#!/bin/bash
#
# Hysteria2 终极优化脚本 (Systemd Drop-in 架构 + BBR/UDP 调优)
#

set -euo pipefail

# --- 变量配置 ---
SERVICE_NAME="hysteria-server.service"
# 目标限制 (65535 足以应付大多数情况，100万也可以)
LIMIT_NUM="65535"

# 配置文件路径 (使用 .d 目录，模块化管理)
LIMITS_FILE="/etc/security/limits.d/99-hysteria2.conf"
SYSCTL_FILE="/etc/sysctl.d/99-hysteria2.conf"
OVERRIDE_DIR="/etc/systemd/system/${SERVICE_NAME}.d"
OVERRIDE_FILE="${OVERRIDE_DIR}/override.conf"

# 颜色
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
PLAIN='\033[0m'

# 检查 Root
if [ "$(id -u)" -ne 0 ]; then
    echo -e "${RED}错误：必须以 root 权限运行。${PLAIN}"
    exit 1
fi

echo -e "${GREEN}=== Hysteria2 终极优化脚本 ===${PLAIN}"

# 0. 检查服务存在性
if ! systemctl cat "${SERVICE_NAME}" >/dev/null 2>&1; then
    echo -e "${RED}错误：未找到服务 ${SERVICE_NAME}${PLAIN}"
    echo -e "请确认服务名正确。"
    exit 1
fi

# -------------------------------------------------
# 1. 模块化配置 limits (文件描述符)
# -------------------------------------------------
echo -e "\n${YELLOW}[1/3] 配置 Limits (使用 /etc/security/limits.d/)...${PLAIN}"

cat > "${LIMITS_FILE}" <<EOF
# Hysteria2 Optimization
* soft nofile ${LIMIT_NUM}
* hard nofile ${LIMIT_NUM}
root soft nofile ${LIMIT_NUM}
root hard nofile ${LIMIT_NUM}
EOF
echo -e "已写入: ${GREEN}${LIMITS_FILE}${PLAIN}"

# 启用 PAM
if [ -f /etc/pam.d/common-session ] && ! grep -q "pam_limits.so" /etc/pam.d/common-session; then
    echo "session required pam_limits.so" >> /etc/pam.d/common-session
fi

# -------------------------------------------------
# 2. 模块化配置 Sysctl (内核网络参数 + BBR)
# -------------------------------------------------
echo -e "\n${YELLOW}[2/3] 配置内核网络参数 (使用 /etc/sysctl.d/)...${PLAIN}"

# 这里使用了我之前提供的参数，加上了 BBR，调整了 buffer 大小为适中的 25MB
cat > "${SYSCTL_FILE}" <<EOF
# --- Hysteria2 / QUIC Tuning ---
fs.file-max = 1000000

# 开启 BBR (关键)
net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr

# 增加 UDP/TCP 缓冲区 (25MB，适合 1Gbps+ 速率)
net.core.rmem_max = 26214400
net.core.wmem_max = 26214400
net.core.rmem_default = 26214400
net.core.wmem_default = 26214400

# 队列与并发
net.core.netdev_max_backlog = 10000
net.core.somaxconn = 10000

# UDP 特定调优
net.ipv4.udp_rmem_min = 8192
net.ipv4.udp_wmem_min = 8192
net.ipv4.udp_mem = 8192 262144 536870912

# 端口范围
net.ipv4.ip_local_port_range = 10000 65000
EOF

echo -e "已写入: ${GREEN}${SYSCTL_FILE}${PLAIN}"
sysctl --system >/dev/null 2>&1
echo "内核参数已重载 (BBR + UDP Buffer)。"

# -------------------------------------------------
# 3. Systemd Override (Drop-in 模式)
# -------------------------------------------------
echo -e "\n${YELLOW}[3/3] 配置 Systemd Override (Drop-in)...${PLAIN}"

mkdir -p "${OVERRIDE_DIR}"
cat > "${OVERRIDE_FILE}" <<EOF
[Service]
LimitNOFILE=${LIMIT_NUM}
EOF

echo -e "已写入覆盖配置: ${GREEN}${OVERRIDE_FILE}${PLAIN}"
systemctl daemon-reload

# -------------------------------------------------
# 4. 重启与验证
# -------------------------------------------------
echo -e "\n正在重启服务..."
systemctl restart "${SERVICE_NAME}"
sleep 2

# 严谨的 PID 获取方式
PID=$(systemctl show -p MainPID --value "${SERVICE_NAME}" 2>/dev/null | tr -d ' ')

if [ -z "${PID}" ] || [ "${PID}" = "0" ]; then
    echo -e "${RED}服务未启动或 PID 获取失败，请手动检查。${PLAIN}"
    exit 1
fi

# 读取限制
SOFT_LIMIT=$(awk '/Max open files/ {print $4}' "/proc/${PID}/limits")

if [ "$SOFT_LIMIT" == "$LIMIT_NUM" ]; then
    echo -e "${GREEN}验证成功！${PLAIN}"
    echo -e "PID: $PID | Limit: $SOFT_LIMIT"
    echo -e "优化策略: Systemd Override + Limit.d + Sysctl.d (BBR Enabled)"
else
    echo -e "${RED}验证失败。当前 Limit: $SOFT_LIMIT${PLAIN}"
fi