// Copyright 2018 Google LLC
//
// 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 fsgofer

import (
	"syscall"
	"unsafe"

	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
	"gvisor.googlesource.com/gvisor/pkg/syserr"
)

func statAt(dirFd int, name string) (syscall.Stat_t, error) {
	nameBytes, err := syscall.BytePtrFromString(name)
	if err != nil {
		return syscall.Stat_t{}, err
	}
	namePtr := unsafe.Pointer(nameBytes)

	var stat syscall.Stat_t
	statPtr := unsafe.Pointer(&stat)

	if _, _, errno := syscall.Syscall6(
		syscall.SYS_NEWFSTATAT,
		uintptr(dirFd),
		uintptr(namePtr),
		uintptr(statPtr),
		linux.AT_SYMLINK_NOFOLLOW,
		0,
		0); errno != 0 {

		return syscall.Stat_t{}, syserr.FromHost(errno).ToError()
	}
	return stat, nil
}

func utimensat(dirFd int, name string, times [2]syscall.Timespec, flags int) error {
	// utimensat(2) doesn't accept empty name, instead name must be nil to make it
	// operate directly on 'dirFd' unlike other *at syscalls.
	var namePtr unsafe.Pointer
	if name != "" {
		nameBytes, err := syscall.BytePtrFromString(name)
		if err != nil {
			return err
		}
		namePtr = unsafe.Pointer(nameBytes)
	}

	timesPtr := unsafe.Pointer(&times[0])

	if _, _, errno := syscall.Syscall6(
		syscall.SYS_UTIMENSAT,
		uintptr(dirFd),
		uintptr(namePtr),
		uintptr(timesPtr),
		uintptr(flags),
		0,
		0); errno != 0 {

		return syserr.FromHost(errno).ToError()
	}
	return nil
}

func renameat(oldDirFD int, oldName string, newDirFD int, newName string) error {
	var oldNamePtr unsafe.Pointer
	if oldName != "" {
		nameBytes, err := syscall.BytePtrFromString(oldName)
		if err != nil {
			return err
		}
		oldNamePtr = unsafe.Pointer(nameBytes)
	}
	var newNamePtr unsafe.Pointer
	if newName != "" {
		nameBytes, err := syscall.BytePtrFromString(newName)
		if err != nil {
			return err
		}
		newNamePtr = unsafe.Pointer(nameBytes)
	}

	if _, _, errno := syscall.Syscall6(
		syscall.SYS_RENAMEAT,
		uintptr(oldDirFD),
		uintptr(oldNamePtr),
		uintptr(newDirFD),
		uintptr(newNamePtr),
		0,
		0); errno != 0 {

		return syserr.FromHost(errno).ToError()
	}
	return nil
}