# nginx reverse proxy — single-origin deployment (SPEC §4).
# Serves the built SPA and proxies /api, /health, /ready to the Express API
# so the browser talks to exactly one origin (cookies stay SameSite=Lax safe).
# Mounted read-only at /etc/nginx/nginx.conf by docker-compose.prod.yml.

worker_processes auto;

events {
  worker_connections 1024;
}

http {
  # Hide nginx version from error pages and Server headers.
  server_tokens off;

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

  sendfile on;
  tcp_nopush on;
  keepalive_timeout 65;
  client_max_body_size 1m;

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

  # ---- Compression ----
  gzip on;
  gzip_vary on;
  gzip_comp_level 6;
  gzip_min_length 1024;
  gzip_types text/plain text/css text/xml text/javascript
             application/javascript application/json
             application/xml application/rss+xml
             image/svg+xml;

  # ---- Security headers (inherited by every location unless a location sets
  # its own add_header, in which case it is re-declared there) ----
  add_header X-Content-Type-Options "nosniff" always;
  add_header X-Frame-Options "DENY" always;
  add_header Referrer-Policy "strict-origin-when-cross-origin" always;

  upstream api {
    server api:4000;
  }

  server {
    listen 80;
    server_name _;

    root /usr/share/nginx/html;
    index index.html;

    # ---- API: forward the original URI untouched (/api/... -> /api/...) ----
    # X-Forwarded-* headers let the API's TRUST_PROXY_HOPS resolve the real
    # client IP for rate limiting (SPEC §8.4).
    location /api/ {
      proxy_pass http://api;
      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;
      proxy_set_header Connection "";
      proxy_buffering off;
      proxy_read_timeout 600s;
    }

    # ---- Public health / readiness (unversioned) ----
    location = /health {
      proxy_pass http://api/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;
      proxy_set_header X-Forwarded-Proto $scheme;
    }

    location = /ready {
      proxy_pass http://api/ready;
      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;
    }

    # ---- Hashed build assets: cache aggressively (immutable), never HTML ----
    location ~* \.(?:js|css|map|svg|png|jpg|jpeg|gif|webp|ico|woff2?|ttf|eot)$ {
      expires 1y;
      add_header Cache-Control "public, max-age=31536000, immutable" always;
      add_header X-Content-Type-Options "nosniff" always;
      add_header X-Frame-Options "DENY" always;
      add_header Referrer-Policy "strict-origin-when-cross-origin" always;
      try_files $uri =404;
    }

    # ---- SPA fallback: everything else -> index.html (never cached) ----
    location / {
      add_header Cache-Control "no-store" always;
      add_header X-Content-Type-Options "nosniff" always;
      add_header X-Frame-Options "DENY" always;
      add_header Referrer-Policy "strict-origin-when-cross-origin" always;
      try_files $uri $uri/ /index.html;
    }
  }
}