worker_processes auto;
error_log /var/log/nginx/error.log warn;

events {
    worker_connections 1024;
}

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"';
    access_log /var/log/nginx/access.log main;

    sendfile on;
    keepalive_timeout 65;
    client_max_body_size 50M;                 # PDF uploads up to 50MB

    # Gzip
    gzip on;
    gzip_types text/plain application/json application/javascript text/css;

    # Security headers applied to all responses
    add_header X-Frame-Options "DENY" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Permissions-Policy "camera=(), microphone=(self), geolocation=()" always;

    upstream frontend {
        server frontend:3000;
    }

    upstream backend {
        server backend:8000;
    }

    # HTTP → HTTPS redirect
    server {
        listen 80;
        server_name _;
        return 301 https://$host$request_uri;
    }

    # Main HTTPS server
    server {
        listen 443 ssl http2;
        server_name _;                        # replace with your domain

        ssl_certificate     /etc/letsencrypt/live/YOUR_DOMAIN/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/YOUR_DOMAIN/privkey.pem;
        ssl_protocols       TLSv1.2 TLSv1.3;
        ssl_ciphers         ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384;
        ssl_prefer_server_ciphers off;
        ssl_session_timeout 1d;
        ssl_session_cache shared:SSL:10m;

        add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
        add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; connect-src 'self' ws: wss:; font-src 'self';" always;

        # Health check — no auth, no log
        location = /health {
            proxy_pass http://backend;
            proxy_set_header Host $host;
            access_log off;
        }

        # Backend API — all /api/v1/* routes
        location /api/v1/ {
            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;

            # SSE streaming — disable buffering
            proxy_set_header Connection '';
            proxy_buffering off;
            proxy_cache off;
            proxy_read_timeout 300s;          # long timeout for SSE streams
        }

        # Frontend — everything else
        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_cache_bypass $http_upgrade;
        }

        # Static assets cache
        location /_next/static/ {
            proxy_pass http://frontend;
            add_header Cache-Control "public, max-age=31536000, immutable";
        }
    }
}