// +build !windows

/*
   Copyright The containerd Authors.

   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 oci

import (
	"io/ioutil"
	"os"
	"path/filepath"

	specs "github.com/opencontainers/runtime-spec/specs-go"
	"github.com/pkg/errors"
	"golang.org/x/sys/unix"
)

var errNotADevice = errors.New("not a device node")

// HostDevices returns all devices that can be found under /dev directory.
func HostDevices() ([]specs.LinuxDevice, error) {
	return getDevices("/dev", "")
}

func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
	stat, err := os.Stat(path)
	if err != nil {
		return nil, errors.Wrap(err, "error stating device path")
	}

	if !stat.IsDir() {
		dev, err := deviceFromPath(path)
		if err != nil {
			return nil, err
		}
		if containerPath != "" {
			dev.Path = containerPath
		}
		return []specs.LinuxDevice{*dev}, nil
	}

	files, err := ioutil.ReadDir(path)
	if err != nil {
		return nil, err
	}
	var out []specs.LinuxDevice
	for _, f := range files {
		switch {
		case f.IsDir():
			switch f.Name() {
			// ".lxc" & ".lxd-mounts" added to address https://github.com/lxc/lxd/issues/2825
			// ".udev" added to address https://github.com/opencontainers/runc/issues/2093
			case "pts", "shm", "fd", "mqueue", ".lxc", ".lxd-mounts", ".udev":
				continue
			default:
				var cp string
				if containerPath != "" {
					cp = filepath.Join(containerPath, filepath.Base(f.Name()))
				}
				sub, err := getDevices(filepath.Join(path, f.Name()), cp)
				if err != nil {
					return nil, err
				}

				out = append(out, sub...)
				continue
			}
		case f.Name() == "console":
			continue
		}
		device, err := deviceFromPath(filepath.Join(path, f.Name()))
		if err != nil {
			if err == errNotADevice {
				continue
			}
			if os.IsNotExist(err) {
				continue
			}
			return nil, err
		}
		if containerPath != "" {
			device.Path = filepath.Join(containerPath, filepath.Base(f.Name()))
		}
		out = append(out, *device)
	}
	return out, nil
}

func deviceFromPath(path string) (*specs.LinuxDevice, error) {
	var stat unix.Stat_t
	if err := unix.Lstat(path, &stat); err != nil {
		return nil, err
	}

	var (
		devNumber = uint64(stat.Rdev) //nolint: unconvert // the type is 32bit on mips.
		major     = unix.Major(devNumber)
		minor     = unix.Minor(devNumber)
	)
	if major == 0 {
		return nil, errNotADevice
	}

	var (
		devType string
		mode    = stat.Mode
	)
	switch {
	case mode&unix.S_IFBLK == unix.S_IFBLK:
		devType = "b"
	case mode&unix.S_IFCHR == unix.S_IFCHR:
		devType = "c"
	}
	fm := os.FileMode(mode &^ unix.S_IFMT)
	return &specs.LinuxDevice{
		Type:     devType,
		Path:     path,
		Major:    int64(major),
		Minor:    int64(minor),
		FileMode: &fm,
		UID:      &stat.Uid,
		GID:      &stat.Gid,
	}, nil
}