Inject persistent top navbar (with printer switcher) into proxied Brother pages

app.rb

@@ -102,13 +102,18 @@ helpers do
 
     res = Net::HTTP.start(uri.host, uri.port) { |http| http.request(proxied) }
 
+    body = res.body || ''
+    if res['Content-Type']&.include?('text/html')
+      body = body.sub(/(<body[^>]*>)/i) { "#{Regexp.last_match(1)}\n#{erb(:_navbar, layout: false)}" }
+    end
+
     headers = {}
     res.each_header do |key, value|
       next if %w[transfer-encoding connection content-length].include?(key.downcase)
 
       headers[key] = value
     end
-    [res.code.to_i, headers, [res.body || '']]
+    [res.code.to_i, headers, [body]]
   end
 end
 

views/_navbar.erb

@@ -0,0 +1,27 @@
+<nav class="navbar navbar-expand-lg navbar-light bg-light">
+  <div class="container-fluid">
+    <a class="navbar-brand" href="/">Print server</a>
+    <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
+      <span class="navbar-toggler-icon"></span>
+    </button>
+    <div class="collapse navbar-collapse" id="navbarNavDropdown">
+      <ul class="navbar-nav me-auto">
+        <li class="nav-item">
+          <a class="nav-link" href="/">Home</a>
+        </li>
+        <li class="nav-item">
+          <a class="nav-link" href="/upload">Shipping labels</a>
+        </li>
+      </ul>
+      <span class="navbar-text me-2">Brother:</span>
+      <div class="d-flex gap-1">
+        <% BROTHER_PRINTERS.each do |key, info| %>
+          <form action="/brother/select" method="POST" class="m-0">
+            <input type="hidden" name="printer" value="<%= key %>">
+            <button type="submit" class="btn btn-sm <%= session[:brother_printer] == key ? 'btn-primary' : 'btn-outline-secondary' %>"><%= info[:label].sub('Brother ', '') %></button>
+          </form>
+        <% end %>
+      </div>
+    </div>
+  </div>
+</nav>

views/layout.erb

@@ -10,27 +10,7 @@
   </head>
   <body>
     <div class="container">
-      <nav class="navbar navbar-expand-lg navbar-light bg-light">
-        <div class="container-fluid">
-          <a class="navbar-brand" href="/">Print server</a>
-          <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
-            <span class="navbar-toggler-icon"></span>
-          </button>
-          <div class="collapse navbar-collapse" id="navbarNavDropdown">
-            <ul class="navbar-nav">
-              <li class="nav-item">
-                <a class="nav-link active" aria-current="page" href="/">Home</a>
-              </li>
-              <li class="nav-item">
-                <a class="nav-link" href="/upload">Shipping labels</a>
-              </li>
-              <li class="nav-item">
-                <a class="nav-link" href="/brother">Brother printers</a>
-              </li>
-            </ul>
-          </div>
-        </div>
-      </nav>
+      <%= erb :_navbar, layout: false %>
       <div class="row">
         <% if @alert_success then %>
 	  <div class="alert alert-success"><%=@alert_success%></div>