#!/bin/bash

# 颜色定义
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
BLUE='\033[0;34m'
PURPLE='\033[0;35m'
CYAN='\033[0;36m'
NC='\033[0m'

# 日志函数
log_info() { echo -e "${BLUE}📦 $1${NC}"; }
log_success() { echo -e "${GREEN}✅ $1${NC}"; }
log_warning() { echo -e "${YELLOW}⚠️  $1${NC}"; }
log_error() { echo -e "${RED}❌ $1${NC}"; }
log_result() { echo -e "${CYAN}📊 $1${NC}"; }

# DNS提供商配置
declare -A DNS_PROVIDERS=(
    ["1"]="腾讯DNS:119.29.29.29,119.28.28.28"
    ["2"]="阿里DNS:223.5.5.5,223.6.6.6"
    ["3"]="114DNS:114.114.114.114,114.114.115.115"
    ["4"]="Cloudflare:1.1.1.1,1.0.0.1"
    ["5"]="GoogleDNS:8.8.8.8,8.8.4.4"
    ["6"]="OpenDNS:208.67.222.222,208.67.220.220"
    ["7"]="百度DNS:180.76.76.76"
    ["8"]="CNNICSDNS:1.2.4.8,210.2.4.8"
)

# 检测当前DNS
detect_current_dns() {
    echo -e "${PURPLE}"
    echo "=================================================="
    echo "              🌈 当前DNS检测结果"
    echo "=================================================="
    echo -e "${NC}"
    
    if [ -f /etc/resolv.conf ]; then
        current_dns=$(grep -E '^nameserver' /etc/resolv.conf | awk '{print $2}' | tr '\n' ' ')
        if [ -n "$current_dns" ]; then
            log_result "当前DNS服务器: $current_dns"
            
            # 识别DNS提供商
            for provider in "${!DNS_PROVIDERS[@]}"; do
                dns_ips=${DNS_PROVIDERS[$provider]#*:}
                primary_dns=${dns_ips%,*}
                if [[ "$current_dns" == *"$primary_dns"* ]]; then
                    provider_name=${DNS_PROVIDERS[$provider]%:*}
                    log_success "识别为: $provider_name"
                    break
                fi
            done
        else
            log_warning "未检测到DNS配置"
        fi
    else
        log_error "未找到 resolv.conf 文件"
    fi
    echo ""
}

# 测试DNS速度
test_dns_speed() {
    local dns_ips=$1
    local provider_name=$2
    
    log_info "测试 $provider_name 速度..."
    IFS=',' read -ra dns_array <<< "$dns_ips"
    
    for dns_ip in "${dns_array[@]}"; do
        if ping -c 2 -W 2 "$dns_ip" >/dev/null 2>&1; then
            start_time=$(date +%s%N)
            nslookup baidu.com "$dns_ip" >/dev/null 2>&1
            end_time=$(date +%s%N)
            time_ms=$(( (end_time - start_time) / 1000000 ))
            
            if [ $time_ms -lt 50 ]; then
                echo -e "  ${GREEN}$dns_ip: ${time_ms}ms ✅${NC}"
            elif [ $time_ms -lt 100 ]; then
                echo -e "  ${YELLOW}$dns_ip: ${time_ms}ms ⚠️${NC}"
            else
                echo -e "  ${RED}$dns_ip: ${time_ms}ms ❌${NC}"
            fi
        else
            echo -e "  ${RED}$dns_ip: 无法连接 ❌${NC}"
        fi
    done
}

# 显示DNS菜单
show_dns_menu() {
    echo -e "${PURPLE}"
    echo "=================================================="
    echo "              🌈 主流DNS提供商"
    echo "=================================================="
    echo -e "${NC}"
    
    for key in "${!DNS_PROVIDERS[@]}"; do
        provider_name=${DNS_PROVIDERS[$key]%:*}
        dns_ips=${DNS_PROVIDERS[$key]#*:}
        echo -e "  ${CYAN}$key. $provider_name${NC}"
        echo -e "     ${BLUE}$dns_ips${NC}"
    done
    echo ""
}

# 临时设置DNS
set_dns_temporary() {
    local provider_key=$1
    local provider_name=${DNS_PROVIDERS[$provider_key]%:*}
    local dns_ips=${DNS_PROVIDERS[$provider_key]#*:}
    
    log_info "临时设置为: $provider_name"
    
    # 备份当前配置
    cp /etc/resolv.conf /etc/resolv.conf.backup.$(date +%Y%m%d_%H%M%S)
    
    # 生成新的resolv.conf
    echo "# 临时设置 - $provider_name ($(date))" > /etc/resolv.conf
    IFS=',' read -ra dns_array <<< "$dns_ips"
    for dns_ip in "${dns_array[@]}"; do
        echo "nameserver $dns_ip" >> /etc/resolv.conf
    done
    echo "options timeout:2 attempts:3" >> /etc/resolv.conf
    
    log_success "临时DNS设置完成 (重启后恢复)"
}

# 永久设置DNS
set_dns_permanent() {
    local provider_key=$1
    local provider_name=${DNS_PROVIDERS[$provider_key]%:*}
    local dns_ips=${DNS_PROVIDERS[$provider_key]#*:}
    
    log_info "永久设置为: $provider_name"
    
    # 备份当前配置
    cp /etc/resolv.conf /etc/resolv.conf.backup.$(date +%Y%m%d_%H%M%S)
    
    # 检查并禁用systemd-resolved
    if systemctl is-active systemd-resolved >/dev/null 2>&1; then
        log_warning "检测到systemd-resolved，正在禁用..."
        systemctl stop systemd-resolved
        systemctl disable systemd-resolved
    fi
    
    # 生成永久配置
    echo "# 永久设置 - $provider_name ($(date))" > /etc/resolv.conf
    IFS=',' read -ra dns_array <<< "$dns_ips"
    for dns_ip in "${dns_array[@]}"; do
        echo "nameserver $dns_ip" >> /etc/resolv.conf
    done
    echo "options timeout:2 attempts:3" >> /etc/resolv.conf
    
    # 防止NetworkManager覆盖
    if command -v NetworkManager >/dev/null 2>&1; then
        log_info "配置NetworkManager..."
        nmcli connection show | grep -v NAME | awk '{print $1}' | while read conn; do
            nmcli connection modify "$conn" ipv4.ignore-auto-dns yes
            for dns_ip in "${dns_array[@]}"; do
                nmcli connection modify "$conn" ipv4.dns "$dns_ip"
            done
        done
    fi
    
    # 设置文件属性防止被覆盖
    chattr +i /etc/resolv.conf 2>/dev/null || true
    
    log_success "永久DNS设置完成"
}

# 恢复备份
restore_backup() {
    local backup_files=($(ls -t /etc/resolv.conf.backup.* 2>/dev/null))
    
    if [ ${#backup_files[@]} -eq 0 ]; then
        log_error "未找到备份文件"
        return 1
    fi
    
    echo -e "${YELLOW}可用的备份文件:${NC}"
    for i in "${!backup_files[@]}"; do
        echo "  $((i+1)). ${backup_files[$i]}"
    done
    
    read -p "选择要恢复的备份编号 (1-${#backup_files[@]}): " backup_choice
    if [[ $backup_choice =~ ^[0-9]+$ ]] && [ $backup_choice -ge 1 ] && [ $backup_choice -le ${#backup_files[@]} ]; then
        selected_backup="${backup_files[$((backup_choice-1))]}"
        
        # 解除文件锁定
        chattr -i /etc/resolv.conf 2>/dev/null || true
        
        cp "$selected_backup" /etc/resolv.conf
        log_success "已从 $selected_backup 恢复DNS设置"
    else
        log_error "无效的选择"
    fi
}

# 主函数
main() {
    # 检测当前DNS
    detect_current_dns
    
    while true; do
        echo -e "${PURPLE}"
        echo "=================================================="
        echo "              🌈 DNS切换管理脚本"
        echo "=================================================="
        echo -e "${NC}"
        
        echo -e "${CYAN}请选择操作:${NC}"
        echo "  1. 切换DNS提供商"
        echo "  2. 测试所有DNS速度"
        echo "  3. 恢复DNS备份"
        echo "  4. 显示当前DNS"
        echo "  5. 退出"
        echo ""
        
        read -p "请输入选择 (1-5): " main_choice
        
        case $main_choice in
            1)
                show_dns_menu
                read -p "选择DNS提供商 (1-8): " dns_choice
                if [[ -n "${DNS_PROVIDERS[$dns_choice]}" ]]; then
                    echo ""
                    echo -e "${CYAN}请选择设置方式:${NC}"
                    echo "  1. 临时设置 (重启后失效)"
                    echo "  2. 永久设置"
                    read -p "请输入选择 (1-2): " set_type
                    
                    case $set_type in
                        1) set_dns_temporary "$dns_choice" ;;
                        2) set_dns_permanent "$dns_choice" ;;
                        *) log_error "无效的选择" ;;
                    esac
                else
                    log_error "无效的DNS选择"
                fi
                ;;
            2)
                echo ""
                log_info "测试所有DNS提供商速度..."
                for key in "${!DNS_PROVIDERS[@]}"; do
                    provider_name=${DNS_PROVIDERS[$key]%:*}
                    dns_ips=${DNS_PROVIDERS[$key]#*:}
                    test_dns_speed "$dns_ips" "$provider_name"
                    echo ""
                done
                ;;
            3)
                restore_backup
                ;;
            4)
                detect_current_dns
                ;;
            5)
                log_success "再见！"
                exit 0
                ;;
            *)
                log_error "无效的选择"
                ;;
        esac
        
        echo ""
        read -p "按回车键继续..."
        clear
    done
}

# 脚本入口
if [ "$(id -u)" -ne 0 ]; then
    log_error "请使用root权限运行此脚本"
    exit 1
fi

main