Add 'environment' package

This commit adds a new environment package that manages all calls to the
underlying operating system.

pkg/environment/environment.go

@@ -0,0 +1,58 @@
+package environment
+
+import (
+	"io"
+	"io/fs"
+	"net"
+	"time"
+
+	"github.com/tkw1536/goprogram/stream"
+)
+
+// Environment represents an environment that a program can run it.
+// It mostly mimics the interfaces of the [os] package.
+type Environment interface {
+	isEnv()
+
+	GetEnv(name string) string
+
+	Stat(path string) (fs.FileInfo, error)
+	Lstat(path string) (fs.FileInfo, error)
+
+	Readlink(path string) (string, error)
+	Symlink(oldname, newname string) error
+
+	ReadDir(name string) ([]fs.DirEntry, error)
+
+	Open(path string) (fs.File, error)
+	Chtimes(name string, atime time.Time, mtime time.Time) error
+	SameFile(f1, f2 fs.FileInfo) bool
+
+	Create(path string, mode fs.FileMode) (WritableFile, error)
+
+	Mkdir(path string, mode fs.FileMode) error
+	MkdirAll(path string, mode fs.FileMode) error
+
+	Remove(path string) error
+	RemoveAll(path string) error
+
+	WalkDir(root string, fn fs.WalkDirFunc) error
+
+	Abs(path string) (string, error)
+
+	Listen(network, address string) (net.Listener, error)
+	Dial(network, address string) (net.Conn, error)
+
+	Executable() (string, error)
+	Exec(io stream.IOStream, workdir string, exe string, argv ...string) int
+	LookPathAbs(name string) (string, error)
+}
+
+type WritableFile interface {
+	fs.File
+	io.Writer
+}
+
+func init() {
+	var _ Environment = Native{}
+}

pkg/environment/globals.go

@@ -0,0 +1,69 @@
+package environment
+
+import (
+	"bytes"
+	"io"
+	"io/fs"
+	"os"
+
+	"github.com/tkw1536/goprogram/stream"
+)
+
+// ExecCommandError is returned by Exec when a command could not be executed.
+// This typically hints that the executable cannot be found, but may have other causes.
+const ExecCommandError = 127
+
+// DefaultFilePerm is the default mode to use for files
+const DefaultFilePerm fs.FileMode = 0666
+
+// DefaultDirPerm is the default mode to use for directories
+const DefaultDirPerm fs.FileMode = os.ModeDir & fs.ModePerm
+
+// IsExist checks if the provided error represents a 'does not exist' errror
+func IsExist(err error) bool {
+	return os.IsExist(err)
+}
+
+// IsNotExist checks if the provided error represents a 'does exist' error
+func IsNotExist(err error) bool {
+	return os.IsNotExist(err)
+}
+
+// WriteFile is like [os.WriteFile].
+func WriteFile(env Environment, path string, data []byte, mode fs.FileMode) error {
+	handle, err := env.Create(path, mode)
+	if err != nil {
+		return err
+	}
+	defer handle.Close()
+
+	if _, err := handle.Write(data); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// ReadFile is like [os.ReadFile]
+func ReadFile(env Environment, path string) ([]byte, error) {
+	// open the file!
+	file, err := env.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	// copy everything into a buffer!
+	var buffer bytes.Buffer
+	if _, err := io.Copy(&buffer, file); err != nil {
+		return nil, err
+	}
+
+	// return the buffer contents!
+	return buffer.Bytes(), nil
+}
+
+// MustExec is like Exec, except that it returns true if the command exited successfully, and else false.
+func MustExec(env Environment, io stream.IOStream, workdir string, exe string, argv ...string) bool {
+	return env.Exec(io, workdir, exe, argv...) == 0
+}

pkg/environment/native_exec.go

@@ -0,0 +1,44 @@
+package environment
+
+import (
+	"os/exec"
+
+	"github.com/tkw1536/goprogram/stream"
+)
+
+// Exec executes a system command with the specified input/output streams, working directory, and arguments.
+//
+// If the command executes, it's exit code will be returned.
+// If the command can not be executed, returns [ExecCommandError].
+func (Native) Exec(io stream.IOStream, workdir string, exe string, argv ...string) int {
+	// setup the command
+	cmd := exec.Command(exe, argv...)
+	cmd.Dir = workdir
+	cmd.Stdin = io.Stdin
+	cmd.Stdout = io.Stdout
+	cmd.Stderr = io.Stderr
+
+	// run it
+	err := cmd.Run()
+
+	// non-zero exit
+	if err, ok := err.(*exec.ExitError); ok {
+		return err.ExitCode()
+	}
+
+	// unknown error
+	if err != nil {
+		return ExecCommandError
+	}
+
+	// everything is fine!
+	return 0
+}
+
+func (n Native) LookPathAbs(file string) (string, error) {
+	path, err := exec.LookPath(file)
+	if err != nil {
+		return "", err
+	}
+	return n.Abs(path)
+}

pkg/environment/native_fs.go

@@ -0,0 +1,80 @@
+package environment
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+type Native struct{}
+
+func (Native) isEnv() {}
+
+func (Native) GetEnv(name string) string {
+	return os.Getenv(name)
+}
+
+func (Native) Stat(path string) (fs.FileInfo, error) {
+	return os.Stat(path)
+}
+
+func (Native) Lstat(path string) (fs.FileInfo, error) {
+	return os.Lstat(path)
+}
+
+func (Native) Readlink(path string) (string, error) {
+	return os.Readlink(path)
+}
+
+func (Native) Symlink(oldname, newname string) error {
+	return os.Symlink(oldname, newname)
+}
+
+func (Native) ReadDir(name string) ([]fs.DirEntry, error) {
+	return os.ReadDir(name)
+}
+
+func (Native) SameFile(f1, f2 fs.FileInfo) bool {
+	return os.SameFile(f1, f2)
+}
+
+func (Native) WalkDir(path string, f fs.WalkDirFunc) error {
+	return filepath.WalkDir(path, f)
+}
+
+func (Native) Executable() (string, error) {
+	return os.Executable() // TODO: not sure this works with the remote concepts
+}
+
+func (Native) Open(path string) (fs.File, error) {
+	return os.Open(path)
+}
+
+func (Native) Create(path string, mode fs.FileMode) (WritableFile, error) {
+	return os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, mode)
+}
+
+func (Native) Chtimes(name string, atime time.Time, mtime time.Time) error {
+	return os.Chtimes(name, atime, mtime)
+}
+
+func (Native) Mkdir(path string, mode fs.FileMode) error {
+	return os.Mkdir(path, mode)
+}
+
+func (Native) MkdirAll(path string, mode fs.FileMode) error {
+	return os.MkdirAll(path, mode)
+}
+
+func (Native) Remove(path string) error {
+	return os.Remove(path)
+}
+
+func (Native) RemoveAll(path string) error {
+	return os.RemoveAll(path)
+}
+
+func (Native) Abs(path string) (string, error) {
+	return filepath.Abs(path)
+}

pkg/environment/native_net.go

@@ -0,0 +1,11 @@
+package environment
+
+import "net"
+
+func (Native) Listen(network, address string) (net.Listener, error) {
+	return net.Listen(network, address)
+}
+
+func (Native) Dial(network, address string) (net.Conn, error) {
+	return net.Dial(network, address)
+}