Remove legacy `unknwon/com` package (#19298)

Follows: #19284
* The `CopyDir` is only used inside test code
* Rewrite `ToSnakeCase` with more test cases
* The `RedisCacher` only put strings into cache, here we use internal `toStr` to replace the legacy `ToStr`
* The `UniqueQueue` can use string as ID directly, no need to call `ToStr`

4 files changed, 187 insertions, 22 deletions

diff --git a/modules/util/legacy.go b/modules/util/legacy.go
index c7da541534..d319faad09 100644
--- a/modules/util/legacy.go
+++ b/modules/util/legacy.go
@@ -9,29 +9,37 @@ import (
 	"crypto/cipher"
 	"crypto/rand"
 	"errors"
-
-	"github.com/unknwon/com" //nolint:depguard
+	"io"
+	"os"
 )
 
 // CopyFile copies file from source to target path.
 func CopyFile(src, dest string) error {
-	return com.Copy(src, dest)
-}
+	si, err := os.Lstat(src)
+	if err != nil {
+		return err
+	}
 
-// CopyDir copy files recursively from source to target directory.
-// It returns error when error occurs in underlying functions.
-func CopyDir(srcPath, destPath string) error {
-	return com.CopyDir(srcPath, destPath)
-}
+	sr, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer sr.Close()
 
-// ToStr converts any interface to string. should be replaced.
-func ToStr(value interface{}, args ...int) string {
-	return com.ToStr(value, args...)
-}
+	dw, err := os.Create(dest)
+	if err != nil {
+		return err
+	}
+	defer dw.Close()
 
-// ToSnakeCase converts a string to snake_case. should be replaced.
-func ToSnakeCase(str string) string {
-	return com.ToSnakeCase(str)
+	if _, err = io.Copy(dw, sr); err != nil {
+		return err
+	}
+
+	if err = os.Chtimes(dest, si.ModTime(), si.ModTime()); err != nil {
+		return err
+	}
+	return os.Chmod(dest, si.Mode())
 }
 
 // AESGCMEncrypt (from legacy package): encrypts plaintext with the given key using AES in GCM mode. should be replaced.
diff --git a/modules/util/legacy_test.go b/modules/util/legacy_test.go
index cfda93d3ad..c41f7a008c 100644
--- a/modules/util/legacy_test.go
+++ b/modules/util/legacy_test.go
@@ -7,12 +7,38 @@ package util
 import (
 	"crypto/aes"
 	"crypto/rand"
+	"fmt"
+	"os"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
-	"github.com/unknwon/com" //nolint:depguard
 )
 
+func TestCopyFile(t *testing.T) {
+	testContent := []byte("hello")
+
+	tmpDir := os.TempDir()
+	now := time.Now()
+	srcFile := fmt.Sprintf("%s/copy-test-%d-src.txt", tmpDir, now.UnixMicro())
+	dstFile := fmt.Sprintf("%s/copy-test-%d-dst.txt", tmpDir, now.UnixMicro())
+
+	_ = os.Remove(srcFile)
+	_ = os.Remove(dstFile)
+	defer func() {
+		_ = os.Remove(srcFile)
+		_ = os.Remove(dstFile)
+	}()
+
+	err := os.WriteFile(srcFile, testContent, 0o777)
+	assert.NoError(t, err)
+	err = CopyFile(srcFile, dstFile)
+	assert.NoError(t, err)
+	dstContent, err := os.ReadFile(dstFile)
+	assert.NoError(t, err)
+	assert.Equal(t, testContent, dstContent)
+}
+
 func TestAESGCM(t *testing.T) {
 	t.Parallel()
 
@@ -29,9 +55,4 @@ func TestAESGCM(t *testing.T) {
 	assert.NoError(t, err)
 
 	assert.Equal(t, plaintext, decrypted)
-
-	// at the moment, we make sure the result is the same as the legacy package, this assertion can be removed in next round refactoring
-	legacy, err := com.AESGCMDecrypt(key, ciphertext)
-	assert.NoError(t, err)
-	assert.Equal(t, legacy, plaintext)
 }
diff --git a/modules/util/string.go b/modules/util/string.go
new file mode 100644
index 0000000000..4301f75f99
--- /dev/null
+++ b/modules/util/string.go
@@ -0,0 +1,88 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import "github.com/yuin/goldmark/util"
+
+func isSnakeCaseUpper(c byte) bool {
+	return 'A' <= c && c <= 'Z'
+}
+
+func isSnakeCaseLowerOrNumber(c byte) bool {
+	return 'a' <= c && c <= 'z' || '0' <= c && c <= '9'
+}
+
+// ToSnakeCase convert the input string to snake_case format.
+//
+// Some samples.
+//     "FirstName"  => "first_name"
+//     "HTTPServer" => "http_server"
+//     "NoHTTPS"    => "no_https"
+//     "GO_PATH"    => "go_path"
+//     "GO PATH"    => "go_path"      // space is converted to underscore.
+//     "GO-PATH"    => "go_path"      // hyphen is converted to underscore.
+//
+func ToSnakeCase(input string) string {
+	if len(input) == 0 {
+		return ""
+	}
+
+	var res []byte
+	if len(input) == 1 {
+		c := input[0]
+		if isSnakeCaseUpper(c) {
+			res = []byte{c + 'a' - 'A'}
+		} else if isSnakeCaseLowerOrNumber(c) {
+			res = []byte{c}
+		} else {
+			res = []byte{'_'}
+		}
+	} else {
+		res = make([]byte, 0, len(input)*4/3)
+		pos := 0
+		needSep := false
+		for pos < len(input) {
+			c := input[pos]
+			if c >= 0x80 {
+				res = append(res, c)
+				pos++
+				continue
+			}
+			isUpper := isSnakeCaseUpper(c)
+			if isUpper || isSnakeCaseLowerOrNumber(c) {
+				end := pos + 1
+				if isUpper {
+					// skip the following upper letters
+					for end < len(input) && isSnakeCaseUpper(input[end]) {
+						end++
+					}
+					if end-pos > 1 && end < len(input) && isSnakeCaseLowerOrNumber(input[end]) {
+						end--
+					}
+				}
+				// skip the following lower or number letters
+				for end < len(input) && (isSnakeCaseLowerOrNumber(input[end]) || input[end] >= 0x80) {
+					end++
+				}
+				if needSep {
+					res = append(res, '_')
+				}
+				res = append(res, input[pos:end]...)
+				pos = end
+				needSep = true
+			} else {
+				res = append(res, '_')
+				pos++
+				needSep = false
+			}
+		}
+		for i := 0; i < len(res); i++ {
+			if isSnakeCaseUpper(res[i]) {
+				res[i] += 'a' - 'A'
+			}
+		}
+	}
+	return util.BytesToReadOnlyString(res)
+}
diff --git a/modules/util/string_test.go b/modules/util/string_test.go
new file mode 100644
index 0000000000..49de29ab67
--- /dev/null
+++ b/modules/util/string_test.go
@@ -0,0 +1,48 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestToSnakeCase(t *testing.T) {
+	cases := map[string]string{
+		// all old cases from the legacy package
+		"HTTPServer":         "http_server",
+		"_camelCase":         "_camel_case",
+		"NoHTTPS":            "no_https",
+		"Wi_thF":             "wi_th_f",
+		"_AnotherTES_TCaseP": "_another_tes_t_case_p",
+		"ALL":                "all",
+		"_HELLO_WORLD_":      "_hello_world_",
+		"HELLO_WORLD":        "hello_world",
+		"HELLO____WORLD":     "hello____world",
+		"TW":                 "tw",
+		"_C":                 "_c",
+
+		"  sentence case  ": "__sentence_case__",
+		" Mixed-hyphen case _and SENTENCE_case and UPPER-case": "_mixed_hyphen_case__and_sentence_case_and_upper_case",
+
+		// new cases
+		" ":        "_",
+		"A":        "a",
+		"A0":       "a0",
+		"a0":       "a0",
+		"Aa0":      "aa0",
+		"啊":        "啊",
+		"A啊":       "a啊",
+		"Aa啊b":     "aa啊b",
+		"A啊B":      "a啊_b",
+		"Aa啊B":     "aa啊_b",
+		"TheCase2": "the_case2",
+		"ObjIDs":   "obj_i_ds", // the strange database column name which already exists
+	}
+	for input, expected := range cases {
+		assert.Equal(t, expected, ToSnakeCase(input))
+	}
+}