// Linsk - A utility to access Linux-native file systems on non-Linux operating systems.
// Copyright (c) 2023 The Linsk Authors.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

//go:build !windows

package osspecifics

import (
	"fmt"
	"os"
	"os/exec"
	"os/user"
	"path/filepath"
	"strings"
	"syscall"

	"github.com/pkg/errors"
)

func SetNewProcessGroupCmd(cmd *exec.Cmd) {
	// This is to prevent Ctrl+C propagating to the child process.
	cmd.SysProcAttr = &syscall.SysProcAttr{
		Setpgid: true,
	}
}

func TerminateProcess(pid int) error {
	return syscall.Kill(-pid, syscall.SIGTERM)
}

// This is never used except for a band-aid that would check
// that there are no double-mounts.
func CheckDeviceSeemsMounted(devPathPrefix string) (bool, error) {
	// Quite a bit hacky implementation, but it's to be used as a failsafe band-aid anyway.
	devPathPrefix = filepath.Clean(devPathPrefix)

	absDevPathPrefix, err := filepath.Abs(devPathPrefix)
	if err != nil {
		return false, errors.Wrap(err, "get abs path")
	}

	mounts, err := exec.Command("mount").Output()
	if err != nil {
		return false, errors.Wrap(err, "run mount command")
	}

	for _, line := range strings.Split(string(mounts), "\n") {
		// I know, I know, this is a rare band-aid.
		if strings.HasPrefix(line, devPathPrefix) || strings.HasPrefix(line, absDevPathPrefix) {
			return true, nil
		}
	}

	return false, nil
}

func CheckValidDevicePath(devPath string) error {
	stat, err := os.Stat(devPath)
	if err != nil {
		return errors.Wrap(err, "stat path")
	}

	isDev := stat.Mode()&os.ModeDevice != 0
	if !isDev {
		return fmt.Errorf("file mode is not device (%v)", stat.Mode())
	}

	return nil
}

func CheckRunAsRoot() (bool, error) {
	currentUser, err := user.Current()
	if err != nil {
		return false, errors.Wrap(err, "get current user")
	}

	return currentUser.Username == "root", nil
}

func GetDeviceLogicalBlockSize(devPath string) (uint64, error) {
	fd, err := os.Open(devPath)
	if err != nil {
		return 0, errors.Wrap(err, "open device")
	}

	defer func() { _ = fd.Close() }()

	bs, err := getDeviceLogicalBlockSizeInner(fd.Fd())
	if err != nil {
		return 0, errors.Wrap(err, "get block size inner")
	}

	if bs <= 0 {
		return 0, fmt.Errorf("retrieved block size is zero (or negative): '%v'", bs)
	}

	return uint64(bs), nil
}