package golanghelper

import "strings"

const (
	EMPTY = ""
	SPACE = " "
)

type StringUtils struct {
}

// IsEmpty 會檢查 str 是否為空值
func (s *StringUtils) IsEmpty(str string) bool {
	return len(str) == 0
}

// LeftPad 將 padStr 以 size 做為長度，向左填滿 str
func (s *StringUtils) LeftPad(str string, size int, padStr string) string {
	if s.IsEmpty(padStr) {
		padStr = SPACE
	}

	padStrLen := len(padStr)
	padCount := size - len(str)

	if padCount <= 0 || padCount < padStrLen {
		return str
	}
	if padCount == padStrLen {
		return padStr + str
	}

	return strings.Repeat(padStr, padCount) + str
}

func (s *StringUtils) Substring(str string, start, end int) string {
	if str == "" {
		return str
	}

	runes := []rune(str)

	if end < 0 {
		end = len(runes) + end
	}
	if start < 0 {
		start = len(runes) + start
	}

	if end > len(str) {
		end = len(str)
	}

	if start > end {
		return EMPTY
	}

	if start < 0 {
		start = 0
	}

	if end < 0 {
		end = 0
	}

	return string(runes[start:end])
}