Derive SEO metadata from existing config (#153)

README.md

@@ -73,6 +73,10 @@ The web app can be configured with environment variables (defaults shown):
 * `MAX_NODE_DISTANCE_KM` - hide nodes farther than this distance from the center (default: `137`)
 * `MATRIX_ROOM` - matrix room id for a footer link (default: `#meshtastic-berlin:matrix.org`)
 
+The application derives SEO-friendly document titles, descriptions, and social
+preview tags from these existing configuration values and reuses the bundled
+logo for Open Graph and Twitter cards.
+
 Example:
 
 ```bash

web/app.rb

@@ -42,6 +42,14 @@ MAX_JSON_BODY_BYTES = begin
   end
 VERSION_FALLBACK = "v0.2.1"
 
+def fetch_config_string(key, default)
+  value = ENV[key]
+  return default if value.nil?
+
+  trimmed = value.strip
+  trimmed.empty? ? default : trimmed
+end
+
 def determine_app_version
   repo_root = File.expand_path("..", __dir__)
   git_dir = File.join(repo_root, ".git")
@@ -71,15 +79,85 @@ APP_VERSION = determine_app_version
 set :public_folder, File.join(__dir__, "public")
 set :views, File.join(__dir__, "views")
 
-SITE_NAME = ENV.fetch("SITE_NAME", "Meshtastic Berlin")
-DEFAULT_CHANNEL = ENV.fetch("DEFAULT_CHANNEL", "#MediumFast")
-DEFAULT_FREQUENCY = ENV.fetch("DEFAULT_FREQUENCY", "868MHz")
+SITE_NAME = fetch_config_string("SITE_NAME", "Meshtastic Berlin")
+DEFAULT_CHANNEL = fetch_config_string("DEFAULT_CHANNEL", "#MediumFast")
+DEFAULT_FREQUENCY = fetch_config_string("DEFAULT_FREQUENCY", "868MHz")
 MAP_CENTER_LAT = ENV.fetch("MAP_CENTER_LAT", "52.502889").to_f
 MAP_CENTER_LON = ENV.fetch("MAP_CENTER_LON", "13.404194").to_f
 MAX_NODE_DISTANCE_KM = ENV.fetch("MAX_NODE_DISTANCE_KM", "137").to_f
 MATRIX_ROOM = ENV.fetch("MATRIX_ROOM", "#meshtastic-berlin:matrix.org")
 DEBUG = ENV["DEBUG"] == "1"
 
+def sanitized_string(value)
+  value.to_s.strip
+end
+
+def sanitized_site_name
+  sanitized_string(SITE_NAME)
+end
+
+def sanitized_default_channel
+  sanitized_string(DEFAULT_CHANNEL)
+end
+
+def sanitized_default_frequency
+  sanitized_string(DEFAULT_FREQUENCY)
+end
+
+def sanitized_matrix_room
+  value = sanitized_string(MATRIX_ROOM)
+  value.empty? ? nil : value
+end
+
+def sanitized_max_distance_km
+  return nil unless defined?(MAX_NODE_DISTANCE_KM)
+
+  distance = MAX_NODE_DISTANCE_KM
+  return nil unless distance.is_a?(Numeric)
+  return nil unless distance.positive?
+
+  distance
+end
+
+def formatted_distance_km(distance)
+  format("%.1f", distance).sub(/\.0\z/, "")
+end
+
+def meta_description
+  site = sanitized_site_name
+  channel = sanitized_default_channel
+  frequency = sanitized_default_frequency
+  matrix = sanitized_matrix_room
+
+  summary = "Live Meshtastic mesh map for #{site}"
+  if channel.empty? && frequency.empty?
+    summary += "."
+  elsif channel.empty?
+    summary += " tuned to #{frequency}."
+  elsif frequency.empty?
+    summary += " on #{channel}."
+  else
+    summary += " on #{channel} (#{frequency})."
+  end
+
+  sentences = [summary, "Track nodes, messages, and coverage in real time."]
+  if (distance = sanitized_max_distance_km)
+    sentences << "Shows nodes within roughly #{formatted_distance_km(distance)} km of the map center."
+  end
+  sentences << "Join the community in #{matrix} on Matrix." if matrix
+
+  sentences.join(" ")
+end
+
+def meta_configuration
+  site = sanitized_site_name
+  {
+    title: site,
+    name: site,
+    description: meta_description,
+  }
+end
+
 class << Sinatra::Application
   def apply_logger_level!
     logger = settings.logger
@@ -569,14 +647,19 @@ end
 #
 # Renders the main site with configuration-driven defaults for the template.
 get "/" do
+  meta = meta_configuration
+
   erb :index, locals: {
-                site_name: SITE_NAME,
-                default_channel: DEFAULT_CHANNEL,
-                default_frequency: DEFAULT_FREQUENCY,
+                site_name: meta[:name],
+                meta_title: meta[:title],
+                meta_name: meta[:name],
+                meta_description: meta[:description],
+                default_channel: sanitized_default_channel,
+                default_frequency: sanitized_default_frequency,
                 map_center_lat: MAP_CENTER_LAT,
                 map_center_lon: MAP_CENTER_LON,
                 max_node_distance_km: MAX_NODE_DISTANCE_KM,
-                matrix_room: MATRIX_ROOM,
+                matrix_room: sanitized_matrix_room,
                 version: APP_VERSION,
               }
 end

web/spec/app_spec.rb

@@ -189,6 +189,23 @@ RSpec.describe "Potato Mesh Sinatra app" do
       get "/"
       expect(last_response.body).to include("#{APP_VERSION}")
     end
+
+    it "includes SEO metadata from configuration" do
+      stub_const("SITE_NAME", "Spec Mesh Title")
+      stub_const("DEFAULT_CHANNEL", "#SpecChannel")
+      stub_const("DEFAULT_FREQUENCY", "915MHz")
+      stub_const("MAX_NODE_DISTANCE_KM", 120.5)
+      stub_const("MATRIX_ROOM", " #spec-room:example.org ")
+
+      expected_description = "Live Meshtastic mesh map for Spec Mesh Title on #SpecChannel (915MHz). Track nodes, messages, and coverage in real time. Shows nodes within roughly 120.5 km of the map center. Join the community in #spec-room:example.org on Matrix."
+
+      get "/"
+
+      expect(last_response.body).to include(%(meta name="description" content="#{expected_description}" />))
+      expect(last_response.body).to include('<meta property="og:title" content="Spec Mesh Title" />')
+      expect(last_response.body).to include('<meta property="og:site_name" content="Spec Mesh Title" />')
+      expect(last_response.body).to include('<meta name="twitter:image" content="http://example.org/potatomesh-logo.svg" />')
+    end
   end
 
   describe "database initialization" do

web/views/index.erb

@@ -20,7 +20,32 @@
 <head>
   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width,initial-scale=1" />
-  <title><%= site_name %></title>
+  <% meta_title_html = Rack::Utils.escape_html(meta_title) %>
+  <% meta_name_html = Rack::Utils.escape_html(meta_name) %>
+  <% meta_description_html = Rack::Utils.escape_html(meta_description) %>
+  <% request_path = request.path.to_s.empty? ? "/" : request.path %>
+  <% canonical_url = "#{request.base_url}#{request_path}" %>
+  <% canonical_html = Rack::Utils.escape_html(canonical_url) %>
+  <% logo_url = "#{request.base_url}/potatomesh-logo.svg" %>
+  <% logo_url_html = Rack::Utils.escape_html(logo_url) %>
+  <% logo_alt_html = Rack::Utils.escape_html("#{meta_name} logo") %>
+  <title><%= meta_title_html %></title>
+  <meta name="application-name" content="<%= meta_name_html %>" />
+  <meta name="apple-mobile-web-app-title" content="<%= meta_name_html %>" />
+  <meta name="description" content="<%= meta_description_html %>" />
+  <link rel="canonical" href="<%= canonical_html %>" />
+  <meta property="og:title" content="<%= meta_title_html %>" />
+  <meta property="og:site_name" content="<%= meta_name_html %>" />
+  <meta property="og:description" content="<%= meta_description_html %>" />
+  <meta property="og:type" content="website" />
+  <meta property="og:url" content="<%= canonical_html %>" />
+  <meta property="og:image" content="<%= logo_url_html %>" />
+  <meta property="og:image:alt" content="<%= logo_alt_html %>" />
+  <meta name="twitter:card" content="summary" />
+  <meta name="twitter:title" content="<%= meta_title_html %>" />
+  <meta name="twitter:description" content="<%= meta_description_html %>" />
+  <meta name="twitter:image" content="<%= logo_url_html %>" />
+  <meta name="twitter:image:alt" content="<%= logo_alt_html %>" />
   <link rel="icon" type="image/svg+xml" href="/potatomesh-logo.svg" />
   <% refresh_interval_seconds = 60 %>
   <% tile_filter_light = "grayscale(1) saturate(0) brightness(0.92) contrast(1.05)" %>