package usershell

import (

"os"

"os/user"

"github.com/spf13/afero"

"golang.org/x/xerrors"

)

// homeDir returns the home directory of the current user, giving

// priority to the $HOME environment variable. It backs

// SystemEnvInfo.HomeDir. Callers outside this package resolve the home

// directory through an EnvInfoer so the injected environment is honored.

func homeDir() (string, error) {

// First we check the environment.

homedir, err := os.UserHomeDir()

if err == nil {

return homedir, nil

}

// As a fallback, we try the user information.

u, err := user.Current()

if err != nil {

return "", xerrors.Errorf("current user: %w", err)

}

return u.HomeDir, nil

}

// ResolveWorkingDirectory returns dir when it is non-empty and an existing

// directory on fs. Otherwise it falls back to the home directory

// reported by ei. SSH sessions and the process API share this so their

// working directory resolution cannot drift, and the home fallback goes

// through the injected EnvInfoer rather than the host directly.

func ResolveWorkingDirectory(fs afero.Fs, ei EnvInfoer, dir string) (string, error) {

if dir != "" {

if info, err := fs.Stat(dir); err == nil && info.IsDir() {

return dir, nil

}

}

return ei.HomeDir()

}

// EnvInfoer encapsulates external information about the environment.

type EnvInfoer interface {

// User returns the current user.

User() (*user.User, error)

// Environ returns the environment variables of the current process.

Environ() []string

// HomeDir returns the home directory of the current user.

HomeDir() (string, error)

// Shell returns the shell of the given user.

Shell(username string) (string, error)

// ModifyCommand modifies the command and arguments before execution based on

// the environment. This is useful for executing a command inside a container.

// In the default case, the command and arguments are returned unchanged.

ModifyCommand(name string, args ...string) (string, []string)

}

// SystemEnvInfo encapsulates the information about the environment

// just using the default Go implementations.

type SystemEnvInfo struct{}

func (SystemEnvInfo) User() (*user.User, error) {

return user.Current()

}

func (SystemEnvInfo) Environ() []string {

var env []string

for _, e := range os.Environ() {

// Ignore GOTRACEBACK=none, as it disables stack traces, it can

// be set on the agent due to changes in capabilities.

// https://pkg.go.dev/runtime#hdr-Security.

if e == "GOTRACEBACK=none" {

continue

}

env = append(env, e)

}

return env

}

func (SystemEnvInfo) HomeDir() (string, error) {

return homeDir()

}

func (SystemEnvInfo) Shell(username string) (string, error) {

return get(username)

}

func (SystemEnvInfo) ModifyCommand(name string, args ...string) (string, []string) {

return name, args

}