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

// The handlers of the remaining NFSv4.1 operations: the parent lookup,
// the attribute comparisons, the lock owner retirement and the session
// binding family.

package nfs4server

import (
	"errors"

	"sourcedock.dev/petrbalvin/nfs/internal/nfs4"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsfs"
	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
)

// maxOps bounds the TEST_STATEID array, matching the COMPOUND bound of
// the wire codecs.
const maxOps = 1024

// lookuppOp serves LOOKUPP: the current handle becomes its parent
// directory.
func (h *Handler) lookuppOp(reg *fhreg) ([]byte, uint32, error) {
	if !reg.haveCur {
		return nil, nfs4.ErrNoFileHandle, nil
	}
	parent, _, err := h.FS.Parent(reg.cur)
	if err != nil {
		return nil, mapErr(err), nil
	}
	reg.cur, reg.haveCur = parent, true
	return nil, nfs4.ErrOK, nil
}

// verifyOp serves VERIFY and NVERIFY: the compound proceeds only when the
// file carries, or with the negated form does not carry, every attribute
// the arguments assert. A value this build cannot compare answers
// ATTRNOTSUPP.
func (h *Handler) verifyOp(d *xdr.Decoder, reg *fhreg, negate bool) ([]byte, uint32, error) {
	if !reg.haveCur {
		return nil, nfs4.ErrNoFileHandle, nil
	}
	request, err := nfs4.ReadBitmap(d)
	if err != nil {
		return nil, 0, err
	}
	blob, err := d.VarOpaque()
	if err != nil {
		return nil, 0, err
	}
	updates, err := nfs4.DecodeSetattrBlob(blob, request)
	if err != nil {
		if err == nfs4.ErrAttrNotSettable {
			return nil, nfs4.ErrAttrNotSupp, nil
		}
		return nil, 0, err
	}
	info, ferr := h.FS.Getattr(reg.cur)
	if ferr != nil {
		return nil, mapErr(ferr), nil
	}
	mismatch := false
	switch {
	case updates.HasMode && uint32(info.Mode.Perm()) != updates.Mode:
		mismatch = true
	case updates.HasSize && uint64(info.Size) != updates.Size:
		mismatch = true
	case updates.UID != nil && info.UID != *updates.UID:
		mismatch = true
	case updates.GID != nil && info.GID != *updates.GID:
		mismatch = true
	case updates.Atime != nil && !nfsTimeMatches(updates.Atime, info):
		mismatch = true
	case updates.Mtime != nil && !nfsTimeMatches(updates.Mtime, info):
		mismatch = true
	}
	if mismatch == negate {
		return nil, nfs4.ErrOK, nil
	}
	if negate {
		return nil, nfs4.ErrSame, nil
	}
	return nil, nfs4.ErrNotSame, nil
}

// nfsTimeMatches reports whether the asserted time is the file time the
// backend reports. A server time assertion never matches a fixed value;
// only the seconds and nanoseconds a client carries count.
func nfsTimeMatches(set *nfs4.NfsTimeSet, info nfsfs.Info) bool {
	if set.Server {
		return false
	}
	got := info.ModTime
	return got.Unix() == set.Time.Seconds && int64(uint32(got.Nanosecond())) == int64(set.Time.Nseconds)
}

// errTooManyStateids marks a TEST_STATEID whose array exceeds the bound
// every COMPOUND array of this build obeys.
var errTooManyStateids = errors.New("nfs4server: too many stateids in one test")

// releaseLockOwnerOp serves RELEASE_LOCKOWNER: every lock state the
// owner holds dies with the owner. The owner must belong to the asking
// client, RFC 8881 section 18.38.
func (h *Handler) releaseLockOwnerOp(d *xdr.Decoder, sessionClientid uint64) ([]byte, uint32, error) {
	clientid, err := d.Uint64()
	if err != nil {
		return nil, 0, err
	}
	owner, err := d.VarOpaque()
	if err != nil {
		return nil, 0, err
	}
	if sessionClientid != 0 && clientid != sessionClientid {
		return nil, nfs4.ErrBadOwner, nil
	}
	h.locks().releaseOwner(clientid, owner)
	return nil, nfs4.ErrOK, nil
}

// delegReturnOp serves DELEGRETURN: the client gives its own delegation
// back. A stateid the store holds is dropped; anything else is answered
// OK just the same, because the release of a state the server does not
// carry is already done and the reply only tells the client to forget
// the stateid.
func (h *Handler) delegReturnOp(d *xdr.Decoder, sessionClientid uint64) ([]byte, uint32, error) {
	var st nfs4.Stateid
	raw, err := d.Raw(16)
	if err != nil {
		return nil, 0, err
	}
	copy(st[:], raw)
	h.delegs().dropStateid(st, sessionClientid)
	return nil, nfs4.ErrOK, nil
}

// backchannelCtlOp serves BACKCHANNEL_CTL: the client names the program
// its future back channels run.
func (h *Handler) backchannelCtlOp(d *xdr.Decoder, ctx *connCB) ([]byte, uint32, error) {
	program, err := d.Uint32()
	if err != nil {
		return nil, 0, err
	}
	if ctx != nil {
		ctx.setProgram(program)
	}
	return nil, nfs4.ErrOK, nil
}

// bindConnToSessionOp serves BIND_CONN_TO_SESSION: the connection the
// request rode in on joins the session as a fore channel, a back channel
// or both. The session must belong to the asking client, so one client
// cannot graft its connection onto another's callbacks, and the
// callback program comes from CREATE_SESSION, which stores it with the
// session.
func (h *Handler) bindConnToSessionOp(d *xdr.Decoder, ctx *connCB, sessionClientid uint64) ([]byte, uint32, error) {
	var id nfs4.SessionID
	raw, err := d.Raw(16)
	if err != nil {
		return nil, 0, err
	}
	copy(id[:], raw)
	dir, err := d.Uint32()
	if err != nil {
		return nil, 0, err
	}
	if _, err = d.Bool(); err != nil { // use conn in RDMA mode
		return nil, 0, err
	}
	if _, status := h.sessions().lookupSession(id); status != nfs4.ErrOK {
		return nil, status, nil
	}
	// A compound that carries a session may bind only its own: one
	// client must not graft its connection onto another's callbacks.
	if sessionClientid != 0 && id.ClientIDOf() != sessionClientid {
		return nil, nfs4.ErrBadSession, nil
	}
	switch dir {
	case nfs4.Cdfc4Back, nfs4.Cdfc4BackOrBoth:
		if ctx == nil {
			return nil, nfs4.ErrConnNotBound, nil
		}
		h.sessions().attachCB(id, ctx)
		return nfs4.AppendBindConnToSessionRes(nil, id, nfs4.Cdfs4Both), nfs4.ErrOK, nil
	case nfs4.Cdfc4Fore, nfs4.Cdfc4ForeOrBoth:
		return nfs4.AppendBindConnToSessionRes(nil, id, nfs4.Cdfs4Fore), nfs4.ErrOK, nil
	default:
		return nil, nfs4.ErrInval, nil
	}
}

// freeStateidOp serves FREE_STATEID: the client retires a lock stateid
// of its own whose owner holds no locks any more.
func (h *Handler) freeStateidOp(d *xdr.Decoder, sessionClientid uint64) ([]byte, uint32, error) {
	var st nfs4.Stateid
	raw, err := d.Raw(16)
	if err != nil {
		return nil, 0, err
	}
	copy(st[:], raw)
	if status := h.locks().freeStateid(st, sessionClientid); status != nfs4.ErrOK {
		return nil, status, nil
	}
	return nil, nfs4.ErrOK, nil
}

// testStateidOp serves TEST_STATEID: one status per stateid, no state
// touched.
func (h *Handler) testStateidOp(d *xdr.Decoder) ([]byte, uint32, error) {
	n, err := d.Uint32()
	if err != nil {
		return nil, 0, err
	}
	if n > maxOps {
		return nil, 0, errTooManyStateids
	}
	var statuses []uint32
	for range n {
		var st nfs4.Stateid
		raw, rerr := d.Raw(16)
		if rerr != nil {
			return nil, 0, rerr
		}
		copy(st[:], raw)
		status := h.openStates().testStateid(st)
		if status == nfs4.ErrBadStateid {
			switch {
			case h.locks().hasStateid(st):
				status = nfs4.ErrOK
			case h.delegs().hasStateid(st):
				status = nfs4.ErrOK
			}
		}
		statuses = append(statuses, status)
	}
	return nfs4.AppendTestStateidRes(nil, statuses), nfs4.ErrOK, nil
}