feat: add cart page, cart drawer, and shared cart infrastructure

- Cart context with pure functions for add/remove/update/hydrate
- Price formatting via ex_money (replaces all float division)
- CartHook on_mount with attach_hook for shared event handlers
  (open/close drawer, remove item, PubSub sync)
- Accessible cart drawer with focus trap, scroll lock, aria-live
- Cart page with increment/decrement quantity controls
- Preview mode cart drawer support in theme editor
- Cart persistence to session via JS hook + API endpoint
- 19 tests covering all Cart pure functions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PROGRESS.md

@@ -10,15 +10,16 @@
 - Shop pages (home, collections, products, cart, about, contact)
 - Mobile-first design with bottom navigation
 - 100% PageSpeed score
+- Variant selector with color swatches and size buttons
 
 **In Progress:**
-- Products context with provider integration (wired to shop views, variant selector next)
+- Session-based cart
 
 ## Next Up
 
-1. **Variant Selector Component** - Size/colour picker on product pages
-2. **Session-based Cart** - Real cart with actual variants
-3. **Stripe Checkout Integration** - Payment processing
+1. **Session-based Cart** - Real cart with actual variants
+2. **Stripe Checkout Integration** - Payment processing
+3. **Orders & Fulfillment** - Submit orders to Printify
 
 ---
 
@@ -52,9 +53,8 @@
 See: [docs/plans/image-optimization.md](docs/plans/image-optimization.md) for implementation details
 
 ### Products & Provider Integration
-**Status:** In Progress
+**Status:** Complete
 
-#### Completed
 - [x] Products context with schemas (c5c06d9)
 - [x] Provider abstraction layer
 - [x] Printify client integration
@@ -64,21 +64,16 @@ See: [docs/plans/image-optimization.md](docs/plans/image-optimization.md) for im
 - [x] Slug-based fallback matching for changed provider IDs
 - [x] Printify webhook endpoint with HMAC verification (a9c15ea)
   - Note: Printify only supports `product:deleted` and `product:publish:*` events (no `product:updated`)
-
-#### Remaining Tasks
-- [ ] Add variant selector component (~2hr)
-
-#### Recently Completed
-- [x] Product image download pipeline
+- [x] Product image download pipeline (1b49b47)
   - Downloads Printify CDN images via ImageDownloadWorker
   - Processes through Media pipeline (WebP conversion, AVIF/WebP variants)
-  - PreviewData uses local images for responsive `<picture>` elements
-  - sync_product_images preserves image_id when URL unchanged
   - Startup recovery and `mix simpleshop.download_images` backfill
-- [x] Wire shop LiveViews to Products context
-  - PreviewData now uses real products when available
-  - Fixed Printify image sync (position was string, not integer)
-  - Improved category extraction from Printify tags
+- [x] Variant selector component (880e7a2)
+  - Color swatches with hex colors, size buttons
+  - Fixed Printify options parsing (Color/Size swap bug)
+  - Filters to only published variants (not full catalog)
+  - Price updates on variant change
+  - Startup recovery for stale sync status
 
 #### Future Enhancements (post-MVP)
 - [ ] Pre-checkout variant validation (verify availability before order)
@@ -124,9 +119,12 @@ See: [docs/plans/page-builder.md](docs/plans/page-builder.md) for design
 
 | Feature | Commit | Notes |
 |---------|--------|-------|
+| Variant selector | 880e7a2 | Color swatches, size buttons, price updates |
+| Product image download | 1b49b47 | PageSpeed 100% with local images |
+| Wire shop to real data | c818d03 | PreviewData uses Products context |
+| Printify webhooks | a9c15ea | Deletion + publish events |
 | Products context Phase 1 | c5c06d9 | Schemas, provider abstraction |
 | Admin provider setup UI | 5b736b9 | Connect, test, sync with pagination |
-| Printify webhooks | a9c15ea | Deletion + publish events (no update event available) |
 | Oban Lifeline plugin | c1e1988 | Rescue orphaned jobs |
 | Image optimization | Multiple | Full pipeline complete |
 | Self-hosted fonts | - | 10 typefaces, 728KB |

assets/css/theme-semantic.css

@@ -220,10 +220,13 @@
   font-weight: 600;
   text-decoration: none;
   transition: top 0.2s ease;
+  outline: none;
+}
 
-  &:focus {
+.skip-link:focus {
   top: 1rem;
-  }
+  outline: 3px solid var(--t-text-primary);
+  outline-offset: 2px;
 }
 
 /* Nav link styling with active state indicator */

assets/js/app.js

@@ -43,6 +43,154 @@ const ColorSync = {
   }
 }
 
+// Hook to persist cart to session via API
+const CartPersist = {
+  mounted() {
+    this.handleEvent("persist_cart", ({items}) => {
+      const csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
+      fetch("/api/cart", {
+        method: "POST",
+        headers: {
+          "Content-Type": "application/json",
+          "x-csrf-token": csrfToken
+        },
+        body: JSON.stringify({items})
+      })
+    })
+  }
+}
+
+// Hook for accessible cart drawer (WAI-ARIA dialog pattern)
+const CartDrawer = {
+  mounted() {
+    this.triggerElement = null
+    this.boundKeydown = this.handleKeydown.bind(this)
+    this.boundTouchmove = this.handleTouchmove.bind(this)
+    this.scrollY = 0
+    this.isOpen = this.el.classList.contains('open')
+
+    if (this.isOpen) {
+      this.lockScroll()
+      document.addEventListener('keydown', this.boundKeydown)
+    }
+  },
+
+  updated() {
+    const nowOpen = this.el.classList.contains('open')
+    if (nowOpen && !this.isOpen) {
+      this.onOpen()
+    } else if (!nowOpen && this.isOpen) {
+      this.onClose()
+    }
+    this.isOpen = nowOpen
+  },
+
+  lockScroll() {
+    // Store current scroll position
+    this.scrollY = window.scrollY
+
+    // Lock body scroll (works on mobile too)
+    document.body.style.position = 'fixed'
+    document.body.style.top = `-${this.scrollY}px`
+    document.body.style.left = '0'
+    document.body.style.right = '0'
+    document.body.style.overflow = 'hidden'
+
+    // Prevent touchmove on document (extra safety for iOS)
+    document.addEventListener('touchmove', this.boundTouchmove, { passive: false })
+  },
+
+  unlockScroll() {
+    // Restore body scroll
+    document.body.style.position = ''
+    document.body.style.top = ''
+    document.body.style.left = ''
+    document.body.style.right = ''
+    document.body.style.overflow = ''
+
+    // Restore scroll position
+    window.scrollTo(0, this.scrollY)
+
+    // Remove touchmove listener
+    document.removeEventListener('touchmove', this.boundTouchmove)
+  },
+
+  handleTouchmove(e) {
+    // Allow scrolling inside the drawer itself
+    if (this.el.contains(e.target)) {
+      return
+    }
+    e.preventDefault()
+  },
+
+  onOpen() {
+    // Store trigger for focus return
+    this.triggerElement = document.activeElement
+
+    // Lock scroll
+    this.lockScroll()
+
+    // Focus first focusable element (close button)
+    const firstFocusable = this.el.querySelector(
+      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
+    )
+    if (firstFocusable) {
+      setTimeout(() => firstFocusable.focus(), 50)
+    }
+
+    // Enable focus trap and Escape handling
+    document.addEventListener('keydown', this.boundKeydown)
+  },
+
+  onClose() {
+    // Unlock scroll
+    this.unlockScroll()
+
+    // Remove keyboard listener
+    document.removeEventListener('keydown', this.boundKeydown)
+
+    // Return focus to trigger element
+    if (this.triggerElement) {
+      this.triggerElement.focus()
+    }
+  },
+
+  handleKeydown(e) {
+    // Close on Escape - let server handle the state change
+    if (e.key === 'Escape') {
+      this.pushEvent("close_cart_drawer")
+      return
+    }
+
+    // Focus trap on Tab
+    if (e.key === 'Tab') {
+      const focusable = this.el.querySelectorAll(
+        'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
+      )
+      const first = focusable[0]
+      const last = focusable[focusable.length - 1]
+
+      if (e.shiftKey && document.activeElement === first) {
+        e.preventDefault()
+        last.focus()
+      } else if (!e.shiftKey && document.activeElement === last) {
+        e.preventDefault()
+        first.focus()
+      }
+    }
+  },
+
+  destroyed() {
+    document.removeEventListener('keydown', this.boundKeydown)
+    document.removeEventListener('touchmove', this.boundTouchmove)
+    document.body.style.position = ''
+    document.body.style.top = ''
+    document.body.style.left = ''
+    document.body.style.right = ''
+    document.body.style.overflow = ''
+  }
+}
+
 // Hook for PDP image lightbox
 const Lightbox = {
   mounted() {
@@ -140,7 +288,7 @@ const csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute
 const liveSocket = new LiveSocket("/live", Socket, {
   longPollFallbackMs: 2500,
   params: {_csrf_token: csrfToken},
-  hooks: {...colocatedHooks, ColorSync, Lightbox},
+  hooks: {...colocatedHooks, ColorSync, Lightbox, CartPersist, CartDrawer},
 })
 
 // Show progress bar on live navigation and form submits

lib/simpleshop_theme/cart.ex

@@ -0,0 +1,233 @@
+defmodule SimpleshopTheme.Cart do
+  @moduledoc """
+  The Cart context.
+
+  Manages shopping cart operations stored in session. Cart items are stored
+  as a list of {variant_id, quantity} tuples for minimal session storage.
+  Items are hydrated with full product/variant data when needed for display.
+  """
+
+  alias SimpleshopTheme.Products
+
+  @session_key "cart"
+
+  # =============================================================================
+  # Session Operations
+  # =============================================================================
+
+  @doc """
+  Gets cart items from session.
+
+  Returns a list of {variant_id, quantity} tuples.
+  """
+  def get_from_session(session) do
+    case Map.get(session, @session_key) do
+      nil -> []
+      items when is_list(items) -> items
+      _ -> []
+    end
+  end
+
+  @doc """
+  Puts cart items in session via Plug.Conn.
+
+  Used by the CartController to persist cart to session cookie.
+  """
+  def put_in_session(conn, cart_items) do
+    Plug.Conn.put_session(conn, @session_key, cart_items)
+  end
+
+  # =============================================================================
+  # Cart Operations
+  # =============================================================================
+
+  @doc """
+  Adds an item to the cart.
+
+  If the variant is already in the cart, increments the quantity.
+  Returns the updated cart items list.
+  """
+  def add_item(cart_items, variant_id, quantity \\ 1)
+      when is_integer(quantity) and quantity > 0 do
+    case List.keyfind(cart_items, variant_id, 0) do
+      nil ->
+        cart_items ++ [{variant_id, quantity}]
+
+      {^variant_id, existing_qty} ->
+        List.keyreplace(cart_items, variant_id, 0, {variant_id, existing_qty + quantity})
+    end
+  end
+
+  @doc """
+  Updates the quantity of an item in the cart.
+
+  If quantity is 0 or less, removes the item.
+  Returns the updated cart items list.
+  """
+  def update_quantity(cart_items, variant_id, quantity) when is_integer(quantity) do
+    if quantity <= 0 do
+      remove_item(cart_items, variant_id)
+    else
+      case List.keyfind(cart_items, variant_id, 0) do
+        nil ->
+          cart_items
+
+        {^variant_id, _} ->
+          List.keyreplace(cart_items, variant_id, 0, {variant_id, quantity})
+      end
+    end
+  end
+
+  @doc """
+  Removes an item from the cart.
+
+  Returns the updated cart items list.
+  """
+  def remove_item(cart_items, variant_id) do
+    List.keydelete(cart_items, variant_id, 0)
+  end
+
+  @doc """
+  Gets the quantity of a specific variant in the cart.
+
+  Returns 0 if not found.
+  """
+  def get_quantity(cart_items, variant_id) do
+    case List.keyfind(cart_items, variant_id, 0) do
+      nil -> 0
+      {_, qty} -> qty
+    end
+  end
+
+  # =============================================================================
+  # Hydration
+  # =============================================================================
+
+  @doc """
+  Hydrates cart items with full variant and product data.
+
+  Takes a list of {variant_id, quantity} tuples and returns a list of maps
+  with full display data including product name, variant options, price, and image.
+  """
+  def hydrate(cart_items) when is_list(cart_items) do
+    variant_ids = Enum.map(cart_items, fn {id, _qty} -> id end)
+
+    if variant_ids == [] do
+      []
+    else
+      variants_map = Products.get_variants_with_products(variant_ids)
+
+      cart_items
+      |> Enum.map(fn {variant_id, quantity} ->
+        case Map.get(variants_map, variant_id) do
+          nil ->
+            nil
+
+          variant ->
+            %{
+              variant_id: variant.id,
+              name: variant.product.title,
+              variant: format_variant_options(variant.options),
+              price: variant.price,
+              quantity: quantity,
+              image: variant_image_url(variant.product)
+            }
+        end
+      end)
+      |> Enum.reject(&is_nil/1)
+    end
+  end
+
+  defp format_variant_options(options) when is_map(options) and map_size(options) > 0 do
+    options
+    |> Map.values()
+    |> Enum.join(" / ")
+  end
+
+  defp format_variant_options(_), do: nil
+
+  defp variant_image_url(product) do
+    # Get first image from preloaded images
+    case product.images do
+      [first | _] ->
+        if first.image_id do
+          "/images/#{first.image_id}/variant/400.webp"
+        else
+          first.src
+        end
+
+      _ ->
+        nil
+    end
+  end
+
+  # =============================================================================
+  # Helpers
+  # =============================================================================
+
+  @doc """
+  Returns the total item count in the cart.
+  """
+  def item_count(cart_items) do
+    Enum.reduce(cart_items, 0, fn {_, qty}, acc -> acc + qty end)
+  end
+
+  @doc """
+  Calculates the subtotal from hydrated cart items.
+
+  Returns the total in pence.
+  """
+  def calculate_subtotal(hydrated_items) do
+    Enum.reduce(hydrated_items, 0, fn item, acc ->
+      acc + item.price * item.quantity
+    end)
+  end
+
+  @doc """
+  Formats a price in pence as a currency string using ex_money.
+  """
+  def format_price(price_pence) when is_integer(price_pence) do
+    price_pence
+    |> Decimal.new()
+    |> Decimal.div(100)
+    |> then(&Money.new(:GBP, &1))
+    |> Money.to_string!()
+  end
+
+  def format_price(_), do: format_price(0)
+
+  @doc """
+  Formats the subtotal from hydrated items as a GBP string.
+  """
+  def format_subtotal(hydrated_items) do
+    hydrated_items
+    |> calculate_subtotal()
+    |> format_price()
+  end
+
+  @doc """
+  Serializes cart items for JSON transport.
+
+  Converts {variant_id, quantity} tuples to [variant_id, quantity] lists
+  for JSON compatibility.
+  """
+  def serialize(cart_items) do
+    Enum.map(cart_items, fn {id, qty} -> [id, qty] end)
+  end
+
+  @doc """
+  Deserializes cart items from JSON transport.
+
+  Converts [variant_id, quantity] lists back to {variant_id, quantity} tuples.
+  """
+  def deserialize(items) when is_list(items) do
+    items
+    |> Enum.map(fn
+      [id, qty] when is_binary(id) and is_integer(qty) -> {id, qty}
+      _ -> nil
+    end)
+    |> Enum.reject(&is_nil/1)
+  end
+
+  def deserialize(_), do: []
+end

lib/simpleshop_theme/products.ex

@@ -411,6 +411,21 @@ defmodule SimpleshopTheme.Products do
   # Product Variants
   # =============================================================================
 
+  @doc """
+  Gets multiple variants by their IDs with associated products and images.
+
+  Returns a map of variant_id => variant struct for efficient lookup.
+  Used by Cart.hydrate/1 to fetch variant data for display.
+  """
+  def get_variants_with_products(variant_ids) when is_list(variant_ids) do
+    from(v in ProductVariant,
+      where: v.id in ^variant_ids,
+      preload: [product: [images: :image]]
+    )
+    |> Repo.all()
+    |> Map.new(&{&1.id, &1})
+  end
+
   @doc """
   Creates a product variant.
   """

lib/simpleshop_theme/theme/preview_data.ex

@@ -32,19 +32,25 @@ defmodule SimpleshopTheme.Theme.PreviewData do
 
   @doc """
   Returns cart drawer items formatted for the cart drawer component.
+
+  Format matches Cart.hydrate/1 output for consistency between preview and live modes.
   """
   def cart_drawer_items do
     [
       %{
+        variant_id: "preview-1",
         name: "Mountain Sunrise Art Print",
         variant: "12″ x 18″ / Matte",
-        price: "£24.00",
+        price: 2400,
+        quantity: 1,
         image: "/mockups/mountain-sunrise-print-1.jpg"
       },
       %{
+        variant_id: "preview-2",
         name: "Fern Leaf Mug",
         variant: "11oz / White",
-        price: "£14.99",
+        price: 1499,
+        quantity: 2,
         image: "/mockups/fern-leaf-mug-1.jpg"
       }
     ]

lib/simpleshop_theme_web/cart_hook.ex

@@ -0,0 +1,115 @@
+defmodule SimpleshopThemeWeb.CartHook do
+  @moduledoc """
+  LiveView on_mount hook for cart state and shared event handling.
+
+  Mounted in the public_shop live_session to give all shop LiveViews
+  cart state, PubSub sync, and shared event handlers via attach_hook.
+
+  Handles these events so individual LiveViews don't have to:
+  - `open_cart_drawer` / `close_cart_drawer` - toggle drawer visibility
+  - `remove_item` - remove item from cart
+  - `{:cart_updated, cart}` info - cross-tab cart sync via PubSub
+
+  LiveViews with custom cart logic (add_to_cart, increment, decrement)
+  can call `update_cart_assigns/2` and `broadcast_and_update/2` directly.
+  """
+
+  import Phoenix.Component, only: [assign: 3]
+  import Phoenix.LiveView, only: [attach_hook: 4, connected?: 1, push_event: 3]
+
+  alias SimpleshopTheme.Cart
+
+  def on_mount(:mount_cart, _params, session, socket) do
+    cart_items = Cart.get_from_session(session)
+    hydrated = Cart.hydrate(cart_items)
+
+    socket =
+      socket
+      |> assign(:raw_cart, cart_items)
+      |> assign(:cart_items, hydrated)
+      |> assign(:cart_count, Cart.item_count(cart_items))
+      |> assign(:cart_subtotal, Cart.format_subtotal(hydrated))
+      |> assign(:cart_drawer_open, false)
+      |> assign(:cart_status, nil)
+      |> attach_hook(:cart_events, :handle_event, &handle_cart_event/3)
+      |> attach_hook(:cart_info, :handle_info, &handle_cart_info/2)
+
+    socket =
+      if connected?(socket) do
+        csrf_token = Map.get(session, "_csrf_token", "default")
+        topic = "cart:#{csrf_token}"
+        Phoenix.PubSub.subscribe(SimpleshopTheme.PubSub, topic)
+        assign(socket, :cart_topic, topic)
+      else
+        assign(socket, :cart_topic, nil)
+      end
+
+    {:cont, socket}
+  end
+
+  # Shared event handlers
+
+  defp handle_cart_event("open_cart_drawer", _params, socket) do
+    {:halt, assign(socket, :cart_drawer_open, true)}
+  end
+
+  defp handle_cart_event("close_cart_drawer", _params, socket) do
+    {:halt, assign(socket, :cart_drawer_open, false)}
+  end
+
+  defp handle_cart_event("remove_item", %{"id" => variant_id}, socket) do
+    cart = Cart.remove_item(socket.assigns.raw_cart, variant_id)
+
+    socket =
+      socket
+      |> broadcast_and_update(cart)
+      |> assign(:cart_status, "Item removed from cart")
+
+    {:halt, socket}
+  end
+
+  defp handle_cart_event(_event, _params, socket), do: {:cont, socket}
+
+  # Shared info handlers
+
+  defp handle_cart_info({:cart_updated, cart}, socket) do
+    {:halt, update_cart_assigns(socket, cart)}
+  end
+
+  defp handle_cart_info(_msg, socket), do: {:cont, socket}
+
+  # Public helpers for LiveViews with custom cart logic
+
+  @doc """
+  Updates all cart-related assigns from raw cart data.
+  """
+  def update_cart_assigns(socket, cart) do
+    hydrated = Cart.hydrate(cart)
+
+    socket
+    |> assign(:raw_cart, cart)
+    |> assign(:cart_items, hydrated)
+    |> assign(:cart_count, Cart.item_count(cart))
+    |> assign(:cart_subtotal, Cart.format_subtotal(hydrated))
+  end
+
+  @doc """
+  Broadcasts cart update to other tabs and updates local assigns.
+
+  Uses broadcast_from to avoid notifying self (prevents double-update).
+  """
+  def broadcast_and_update(socket, cart) do
+    if socket.assigns.cart_topic do
+      Phoenix.PubSub.broadcast_from(
+        SimpleshopTheme.PubSub,
+        self(),
+        socket.assigns.cart_topic,
+        {:cart_updated, cart}
+      )
+    end
+
+    socket
+    |> update_cart_assigns(cart)
+    |> push_event("persist_cart", %{items: Cart.serialize(cart)})
+  end
+end

lib/simpleshop_theme_web/components/page_templates/about.html.heex

@@ -1,4 +1,6 @@
 <div
+  id="shop-container"
+  phx-hook="CartPersist"
   class="shop-container min-h-screen pb-20 md:pb-0"
   style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
 >
@@ -31,7 +33,14 @@
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+    cart_status={assigns[:cart_status]}
+  />
 
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 

lib/simpleshop_theme_web/components/page_templates/cart.html.heex

@@ -1,4 +1,6 @@
 <div
+  id="shop-container"
+  phx-hook="CartPersist"
   class="shop-container min-h-screen pb-20 md:pb-0"
   style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
 >
@@ -19,12 +21,45 @@
 
   <main id="main-content" class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
     <.page_title text="Your basket" />
-    <.cart_layout items={@cart_page_items} subtotal={@cart_page_subtotal} mode={@mode} />
+
+    <%= if @cart_items == [] do %>
+      <.cart_empty_state mode={@mode} />
+    <% else %>
+      <div class="grid grid-cols-1 lg:grid-cols-3 gap-8">
+        <div class="lg:col-span-2">
+          <ul
+            role="list"
+            aria-label="Cart items"
+            class="flex flex-col gap-4"
+            style="list-style: none; margin: 0; padding: 0;"
+          >
+            <%= for item <- @cart_items do %>
+              <li>
+                <.shop_card class="p-4">
+                  <.cart_item_row item={item} size={:default} show_quantity_controls mode={@mode} />
+                </.shop_card>
+              </li>
+            <% end %>
+          </ul>
+        </div>
+
+        <div>
+          <.order_summary subtotal={@cart_page_subtotal} mode={@mode} />
+        </div>
+      </div>
+    <% end %>
   </main>
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+    cart_status={assigns[:cart_status]}
+  />
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 
   <.mobile_bottom_nav active_page="cart" mode={@mode} />

lib/simpleshop_theme_web/components/page_templates/collection.html.heex

@@ -1,4 +1,6 @@
 <div
+  id="shop-container"
+  phx-hook="CartPersist"
   class="shop-container min-h-screen pb-20 md:pb-0"
   style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
 >
@@ -39,7 +41,13 @@
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+  />
 
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 

lib/simpleshop_theme_web/components/page_templates/contact.html.heex

@@ -1,4 +1,6 @@
 <div
+  id="shop-container"
+  phx-hook="CartPersist"
   class="shop-container min-h-screen pb-20 md:pb-0"
   style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
 >
@@ -54,7 +56,14 @@
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+    cart_status={assigns[:cart_status]}
+  />
 
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 

lib/simpleshop_theme_web/components/page_templates/error.html.heex

@@ -50,7 +50,14 @@
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+    cart_status={assigns[:cart_status]}
+  />
 
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 </div>

lib/simpleshop_theme_web/components/page_templates/home.html.heex

@@ -1,4 +1,6 @@
 <div
+  id="shop-container"
+  phx-hook="CartPersist"
   class="shop-container min-h-screen pb-20 md:pb-0"
   style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
 >
@@ -47,7 +49,14 @@
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+    cart_status={assigns[:cart_status]}
+  />
 
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 

lib/simpleshop_theme_web/components/page_templates/pdp.html.heex

@@ -1,4 +1,6 @@
 <div
+  id="shop-container"
+  phx-hook="CartPersist"
   class="shop-container min-h-screen pb-20 md:pb-0"
   style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
 >
@@ -66,7 +68,7 @@
         </div>
 
         <.quantity_selector quantity={@quantity} in_stock={@product.in_stock} />
-        <.add_to_cart_button />
+        <.add_to_cart_button mode={@mode} />
         <.trust_badges :if={@theme_settings.pdp_trust_badges} />
         <.product_details product={@product} />
       </div>
@@ -89,7 +91,14 @@
 
   <.shop_footer theme_settings={@theme_settings} mode={@mode} />
 
-  <.cart_drawer cart_items={@cart_items} subtotal={@cart_subtotal} mode={@mode} />
+  <.cart_drawer
+    cart_items={@cart_items}
+    subtotal={@cart_subtotal}
+    cart_count={@cart_count}
+    mode={@mode}
+    open={assigns[:cart_drawer_open] || false}
+    cart_status={assigns[:cart_status]}
+  />
   <.search_modal hint_text={~s(Try searching for "mountain", "forest", or "ocean")} />
 
   <.mobile_bottom_nav active_page="pdp" mode={@mode} />

lib/simpleshop_theme_web/components/shop_components.ex

@@ -898,10 +898,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
           type="button"
           class="header-icon-btn w-9 h-9 flex items-center justify-center transition-all relative"
           style="color: var(--t-text-secondary); background: none; border: none; cursor: pointer; border-radius: var(--t-radius-button);"
-          phx-click={
-            Phoenix.LiveView.JS.add_class("open", to: "#cart-drawer")
-            |> Phoenix.LiveView.JS.add_class("open", to: "#cart-drawer-overlay")
-          }
+          phx-click={open_cart_drawer_js()}
           aria-label="Cart"
         >
           <svg class="w-5 h-5" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
@@ -1064,17 +1061,26 @@ defmodule SimpleshopThemeWeb.ShopComponents do
     """
   end
 
+  defp open_cart_drawer_js do
+    Phoenix.LiveView.JS.push("open_cart_drawer")
+  end
+
+  defp close_cart_drawer_js do
+    Phoenix.LiveView.JS.push("close_cart_drawer")
+  end
+
   @doc """
   Renders the cart drawer (floating sidebar).
 
   The drawer slides in from the right when opened. It displays cart items
-  and checkout options.
+  and checkout options. Follows WAI-ARIA dialog pattern for accessibility.
 
   ## Attributes
 
   * `cart_items` - List of cart items to display. Each item should have
-    `image`, `name`, `variant`, and `price` keys. Default: []
+    `image`, `name`, `variant`, `price`, and `variant_id` keys. Default: []
   * `subtotal` - The subtotal to display. Default: nil (shows "£0.00")
+  * `cart_count` - Number of items for screen reader description. Default: 0
   * `mode` - Either `:live` (default) for real stores or `:preview` for theme editor.
     In preview mode, "View basket" navigates via LiveView JS commands.
 
@@ -1083,9 +1089,13 @@ defmodule SimpleshopThemeWeb.ShopComponents do
       <.cart_drawer cart_items={@cart.items} subtotal={@cart.subtotal} />
       <.cart_drawer cart_items={demo_items} subtotal="£72.00" mode={:preview} />
   """
+
   attr :cart_items, :list, default: []
   attr :subtotal, :string, default: nil
+  attr :cart_count, :integer, default: 0
+  attr :cart_status, :string, default: nil
   attr :mode, :atom, default: :live
+  attr :open, :boolean, default: false
 
   def cart_drawer(assigns) do
     assigns =
@@ -1094,27 +1104,51 @@ defmodule SimpleshopThemeWeb.ShopComponents do
       end)
 
     ~H"""
+    <%!-- Screen reader announcements for cart changes --%>
+    <div aria-live="polite" aria-atomic="true" class="sr-only">
+      {@cart_status}
+    </div>
+
+    <!-- Cart Drawer Overlay -->
+    <div
+      id="cart-drawer-overlay"
+      class={["cart-drawer-overlay", @open && "open"]}
+      aria-hidden={to_string(!@open)}
+      style="position: fixed; inset: 0; background: rgba(0,0,0,0.4); z-index: 999; opacity: 0; visibility: hidden; transition: opacity 0.3s ease, visibility 0.3s ease;"
+      phx-click={close_cart_drawer_js()}
+    >
+    </div>
+
     <!-- Cart Drawer -->
     <div
       id="cart-drawer"
-      class="cart-drawer"
+      role="dialog"
+      aria-modal="true"
+      aria-labelledby="cart-drawer-title"
+      aria-describedby="cart-drawer-description"
+      aria-hidden={to_string(!@open)}
+      phx-hook="CartDrawer"
+      class={["cart-drawer", @open && "open"]}
       style="position: fixed; top: 0; right: -400px; width: 400px; max-width: 90vw; height: 100vh; background: var(--t-surface-raised); z-index: 1001; display: flex; flex-direction: column; transition: right 0.3s ease; box-shadow: -4px 0 20px rgba(0,0,0,0.15);"
     >
+      <p id="cart-drawer-description" class="sr-only">
+        Shopping basket with {@cart_count} {if @cart_count == 1, do: "item", else: "items"}. Press Escape to close.
+      </p>
       <div
         class="cart-drawer-header"
         style="display: flex; justify-content: space-between; align-items: center; padding: 1rem 1.5rem; border-bottom: 1px solid var(--t-border-default);"
       >
-        <h2 style="font-family: var(--t-font-heading); font-weight: var(--t-heading-weight); font-size: var(--t-text-large); color: var(--t-text-primary); margin: 0;">
+        <h2
+          id="cart-drawer-title"
+          style="font-family: var(--t-font-heading); font-weight: var(--t-heading-weight); font-size: var(--t-text-large); color: var(--t-text-primary); margin: 0;"
+        >
           Your basket
         </h2>
         <button
           type="button"
           class="cart-drawer-close"
           style="background: none; border: none; padding: 0.5rem; cursor: pointer; color: var(--t-text-secondary);"
-          phx-click={
-            Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer")
-            |> Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer-overlay")
-          }
+          phx-click={close_cart_drawer_js()}
           aria-label="Close cart"
         >
           <svg class="w-5 h-5" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
@@ -1125,39 +1159,16 @@ defmodule SimpleshopThemeWeb.ShopComponents do
       </div>
 
       <div class="cart-drawer-items" style="flex: 1; overflow-y: auto; padding: 1rem;">
+        <%= if @cart_items == [] do %>
+          <.cart_empty_state mode={@mode} />
+        <% else %>
+          <ul role="list" aria-label="Cart items" style="list-style: none; margin: 0; padding: 0;">
             <%= for item <- @cart_items do %>
-          <div
-            class="cart-drawer-item"
-            style="display: flex; gap: 0.75rem; padding: 0.75rem 0; border-bottom: 1px solid var(--t-border-default);"
-          >
-            <div
-              class="cart-drawer-item-image"
-              style={"width: 60px; height: 60px; border-radius: var(--t-radius-card); background-size: cover; background-position: center; background-image: url('#{item.image}'); flex-shrink: 0;"}
-            >
-            </div>
-            <div class="cart-drawer-item-details" style="flex: 1;">
-              <h3 style="font-family: var(--t-font-body); font-size: var(--t-text-small); font-weight: 500; color: var(--t-text-primary); margin: 0 0 2px;">
-                {item.name}
-              </h3>
-              <p style="font-family: var(--t-font-body); font-size: var(--t-text-caption); color: var(--t-text-tertiary); margin: 0;">
-                {item.variant}
-              </p>
-              <div style="display: flex; justify-content: space-between; align-items: center; margin-top: 4px;">
-                <p
-                  class="cart-drawer-item-price"
-                  style="color: var(--t-text-primary); font-weight: 500; font-size: var(--t-text-small); margin: 0;"
-                >
-                  {item.price}
-                </p>
-                <button
-                  type="button"
-                  style="background: none; border: none; padding: 0; cursor: pointer; font-family: var(--t-font-body); font-size: var(--t-text-caption); color: var(--t-text-tertiary); text-decoration: underline;"
-                >
-                  Remove
-                </button>
-              </div>
-            </div>
-          </div>
+              <li style="border-bottom: 1px solid var(--t-border-default);">
+                <.cart_item_row item={item} size={:compact} mode={@mode} />
+              </li>
+            <% end %>
+          </ul>
         <% end %>
       </div>
 
@@ -1187,8 +1198,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
           <a
             href="#"
             phx-click={
-              Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer")
-              |> Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer-overlay")
+              close_cart_drawer_js()
               |> Phoenix.LiveView.JS.push("change_preview_page", value: %{page: "cart"})
             }
             class="cart-drawer-link"
@@ -1199,10 +1209,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
         <% else %>
           <a
             href="/cart"
-            phx-click={
-              Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer")
-              |> Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer-overlay")
-            }
+            phx-click={close_cart_drawer_js()}
             class="cart-drawer-link"
             style="display: block; text-align: center; font-family: var(--t-font-body); font-size: var(--t-text-small); color: var(--t-text-secondary); text-decoration: underline; cursor: pointer;"
           >
@@ -1211,18 +1218,153 @@ defmodule SimpleshopThemeWeb.ShopComponents do
         <% end %>
       </div>
     </div>
+    """
+  end
 
-    <!-- Cart Drawer Overlay -->
+  @doc """
+  Shared cart item row component used by both drawer and cart page.
+
+  ## Attributes
+
+  * `item` - Required. Cart item with `name`, `variant`, `price`, `quantity`, `image`, `variant_id`.
+  * `size` - Either `:compact` (drawer) or `:default` (cart page). Default: :default
+  * `show_quantity_controls` - Show +/- buttons. Default: false
+  * `mode` - Either `:live` or `:preview`. Default: :live
+  """
+  attr :item, :map, required: true
+  attr :size, :atom, default: :default
+  attr :show_quantity_controls, :boolean, default: false
+  attr :mode, :atom, default: :live
+
+  def cart_item_row(assigns) do
+    ~H"""
     <div
-      id="cart-drawer-overlay"
-      class="cart-drawer-overlay"
-      style="position: fixed; inset: 0; background: rgba(0,0,0,0.4); z-index: 999; opacity: 0; visibility: hidden; transition: opacity 0.3s ease, visibility 0.3s ease;"
-      phx-click={
-        Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer")
-        |> Phoenix.LiveView.JS.remove_class("open", to: "#cart-drawer-overlay")
-      }
+      class="cart-item-row"
+      style={"display: flex; gap: #{if @size == :compact, do: "0.75rem", else: "1rem"}; padding: 0.75rem 0;"}
+    >
+      <div
+        class="cart-item-image"
+        style={"width: #{if @size == :compact, do: "60px", else: "80px"}; height: #{if @size == :compact, do: "60px", else: "80px"}; border-radius: var(--t-radius-card); background-size: cover; background-position: center; flex-shrink: 0; #{if @item.image, do: "background-image: url('#{@item.image}');", else: "background-color: var(--t-surface-sunken);"}"}
       >
       </div>
+      <div class="cart-item-details" style="flex: 1; min-width: 0;">
+        <h3 style={"font-family: var(--t-font-body); font-size: #{if @size == :compact, do: "var(--t-text-small)", else: "var(--t-text-base)"}; font-weight: 500; color: var(--t-text-primary); margin: 0 0 2px;"}>
+          {@item.name}
+        </h3>
+        <%= if @item.variant do %>
+          <p style="font-family: var(--t-font-body); font-size: var(--t-text-caption); color: var(--t-text-tertiary); margin: 0;">
+            {@item.variant}
+          </p>
+        <% end %>
+
+        <div style="display: flex; justify-content: space-between; align-items: center; margin-top: 4px; flex-wrap: wrap; gap: 0.5rem;">
+          <%= if @show_quantity_controls do %>
+            <div
+              class="flex items-center"
+              style="border: 1px solid var(--t-border-default); border-radius: var(--t-radius-input);"
+            >
+              <button
+                type="button"
+                phx-click="decrement"
+                phx-value-id={@item.variant_id}
+                class="px-3 py-1"
+                style="background: none; border: none; cursor: pointer; color: var(--t-text-primary);"
+                aria-label={"Decrease quantity of #{@item.name}"}
+              >
+                −
+              </button>
+              <span
+                class="px-3 py-1 border-x"
+                style="border-color: var(--t-border-default); color: var(--t-text-primary); min-width: 2rem; text-align: center;"
+              >
+                {@item.quantity}
+              </span>
+              <button
+                type="button"
+                phx-click="increment"
+                phx-value-id={@item.variant_id}
+                class="px-3 py-1"
+                style="background: none; border: none; cursor: pointer; color: var(--t-text-primary);"
+                aria-label={"Increase quantity of #{@item.name}"}
+              >
+                +
+              </button>
+            </div>
+          <% else %>
+            <span style="font-size: var(--t-text-caption); color: var(--t-text-tertiary);">
+              Qty: {@item.quantity}
+            </span>
+          <% end %>
+
+          <.cart_remove_button variant_id={@item.variant_id} item_name={@item.name} />
+        </div>
+      </div>
+
+      <div class="text-right" style="flex-shrink: 0;">
+        <p style={"font-weight: 500; font-size: #{if @size == :compact, do: "var(--t-text-small)", else: "var(--t-text-base)"}; color: var(--t-text-primary); margin: 0;"}>
+          {SimpleshopTheme.Cart.format_price(@item.price * @item.quantity)}
+        </p>
+      </div>
+    </div>
+    """
+  end
+
+  @doc """
+  Cart empty state component.
+  """
+  attr :mode, :atom, default: :live
+
+  def cart_empty_state(assigns) do
+    ~H"""
+    <div class="text-center py-8" style="color: var(--t-text-secondary);">
+      <svg
+        class="w-16 h-16 mx-auto mb-4"
+        style="color: var(--t-text-tertiary);"
+        viewBox="0 0 24 24"
+        fill="none"
+        stroke="currentColor"
+        stroke-width="1.5"
+      >
+        <path d="M6 2L3 6v14a2 2 0 002 2h14a2 2 0 002-2V6l-3-4z"></path>
+        <line x1="3" y1="6" x2="21" y2="6"></line>
+        <path d="M16 10a4 4 0 01-8 0"></path>
+      </svg>
+      <p class="mb-4">Your basket is empty</p>
+      <%= if @mode == :preview do %>
+        <button
+          type="button"
+          phx-click="change_preview_page"
+          phx-value-page="collection"
+          style="color: var(--t-text-accent); text-decoration: underline; background: none; border: none; cursor: pointer;"
+        >
+          Continue shopping
+        </button>
+      <% else %>
+        <a href="/collections/all" style="color: var(--t-text-accent); text-decoration: underline;">
+          Continue shopping
+        </a>
+      <% end %>
+    </div>
+    """
+  end
+
+  @doc """
+  Remove button for cart items.
+  """
+  attr :variant_id, :string, required: true
+  attr :item_name, :string, default: "item"
+
+  def cart_remove_button(assigns) do
+    ~H"""
+    <button
+      type="button"
+      phx-click="remove_item"
+      phx-value-id={@variant_id}
+      style="background: none; border: none; padding: 0; cursor: pointer; font-family: var(--t-font-body); font-size: var(--t-text-caption); color: var(--t-text-tertiary); text-decoration: underline;"
+      aria-label={"Remove #{@item_name} from cart"}
+    >
+      Remove
+    </button>
     """
   end
 
@@ -1470,14 +1612,14 @@ defmodule SimpleshopThemeWeb.ShopComponents do
               class="text-lg font-bold"
               style="color: hsl(var(--t-accent-h) var(--t-accent-s) var(--t-accent-l));"
             >
-              £{@product.price / 100}
+              {SimpleshopTheme.Cart.format_price(@product.price)}
             </span>
             <span class="text-sm line-through ml-2" style="color: var(--t-text-tertiary);">
-              £{@product.compare_at_price / 100}
+              {SimpleshopTheme.Cart.format_price(@product.compare_at_price)}
             </span>
           <% else %>
             <span class="text-lg font-bold" style="color: var(--t-text-primary);">
-              £{@product.price / 100}
+              {SimpleshopTheme.Cart.format_price(@product.price)}
             </span>
           <% end %>
         </div>
@@ -1485,18 +1627,18 @@ defmodule SimpleshopThemeWeb.ShopComponents do
         <p class="text-sm" style="color: var(--t-text-secondary);">
           <%= if @product.on_sale do %>
             <span class="line-through mr-1" style="color: var(--t-text-tertiary);">
-              £{@product.compare_at_price / 100}
+              {SimpleshopTheme.Cart.format_price(@product.compare_at_price)}
             </span>
           <% end %>
-          £{@product.price / 100}
+          {SimpleshopTheme.Cart.format_price(@product.price)}
         </p>
       <% :compact -> %>
         <p class="font-bold" style="color: var(--t-text-primary);">
-          £{@product.price / 100}
+          {SimpleshopTheme.Cart.format_price(@product.price)}
         </p>
       <% :minimal -> %>
         <p class="text-xs" style="color: var(--t-text-secondary);">
-          £{@product.price / 100}
+          {SimpleshopTheme.Cart.format_price(@product.price)}
         </p>
     <% end %>
     """
@@ -2834,7 +2976,6 @@ defmodule SimpleshopThemeWeb.ShopComponents do
       <.cart_item item={item} />
   """
   attr :item, :map, required: true
-  attr :currency, :string, default: "£"
 
   def cart_item(assigns) do
     ~H"""
@@ -2887,7 +3028,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
 
       <div class="text-right">
         <p class="font-bold text-lg" style="color: var(--t-text-primary);">
-          {@currency}{@item.product.price / 100 * @item.quantity}
+          {SimpleshopTheme.Cart.format_price(@item.product.price * @item.quantity)}
         </p>
       </div>
     </.shop_card>
@@ -2912,7 +3053,6 @@ defmodule SimpleshopThemeWeb.ShopComponents do
   attr :subtotal, :integer, required: true
   attr :delivery, :integer, default: 800
   attr :vat, :integer, default: 720
-  attr :currency, :string, default: "£"
   attr :mode, :atom, default: :live
 
   def order_summary(assigns) do
@@ -2933,24 +3073,24 @@ defmodule SimpleshopThemeWeb.ShopComponents do
         <div class="flex justify-between">
           <span style="color: var(--t-text-secondary);">Subtotal</span>
           <span style="color: var(--t-text-primary);">
-            {@currency}{Float.round(@subtotal / 100, 2)}
+            {SimpleshopTheme.Cart.format_price(@subtotal)}
           </span>
         </div>
         <div class="flex justify-between">
           <span style="color: var(--t-text-secondary);">Delivery</span>
           <span style="color: var(--t-text-primary);">
-            {@currency}{Float.round(@delivery / 100, 2)}
+            {SimpleshopTheme.Cart.format_price(@delivery)}
           </span>
         </div>
         <div class="flex justify-between">
           <span style="color: var(--t-text-secondary);">VAT (20%)</span>
-          <span style="color: var(--t-text-primary);">{@currency}{Float.round(@vat / 100, 2)}</span>
+          <span style="color: var(--t-text-primary);">{SimpleshopTheme.Cart.format_price(@vat)}</span>
         </div>
         <div class="border-t pt-3" style="border-color: var(--t-border-default);">
           <div class="flex justify-between text-lg">
             <span class="font-semibold" style="color: var(--t-text-primary);">Total</span>
             <span class="font-bold" style="color: var(--t-text-primary);">
-              {@currency}{Float.round(@total / 100, 2)}
+              {SimpleshopTheme.Cart.format_price(@total)}
             </span>
           </div>
         </div>
@@ -3495,7 +3635,6 @@ defmodule SimpleshopThemeWeb.ShopComponents do
       <.product_info product={@product} />
   """
   attr :product, :map, required: true
-  attr :currency, :string, default: "£"
 
   def product_info(assigns) do
     ~H"""
@@ -3513,10 +3652,10 @@ defmodule SimpleshopThemeWeb.ShopComponents do
             class="text-3xl font-bold"
             style="color: hsl(var(--t-accent-h) var(--t-accent-s) var(--t-accent-l));"
           >
-            {@currency}{@product.price / 100}
+            {SimpleshopTheme.Cart.format_price(@product.price)}
           </span>
           <span class="text-xl line-through" style="color: var(--t-text-tertiary);">
-            {@currency}{@product.compare_at_price / 100}
+            {SimpleshopTheme.Cart.format_price(@product.compare_at_price)}
           </span>
           <span
             class="px-2 py-1 text-sm font-bold text-white rounded"
@@ -3528,7 +3667,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
           </span>
         <% else %>
           <span class="text-3xl font-bold" style="color: var(--t-text-primary);">
-            {@currency}{@product.price / 100}
+            {SimpleshopTheme.Cart.format_price(@product.price)}
           </span>
         <% end %>
       </div>
@@ -3710,6 +3849,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
   * `text` - Optional. Button text. Defaults to "Add to basket".
   * `disabled` - Optional. Whether button is disabled. Defaults to false.
   * `sticky` - Optional. Whether to use sticky positioning on mobile. Defaults to true.
+  * `mode` - Either `:live` (sends add_to_cart event) or `:preview` (opens drawer only).
 
   ## Examples
 
@@ -3719,6 +3859,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
   attr :text, :string, default: "Add to basket"
   attr :disabled, :boolean, default: false
   attr :sticky, :boolean, default: true
+  attr :mode, :atom, default: :live
 
   def add_to_cart_button(assigns) do
     ~H"""
@@ -3732,10 +3873,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
     >
       <button
         type="button"
-        phx-click={
-          Phoenix.LiveView.JS.add_class("open", to: "#cart-drawer")
-          |> Phoenix.LiveView.JS.add_class("open", to: "#cart-drawer-overlay")
-        }
+        phx-click={if @mode == :preview, do: open_cart_drawer_js(), else: "add_to_cart"}
         disabled={@disabled}
         class="w-full px-6 py-4 text-lg font-semibold transition-all"
         style={"background-color: #{if @disabled, do: "var(--t-border-default)", else: "hsl(var(--t-accent-h) var(--t-accent-s) var(--t-accent-l))"}; color: var(--t-text-inverse); border-radius: var(--t-radius-button); cursor: #{if @disabled, do: "not-allowed", else: "pointer"}; border: none;"}
@@ -3930,7 +4068,6 @@ defmodule SimpleshopThemeWeb.ShopComponents do
   """
   attr :items, :list, required: true
   attr :subtotal, :integer, required: true
-  attr :currency, :string, default: "£"
   attr :mode, :atom, default: :live
 
   def cart_layout(assigns) do
@@ -3939,7 +4076,7 @@ defmodule SimpleshopThemeWeb.ShopComponents do
       <div class="lg:col-span-2">
         <div class="flex flex-col gap-4">
           <%= for item <- @items do %>
-            <.cart_item item={item} currency={@currency} />
+            <.cart_item item={item} />
           <% end %>
         </div>
       </div>

lib/simpleshop_theme_web/controllers/cart_controller.ex

@@ -0,0 +1,31 @@
+defmodule SimpleshopThemeWeb.CartController do
+  @moduledoc """
+  API controller for cart session persistence.
+
+  LiveView cannot write to session directly, so cart updates are persisted
+  via this API endpoint called from a JS hook after each cart modification.
+  """
+
+  use SimpleshopThemeWeb, :controller
+
+  alias SimpleshopTheme.Cart
+
+  @doc """
+  Updates the cart in session.
+
+  Expects JSON body with `items` as a list of [variant_id, quantity] arrays.
+  """
+  def update(conn, %{"items" => items}) when is_list(items) do
+    cart_items = Cart.deserialize(items)
+
+    conn
+    |> Cart.put_in_session(cart_items)
+    |> json(%{ok: true})
+  end
+
+  def update(conn, _params) do
+    conn
+    |> put_status(:bad_request)
+    |> json(%{error: "Invalid cart data"})
+  end
+end

lib/simpleshop_theme_web/live/shop_live/about.ex

@@ -31,9 +31,6 @@ defmodule SimpleshopThemeWeb.ShopLive.About do
       |> assign(:logo_image, logo_image)
       |> assign(:header_image, header_image)
       |> assign(:mode, :shop)
-      |> assign(:cart_items, [])
-      |> assign(:cart_count, 0)
-      |> assign(:cart_subtotal, "£0.00")
 
     {:ok, socket}
   end
@@ -49,6 +46,8 @@ defmodule SimpleshopThemeWeb.ShopLive.About do
       cart_items={@cart_items}
       cart_count={@cart_count}
       cart_subtotal={@cart_subtotal}
+      cart_drawer_open={@cart_drawer_open}
+      cart_status={@cart_status}
     />
     """
   end

lib/simpleshop_theme_web/live/shop_live/cart.ex

@@ -1,9 +1,10 @@
 defmodule SimpleshopThemeWeb.ShopLive.Cart do
   use SimpleshopThemeWeb, :live_view
 
+  alias SimpleshopTheme.Cart
   alias SimpleshopTheme.Settings
   alias SimpleshopTheme.Media
-  alias SimpleshopTheme.Theme.{CSSCache, CSSGenerator, PreviewData}
+  alias SimpleshopTheme.Theme.{CSSCache, CSSGenerator}
 
   @impl true
   def mount(_params, _session, socket) do
@@ -23,15 +24,6 @@ defmodule SimpleshopThemeWeb.ShopLive.Cart do
     logo_image = Media.get_logo()
     header_image = Media.get_header()
 
-    # For now, use preview data for cart items
-    # In a real implementation, this would come from session/database
-    cart_page_items = PreviewData.cart_items()
-
-    cart_page_subtotal =
-      Enum.reduce(cart_page_items, 0, fn item, acc ->
-        acc + item.product.price * item.quantity
-      end)
-
     socket =
       socket
       |> assign(:page_title, "Cart")
@@ -39,34 +31,56 @@ defmodule SimpleshopThemeWeb.ShopLive.Cart do
       |> assign(:generated_css, generated_css)
       |> assign(:logo_image, logo_image)
       |> assign(:header_image, header_image)
-      |> assign(:cart_page_items, cart_page_items)
-      |> assign(:cart_page_subtotal, cart_page_subtotal)
       |> assign(:mode, :shop)
-      |> assign(:cart_items, PreviewData.cart_drawer_items())
-      |> assign(:cart_count, length(cart_page_items))
-      |> assign(:cart_subtotal, format_subtotal(cart_page_subtotal))
 
     {:ok, socket}
   end
 
+  @impl true
+  def handle_event("increment", %{"id" => variant_id}, socket) do
+    cart = Cart.add_item(socket.assigns.raw_cart, variant_id, 1)
+    new_qty = Cart.get_quantity(cart, variant_id)
+
+    socket =
+      socket
+      |> SimpleshopThemeWeb.CartHook.broadcast_and_update(cart)
+      |> assign(:cart_status, "Quantity updated to #{new_qty}")
+
+    {:noreply, socket}
+  end
+
+  @impl true
+  def handle_event("decrement", %{"id" => variant_id}, socket) do
+    current = Cart.get_quantity(socket.assigns.raw_cart, variant_id)
+    cart = Cart.update_quantity(socket.assigns.raw_cart, variant_id, current - 1)
+    new_qty = Cart.get_quantity(cart, variant_id)
+
+    socket =
+      socket
+      |> SimpleshopThemeWeb.CartHook.broadcast_and_update(cart)
+      |> assign(:cart_status, "Quantity updated to #{new_qty}")
+
+    {:noreply, socket}
+  end
+
   @impl true
   def render(assigns) do
+    cart_page_subtotal = Cart.calculate_subtotal(assigns.cart_items)
+    assigns = assign(assigns, :cart_page_subtotal, cart_page_subtotal)
+
     ~H"""
     <SimpleshopThemeWeb.PageTemplates.cart
       theme_settings={@theme_settings}
       logo_image={@logo_image}
       header_image={@header_image}
-      cart_page_items={@cart_page_items}
+      cart_items={@cart_items}
       cart_page_subtotal={@cart_page_subtotal}
       mode={@mode}
-      cart_items={@cart_items}
       cart_count={@cart_count}
       cart_subtotal={@cart_subtotal}
+      cart_drawer_open={@cart_drawer_open}
+      cart_status={@cart_status}
     />
     """
   end
-
-  defp format_subtotal(subtotal_pence) do
-    "£#{Float.round(subtotal_pence / 100, 2)}"
-  end
 end

lib/simpleshop_theme_web/live/shop_live/collection.ex

@@ -39,9 +39,6 @@ defmodule SimpleshopThemeWeb.ShopLive.Collection do
       |> assign(:logo_image, logo_image)
       |> assign(:header_image, header_image)
       |> assign(:mode, :shop)
-      |> assign(:cart_items, [])
-      |> assign(:cart_count, 0)
-      |> assign(:cart_subtotal, "£0.00")
       |> assign(:categories, PreviewData.categories())
       |> assign(:sort_options, @sort_options)
       |> assign(:current_sort, "featured")
@@ -105,6 +102,8 @@ defmodule SimpleshopThemeWeb.ShopLive.Collection do
   def render(assigns) do
     ~H"""
     <div
+      id="shop-container"
+      phx-hook="CartPersist"
       class="shop-container min-h-screen pb-20 md:pb-0"
       style="background-color: var(--t-surface-base); font-family: var(--t-font-body); color: var(--t-text-primary);"
     >
@@ -169,7 +168,10 @@ defmodule SimpleshopThemeWeb.ShopLive.Collection do
       <SimpleshopThemeWeb.ShopComponents.cart_drawer
         cart_items={@cart_items}
         subtotal={@cart_subtotal}
+        cart_count={@cart_count}
         mode={@mode}
+        open={@cart_drawer_open}
+        cart_status={assigns[:cart_status]}
       />
 
       <SimpleshopThemeWeb.ShopComponents.search_modal hint_text={

lib/simpleshop_theme_web/live/shop_live/contact.ex

@@ -31,9 +31,6 @@ defmodule SimpleshopThemeWeb.ShopLive.Contact do
       |> assign(:logo_image, logo_image)
       |> assign(:header_image, header_image)
       |> assign(:mode, :shop)
-      |> assign(:cart_items, [])
-      |> assign(:cart_count, 0)
-      |> assign(:cart_subtotal, "£0.00")
 
     {:ok, socket}
   end
@@ -49,6 +46,8 @@ defmodule SimpleshopThemeWeb.ShopLive.Contact do
       cart_items={@cart_items}
       cart_count={@cart_count}
       cart_subtotal={@cart_subtotal}
+      cart_drawer_open={@cart_drawer_open}
+      cart_status={@cart_status}
     />
     """
   end

lib/simpleshop_theme_web/live/shop_live/home.ex

@@ -37,9 +37,6 @@ defmodule SimpleshopThemeWeb.ShopLive.Home do
       |> assign(:header_image, header_image)
       |> assign(:preview_data, preview_data)
       |> assign(:mode, :shop)
-      |> assign(:cart_items, [])
-      |> assign(:cart_count, 0)
-      |> assign(:cart_subtotal, "£0.00")
 
     {:ok, socket}
   end
@@ -56,6 +53,8 @@ defmodule SimpleshopThemeWeb.ShopLive.Home do
       cart_items={@cart_items}
       cart_count={@cart_count}
       cart_subtotal={@cart_subtotal}
+      cart_drawer_open={@cart_drawer_open}
+      cart_status={@cart_status}
     />
     """
   end

lib/simpleshop_theme_web/live/shop_live/product_show.ex

@@ -1,6 +1,7 @@
 defmodule SimpleshopThemeWeb.ShopLive.ProductShow do
   use SimpleshopThemeWeb, :live_view
 
+  alias SimpleshopTheme.Cart
   alias SimpleshopTheme.Settings
   alias SimpleshopTheme.Media
   alias SimpleshopTheme.Theme.{CSSCache, CSSGenerator, PreviewData}
@@ -61,9 +62,6 @@ defmodule SimpleshopThemeWeb.ShopLive.ProductShow do
       |> assign(:related_products, related_products)
       |> assign(:quantity, 1)
       |> assign(:mode, :shop)
-      |> assign(:cart_items, [])
-      |> assign(:cart_count, 0)
-      |> assign(:cart_subtotal, "£0.00")
       |> assign(:option_types, option_types)
       |> assign(:variants, variants)
       |> assign(:selected_options, selected_options)
@@ -153,6 +151,25 @@ defmodule SimpleshopThemeWeb.ShopLive.ProductShow do
     {:noreply, socket}
   end
 
+  @impl true
+  def handle_event("add_to_cart", _params, socket) do
+    variant = socket.assigns.selected_variant
+
+    if variant do
+      cart = Cart.add_item(socket.assigns.raw_cart, variant.id, socket.assigns.quantity)
+
+      socket =
+        socket
+        |> SimpleshopThemeWeb.CartHook.broadcast_and_update(cart)
+        |> assign(:cart_drawer_open, true)
+        |> assign(:cart_status, "#{socket.assigns.product.name} added to cart")
+
+      {:noreply, socket}
+    else
+      {:noreply, socket}
+    end
+  end
+
   @impl true
   def render(assigns) do
     ~H"""
@@ -168,6 +185,8 @@ defmodule SimpleshopThemeWeb.ShopLive.ProductShow do
       cart_items={@cart_items}
       cart_count={@cart_count}
       cart_subtotal={@cart_subtotal}
+      cart_drawer_open={@cart_drawer_open}
+      cart_status={@cart_status}
       option_types={@option_types}
       selected_options={@selected_options}
       available_options={@available_options}

lib/simpleshop_theme_web/live/theme_live/index.ex

@@ -33,6 +33,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       |> assign(:header_image, header_image)
       |> assign(:customise_open, false)
       |> assign(:sidebar_collapsed, false)
+      |> assign(:cart_drawer_open, false)
       |> allow_upload(:logo_upload,
         accept: ~w(.png .jpg .jpeg .webp .svg),
         max_entries: 1,
@@ -287,6 +288,16 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
     {:noreply, assign(socket, :sidebar_collapsed, !socket.assigns.sidebar_collapsed)}
   end
 
+  @impl true
+  def handle_event("open_cart_drawer", _params, socket) do
+    {:noreply, assign(socket, :cart_drawer_open, true)}
+  end
+
+  @impl true
+  def handle_event("close_cart_drawer", _params, socket) do
+    {:noreply, assign(socket, :cart_drawer_open, false)}
+  end
+
   @impl true
   def handle_event("noop", _params, socket) do
     {:noreply, socket}
@@ -303,6 +314,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
   attr :theme_settings, :map, required: true
   attr :logo_image, :any, required: true
   attr :header_image, :any, required: true
+  attr :cart_drawer_open, :boolean, default: false
 
   defp preview_page(%{page: :home} = assigns) do
     ~H"""
@@ -315,6 +327,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
     />
     """
   end
@@ -330,6 +343,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
     />
     """
   end
@@ -379,6 +393,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
       option_types={@option_types}
       selected_options={@selected_options}
       available_options={@available_options}
@@ -409,6 +424,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
     />
     """
   end
@@ -423,6 +439,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
     />
     """
   end
@@ -437,6 +454,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
     />
     """
   end
@@ -455,6 +473,7 @@ defmodule SimpleshopThemeWeb.ThemeLive.Index do
       cart_items={PreviewData.cart_drawer_items()}
       cart_count={2}
       cart_subtotal="£72.00"
+      cart_drawer_open={@cart_drawer_open}
     />
     """
   end

lib/simpleshop_theme_web/live/theme_live/index.html.heex

@@ -1164,6 +1164,7 @@
             theme_settings={@theme_settings}
             logo_image={@logo_image}
             header_image={@header_image}
+            cart_drawer_open={@cart_drawer_open}
           />
         </div>
       </div>

lib/simpleshop_theme_web/router.ex

@@ -30,7 +30,9 @@ defmodule SimpleshopThemeWeb.Router do
   scope "/", SimpleshopThemeWeb do
     pipe_through [:browser, :shop]
 
-    live_session :public_shop, layout: {SimpleshopThemeWeb.Layouts, :shop} do
+    live_session :public_shop,
+      layout: {SimpleshopThemeWeb.Layouts, :shop},
+      on_mount: [{SimpleshopThemeWeb.CartHook, :mount_cart}] do
       live "/", ShopLive.Home, :index
       live "/about", ShopLive.About, :index
       live "/contact", ShopLive.Contact, :index
@@ -40,6 +42,13 @@ defmodule SimpleshopThemeWeb.Router do
     end
   end
 
+  # Cart API (session persistence for LiveView)
+  scope "/api", SimpleshopThemeWeb do
+    pipe_through [:browser]
+
+    post "/cart", CartController, :update
+  end
+
   # Image serving routes (public, no auth required)
   scope "/images", SimpleshopThemeWeb do
     pipe_through :browser

mise.toml

@@ -0,0 +1,2 @@
+[tools]
+node = "latest"

test/simpleshop_theme/cart_test.exs

@@ -0,0 +1,173 @@
+defmodule SimpleshopTheme.CartTest do
+  use ExUnit.Case, async: true
+
+  alias SimpleshopTheme.Cart
+
+  describe "add_item/3" do
+    test "adds a new item to an empty cart" do
+      cart = Cart.add_item([], "variant-1")
+      assert cart == [{"variant-1", 1}]
+    end
+
+    test "adds a new item with custom quantity" do
+      cart = Cart.add_item([], "variant-1", 3)
+      assert cart == [{"variant-1", 3}]
+    end
+
+    test "increments quantity for existing item" do
+      cart = [{"variant-1", 2}]
+      cart = Cart.add_item(cart, "variant-1", 1)
+      assert cart == [{"variant-1", 3}]
+    end
+
+    test "adds different items separately" do
+      cart =
+        []
+        |> Cart.add_item("variant-1", 1)
+        |> Cart.add_item("variant-2", 2)
+
+      assert cart == [{"variant-1", 1}, {"variant-2", 2}]
+    end
+  end
+
+  describe "update_quantity/3" do
+    test "updates the quantity of an existing item" do
+      cart = [{"variant-1", 2}]
+      cart = Cart.update_quantity(cart, "variant-1", 5)
+      assert cart == [{"variant-1", 5}]
+    end
+
+    test "removes item when quantity is zero" do
+      cart = [{"variant-1", 2}]
+      cart = Cart.update_quantity(cart, "variant-1", 0)
+      assert cart == []
+    end
+
+    test "removes item when quantity is negative" do
+      cart = [{"variant-1", 2}]
+      cart = Cart.update_quantity(cart, "variant-1", -1)
+      assert cart == []
+    end
+
+    test "does nothing for non-existent item" do
+      cart = [{"variant-1", 2}]
+      cart = Cart.update_quantity(cart, "variant-999", 5)
+      assert cart == [{"variant-1", 2}]
+    end
+  end
+
+  describe "remove_item/2" do
+    test "removes an item from the cart" do
+      cart = [{"variant-1", 2}, {"variant-2", 1}]
+      cart = Cart.remove_item(cart, "variant-1")
+      assert cart == [{"variant-2", 1}]
+    end
+
+    test "does nothing for non-existent item" do
+      cart = [{"variant-1", 2}]
+      cart = Cart.remove_item(cart, "variant-999")
+      assert cart == [{"variant-1", 2}]
+    end
+
+    test "returns empty list when removing last item" do
+      cart = Cart.remove_item([{"variant-1", 1}], "variant-1")
+      assert cart == []
+    end
+  end
+
+  describe "get_quantity/2" do
+    test "returns quantity for existing item" do
+      cart = [{"variant-1", 3}]
+      assert Cart.get_quantity(cart, "variant-1") == 3
+    end
+
+    test "returns 0 for non-existent item" do
+      assert Cart.get_quantity([], "variant-1") == 0
+    end
+  end
+
+  describe "item_count/1" do
+    test "sums all quantities" do
+      cart = [{"variant-1", 2}, {"variant-2", 3}]
+      assert Cart.item_count(cart) == 5
+    end
+
+    test "returns 0 for empty cart" do
+      assert Cart.item_count([]) == 0
+    end
+  end
+
+  describe "format_price/1" do
+    test "formats pence as GBP string" do
+      assert Cart.format_price(2400) == "£24.00"
+    end
+
+    test "formats with pence correctly" do
+      assert Cart.format_price(1499) == "£14.99"
+    end
+
+    test "formats zero" do
+      assert Cart.format_price(0) == "£0.00"
+    end
+
+    test "formats single digit pence with padding" do
+      assert Cart.format_price(105) == "£1.05"
+    end
+
+    test "returns fallback for non-integer" do
+      assert Cart.format_price(nil) == "£0.00"
+      assert Cart.format_price("foo") == "£0.00"
+    end
+  end
+
+  describe "calculate_subtotal/1" do
+    test "sums price * quantity for all items" do
+      items = [
+        %{price: 2400, quantity: 1},
+        %{price: 1499, quantity: 2}
+      ]
+
+      assert Cart.calculate_subtotal(items) == 5398
+    end
+
+    test "returns 0 for empty list" do
+      assert Cart.calculate_subtotal([]) == 0
+    end
+  end
+
+  describe "serialize/1 and deserialize/1" do
+    test "round-trips cart data" do
+      cart = [{"variant-1", 2}, {"variant-2", 1}]
+      assert cart == cart |> Cart.serialize() |> Cart.deserialize()
+    end
+
+    test "serialize converts tuples to lists" do
+      assert Cart.serialize([{"v1", 3}]) == [["v1", 3]]
+    end
+
+    test "deserialize drops malformed entries" do
+      assert Cart.deserialize([[1, 2]]) == []
+      assert Cart.deserialize([["valid", 1], [nil, 2]]) == [{"valid", 1}]
+    end
+
+    test "deserialize handles non-list input" do
+      assert Cart.deserialize(nil) == []
+      assert Cart.deserialize("garbage") == []
+    end
+  end
+
+  describe "get_from_session/1" do
+    test "returns cart items from session" do
+      session = %{"cart" => [{"v1", 2}]}
+      assert Cart.get_from_session(session) == [{"v1", 2}]
+    end
+
+    test "returns empty list when no cart in session" do
+      assert Cart.get_from_session(%{}) == []
+    end
+
+    test "returns empty list for invalid cart data" do
+      assert Cart.get_from_session(%{"cart" => "garbage"}) == []
+    end
+  end
+end