package utils

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

// GenerateID 生成唯一 ID
func GenerateID() string {
	b := make([]byte, 16)
	rand.Read(b)
	return hex.EncodeToString(b)
}

// GenerateNodeID 生成节点 ID
func GenerateNodeID(prefix string) string {
	return fmt.Sprintf("%s_%s_%d", prefix, GenerateID()[:8], time.Now().Unix())
}

// FormatBytes 格式化字节数
func FormatBytes(bytes int64) string {
	const unit = 1024
	if bytes < unit {
		return fmt.Sprintf("%d B", bytes)
	}
	div, exp := int64(unit), 0
	for n := bytes / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f %ciB", float64(bytes)/float64(div), "KMGTPE"[exp])
}

// ParseBytes 解析字节字符串
func ParseBytes(s string) (int64, error) {
	s = strings.TrimSpace(s)
	s = strings.ToUpper(s)

	multiplier := int64(1)
	if strings.HasSuffix(s, "KB") {
		multiplier = 1024
		s = strings.TrimSuffix(s, "KB")
	} else if strings.HasSuffix(s, "MB") {
		multiplier = 1024 * 1024
		s = strings.TrimSuffix(s, "MB")
	} else if strings.HasSuffix(s, "GB") {
		multiplier = 1024 * 1024 * 1024
		s = strings.TrimSuffix(s, "GB")
	} else if strings.HasSuffix(s, "TB") {
		multiplier = 1024 * 1024 * 1024 * 1024
		s = strings.TrimSuffix(s, "TB")
	}

	value, err := strconv.ParseInt(strings.TrimSpace(s), 10, 64)
	if err != nil {
		return 0, err
	}

	return value * multiplier, nil
}

// FormatDuration 格式化持续时间
func FormatDuration(d time.Duration) string {
	if d < time.Second {
		return fmt.Sprintf("%dms", d.Milliseconds())
	}
	if d < time.Minute {
		return fmt.Sprintf("%.1fs", d.Seconds())
	}
	if d < time.Hour {
		return fmt.Sprintf("%.1fm", d.Minutes())
	}
	return fmt.Sprintf("%.1fh", d.Hours())
}

// IsPrivateIP 检查是否为私有 IP
func IsPrivateIP(ip string) bool {
	ipAddr := net.ParseIP(ip)
	if ipAddr == nil {
		return false
	}

	privateBlocks := []string{
		"10.0.0.0/8",
		"172.16.0.0/12",
		"192.168.0.0/16",
		"127.0.0.0/8",
	}

	for _, block := range privateBlocks {
		_, cidr, _ := net.ParseCIDR(block)
		if cidr.Contains(ipAddr) {
			return true
		}
	}

	return false
}

// IsValidPort 检查端口是否有效
func IsValidPort(port int) bool {
	return port > 0 && port <= 65535
}

// ParseHostPort 解析主机:端口
func ParseHostPort(addr string) (host string, port int, err error) {
	parts := strings.Split(addr, ":")
	if len(parts) != 2 {
		return "", 0, fmt.Errorf("invalid address format")
	}

	host = parts[0]
	port, err = strconv.Atoi(parts[1])
	if err != nil {
		return "", 0, fmt.Errorf("invalid port: %v", err)
	}

	if !IsValidPort(port) {
		return "", 0, fmt.Errorf("port out of range")
	}

	return host, port, nil
}

// Contains 检查字符串切片是否包含某元素
func Contains(slice []string, item string) bool {
	for _, s := range slice {
		if s == item {
			return true
		}
	}
	return false
}

// Unique 去重
func Unique(slice []string) []string {
	keys := make(map[string]bool)
	result := []string{}
	for _, item := range slice {
		if !keys[item] {
			keys[item] = true
			result = append(result, item)
		}
	}
	return result
}

// Retry 重试函数
func Retry(fn func() error, maxAttempts int, delay time.Duration) error {
	var lastErr error
	for i := 0; i < maxAttempts; i++ {
		if err := fn(); err != nil {
			lastErr = err
			if i < maxAttempts-1 {
				time.Sleep(delay)
			}
			continue
		}
		return nil
	}
	return fmt.Errorf("after %d attempts, last error: %v", maxAttempts, lastErr)
}

// Min 返回最小值
func Min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

// Max 返回最大值
func Max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

// Clamp 将值限制在范围内
func Clamp(value, min, max int) int {
	if value < min {
		return min
	}
	if value > max {
		return max
	}
	return value
}