Add Brother printer switcher proxied through one port, move sinatra to port 80

app.rb

@@ -2,11 +2,12 @@
 require 'sinatra'
 require "sinatra/reloader"
 require 'tmpdir'
+require 'net/http'
 
 set :protection, :except => :frame_options
 set :environment, :production
 set :bind, "::"
-set :port, 4567
+set :port, 80
 
 if !File.exist?('config.json') || !File.readable?('config.json')
   raise RuntimeException, 'Could not read config.json'
@@ -17,6 +18,12 @@ PRINTER_DPI = 203 # DatamaxONeil E4204B Mark III native head resolution
 PRINTER_DARKNESS = 8 # lower than factory default to stop thermal dot-gain from fusing barcode bars
 TEST_LABEL_PDF = File.join(File.dirname(__FILE__), 'test-label.pdf')
 
+BROTHER_PRINTERS = {
+  'ql560'  => { port: 8560, label: 'Brother QL-560' },
+  'ql700'  => { port: 8700, label: 'Brother QL-700' },
+  'ql1100' => { port: 9100, label: 'Brother QL-1100' }
+}.freeze
+
 configure do
   enable :static
   set :session_secret, File.read(File.join(File.dirname(__FILE__), '.session_secret')).strip
@@ -73,6 +80,36 @@ helpers do
 
     "^XA\n^MD#{PRINTER_DARKNESS}\n^PW#{width}\n^LL#{height}\n^FO0,0^GFA,#{total_bytes},#{total_bytes},#{bytes_per_row},#{hexdata}\n^XZ\n"
   end
+
+  # Transparently reverse-proxies the current request to one of the
+  # brother_ql_web instances, so all three printers are reachable through
+  # this single sinatra port instead of their own dedicated ports.
+  def proxy_to_brother(port, path)
+    uri = URI("http://127.0.0.1:#{port}#{path}")
+    uri.query = request.query_string unless request.query_string.empty?
+
+    proxied = Net::HTTP.const_get(request.request_method.capitalize).new(uri)
+    request.env.each do |key, value|
+      next unless key.start_with?('HTTP_') && key != 'HTTP_HOST'
+
+      header = key.sub(/^HTTP_/, '').split('_').map(&:capitalize).join('-')
+      proxied[header] = value
+    end
+    proxied['Content-Type'] = request.content_type if request.content_type
+    proxied['X-Forwarded-Prefix'] = '/brother'
+    proxied['X-Forwarded-Host'] = request.host
+    proxied.body = request.body.read unless request.request_method == 'GET'
+
+    res = Net::HTTP.start(uri.host, uri.port) { |http| http.request(proxied) }
+
+    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 || '']]
+  end
 end
 
 before do
@@ -136,3 +173,26 @@ post '/test-print' do
   end
   redirect '/upload'
 end
+
+get '/brother' do
+  @printers = BROTHER_PRINTERS
+  @selected = session[:brother_printer]
+  erb :brother_picker
+end
+
+post '/brother/select' do
+  key = params[:printer]
+  halt 400, 'unknown printer' unless BROTHER_PRINTERS.key?(key)
+
+  session[:brother_printer] = key
+  redirect '/brother/'
+end
+
+%w[get post put delete].each do |verb|
+  send(verb, '/brother/*') do
+    key = session[:brother_printer]
+    redirect '/brother' unless key
+
+    proxy_to_brother(BROTHER_PRINTERS[key][:port], '/' + params[:splat].first)
+  end
+end

views/brother_picker.erb

@@ -0,0 +1,18 @@
+<h1>Brother printers</h1>
+<p>Choose a printer to open its label designer through this server.</p>
+
+<div class="list-group" style="max-width: 400px;">
+  <% @printers.each do |key, info| %>
+    <form action="/brother/select" method="POST" class="mb-2">
+      <input type="hidden" name="printer" value="<%= key %>">
+      <button type="submit" class="btn <%= @selected == key ? 'btn-primary' : 'btn-outline-primary' %> w-100 text-start">
+        <%= info[:label] %>
+        <% if @selected == key %> (active) <% end %>
+      </button>
+    </form>
+  <% end %>
+</div>
+
+<% if @selected %>
+  <p class="mt-3"><a href="/brother/">Open <%= @printers[@selected][:label] %> &raquo;</a></p>
+<% end %>

views/layout.erb

@@ -24,6 +24,9 @@
               <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>
@@ -53,4 +56,3 @@
     </script>
   </body>
 </html>
-