package pkg

import (
	"math/rand/v2"
)

// GenerateRandomStringCustom 使用自定义字符集
func GenerateRandomStringCustom(n int, charset string) string {
	result := make([]byte, n)
	for i := range result {
		result[i] = charset[rand.IntN(len(charset))]
	}
	return string(result)
}

// 纯数字字符串
func GenerateRandomNumberString(n int) string {
	return GenerateRandomStringCustom(n, "0123456789")
}

// 纯小写字母
func GenerateRandomLowerString(n int) string {
	return GenerateRandomStringCustom(n, "abcdefghijklmnopqrstuvwxyz")
}

// 纯大写字母
func GenerateRandomUpperString(n int) string {
	return GenerateRandomStringCustom(n, "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
}

// 使用自定义随机源（例如固定种子）
func GenerateRandomStringWithSeed(n int, seed uint64) string {
	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

	rng := rand.New(rand.NewPCG(seed, seed))
	result := make([]byte, n)
	for i := range result {
		result[i] = charset[rng.IntN(len(charset))]
	}
	return string(result)
}