nginx-reverse-proxy.conf

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;

events {
    worker_connections 4096;
    use epoll;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    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 buffer=32k;

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    client_max_body_size 50M;

    # Gzip compression
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_types text/plain text/css text/xml text/javascript 
               application/x-javascript application/xml+rss 
               application/json application/javascript;

    # 🛡️ RATE LIMITING - Auth API Rate Limit
    limit_req_zone $binary_remote_addr zone=auth_limit:10m rate=5r/s;
    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=20r/s;
    limit_req_status 429;

    # 📦 CACHING - Resume Upload Cache
    proxy_cache_path /var/cache/nginx/resume levels=1:2 keys_zone=resume_cache:10m max_size=1g inactive=30d;
    proxy_cache_path /var/cache/nginx/api levels=1:2 keys_zone=api_cache:10m max_size=500m inactive=1h;

    # Upstream services
    upstream frontend {
        server frontend:80;
    }

    upstream backend {
        server backend:3001;
        keepalive 32;
    }

    # 🔌 WEBSOCKET - WebSocket upstream for AI Interview
    upstream websocket {
        server backend:3001;
    }

    # HTTP to HTTPS redirect
    server {
        listen 80;
        server_name _;
        
        # Health check endpoint (no redirect)
        location /health {
            access_log off;
            return 200 "healthy\n";
            add_header Content-Type text/plain;
        }
        
        # Allow ACME challenges
        location /.well-known/acme-challenge/ {
            root /var/www/certbot;
        }
        
        # Redirect all HTTP to HTTPS
        location / {
            return 301 https://$host$request_uri;
        }
    }

    # 🔒 HTTPS Server with SSL
    server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;
        server_name _;

        # SSL Configuration
        ssl_certificate /etc/nginx/certs/cert.pem;
        ssl_certificate_key /etc/nginx/certs/key.pem;
        ssl_protocols TLSv1.2 TLSv1.3;
        ssl_ciphers HIGH:!aNULL:!MD5:!AEAD;
        ssl_prefer_server_ciphers on;
        ssl_session_cache shared:SSL:10m;
        ssl_session_timeout 10m;
        ssl_stapling on;
        ssl_stapling_verify on;

        client_max_body_size 50M;

        # Security Headers
        add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-XSS-Protection "1; mode=block" always;
        add_header Referrer-Policy "strict-origin-when-cross-origin" always;
        add_header Permissions-Policy "geolocation=(), microphone=(self), camera=(self)" always;

        # Health check endpoint
        location /health {
            access_log off;
            return 200 "healthy\n";
            add_header Content-Type text/plain;
        }

        # 🛡️ RATE LIMIT - Authentication Endpoints (Max 5 req/sec)
        location ~ ^/api/auth/ {
            limit_req zone=auth_limit burst=10 nodelay;
            limit_req_log_level warn;

            proxy_pass http://backend;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection 'upgrade';
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_cache_bypass $http_upgrade;

            proxy_connect_timeout 30s;
            proxy_send_timeout 30s;
            proxy_read_timeout 30s;
        }

        # 📦 CACHING - Resume Upload & Retrieval (30 days cache)
        location ~ ^/api/resume/ {
            limit_req zone=api_limit burst=50 nodelay;

            proxy_pass http://backend;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;

            # Cache only GET requests for resume retrieval
            proxy_cache resume_cache;
            proxy_cache_methods GET HEAD;
            proxy_cache_key "$scheme$request_method$host$request_uri$http_authorization";
            proxy_cache_valid 200 30d;
            proxy_cache_valid 404 10m;
            proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504;
            proxy_cache_background_update on;
            proxy_cache_lock on;

            # Add cache status header
            add_header X-Cache-Status $upstream_cache_status;

            proxy_connect_timeout 60s;
            proxy_send_timeout 120s;
            proxy_read_timeout 120s;
        }

        # 🔌 WEBSOCKET - AI Interview Streaming
        location ~ ^/api/interview/stream {
            proxy_pass http://websocket;
            proxy_http_version 1.1;
            
            # WebSocket essentials
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "Upgrade";
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;

            # WebSocket timeout settings
            proxy_read_timeout 86400s;
            proxy_send_timeout 86400s;
            proxy_connect_timeout 60s;

            # Disable buffering for real-time streaming
            proxy_buffering off;
            proxy_request_buffering off;

            # Keep-alive
            proxy_set_header Connection "";

            # Prevent connection breaking
            proxy_set_header Cache-Control no-cache;

            access_log /var/log/nginx/websocket.log main buffer=16k;
        }

        # 🔌 WEBSOCKET - General WebSocket support
        location ~ ^/api/ws/ {
            proxy_pass http://websocket;
            proxy_http_version 1.1;
            
            # WebSocket upgrade headers
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;

            # Timeouts for long-lived connections
            proxy_read_timeout 3600s;
            proxy_send_timeout 3600s;

            # Turn off buffering
            proxy_buffering off;
            proxy_request_buffering off;
        }

        # 🛡️ RATE LIMIT - General API Endpoints (Max 20 req/sec)
        location ~ ^/api/ {
            limit_req zone=api_limit burst=100 nodelay;

            proxy_pass http://backend;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection 'upgrade';
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_cache_bypass $http_upgrade;

            # Cache API responses
            proxy_cache api_cache;
            proxy_cache_methods GET HEAD;
            proxy_cache_key "$scheme$request_method$host$request_uri$http_authorization";
            proxy_cache_valid 200 10m;
            proxy_cache_valid 404 5m;
            add_header X-Cache-Status $upstream_cache_status;

            proxy_connect_timeout 60s;
            proxy_send_timeout 60s;
            proxy_read_timeout 60s;
        }

        # Backend health endpoint
        location /health/backend {
            proxy_pass http://backend/health;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            access_log off;
        }

        # Frontend routes
        location / {
            proxy_pass http://frontend/;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection 'upgrade';
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_cache_bypass $http_upgrade;
        }

        # Static assets caching
        location ~* \.(jpg|jpeg|png|gif|ico|css|js|svg|woff|woff2|ttf|eot)$ {
            proxy_pass http://frontend;
            proxy_cache_valid 200 30d;
            add_header Cache-Control "public, immutable";
        }
    }

    # Monitoring & Status
    server {
        listen 8080;
        server_name _;

        location /nginx_status {
            stub_status on;
            access_log off;
        }

        location /cache_status {
            access_log off;
            return 200 "Cache paths active";
        }
    }
}