package gobuf

import (
	"bytes"
	"unicode"
)

// calm2Case 驼峰转下划线
func calm2Case(src string) string {
	buffer := new(bytes.Buffer)
	for i, r := range src {
		if unicode.IsUpper(r) {
			if i != 0 {
				buffer.WriteRune('_')
			}
			buffer.WriteRune(unicode.ToLower(r))
		} else {
			buffer.WriteRune(r)
		}
	}
	return buffer.String()
}

func toLowerCamelCase(str string) string {
	if len(str) != 0 {
		return string(unicode.ToLower(rune(str[0]))) + str[1:]
	}
	return ""
}

func toUpperCamlCase(str string) string {
	if len(str) != 0 {
		return string(unicode.ToUpper(rune(str[0]))) + str[1:]
	}
	return ""
}

func getFieldValue(fieldName string, cases TagValueStyle) string {
	switch cases {
	case Underline:
		return calm2Case(fieldName)
	case LowerCase:
		return toLowerCamelCase(fieldName)
	default:
		return fieldName
	}
}