#!/usr/bin/env bash

# ==============================================================================
# Linux TCP/IP & BBR 智能优化脚本
#
# 版本: 1.6.2 (安全与优化修复)
# 改进日志 (v1.6.2):
# - [CRITICAL-FIX] 彻底清除了导致脚本语法错误的非换行空格 (U+00A0)
# - [优化] 移除了已弃用的 'fs.nr_open' 参数，仅保留 'fs.file-max'
# ==============================================================================

# --- 脚本版本号定义 ---
SCRIPT_VERSION="1.6.2"

set -euo pipefail

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

# --- 配置文件路径 ---
CONF_FILE="/etc/sysctl.d/99-bbr.conf"

# --- 系统信息检测函数 ---
get_system_info() {
    TOTAL_MEM=$(free -m | awk '/^Mem:/{print $2}' | tr -d '\r')
    CPU_CORES=$(nproc | tr -d '\r')
    
    if command -v systemd-detect-virt >/dev/null 2>&1; then
        VIRT_TYPE=$(systemd-detect-virt)
    elif grep -q -i "hypervisor" /proc/cpuinfo; then
        VIRT_TYPE="KVM/VMware"
    elif command -v dmidecode >/dev/null 2>&1 && dmidecode -s system-product-name | grep -q -i "virtual"; then
        VIRT_TYPE=$(dmidecode -s system-product-name)
    else
        VIRT_TYPE="unknown"
    fi

    echo -e "${CYAN}>>> 系统信息检测：${NC}"
    echo -e "内存大小   : ${YELLOW}${TOTAL_MEM}MB${NC}"
    echo -e "CPU核心数  : ${YELLOW}${CPU_CORES}${NC}"
    echo -e "虚拟化类型 : ${YELLOW}${VIRT_TYPE}${NC}"
    
    calculate_parameters
}

# --- 动态参数计算函数 ---
calculate_parameters() {
    if [ "$TOTAL_MEM" -le 512 ]; then
        VM_TIER="经典级(≤512MB)"
        RMEM_MAX="8388608"
        WMEM_MAX="8388608"
        TCP_RMEM="4096 65536 8388608"
        TCP_WMEM="4096 65536 8388608"
        SOMAXCONN="32768"
        NETDEV_BACKLOG="16384"
        FILE_MAX="262144"
        CONNTRACK_MAX="131072"
    elif [ "$TOTAL_MEM" -le 1024 ]; then
        VM_TIER="轻量级(512MB-1GB)"
        RMEM_MAX="16777216"
        WMEM_MAX="16777216"
        TCP_RMEM="4096 65536 16777216"
        TCP_WMEM="4096 65536 16777216"
        SOMAXCONN="49152"
        NETDEV_BACKLOG="24576"
        FILE_MAX="524288"
        CONNTRACK_MAX="262144"
    elif [ "$TOTAL_MEM" -le 2048 ]; then
        VM_TIER="标准级(1GB-2GB)"
        RMEM_MAX="33554432"
        WMEM_MAX="33554432"
        TCP_RMEM="4096 87380 33554432"
        TCP_WMEM="4096 65536 33554432"
        SOMAXCONN="65535"
        NETDEV_BACKLOG="32768"
        FILE_MAX="1048576"
        CONNTRACK_MAX="524288"
    elif [ "$TOTAL_MEM" -le 4096 ]; then
        VM_TIER="高性能级(2GB-4GB)"
        RMEM_MAX="67108864"
        WMEM_MAX="67108864"
        TCP_RMEM="4096 131072 67108864"
        TCP_WMEM="4096 87380 67108864"
        SOMAXCONN="65535"
        NETDEV_BACKLOG="65535"
        FILE_MAX="2097152"
        CONNTRACK_MAX="1048576"
    elif [ "$TOTAL_MEM" -le 8192 ]; then
        VM_TIER="企业级(4GB-8GB)"
        RMEM_MAX="134217728"
        WMEM_MAX="134217728"
        TCP_RMEM="8192 131072 134217728"
        TCP_WMEM="8192 87380 134217728"
        SOMAXCONN="65535"
        NETDEV_BACKLOG="65535"
        FILE_MAX="4194304"
        CONNTRACK_MAX="2097152"
    else
        VM_TIER="旗舰级(>8GB)"
        RMEM_MAX="134217728"
        WMEM_MAX="134217728"
        TCP_RMEM="8192 131072 134217728"
        TCP_WMEM="8192 87380 134217728"
        SOMAXCONN="65535"
        NETDEV_BACKLOG="65535"
        FILE_MAX="8388608"
        CONNTRACK_MAX="2097152"
    fi
}

# --- 预检查函数 ---
pre_flight_checks() {
    echo -e "${BLUE}>>> 执行预检查...${NC}"
    if [[ $(id -u) -ne 0 ]]; then
        echo -e "${RED}❌ 错误: 此脚本必须以root权限运行。${NC}"
        exit 1
    fi
    local KERNEL_VERSION
    KERNEL_VERSION=$(uname -r)
    if [[ $(printf '%s\n' "4.9" "$KERNEL_VERSION" | sort -V | head -n1) != "4.9" ]]; then
        echo -e "${RED}❌ 错误: 内核版本 $KERNEL_VERSION 不支持BBR (需要 4.9+)。${NC}"
        exit 1
    else
        echo -e "${GREEN}✅ 内核版本 $KERNEL_VERSION, 支持BBR。${NC}"
    fi
    if ! sysctl net.ipv4.tcp_available_congestion_control | grep -q "bbr"; then
        echo -e "${YELLOW}⚠️  警告: BBR模块未加载，尝试加载...${NC}"
        modprobe tcp_bbr 2>/dev/null || { echo -e "${RED}❌ 无法加载BBR模块, 请检查内核。${NC}"; exit 1; }
    fi
}

# --- 配置写入函数 ---
add_conf() {
    local key="$1"
    local value="$2"
    local comment="$3"
    echo "# $comment" >> "$CONF_FILE"
    echo "$key = $value" >> "$CONF_FILE"
    echo "" >> "$CONF_FILE"
    echo -e "[${GREEN}设置${NC}] $key = ${YELLOW}$value${NC}"
}

# --- 备份管理与清理函数 ---
manage_backups() {
    if [ -f "$CONF_FILE" ]; then
        local BAK_FILE="$CONF_FILE.bak_$(date +%F_%H-%M-%S)"
        echo -e "${YELLOW}>>> 创建当前配置备份: $BAK_FILE${NC}"
        cp "$CONF_FILE" "$BAK_FILE"
    fi
    local old_backups
    set +e
    old_backups=$(ls -t "$CONF_FILE.bak_"* 2>/dev/null | tail -n +2)
    set -e
    if [ -n "$old_backups" ]; then
        echo -e "${CYAN}>>> 清理旧的备份文件...${NC}"
        echo "$old_backups" | xargs rm
        echo -e "${GREEN}✅ 旧备份清理完成。${NC}"
    fi
}

# --- 主要优化配置 ---
apply_optimizations() {
    echo -e "${CYAN}>>> 应用核心网络优化配置 (${YELLOW}${VM_TIER}${CYAN})...${NC}"
    > "$CONF_FILE"
    cat >> "$CONF_FILE" << EOF
# ==========================================================
# TCP/IP & BBR 优化配置 (由脚本自动生成)
# 生成时间: $(date)
# 针对硬件: ${TOTAL_MEM}MB 内存, ${CPU_CORES}核CPU (${VM_TIER})
# ==========================================================
EOF
    add_conf "net.core.default_qdisc" "fq" "使用Fair Queue队列调度器, 配合BBR效果更佳"
    add_conf "net.ipv4.tcp_congestion_control" "bbr" "启用BBR拥塞控制算法"
    add_conf "net.core.rmem_max" "$RMEM_MAX" "最大socket读缓冲区"
    add_conf "net.core.wmem_max" "$WMEM_MAX" "最大socket写缓冲区"
    add_conf "net.ipv4.tcp_rmem" "$TCP_RMEM" "TCP读缓冲区 (min/default/max)"
    add_conf "net.ipv4.tcp_wmem" "$TCP_WMEM" "TCP写缓冲区 (min/default/max)"
    add_conf "net.core.somaxconn" "$SOMAXCONN" "最大监听队列长度"
    add_conf "net.core.netdev_max_backlog" "$NETDEV_BACKLOG" "网络设备最大排队数"
    add_conf "net.ipv4.tcp_max_syn_backlog" "$SOMAXCONN" "SYN队列最大长度"
    add_conf "net.ipv4.tcp_fin_timeout" "15" "缩短FIN_WAIT_2状态超时"
    add_conf "net.ipv4.tcp_tw_reuse" "0" "禁用TIME_WAIT重用"
    add_conf "net.ipv4.tcp_max_tw_buckets" "180000" "增加TIME_WAIT socket最大数量"
    add_conf "fs.file-max" "$FILE_MAX" "系统级最大文件句柄数"
    # [优化] 移除已弃用的 'fs.nr_open'
    add_conf "net.ipv4.tcp_slow_start_after_idle" "0" "禁用空闲后慢启动"
    add_conf "vm.swappiness" "10" "降低Swap使用倾向"
    if [ -f /proc/sys/net/netfilter/nf_conntrack_max ]; then
        add_conf "net.netfilter.nf_conntrack_max" "$CONNTRACK_MAX" "连接跟踪表最大条目数"
    fi
}

# --- 应用与验证 ---
apply_and_verify() {
    echo -e "${CYAN}>>> 使配置生效...${NC}"
    sysctl --system >/dev/null 2>&1 || { echo -e "${RED}❌ 配置应用失败, 请检查 $CONF_FILE 文件格式。${NC}"; exit 1; }
    echo -e "${GREEN}✅ 配置已动态生效。${NC}"
    echo -e "${CYAN}>>> 验证优化结果...${NC}"
    local CURRENT_CC
    CURRENT_CC=$(sysctl -n net.ipv4.tcp_congestion_control)
    local CURRENT_QDISC
    CURRENT_QDISC=$(sysctl -n net.core.default_qdisc)
    echo -e "当前拥塞控制算法: ${YELLOW}$CURRENT_CC${NC}"
    echo -e "当前网络队列调度器: ${YELLOW}$CURRENT_QDISC${NC}"
    if [[ "$CURRENT_CC" == "bbr" && "$CURRENT_QDISC" == "fq" ]]; then
        echo -e "${GREEN}✅ BBR 与 FQ 已成功启用!${NC}"
    else
        echo -e "${RED}❌ 优化未完全生效, 请检查系统日志。${NC}"
    fi
}

# --- 提示信息 ---
show_tips() {
    echo ""
    echo -e "${YELLOW}-------------------- 操作完成 --------------------${NC}"
    echo -e "配置文件已写入: ${CYAN}$CONF_FILE${NC}"
    local bak_file_hint
    bak_file_hint=$(ls -t "$CONF_FILE.bak_"* 2>/dev/null | head -n 1)
    if [ -n "$bak_file_hint" ]; then
        echo -e "如需恢复备份, 可运行:"
        echo -e "${GREEN}mv \"$bak_file_hint\" \"$CONF_FILE\" && sysctl --system${NC}"
    fi
    echo -e "${YELLOW}--------------------------------------------------${NC}"
}

# --- 冲突配置检查函数 (修复版) ---
check_for_conflicts() {
    local key_params=("net.ipv4.tcp_congestion_control" "net.core.default_qdisc")
    local conflicting_files=""
    local pattern
    
    # 构建grep模式
    pattern=$(printf '%s\|' "${key_params[@]}")
    pattern="${pattern%\\|}"  # 移除末尾的\|
    
    # 检查主配置文件
    if grep -qE "$pattern" /etc/sysctl.conf 2>/dev/null; then
        conflicting_files+="\n - /etc/sysctl.conf"
    fi
    
    # 检查其他配置文件
    for conf_file in /etc/sysctl.d/*.conf; do
        if [ "$conf_file" != "$CONF_FILE" ] && [ -f "$conf_file" ]; then
            if grep -qE "$pattern" "$conf_file" 2>/dev/null; then
                conflicting_files+="\n - $conf_file"
            fi
        fi
    done
    
    if [ -n "$conflicting_files" ]; then
        echo -e "\n${YELLOW}---------------------- 注意 ----------------------${NC}"
        echo -e "${YELLOW}⚠️  系统在以下文件中也发现了BBR相关设置:${NC}"
        echo -e "${CYAN}${conflicting_files}${NC}"
        echo -e "${YELLOW}为避免配置混乱, 建议您手动编辑这些文件,${NC}"
        echo -e "${YELLOW}注释或删除其中的冲突行。您的脚本 (${CYAN}$CONF_FILE${YELLOW}) 已生效。${NC}"
        echo -e "${YELLOW}--------------------------------------------------${NC}"
    fi
}

# --- 幂等性检查函数 ---
check_if_already_applied() {
    if grep -q "# 由脚本自动生成" "$CONF_FILE" 2>/dev/null; then
        local current_cc
        current_cc=$(sysctl -n net.ipv4.tcp_congestion_control 2>/dev/null)
        if [[ "$current_cc" == "bbr" ]]; then
            echo -e "${GREEN}✅ 系统已被此脚本优化，且BBR已启用，无需重复操作。${NC}"
            exit 0
        fi
    fi
}

# --- 撤销与卸载函数 ---
revert_optimizations() {
    echo -e "${YELLOW}>>> 正在尝试撤销优化...${NC}"
    local latest_backup
    latest_backup=$(ls -t "$CONF_FILE.bak_"* 2>/dev/null | head -n 1)
    if [ -f "$latest_backup" ]; then
        echo -e "找到最新备份文件: ${CYAN}$latest_backup${NC}"
        if [[ $(id -u) -ne 0 ]]; then
            echo -e "${RED}❌ 错误: 恢复操作必须以root权限运行。${NC}"
            exit 1
        fi
        mv "$latest_backup" "$CONF_FILE"
        echo -e "${GREEN}✅ 已通过备份文件恢复。${NC}"
    elif [ -f "$CONF_FILE" ]; then
        echo -e "${YELLOW}未找到备份文件，将直接删除配置文件...${NC}"
        if [[ $(id -u) -ne 0 ]]; then
            echo -e "${RED}❌ 错误: 删除操作必须以root权限运行。${NC}"
            exit 1
        fi
        rm -f "$CONF_FILE"
        echo -e "${GREEN}✅ 配置文件已删除。${NC}"
    else
        echo -e "${GREEN}✅ 系统未发现优化配置文件，无需操作。${NC}"
        return 0
    fi
    echo -e "${CYAN}>>> 使恢复后的配置生效...${NC}"
    sysctl --system >/dev/null 2>&1
    echo -e "${GREEN}🎉 优化已成功撤销！系统将恢复到内核默认或之前的配置。${NC}"
}

# --- 主函数 ---
main() {
    if [[ "${1:-}" == "uninstall" || "${1:-}" == "--revert" ]]; then
        revert_optimizations
        exit 0
    fi

    echo -e "${CYAN}======================================================${NC}"
    echo -e "${CYAN}     Linux TCP/IP & BBR 智能优化脚本 v${SCRIPT_VERSION}     ${NC}"
    echo -e "${CYAN}======================================================${NC}"
    
    check_if_already_applied
    pre_flight_checks
    get_system_info
    manage_backups
    apply_optimizations
    apply_and_verify
    show_tips
    check_for_conflicts
    
    echo -e "\n${GREEN}🎉 所有优化已完成并生效！${NC}"
    
    exit 0
}

# --- 脚本入口 ---
main "$@"