feat: add string conversion functions (#466)

* feat: add string conversion functions

* fix: fix `Capitalize`, update tests

* fix: fix `Capitalize`, update tests

* update README.md

* update tests

* update `Capitalize`

* style: unify coding style

Author: eiixy

README.md

@@ -1297,6 +1297,72 @@ sub := len("hellô")
 
 [[play](https://go.dev/play/p/tuhgW_lWY8l)]
 
+### PascalCase
+
+Converts string to pascal case.
+
+```go
+str := lo.PascalCase("hello_world")
+// HelloWorld
+```
+
+[[play](https://go.dev/play/p/iZkdeLP9oiB)]
+
+### CamelCase
+
+Converts string to camel case.
+
+```go
+str := lo.CamelCase("hello_world")
+// helloWorld
+```
+
+[[play](https://go.dev/play/p/dtyFB58MBRp)]
+
+### KebabCase
+
+Converts string to kebab case.
+
+```go
+str := lo.KebabCase("helloWorld")
+// hello-world
+```
+
+[[play](https://go.dev/play/p/2YTuPafwECA)]
+
+### SnakeCase
+
+Converts string to snake case.
+
+```go
+str := lo.SnakeCase("HelloWorld")
+// hello_world
+```
+
+[[play](https://go.dev/play/p/QVKJG9nOnDg)]
+
+### Words
+
+Splits string into an array of its words.
+
+```go
+str := lo.Words("helloWorld")
+// []string{"hello", "world"}
+```
+
+[[play](https://go.dev/play/p/2P4zhqqq61g)]
+
+### Capitalize
+
+Converts the first character of string to upper case and the remaining to lower case.
+
+```go
+str := lo.PascalCase("heLLO")
+// Hello
+```
+
+[[play](https://go.dev/play/p/jBIJ_OFtFYp)]
+
 ### T2 -> T9
 
 Creates a tuple from a list of values.

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/thoas/go-funk v0.9.1
 	go.uber.org/goleak v1.2.1
 	golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17
+	golang.org/x/text v0.16.0
 )
 
 require (

go.sum

@@ -22,6 +22,8 @@ go.uber.org/goleak v1.2.1 h1:NBol2c7O1ZokfZ0LEU9K6Whx/KnwvepVetCUhtKja4A=
 go.uber.org/goleak v1.2.1/go.mod h1:qlT2yGI9QafXHhZZLxlSuNsMw3FFLxBr+tBRlmO1xH4=
 golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17 h1:3MTrJm4PyNL9NBqvYDSj3DHl46qQakyfqfWo4jgfaEM=
 golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17/go.mod h1:lgLbSvA5ygNOMpwM/9anMpWVlVJ7Z+cHWq/eFuinpGE=
+golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
+golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f h1:BLraFXnmrev5lT+xlilqcH8XK9/i0At2xKjWk4p6zsU=
 gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

string.go

@@ -1,8 +1,12 @@
 package lo
 
 import (
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
 	"math/rand"
+	"regexp"
 	"strings"
+	"unicode"
 	"unicode/utf8"
 )
 
@@ -14,6 +18,9 @@ var (
 	AlphanumericCharset     = append(LettersCharset, NumbersCharset...)
 	SpecialCharset          = []rune("!@#$%^&*()_+-=[]{}|;':\",./<>?")
 	AllCharset              = append(AlphanumericCharset, SpecialCharset...)
+
+	splitWordReg         = regexp.MustCompile(`([a-z])([A-Z0-9])|([a-zA-Z])([0-9])|([0-9])([a-zA-Z])|([A-Z])([A-Z])([a-z])`)
+	splitNumberLetterReg = regexp.MustCompile(`([0-9])([a-zA-Z])`)
 )
 
 // RandomString return a random string.
@@ -94,3 +101,64 @@ func ChunkString[T ~string](str T, size int) []T {
 func RuneLength(str string) int {
 	return utf8.RuneCountInString(str)
 }
+
+// PascalCase converts string to pascal case.
+func PascalCase(str string) string {
+	items := Words(str)
+	for i, item := range items {
+		items[i] = Capitalize(item)
+	}
+	return strings.Join(items, "")
+}
+
+// CamelCase converts string to camel case.
+func CamelCase(str string) string {
+	items := Words(str)
+	for i, item := range items {
+		item = strings.ToLower(item)
+		if i > 0 {
+			item = Capitalize(item)
+		}
+		items[i] = item
+	}
+	return strings.Join(items, "")
+}
+
+// KebabCase converts string to kebab case.
+func KebabCase(str string) string {
+	items := Words(str)
+	for i, item := range items {
+		items[i] = strings.ToLower(item)
+	}
+	return strings.Join(items, "-")
+}
+
+// SnakeCase converts string to snake case.
+func SnakeCase(str string) string {
+	items := Words(str)
+	for i, item := range items {
+		items[i] = strings.ToLower(item)
+	}
+	return strings.Join(items, "_")
+}
+
+// Words splits string into an array of its words.
+func Words(str string) []string {
+	str = splitWordReg.ReplaceAllString(str, `$1$3$5$7 $2$4$6$8$9`)
+	// example: Int8Value => Int 8Value => Int 8 Value
+	str = splitNumberLetterReg.ReplaceAllString(str, "$1 $2")
+	var result strings.Builder
+	for _, r := range str {
+		if unicode.IsLetter(r) || unicode.IsDigit(r) {
+			result.WriteRune(r)
+		} else {
+			result.WriteRune(' ')
+		}
+	}
+	return strings.Fields(result.String())
+}
+
+// Capitalize converts the first character of string to upper case and the remaining to lower case.
+func Capitalize(str string) string {
+	return cases.Title(language.English).String(str)
+}