lib/os: add function PathFold and PathUnfold

The PathFold replace the path "in" with tilde "~" if its prefix match
with user's home directory from [os.UserHomeDir].

The PathUnfold expand the tilde "~/" prefix into user's home directory
using [os.UserHomeDir] and environment variables using [os.ExpandEnv]
inside the string path "in".

lib/os/os.go

@@ -13,6 +13,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/shuLhan/share/lib/ascii"
 )
@@ -200,6 +201,55 @@ func IsFileExist(parent, relpath string) bool {
 	return true
 }
 
+// PathFold replace the path "in" with tilde "~" if its prefix match with
+// user's home directory from [os.UserHomeDir].
+func PathFold(in string) (out string, err error) {
+	var (
+		logp = `PathFold`
+
+		userHomeDir string
+	)
+
+	in = filepath.Clean(in)
+
+	userHomeDir, err = os.UserHomeDir()
+	if err != nil {
+		return ``, fmt.Errorf(`%s: %s: %w`, logp, in, err)
+	}
+	if strings.HasPrefix(in, userHomeDir) {
+		out = filepath.Join(`~`, in[len(userHomeDir):])
+	} else {
+		out = in
+	}
+	return out, nil
+}
+
+// PathUnfold expand the tilde "~/" prefix into user's home directory using
+// [os.UserHomeDir] and environment variables using [os.ExpandEnv] inside
+// the string path "in".
+func PathUnfold(in string) (out string, err error) {
+	var (
+		logp = `PathUnfold`
+
+		userHomeDir string
+	)
+
+	if strings.HasPrefix(in, `~/`) {
+		userHomeDir, err = os.UserHomeDir()
+		if err != nil {
+			return ``, fmt.Errorf(`%s: %s: %w`, logp, in, err)
+		}
+		out = filepath.Join(userHomeDir, in[2:])
+	} else {
+		out = in
+	}
+
+	out = os.ExpandEnv(out)
+	out = filepath.Clean(out)
+
+	return out, nil
+}
+
 // RmdirEmptyAll remove directory in path if it's empty until one of the
 // parent is not empty.
 func RmdirEmptyAll(path string) error {

lib/os/os_unix_test.go

@@ -0,0 +1,104 @@
+// Copyright 2023, Shulhan <[email protected]>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/shuLhan/share/lib/test"
+)
+
+func TestPathFold(t *testing.T) {
+	type testCase struct {
+		path    string
+		expPath string
+	}
+
+	var (
+		userHomeDir string
+		err         error
+	)
+	userHomeDir, err = os.UserHomeDir()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var listTestCase = []testCase{{
+		path:    filepath.Join(userHomeDir, `tmp`),
+		expPath: `~/tmp`,
+	}, {
+		// Unclean path.
+		path:    `//` + userHomeDir + `///tmp`,
+		expPath: `~/tmp`,
+	}}
+
+	var (
+		c       testCase
+		gotPath string
+	)
+	for _, c = range listTestCase {
+		gotPath, err = PathFold(c.path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		test.Assert(t, c.path, c.expPath, gotPath)
+	}
+}
+
+func TestPathUnfold(t *testing.T) {
+	type testCase struct {
+		path    string
+		expPath string
+	}
+
+	var (
+		username = os.Getenv(`USER`)
+
+		workDir     string
+		userHomeDir string
+		err         error
+	)
+
+	userHomeDir, err = os.UserHomeDir()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	workDir, err = os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var listTestCase = []testCase{{
+		path:    `~/tmp`,
+		expPath: filepath.Join(userHomeDir, `tmp`),
+	}, {
+		path:    `/home/user/~/tmp`,
+		expPath: `/home/user/~/tmp`,
+	}, {
+		path:    `$HOME/tmp`,
+		expPath: filepath.Join(userHomeDir, `tmp`),
+	}, {
+		path:    `/tmp/$USER/adir`,
+		expPath: filepath.Join(`/`, `tmp`, username, `adir`),
+	}, {
+		path:    `~/$PWD/adir`,
+		expPath: filepath.Join(userHomeDir, workDir, `adir`),
+	}}
+
+	var (
+		c       testCase
+		gotPath string
+	)
+	for _, c = range listTestCase {
+		gotPath, err = PathUnfold(c.path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		test.Assert(t, c.path, c.expPath, gotPath)
+	}
+}