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

// The layout type families beyond flexfiles, each with its wire body
// and the device address this build answers for it: files (RFC 5661
// section 13.3), block/volume (RFC 5663), objects (RFC 5664) and SCSI
// (RFC 8154). The metadata server of this build emulates every one of
// them over its own storage, so all bodies name the one device the
// server itself is.

package nfs4

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

// AppendFileLayoutBody encodes the nfsv4_1_file_layout4: the device,
// the stripe unit descriptor, the first stripe index, the pattern
// offset and the file handle list.
func AppendFileLayoutBody(b []byte, device [16]byte, util, firstStripe uint32, patternOffset uint64, fhs [][]byte) []byte {
	b = append(b, device[:]...)
	b = xdr.AppendUint32(b, util)
	b = xdr.AppendUint32(b, firstStripe)
	b = xdr.AppendUint64(b, patternOffset)
	b = xdr.AppendUint32(b, uint32(len(fhs)))
	for _, fh := range fhs {
		b = xdr.AppendVarOpaque(b, fh)
	}
	return b
}

// AppendFileDeviceAddr encodes the nfsv4_1_file_layout_ds_addr4: the
// stripe indices over the multipath list of data server addresses.
func AppendFileDeviceAddr(b []byte, stripeIndices []uint32, addrs []NetAddr) []byte {
	b = xdr.AppendUint32(b, uint32(len(stripeIndices)))
	for _, i := range stripeIndices {
		b = xdr.AppendUint32(b, i)
	}
	b = xdr.AppendUint32(b, uint32(len(addrs)))
	for _, a := range addrs {
		b = xdr.AppendString(b, a.Netid)
		b = xdr.AppendString(b, a.Uaddr)
	}
	return b
}

// A BlockVolume is one pnfs_block_volume4 of the emulated device: a
// simple volume with the given base offset and block count.
type BlockVolume struct {
	// Type is PNFS_BLOCK_VOLUME_SIMPLE (1).
	BaseOffset uint64
	BlockCount uint64
	DeviceID   [16]byte
}

// AppendBlockDeviceAddr encodes the pnfs_block_deviceaddr4 with one
// simple volume, RFC 5663 section 5.1.
func AppendBlockDeviceAddr(b []byte, v BlockVolume) []byte {
	b = xdr.AppendUint32(b, 1) // one volume
	b = xdr.AppendUint32(b, 1) // PNFS_BLOCK_VOLUME_SIMPLE
	b = append(b, v.DeviceID[:]...)
	b = xdr.AppendUint64(b, v.BaseOffset)
	return xdr.AppendUint64(b, v.BlockCount)
}

// AppendScsiLayoutBody encodes the pnfs_scsi_layout4: one extent over
// the emulated volume, RFC 8154 section 5.2.
func AppendScsiLayoutBody(b []byte, device [16]byte, fileOffset, length, storageOffset uint64) []byte {
	b = xdr.AppendUint32(b, 1) // one extent
	b = append(b, device[:]...)
	b = xdr.AppendUint64(b, fileOffset)
	b = xdr.AppendUint64(b, length)
	b = xdr.AppendUint64(b, storageOffset)
	return xdr.AppendUint32(b, 0) // reserved
}

// An ObjectLayout is the emulated pnfs_osd_layout4: the map header and
// one component credential over the emulated OSD.
type ObjectLayout struct {
	NumComponents uint32
	StripeUnit    uint64
	GroupWidth    uint32
	GroupDepth    uint32
	RefTagSize    uint32
}

// AppendObjectLayoutBody encodes a minimal pnfs_osd_layout4 for the
// emulated OSD, RFC 5664 section 3.3: the data map and one component.
func AppendObjectLayoutBody(b []byte, device [16]byte, l ObjectLayout) []byte {
	// pnfs_osd_data_map4
	b = xdr.AppendUint32(b, 0) // odi_odm_raid_algorithm: PNFS_OSD_RAID_0
	b = xdr.AppendUint64(b, l.StripeUnit)
	b = xdr.AppendUint32(b, l.NumComponents)
	b = xdr.AppendUint32(b, l.GroupWidth)
	b = xdr.AppendUint32(b, l.GroupDepth)
	b = xdr.AppendUint32(b, l.RefTagSize)
	// olo_comps_index and the single component
	b = xdr.AppendUint32(b, 0)
	// pnfs_osd_object_cred4: version, credential type, opaque cred
	b = xdr.AppendUint32(b, 0)
	b = xdr.AppendUint32(b, 0)
	b = xdr.AppendVarOpaque(b, nil)
	// object id: partition id + object id
	b = xdr.AppendUint64(b, 0)
	b = xdr.AppendUint64(b, 1)
	_ = device
	return b
}

// AppendGetDeviceListRes encodes the GETDEVICELIST4resok: the cookie,
// its verifier, the device ids and the end of list flag, RFC 5661
// section 18.41.
func AppendGetDeviceListRes(b []byte, cookie uint64, cookieverf [8]byte, devices [][16]byte, eof bool) []byte {
	b = xdr.AppendUint64(b, cookie)
	b = append(b, cookieverf[:]...)
	b = xdr.AppendUint32(b, uint32(len(devices)))
	for _, d := range devices {
		b = append(b, d[:]...)
	}
	return xdr.AppendBool(b, eof)
}

// AppendGetDeviceListArgs encodes the GETDEVICELIST argop: the layout
// type, the device count budget and the resumption cookie, RFC 5661
// section 18.41.
func AppendGetDeviceListArgs(b []byte, layoutType, maxDevices uint32, cookie uint64, cookieverf [8]byte) []byte {
	b = xdr.AppendUint32(b, OpGetDeviceList)
	b = xdr.AppendUint32(b, layoutType)
	b = xdr.AppendUint32(b, maxDevices)
	b = xdr.AppendUint64(b, cookie)
	return append(b, cookieverf[:]...)
}

// LayoutTypeFlexFilesV2 is the layout type of the flexible file layout
// version 2: the layout type number 0x6 of the pNFS Layout Types
// registry, defined by the expired Internet-Draft
// draft-haynes-nfsv4-flex-filesv2-00. The draft never became an RFC;
// the number is stable and Linux clients carry the same one.
const LayoutTypeFlexFilesV2 = 6

// A FlexDataServerV2 is one ffv2_data_server4 of the draft: like the
// version one entry but with an array of stateids, the file handles
// per supported version, and the RPC credential the data server needs
// for loose coupling.
type FlexDataServerV2 struct {
	DeviceID   [16]byte
	Efficiency uint32
	Stateids   []Stateid
	FHs        [][]byte
	User       string
	Group      string
	AuthFlavor uint32
	AuthBody   []byte
}

// A FlexMirrorV2 is one ffv2_mirror4: the data servers of one mirror.
type FlexMirrorV2 struct {
	DataServers []FlexDataServerV2
}

// AppendFlexFileLayoutBodyV2 encodes the ffv2_layout4 of
// draft-haynes-nfsv4-flex-filesv2-00 section 3.1: the stripe unit, the
// mirrors with their data servers, the flags and the stats hint. The
// device address is the version one ff_device_addr4, whose version
// array must carry one entry per stateid and per file handle.
func AppendFlexFileLayoutBodyV2(b []byte, flags uint32, stripeUnit uint64, mirrors []FlexMirrorV2) []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 = xdr.AppendUint32(b, uint32(len(ds.Stateids)))
			for _, st := range ds.Stateids {
				b = st.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)
			// opaque_auth: the flavour and the credential body.
			b = xdr.AppendUint32(b, ds.AuthFlavor)
			b = xdr.AppendVarOpaque(b, ds.AuthBody)
		}
	}
	b = xdr.AppendUint32(b, flags)
	return xdr.AppendUint32(b, 0) // stats collect hint
}