package utils

import (
	"strings"

	"github.com/gin-gonic/gin"
)

// ClientIP 获取客户端真实IP
func ClientIP(c *gin.Context) string {
	// 优先取反向代理头
	for _, header := range []string{"X-Real-IP", "X-Forwarded-For"} {
		if v := c.GetHeader(header); v != "" {
			ips := strings.Split(v, ",")
			ip := strings.TrimSpace(ips[0])
			if ip != "" {
				return ip
			}
		}
	}
	return c.ClientIP()
}

// SanitizePath 清理虚拟路径，防止路径穿越
func SanitizePath(p string) string {
	p = strings.ReplaceAll(p, "\\", "/")
	parts := make([]string, 0, 8)
	for _, seg := range strings.Split(p, "/") {
		seg = strings.TrimSpace(seg)
		if seg == "" || seg == "." {
			continue
		}
		if seg == ".." {
			if len(parts) > 0 {
				parts = parts[:len(parts)-1]
			}
			continue
		}
		parts = append(parts, seg)
	}
	return strings.Join(parts, "/")
}

// IsValidPassword 检查密码强度：至少8位，包含字母和数字
func IsValidPassword(pwd string) bool {
	if len(pwd) < 8 {
		return false
	}
	hasLetter, hasDigit := false, false
	for _, ch := range pwd {
		switch {
		case ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z':
			hasLetter = true
		case ch >= '0' && ch <= '9':
			hasDigit = true
		}
	}
	return hasLetter && hasDigit
}

// IsEmail 简单校验邮箱格式
func IsEmail(s string) bool {
	at := strings.IndexByte(s, '@')
	if at <= 0 || at == len(s)-1 {
		return false
	}
	domain := s[at+1:]
	return strings.Contains(domain, ".") && strings.IndexByte(domain, '.') != 0 && strings.IndexByte(domain, '.') != len(domain)-1
}

// HumanSize 将字节数转为可读大小
func HumanSize(n int64) string {
	const unit = 1024
	if n < unit {
		return itoa(n) + " B"
	}
	div, exp := int64(unit), 0
	for m := n / unit; m >= unit && exp < 4; m /= unit {
		div *= unit
		exp++
	}
	val := float64(n) / float64(div)
	s := trimFloat(val)
	units := []string{"KB", "MB", "GB", "TB", "PB"}
	return s + " " + units[exp]
}

func itoa(n int64) string {
	if n == 0 {
		return "0"
	}
	neg := n < 0
	if neg {
		n = -n
	}
	var buf [20]byte
	i := len(buf)
	for n > 0 {
		i--
		buf[i] = byte('0' + n%10)
		n /= 10
	}
	if neg {
		i--
		buf[i] = '-'
	}
	return string(buf[i:])
}

func trimFloat(f float64) string {
	// 保留两位小数并去掉末尾多余的0
	s := itoa(int64(f))
	frac := f - float64(int64(f))
	if frac < 0.005 {
		return s
	}
	d1 := int64(frac * 10)
	if d1 > 9 {
		d1 = 9
	}
	frac = frac*10 - float64(d1)
	d2 := int64(frac * 10)
	if d2 > 9 {
		d2 = 9
	}
	if d2 < 5 {
		if d1 == 0 {
			return s
		}
		return s + "." + itoa(d1)
	}
	return s + "." + itoa(d1) + itoa(d2)
}