# nginx config for serving SecureBit.chat (static PWA) on Fly.io.
# Mirrors the behavior of the Apache .htaccess: correct JS MIME for ES modules
# (.jsx/.mjs), no-cache for the app shell / service worker / versioning files,
# long-immutable cache for hashed/static assets, security headers, honest 404s.

worker_processes auto;
events { worker_connections 1024; }

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

    # ES modules must be served as JavaScript. nginx's default mime.types maps
    # .js but not .mjs/.jsx — declare them explicitly (this overrides .js too).
    types {
        application/javascript  js mjs jsx;
        text/css                css;
        application/json        json map;
        application/manifest+json webmanifest;
        font/woff2              woff2;
        font/woff               woff;
        image/svg+xml           svg;
    }

    sendfile      on;
    tcp_nopush    on;
    server_tokens off;

    gzip            on;
    gzip_vary       on;
    gzip_proxied    any;
    gzip_comp_level 6;
    gzip_min_length 256;
    gzip_types      text/plain text/css text/javascript
                    application/javascript application/json application/manifest+json
                    application/ld+json application/wasm
                    image/svg+xml image/x-icon font/woff2;

    # Decide Cache-Control from the request path. Keeping all add_header calls at
    # one level avoids nginx's header-inheritance reset between blocks.
    map $uri $sb_cache {
        default                  "public, max-age=31536000, immutable";
        # Quoted because nginx reads a bare { as the start of a block: an unquoted
        # regex with a repetition count fails the config at boot, not at request time.
        # Both anchors matter. These patterns used to be ~^/index\.html$ and ~^/$,
        # which match the English shell and nothing else — so /de/, /ru/index.html and
        # every other localized page fell through to the one-year immutable default
        # below. A visitor who opened a localized page kept that exact HTML, and the
        # ?v= stamps inside it, for a year: no release could reach them.
        "~^/([a-z]{2}/)?(index\.html)?$"    "no-cache, no-store, must-revalidate";
        "~^/([a-z]{2}/)?manifest\.json$"    "no-cache, no-store, must-revalidate";
        ~^/sw\.js$               "no-cache, no-store, must-revalidate";
        ~^/meta\.json$           "no-cache, no-store, must-revalidate";
        # Operator ICE/TURN config: must never be cached long, or the browser
        # locks onto a stale server list (default was max-age=1y immutable).
        ~^/config/ice-servers\.js$ "no-cache, no-store, must-revalidate";
        # dist/ bundles are query-versioned (?v=) in index.html. "no-cache" forces
        # revalidation on every load, but dropping "no-store" lets the browser reuse
        # the cached copy on a 304 — avoiding a full re-download of the large bundles
        # (e.g. qr-local.js ~1.2MB) when nothing changed, while still picking up
        # new releases immediately.
        ~^/dist/                 "no-cache, must-revalidate";
        # The install prompt is a plain browser module and imports the dictionary by a
        # bare path, so that import carries no ?v= to bust the cache with. Left on the
        # default one-year immutable rule below, a visitor would keep the translations
        # they first loaded for a year.
        ~^/src/i18n/             "no-cache, must-revalidate";
        # Crawler-facing files must stay re-fetchable: the default below is a
        # one-year immutable cache, which would freeze a sitemap for a year.
        ~^/robots\.txt$          "public, max-age=3600";
        ~^/sitemap\.xml$         "public, max-age=3600";
    }

    # CDN-Cache-Control is read by Cloudflare (and other CDNs) *independently* of the
    # browser Cache-Control above, and takes precedence at the edge. We force "no-store"
    # for the app shell, service worker and version files so a CDN can never serve a
    # stale meta.json / index.html / sw.js — which would silently break the in-app
    # update notification. The empty default emits no header (nginx skips empty values),
    # so immutable hashed assets keep being edge-cached normally for performance.
    map $uri $sb_cdn_cache {
        default                  "";
        # Same anchoring fix as above: Cloudflare was edge-caching the localized
        # shells for a year too.
        "~^/([a-z]{2}/)?(index\.html)?$" "no-store";
        "~^/([a-z]{2}/)?manifest\.json$" "no-store";
        ~^/sw\.js$               "no-store";
        ~^/meta\.json$           "no-store";
        ~^/config/ice-servers\.js$ "no-store";
        ~^/dist/                 "no-store";
        ~^/src/i18n/             "no-store";
    }

    server {
        listen      8080 default_server;
        listen      [::]:8080 default_server;
        server_name _;
        root        /usr/share/nginx/html;
        index       index.html;

        # Security headers (frame-ancestors complements the in-page CSP meta tag).
        add_header X-Content-Type-Options   "nosniff"                          always;
        add_header Referrer-Policy          "strict-origin-when-cross-origin"  always;
        add_header X-Frame-Options          "DENY"                             always;
        add_header Content-Security-Policy   "frame-ancestors 'none';"         always;
        # Force HTTPS for two years and preload, closing the first-visit SSL-strip
        # window that upgrade-insecure-requests alone does not cover.
        add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
        # Lock down powerful features. Camera + microphone are allowed for QR
        # scanning and encrypted voice/video calls; other sensors are denied.
        add_header Permissions-Policy        "camera=(self), microphone=(self), geolocation=(), payment=(), usb=(), magnetometer=(), gyroscope=(), accelerometer=()" always;
        add_header Cache-Control            $sb_cache                          always;
        # Edge-cache directive for Cloudflare/CDNs (empty value → header is omitted).
        add_header CDN-Cache-Control        $sb_cdn_cache                      always;
        add_header Service-Worker-Allowed   "/"                                always;

        # Real asset files must return 404 when missing — never fall back to the
        # HTML shell, which would be served with the wrong content type and break
        # module/script loading (e.g. a missing config/ice-servers.js).
        location ~* \.(js|mjs|jsx|css|json|map|xml|txt|woff2?|ttf|otf|png|jpe?g|gif|webp|svg|ico|mp3|mp4|webm)$ {
            try_files $uri =404;
        }

        # The app has no client-side routes: every real address is either a file, the
        # root, or a locale directory, and $uri/ resolves /de/ through the index
        # directive. So an unknown path is a typo or a scanner probe, not a route.
        # Answering those with the app shell under 200 OK made every one of them an
        # indexable "page" — an infinite URL space that Search Console reports as soft
        # 404s and duplicates, spending crawl budget on addresses that do not exist.
        location / {
            try_files $uri $uri/ =404;
        }

        # A real page for a real 404, rather than nginx's own. Served from the root, so
        # the block above resolves it as an ordinary file; the 404 status is preserved.
        error_page 404 /404.html;
    }

    # One canonical hostname. www.securebit.chat has its own Fly certificate (so
    # Cloudflare's origin handshake succeeds), but it must not serve the app as a
    # second address — that splits search ranking and canonical links. Cloudflare
    # passes the original Host through, so an exact server_name match catches it
    # here; everything else falls through to the default server above.
    server {
        listen      8080;
        listen      [::]:8080;
        server_name www.securebit.chat;

        # /sw.js is the one path that must NOT redirect. Visitors who reached www in
        # the window between its certificate being issued and this redirect shipping
        # registered the site's service worker against this origin, and that worker
        # still serves its cached app shell — so those browsers never see the 301,
        # while their subresource requests do get redirected and are then blocked by
        # the page's own `script-src 'self'`. A 301 here would make that permanent:
        # a service worker update fails outright if the script URL redirects. So this
        # origin answers with a worker that unregisters itself and reloads the tab.
        # See deploy/www-sw.js.
        location = /sw.js {
            alias /etc/nginx/www-sw.js;
            # add_header in a location REPLACES the server-level set rather than
            # merging, so the security header has to be restated here.
            add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
            # Re-checked on every navigation instead of being trusted for 24 hours,
            # which is how quickly a stuck visitor gets rescued.
            add_header Cache-Control     "no-cache, no-store, must-revalidate" always;
            add_header CDN-Cache-Control "no-store"                            always;
        }

        location / {
            # The redirect itself must carry HSTS: it is the first response a
            # first-time www visitor sees, and the preload list covers subdomains.
            add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;

            return 301 https://securebit.chat$request_uri;
        }
    }

}