feat: add centralized fonts module for dynamic font loading

Create a DRY Fonts module that centralizes all font definitions and
generates @font-face declarations dynamically based on typography preset.

- Add Fonts module with typography font mappings
- Generate @font-face CSS in CSSGenerator based on active preset
- Add font preload links in shop_root layout for performance
- Remove hardcoded font-face declarations from CSS

This improves font loading performance by only loading fonts for the
active typography preset and preloading critical fonts.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/simpleshop_theme/theme/css_generator.ex

@@ -11,6 +11,7 @@ defmodule SimpleshopTheme.Theme.CSSGenerator do
   """
 
   alias SimpleshopTheme.Settings.ThemeSettings
+  alias SimpleshopTheme.Theme.Fonts
 
   @doc """
   Generates CSS for theme settings.
@@ -18,9 +19,14 @@ defmodule SimpleshopTheme.Theme.CSSGenerator do
   Returns a string of CSS custom properties that can be injected into a <style> tag.
   This includes ALL theme tokens (mood, typography, shape, density) so the shop
   pages don't need the attribute-based CSS selectors.
+
+  Also includes @font-face declarations for the fonts used by the typography preset.
   """
   def generate(%ThemeSettings{} = settings) do
     """
+    /* Font faces for #{settings.typography} typography */
+    #{Fonts.generate_font_faces(settings.typography)}
+
     /* Theme Tokens - Layer 2 (dynamically generated) */
     .themed {
       /* Mood colors */
@@ -113,73 +119,31 @@ defmodule SimpleshopTheme.Theme.CSSGenerator do
   # Fallback for any other mood value
   defp generate_mood(_), do: generate_mood("neutral")
 
+  # Typography style settings (weight and tracking per preset)
+  @typography_styles %{
+    "clean" => %{weight: 600, tracking: "-0.02em"},
+    "editorial" => %{weight: 500, tracking: "-0.01em"},
+    "modern" => %{weight: 500, tracking: "-0.03em"},
+    "classic" => %{weight: 500, tracking: "0"},
+    "friendly" => %{weight: 600, tracking: "-0.01em"},
+    "minimal" => %{weight: 500, tracking: "0"},
+    "impulse" => %{weight: 300, tracking: "0.02em"}
+  }
+
   # Typography - font families, weights, and tracking
-  defp generate_typography("clean") do
+  # Uses Fonts module for DRY font-family declarations
+  defp generate_typography(typography) do
+    %{heading: heading_key, body: body_key} = Fonts.fonts_for_typography(typography)
+    style = Map.get(@typography_styles, typography, @typography_styles["clean"])
+
     """
-    --t-font-heading: 'Manrope', system-ui, sans-serif;
+    --t-font-heading: #{Fonts.font_family(heading_key)};
-      --t-font-body: 'Inter', system-ui, sans-serif;
+      --t-font-body: #{Fonts.font_family(body_key)};
-      --t-heading-weight: 600;
+      --t-heading-weight: #{style.weight};
-      --t-heading-tracking: -0.02em;
+      --t-heading-tracking: #{style.tracking};
     """
   end
 
-  defp generate_typography("editorial") do
-    """
-    --t-font-heading: 'Playfair Display', Georgia, serif;
-      --t-font-body: 'Raleway', system-ui, sans-serif;
-      --t-heading-weight: 500;
-      --t-heading-tracking: -0.01em;
-    """
-  end
-
-  defp generate_typography("modern") do
-    """
-    --t-font-heading: 'Space Grotesk', system-ui, sans-serif;
-      --t-font-body: 'Inter', system-ui, sans-serif;
-      --t-heading-weight: 500;
-      --t-heading-tracking: -0.03em;
-    """
-  end
-
-  defp generate_typography("classic") do
-    """
-    --t-font-heading: 'Cormorant Garamond', Georgia, serif;
-      --t-font-body: 'Source Serif 4', Georgia, serif;
-      --t-heading-weight: 500;
-      --t-heading-tracking: 0;
-    """
-  end
-
-  defp generate_typography("friendly") do
-    """
-    --t-font-heading: 'Fraunces', Georgia, serif;
-      --t-font-body: 'Work Sans', system-ui, sans-serif;
-      --t-heading-weight: 600;
-      --t-heading-tracking: -0.01em;
-    """
-  end
-
-  defp generate_typography("minimal") do
-    """
-    --t-font-heading: 'DM Sans', system-ui, sans-serif;
-      --t-font-body: 'Source Serif 4', Georgia, serif;
-      --t-heading-weight: 500;
-      --t-heading-tracking: 0;
-    """
-  end
-
-  defp generate_typography("impulse") do
-    """
-    --t-font-heading: 'Raleway', system-ui, sans-serif;
-      --t-font-body: 'Inter', system-ui, sans-serif;
-      --t-heading-weight: 300;
-      --t-heading-tracking: 0.02em;
-    """
-  end
-
-  # Fallback for any other typography value
-  defp generate_typography(_), do: generate_typography("clean")
-
   # Shape - border radii
   defp generate_shape("soft") do
     """

lib/simpleshop_theme/theme/fonts.ex

@@ -0,0 +1,214 @@
+defmodule SimpleshopTheme.Theme.Fonts do
+  @moduledoc """
+  Centralized font configuration for the theme system.
+
+  This module defines all available fonts and their variants, maps typography
+  presets to font pairs, and generates CSS @font-face declarations.
+
+  Font files are expected to be in /priv/static/fonts/ and served at /fonts/.
+  """
+
+  # Font definitions: family name, file prefix, and available weights
+  @fonts %{
+    inter: %{
+      family: "Inter",
+      file_prefix: "inter-v20-latin",
+      weights: [300, 400, 500, 600, 700],
+      fallback: "system-ui, sans-serif"
+    },
+    manrope: %{
+      family: "Manrope",
+      file_prefix: "manrope-v20-latin",
+      weights: [400, 500, 600, 700],
+      fallback: "system-ui, sans-serif"
+    },
+    raleway: %{
+      family: "Raleway",
+      file_prefix: "raleway-v37-latin",
+      weights: [300, 400, 500],
+      fallback: "system-ui, sans-serif"
+    },
+    playfair: %{
+      family: "Playfair Display",
+      file_prefix: "playfair-display-v40-latin",
+      weights: [400, 500, 700],
+      fallback: "Georgia, serif"
+    },
+    space_grotesk: %{
+      family: "Space Grotesk",
+      file_prefix: "space-grotesk-v22-latin",
+      weights: [400, 500, 600],
+      fallback: "system-ui, sans-serif"
+    },
+    cormorant: %{
+      family: "Cormorant Garamond",
+      file_prefix: "cormorant-garamond-v21-latin",
+      weights: [400, 500, 600],
+      fallback: "Georgia, serif"
+    },
+    source_serif: %{
+      family: "Source Serif 4",
+      file_prefix: "source-serif-4-v14-latin",
+      weights: [400, 600],
+      fallback: "Georgia, serif"
+    },
+    fraunces: %{
+      family: "Fraunces",
+      file_prefix: "fraunces-v38-latin",
+      weights: [400, 500, 600, 700],
+      fallback: "Georgia, serif"
+    },
+    work_sans: %{
+      family: "Work Sans",
+      file_prefix: "work-sans-v24-latin",
+      weights: [300, 400, 500, 600],
+      fallback: "system-ui, sans-serif"
+    },
+    dm_sans: %{
+      family: "DM Sans",
+      file_prefix: "dm-sans-v17-latin",
+      weights: [400, 500, 600, 700],
+      fallback: "system-ui, sans-serif"
+    }
+  }
+
+  # Typography presets map to heading and body font keys
+  @typography_fonts %{
+    "clean" => %{heading: :manrope, body: :inter},
+    "editorial" => %{heading: :playfair, body: :raleway},
+    "modern" => %{heading: :space_grotesk, body: :inter},
+    "classic" => %{heading: :cormorant, body: :source_serif},
+    "friendly" => %{heading: :fraunces, body: :work_sans},
+    "minimal" => %{heading: :dm_sans, body: :source_serif},
+    "impulse" => %{heading: :raleway, body: :inter}
+  }
+
+  @doc """
+  Returns the font configuration for a given font key.
+  """
+  def get_font(key), do: Map.get(@fonts, key)
+
+  @doc """
+  Returns all font configurations.
+  """
+  def all_fonts, do: @fonts
+
+  @doc """
+  Returns the heading and body font keys for a typography preset.
+  """
+  def fonts_for_typography(typography) do
+    Map.get(@typography_fonts, typography, @typography_fonts["clean"])
+  end
+
+  @doc """
+  Returns the CSS font-family declaration (with fallbacks) for a font key.
+  """
+  def font_family(key) do
+    case get_font(key) do
+      %{family: family, fallback: fallback} -> "'#{family}', #{fallback}"
+      nil -> "system-ui, sans-serif"
+    end
+  end
+
+  @doc """
+  Generates @font-face CSS for a specific typography preset.
+
+  Only includes the fonts needed for that preset.
+  """
+  def generate_font_faces(typography) do
+    %{heading: heading_key, body: body_key} = fonts_for_typography(typography)
+
+    font_keys =
+      if heading_key == body_key do
+        [heading_key]
+      else
+        [heading_key, body_key]
+      end
+
+    font_keys
+    |> Enum.map(&generate_font_face_for_font/1)
+    |> Enum.join("\n")
+  end
+
+  @doc """
+  Generates @font-face CSS for ALL fonts.
+
+  Used in the theme editor where users can switch between typography presets.
+  """
+  def generate_all_font_faces do
+    @fonts
+    |> Map.keys()
+    |> Enum.map(&generate_font_face_for_font/1)
+    |> Enum.join("\n")
+  end
+
+  @doc """
+  Generates preload link tags for a specific typography preset.
+
+  Returns a list of maps with href, as, type, and crossorigin attributes.
+  """
+  def preload_links(typography) do
+    %{heading: heading_key, body: body_key} = fonts_for_typography(typography)
+
+    # Preload the most commonly used weights
+    preload_weights = %{
+      # For headings, preload the typical heading weight (500-600)
+      heading: [500, 600],
+      # For body, preload regular and semibold
+      body: [400, 600]
+    }
+
+    heading_links = generate_preload_links_for_font(heading_key, preload_weights.heading)
+    body_links = generate_preload_links_for_font(body_key, preload_weights.body)
+
+    # Deduplicate in case heading and body use the same font
+    (heading_links ++ body_links) |> Enum.uniq_by(& &1.href)
+  end
+
+  # Private functions
+
+  defp generate_font_face_for_font(key) do
+    case get_font(key) do
+      %{family: family, file_prefix: prefix, weights: weights} ->
+        weights
+        |> Enum.map(fn weight ->
+          weight_suffix = if weight == 400, do: "regular", else: to_string(weight)
+
+          """
+          @font-face {
+            font-family: '#{family}';
+            font-style: normal;
+            font-weight: #{weight};
+            font-display: swap;
+            src: url('/fonts/#{prefix}-#{weight_suffix}.woff2') format('woff2');
+          }
+          """
+        end)
+        |> Enum.join("")
+
+      nil ->
+        ""
+    end
+  end
+
+  defp generate_preload_links_for_font(key, weights) do
+    case get_font(key) do
+      %{file_prefix: prefix, weights: available_weights} ->
+        weights
+        |> Enum.filter(&(&1 in available_weights))
+        |> Enum.map(fn weight ->
+          weight_suffix = if weight == 400, do: "regular", else: to_string(weight)
+
+          %{
+            href: "/fonts/#{prefix}-#{weight_suffix}.woff2",
+            as: "font",
+            type: "font/woff2",
+            crossorigin: true
+          }
+        end)
+
+      nil ->
+        []
+    end
+  end
+end

lib/simpleshop_theme_web/components/layouts/shop_root.html.heex

@@ -6,10 +6,14 @@
     <meta name="csrf-token" content={get_csrf_token()} />
     <meta name="description" content={assigns[:page_description] || @theme_settings.site_description || "Welcome to #{@theme_settings.site_name}"} />
     <.live_title><%= assigns[:page_title] || @theme_settings.site_name %></.live_title>
+    <!-- Preload critical fonts for the current typography preset -->
+    <%= for preload <- SimpleshopTheme.Theme.Fonts.preload_links(@theme_settings.typography) do %>
+      <link rel="preload" href={preload.href} as={preload.as} type={preload.type} crossorigin />
+    <% end %>
     <link phx-track-static rel="stylesheet" href={~p"/assets/css/app.css"} />
-    <script defer phx-track-static type="text/javascript" src={~p"/assets/js/app.js"}>
+    <script defer phx-track-static src={~p"/assets/js/app.js"}>
     </script>
-    <!-- Generated theme CSS (only active values, not all variants) -->
+    <!-- Generated theme CSS with @font-face declarations -->
     <style id="theme-css"><%= Phoenix.HTML.raw(@generated_css) %></style>
   </head>
   <body class="h-full">