# ==============================
# Main Context (全局配置)
# ==============================
# 最外层，没有显式块包裹
user nginx nginx;                     # 运行用户
worker_processes auto;                # 工作进程数
pid /var/run/nginx.pid;              # PID文件路径
error_log /var/log/nginx/error.log warn;  # 错误日志
daemon on;                            # 守护进程模式
worker_rlimit_nofile 65535;           # 文件描述符限制
load_module modules/ngx_http_geoip_module.so;  # 动态模块加载

# ==============================
# Events Context (事件模块)
# ==============================
events {
    worker_connections 1024;         # 每个worker连接数
    use epoll;                        # 事件驱动模型
    accept_mutex on;                  # 连接互斥锁
    multi_accept on;                  # 多连接接受
}

# ==============================
# HTTP Context (HTTP模块)
# ==============================
http {
    # ---------- 基础配置 ----------
    include /etc/nginx/mime.types;    # MIME类型
    default_type application/octet-stream;  # 默认类型
    
    # ---------- 日志格式 ----------
    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for"';
    
    access_log /var/log/nginx/access.log main;  # 访问日志
    
    # ---------- 核心模块 ----------
    
    # 1. Upstream模块 (负载均衡)
    upstream backend_cluster {
        server 192.168.1.10:8080 weight=3;
        server 192.168.1.11:8080;
        server 192.168.1.12:8080 backup;
        
        # 负载均衡方法
        least_conn;                   # 最少连接
        
        # 健康检查
        max_fails=3 fail_timeout=30s;
    }
    
    # 2. 缓存配置
    proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=my_cache:10m;
    
    # 3. 限流配置
    limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
    
    # ---------- Server Context ----------
    server {
        listen 80;                    # 监听端口
        server_name example.com www.example.com;  # 服务器名
        
        # ---------- Location Context ----------
        location / {
            proxy_pass http://backend_cluster;  # 代理到upstream
            # 请求头配置
            proxy_set_header Host $host;  # 传递客户端请求的主机名（容错性强，无 Host 头时回退到 server_name）
            proxy_set_header X-Real-IP $remote_addr; # 传递客户端真实 IP（直接与 Nginx 连接的 IP）
            proxy_set_header X-Real-Port $remote_port; # 传递客户端真实访问端口（补充端口信息，便于后端统计）
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; # 传递代理链路 IP 列表（格式：客户端IP, 一级代理IP, 二级...）
            proxy_set_header X-Forwarded-Proto $scheme;  # 传递真实协议（http/https，解决代理后后端无法识别协议的问题）
            proxy_set_header X-Forwarded-Path $request_uri; # 传递客户端请求的完整路径（含参数）
            
            # ---------- 嵌套if Context ----------
            if ($request_method = POST) {
                limit_req zone=one burst=5;
            }
        }
        
        location /static/ {
            root /var/www/html;        # 静态文件
            expires 30d;               # 缓存时间
            
            # ---------- 嵌套location ----------
            location ~* \.(css|js)$ {
                gzip_static on;
            }
        }
        
        location /api/ {
            # ---------- 嵌套limit_except ----------
            limit_except GET POST {
                deny all;
            }
        }
    }
    
    # ---------- 多个Server ----------
    server {
        listen 443 ssl http2;
        server_name secure.example.com;
        
        ssl_certificate /path/to/cert.pem;
        ssl_certificate_key /path/to/key.pem;
    }
}

# ==============================
# Mail Context (邮件代理模块)
# ==============================
mail {
    auth_http localhost:9000/auth;    # 认证服务器
    
    # ---------- Mail Server ----------
    server {
        listen 25;                     # SMTP
        protocol smtp;
        
        # ---------- 认证配置 ----------
        auth_http_header X-Auth-Key "secret";
    }
    
    server {
        listen 110;                     # POP3
        protocol pop3;
        proxy on;
    }
    
    server {
        listen 143;                     # IMAP
        protocol imap;
        proxy on;
    }
}

# ==============================
# Stream Context (四层代理模块)
# ==============================
stream {
    # ---------- Stream Upstream ----------
    upstream database_cluster {
        server 192.168.2.10:3306;
        server 192.168.2.11:3306;
        
        # 四层负载均衡
        hash $remote_addr consistent;  # 一致性哈希
    }
    
    upstream redis_cluster {
        server 192.168.2.20:6379;
        server 192168.2.21:6379;
    }
    
    # ---------- Stream Server ----------
    server {
        listen 13306;                  # MySQL代理
        proxy_pass database_cluster;
        proxy_timeout 3s;
        
        # ---------- SSL终止 ----------
        ssl_preread on;
    }
    
    server {
        listen 16379;                  # Redis代理
        proxy_pass redis_cluster;
    }
    
    # ---------- UDP代理 ----------
    server {
        listen 53 udp;                 # DNS代理
        proxy_pass 8.8.8.8:53;
    }
}

# ==============================
# 动态模块配置
# ==============================
# 1. RTMP模块 (视频流)
rtmp {
    server {
        listen 1935;                   # RTMP端口
        chunk_size 4096;
        
        application live {
            live on;
            record off;
            
            # ---------- 推流配置 ----------
            push rtmp://live.example.com;
        }
    }
}

# 2. Perl模块
perl 'sub {
    my $r = shift;
    $r->send_http_header("text/html");
    return "Hello from Perl!";
}';

# 3. Lua模块
lua_shared_dict my_cache 10m;