package utils

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"strings"
	"time"
)

// GenerateLicenseKey 生成 License 密钥（格式: LIC-YYYY-XXXX-XXXX-XXXX-XXXX） // Logan.Li
func GenerateLicenseKey() string {
	bytes := make([]byte, 16)
	_, _ = rand.Read(bytes)

	year := time.Now().Year()
	part1 := hex.EncodeToString(bytes[0:4])
	part2 := hex.EncodeToString(bytes[4:8])
	part3 := hex.EncodeToString(bytes[8:12])
	part4 := hex.EncodeToString(bytes[12:16])

	return fmt.Sprintf("LIC-%d-%s-%s-%s-%s",
		year,
		strings.ToUpper(part1[:4]),
		strings.ToUpper(part2[:4]),
		strings.ToUpper(part3[:4]),
		strings.ToUpper(part4[:4]))
}

// GenerateOrderNo 生成唯一订单号（格式: ORD-YYYYMMDD-XXXXXXXX） // Logan.Li
func GenerateOrderNo() string {
	bytes := make([]byte, 4)
	_, _ = rand.Read(bytes)
	return fmt.Sprintf("ORD-%s-%s", time.Now().Format("20060102"), strings.ToUpper(hex.EncodeToString(bytes)))
}

// CalculateDaysLeft 计算剩余天数（向下取整，最小为 0） // Logan.Li
func CalculateDaysLeft(endDate time.Time) int {
	diff := endDate.Sub(time.Now())
	days := int(diff.Hours() / 24)
	if days < 0 {
		return 0
	}
	return days
}

// IsLicenseExpired 检查 License 是否过期 // Logan.Li
func IsLicenseExpired(endDate time.Time) bool {
	return time.Now().After(endDate)
}

// IsExpiringSoon 检查 License 是否即将到期 // Logan.Li
func IsExpiringSoon(endDate time.Time, warningDays int) bool {
	daysLeft := CalculateDaysLeft(endDate)
	return daysLeft > 0 && daysLeft <= warningDays
}

// ParseFeatures 解析产品功能列表 JSON 为字符串切片 // Logan.Li
func ParseFeatures(featuresJSON string) []string {
	if featuresJSON == "" {
		return []string{}
	}
	trimmed := strings.Trim(featuresJSON, "[]")
	if trimmed == "" {
		return []string{}
	}
	// 简单解析：去引号后按逗号分割 // Logan.Li
	trimmed = strings.ReplaceAll(trimmed, `"`, "")
	parts := strings.Split(trimmed, ",")
	result := make([]string, 0, len(parts))
	for _, p := range parts {
		if s := strings.TrimSpace(p); s != "" {
			result = append(result, s)
		}
	}
	return result
}

// FormatFeatures 将功能列表格式化为 JSON 字符串 // Logan.Li
func FormatFeatures(features []string) string {
	if len(features) == 0 {
		return "[]"
	}
	quoted := make([]string, len(features))
	for i, f := range features {
		quoted[i] = fmt.Sprintf(`"%s"`, f)
	}
	return fmt.Sprintf("[%s]", strings.Join(quoted, ","))
}