateType, a.UpdateBody)
}

// A FlexDataServer is one ff_data_server4: the device the client reads
// and writes through, in the shape of RFC 8435 section 5.1.
type FlexDataServer struct {
	DeviceID   [16]byte
	Efficiency uint32
	Stateid    Stateid
	// FHs carries one file handle per file handle format the data server
	// speaks; one entry is the common case.
	FHs   [][]byte
	User  string
	Group string
}

// A FlexMirror is one ff_mirror4: a list of equivalent data servers that
// hold the same bytes.
type FlexMirror struct {
	DataServers []FlexDataServer
}

// AppendFlexFileLayoutBody encodes the ff_layout4: the stripe unit, the
// mirrors with their data servers, the flags and the stats hint.
func AppendFlexFileLayoutBody(b []byte, flags uint32, stripeUnit uint64, mirrors []FlexMirror) []byte {
	b = xdr.AppendUint64(b, stripeUnit)
	b = xdr.AppendUint32(b, uint32(len(mirrors)))
	for _, m := range mirrors {
		b = xdr.AppendUint32(b, uint32(len(m.DataServers)))
		for _, ds := range m.DataServers {
			b = append(b, ds.DeviceID[:]...)
			b = xdr.AppendUint32(b, ds.Efficiency)
			b = ds.Stateid.Append(b)
			b = xdr.AppendUint32(b, uint32(len(ds.FHs)))
			for _, fh := range ds.FHs {
				b = xdr.AppendVarOpaque(b, fh)
			}
			b = xdr.AppendString(b, ds.User)
			b = xdr.AppendString(b, ds.Group)
		}
	}
	b = xdr.AppendUint32(b, flags)
	return xdr.AppendUint32(b, 0) // stats collect hint
}

// A FlexDeviceAddr is one ff_device_addr4: the net addresses of the data
// servers and the versions they speak.
type FlexDeviceAddr struct {
	NetAddrs []NetAddr
	Versions []FlexVersion
}

// A NetAddr is one netaddr4 of RFC 5661: a netid and a universal address.
type NetAddr struct {
	Netid string
	Uaddr string
}

// A FlexVersion is one ff_device_versions4: an NFS version a data server
// speaks and the transfer sizes it allows.
type FlexVersion struct {
	Version      uint32
	MinorVersion uint32
	RSize        uint32
	WSize        uint32
	TightlyBound bool
}

// AppendFlexDeviceAddr encodes the ff_device_addr4: the net addresses and
// the NFS versions the data servers speak.
func AppendFlexDeviceAddr(b []byte, d FlexDeviceAddr) []byte {
	b = xdr.AppendUint32(b, uint32(len(d.NetAddrs)))
	for _, na := range d.NetAddrs {
		b = xdr.AppendString(b, na.Netid)
		b = xdr.AppendString(b, na.Uaddr)
	}
	b = xdr.AppendUint32(b, uint32(len(d.Versions)))
	for _, v := range d.Versions {
		b = xdr.AppendUint32(b, v.Version)
		b = xdr.AppendUint32(b, v.MinorVersion)
		b = xdr.AppendUint32(b, v.RSize)
		b = xdr.AppendUint32(b, v.WSize)
		b = xdr.AppendBool(b, v.TightlyBound)
	}
	return b
}

// DecodeFlexDeviceAddr decodes an ff_device_addr4 body.
func DecodeFlexDeviceAddr(body []byte) (FlexDeviceAddr, error) {
	d := xdr.NewDecoder(body)
	var out FlexDeviceAddr
	netCount, err := d.Uint32()
	if err != nil {
		return out, err
	}
	for range netCount {
		netid, err := d.String()
		if err != nil {
			return out, err
		}
		uaddr, err := d.String()
		if err != nil {
			return out, err
		}
		out.NetAddrs = append(out.NetAddrs, NetAddr{Netid: netid, Uaddr: uaddr})
	}
	verCount, err := d.Uint32()
	if err != nil {
		return out, err
	}
	for range verCount {
		v, err := d.Uint32()
		if err != nil {
			return out, err
		}
		minor, err := d.Uint32()
		if err != nil {
			return out, err
		}
		rsize, err := d.Uint32()
		if err != nil {
			return out, err
		}
		wsize, err := d.Uint32()
		if err != nil {
			return out, err
		}
		tight, err := d.Bool()
		if err != nil {
			return out, err
		}
		out.Versions = append(out.Versions, FlexVersion{Version: v, MinorVersion: minor, RSize: rsize, WSize: wsize, TightlyBound: tight})
	}
	return out, nil
}