/**
 * @author chengliang
 * @date 2026/1/27 11:18
 * @brief
 *
 **/

package whiteip

import (
	"fmt"
	//"github.com/dlclark/regexp2" // 支持更复杂的正则表达式
	"github.com/gin-gonic/gin"
	"net"
	"regexp"
	"strings"
)

// 支持正则的IP白名单中间件
type TWhiteIpMgr struct {
	// 预编译的正则表达式列表
	ipPatterns []*regexp.Regexp
	// 是否允许内网IP（默认允许）
	allowInternal bool
	// 是否启用IP检查（默认启用）
	enabled bool
}

// 创建白名单中间件
func NewIPWhiteListMiddleware(patterns []string, allowInternal bool) *TWhiteIpMgr {
	m := &TWhiteIpMgr{
		allowInternal: allowInternal,
		enabled:       true,
	}

	// 编译正则表达式
	for _, pattern := range patterns {
		// 支持简写语法
		compiledPattern := normalizePattern(pattern)

		re, err := regexp.Compile(compiledPattern)
		if err != nil {
			// 如果编译失败，记录错误但仍继续
			fmt.Printf("warning：IP white list compile failed: %s, error: %v\n", pattern, err)
			continue
		}

		m.ipPatterns = append(m.ipPatterns, re)
	}

	return m
}

func (this *TWhiteIpMgr) UpdatePattern(patterns []string, allowInternal bool, enabled bool) {
	this.enabled = enabled
	this.allowInternal = allowInternal
	this.ipPatterns = make([]*regexp.Regexp, len(patterns))
	for _, pattern := range patterns {
		compiledPattern := normalizePattern(pattern)

		re, err := regexp.Compile(compiledPattern)
		if err != nil {
			// 如果编译失败，记录错误但仍继续
			fmt.Printf("warning：IP white list compile failed: %s, error: %v\n", pattern, err)
			continue
		}

		this.ipPatterns = append(this.ipPatterns, re)
	}

}

// 标准化IP模式
func normalizePattern(pattern string) string {
	// 支持CIDR表示法转换成正则表达式
	if strings.Contains(pattern, "/") {
		return cidrToRegex(pattern)
	}

	// 支持IP段简写，如: 192.168.1.* 或 192.168.1.1-100
	pattern = strings.ReplaceAll(pattern, "*", `\d+`)

	// 支持IP范围，如: 192.168.1.1-100
	if strings.Contains(pattern, "-") {
		parts := strings.Split(pattern, ".")
		for i, part := range parts {
			if strings.Contains(part, "-") {
				rangeParts := strings.Split(part, "-")
				if len(rangeParts) == 2 {
					parts[i] = fmt.Sprintf(`(%s)`, buildRangeRegex(rangeParts[0], rangeParts[1]))
				}
			}
		}
		return "^" + strings.Join(parts, `\.`) + "$"
	}

	// 如果是普通IP，确保完全匹配
	if !strings.HasPrefix(pattern, "^") {
		pattern = "^" + pattern
	}
	if !strings.HasSuffix(pattern, "$") {
		pattern = pattern + "$"
	}

	return pattern
}

// cidrToRegex 将CIDR表示法转换为正则表达式
func cidrToRegex(cidr string) string {
	ip, ipNet, err := net.ParseCIDR(cidr)
	if err != nil {
		return cidr // 如果解析失败，返回原字符串
	}

	// 获取网络掩码
	mask := ipNet.Mask
	ones, bits := mask.Size()

	if bits != 32 {
		return cidr // 仅支持IPv4
	}

	// 将IP转换为整数
	ipInt := ipToInt(ip.To4())

	// 计算网络地址和广播地址
	network := ipInt & (^uint32(0) << uint32(bits-ones))
	broadcast := network | (^uint32(0) >> uint32(ones))

	// 生成正则表达式
	return fmt.Sprintf(`^%s$`, ipRangeToRegex(intToIP(network), intToIP(broadcast)))
}

// ipToInt IP转整数
func ipToInt(ip net.IP) uint32 {
	if len(ip) == 16 {
		return uint32(ip[12])<<24 | uint32(ip[13])<<16 | uint32(ip[14])<<8 | uint32(ip[15])
	}
	return uint32(ip[0])<<24 | uint32(ip[1])<<16 | uint32(ip[2])<<8 | uint32(ip[3])
}

// intToIP 整数转IP
func intToIP(n uint32) net.IP {
	return net.IPv4(byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
}

// ipRangeToRegex IP范围转正则表达式
func ipRangeToRegex(start, end net.IP) string {
	startParts := strings.Split(start.String(), ".")
	endParts := strings.Split(end.String(), ".")

	var regexParts []string
	for i := 0; i < 4; i++ {
		startNum := parseInt(startParts[i])
		endNum := parseInt(endParts[i])

		if startNum == endNum {
			regexParts = append(regexParts, fmt.Sprintf("%d", startNum))
		} else {
			regexParts = append(regexParts, fmt.Sprintf("(%s)", buildRangeRegex(startParts[i], endParts[i])))
		}
	}

	return strings.Join(regexParts, `\.`)
}

// buildRangeRegex 构建数字范围的正则表达式
func buildRangeRegex(start, end string) string {
	startNum := parseInt(start)
	endNum := parseInt(end)

	if startNum == endNum {
		return start
	}

	// 简单处理：如果范围小，直接列举
	if endNum-startNum < 10 {
		var options []string
		for i := startNum; i <= endNum; i++ {
			options = append(options, fmt.Sprintf("%d", i))
		}
		return strings.Join(options, "|")
	}

	// 复杂范围，使用正则表达式模式
	return fmt.Sprintf("%d|%d|[1-9]\\d{0,2}", startNum, endNum) // 简化处理
}

// parseInt 字符串转整数
func parseInt(s string) int {
	var result int
	fmt.Sscanf(s, "%d", &result)
	return result
}

// 检查是否为内网IP
func isInternalIP(ipStr string) bool {
	ip := net.ParseIP(ipStr)
	if ip == nil {
		return false
	}

	// IPv4 检查
	if ip4 := ip.To4(); ip4 != nil {
		return ip4[0] == 10 ||
			(ip4[0] == 172 && ip4[1] >= 16 && ip4[1] <= 31) ||
			(ip4[0] == 192 && ip4[1] == 168) ||
			ip4[0] == 127
	}

	// IPv6 检查
	return ip.IsLoopback() || ip.IsPrivate()
}

// GetClientIP 获取客户端真实IP
func GetClientIP(c *gin.Context) string {
	// 从代理头获取
	if ip := c.GetHeader("X-Forwarded-For"); ip != "" {
		ips := strings.Split(ip, ",")
		if len(ips) > 0 {
			return strings.TrimSpace(ips[0])
		}
	}

	if ip := c.GetHeader("X-Real-IP"); ip != "" {
		return ip
	}

	// 直接获取 RemoteAddr
	remoteAddr := c.Request.RemoteAddr
	if ip, _, err := net.SplitHostPort(remoteAddr); err == nil {
		return ip
	}
	return remoteAddr
}

// Middleware 返回Gin中间件函数
func (m *TWhiteIpMgr) Middleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		if !m.enabled {
			c.Next()
			return
		}

		clientIP := GetClientIP(c)

		// 检查内网IP
		if m.allowInternal && isInternalIP(clientIP) {
			c.Next()
			return
		}

		// 检查白名单
		if m.isIPAllowed(clientIP) {
			c.Next()
			return
		}

		// 拒绝访问
		c.JSON(403, gin.H{
			"code":    403,
			"message": fmt.Sprintf("IP %s 不在白名单中", clientIP),
			"data":    nil,
		})
		c.Abort()
	}
}

// isIPAllowed 检查IP是否被允许
func (m *TWhiteIpMgr) isIPAllowed(ip string) bool {
	// 如果没有设置任何模式，拒绝所有（除非是内网）
	if len(m.ipPatterns) == 0 {
		return false
	}

	for _, pattern := range m.ipPatterns {
		if pattern.MatchString(ip) {
			return true
		}
	}

	return false
}

// Enable 启用中间件
func (m *TWhiteIpMgr) Enable() {
	m.enabled = true
}

// Disable 禁用中间件
func (m *TWhiteIpMgr) Disable() {
	m.enabled = false
}

// AddPattern 动态添加IP模式
func (m *TWhiteIpMgr) AddPattern(pattern string) error {
	compiledPattern := normalizePattern(pattern)

	re, err := regexp.Compile(compiledPattern)
	if err != nil {
		return err
	}

	m.ipPatterns = append(m.ipPatterns, re)
	return nil
}