add FTS5 full-text product search

Adds SQLite FTS5 search index with BM25 ranking across product title,
category, variant attributes, and description. Search modal now has
live results with thumbnails, prices, and click-to-navigate. Index
rebuilds automatically after each provider sync.

Also fixes Access syntax on Product/ProductImage structs (Map.get
instead of bracket notation) which was causing crashes when real
products were loaded from the database.

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

lib/simpleshop_theme/search.ex

@@ -0,0 +1,192 @@
+defmodule SimpleshopTheme.Search do
+  @moduledoc """
+  Full-text product search backed by SQLite FTS5.
+
+  Uses a contentless FTS5 index with BM25 ranking. The index is rebuilt
+  from the products table after each provider sync.
+  """
+
+  import Ecto.Query
+
+  alias SimpleshopTheme.Products.Product
+  alias SimpleshopTheme.Repo
+
+  @listing_preloads [images: :image]
+
+  # BM25 column weights: title(10), category(5), variant_info(3), description(1)
+  @bm25_weights "10.0, 5.0, 3.0, 1.0"
+
+  @doc """
+  Searches products by query string. Returns ranked list of Product structs
+  with listing preloads, or empty list for blank/short queries.
+  """
+  def search(query) when is_binary(query) do
+    query = String.trim(query)
+
+    if String.length(query) < 2 do
+      []
+    else
+      fts_query = build_fts_query(query)
+      search_fts(fts_query)
+    end
+  end
+
+  def search(_), do: []
+
+  @doc """
+  Rebuilds the entire FTS5 index from visible, active products.
+  """
+  def rebuild_index do
+    Repo.transaction(fn ->
+      # Clear existing index data
+      Repo.query!("DELETE FROM products_search_map")
+      Repo.query!("DELETE FROM products_search")
+
+      # Load all visible products with variants for indexing
+      products =
+        Product
+        |> where([p], p.visible == true and p.status == "active")
+        |> preload([:variants])
+        |> Repo.all()
+
+      Enum.each(products, &insert_into_index/1)
+    end)
+  end
+
+  @doc """
+  Indexes or reindexes a single product.
+  Removes existing entry first if present.
+  """
+  def index_product(%Product{} = product) do
+    product = Repo.preload(product, [:variants], force: true)
+    remove_from_index(product.id)
+    insert_into_index(product)
+  end
+
+  # Build an FTS5 MATCH query from user input.
+  # Strips special chars, splits into tokens, adds * prefix match to last token.
+  defp build_fts_query(input) do
+    tokens =
+      input
+      |> String.replace(~r/[^\w\s]/, "")
+      |> String.split(~r/\s+/, trim: true)
+
+    case tokens do
+      [] ->
+        nil
+
+      tokens ->
+        {complete, [last]} = Enum.split(tokens, -1)
+
+        parts =
+          Enum.map(complete, &~s("#{&1}")) ++
+            [~s("#{last}" *)]
+
+        Enum.join(parts, " ")
+    end
+  end
+
+  defp search_fts(nil), do: []
+
+  defp search_fts(fts_query) do
+    result =
+      Repo.query!(
+        """
+        SELECT m.product_id, bm25(products_search, #{@bm25_weights}) AS rank
+        FROM products_search
+        JOIN products_search_map m ON m.rowid = products_search.rowid
+        WHERE products_search MATCH ?1
+        ORDER BY rank
+        LIMIT 20
+        """,
+        [fts_query]
+      )
+
+    product_ids = Enum.map(result.rows, fn [id, _rank] -> id end)
+
+    if product_ids == [] do
+      []
+    else
+      # Fetch full structs preserving rank order
+      products_by_id =
+        Product
+        |> where([p], p.id in ^product_ids)
+        |> where([p], p.visible == true and p.status == "active")
+        |> preload(^@listing_preloads)
+        |> Repo.all()
+        |> Map.new(&{&1.id, &1})
+
+      Enum.flat_map(product_ids, fn id ->
+        case Map.get(products_by_id, id) do
+          nil -> []
+          product -> [product]
+        end
+      end)
+    end
+  end
+
+  defp insert_into_index(%Product{} = product) do
+    # Insert mapping row
+    Repo.query!(
+      "INSERT INTO products_search_map (product_id) VALUES (?1)",
+      [product.id]
+    )
+
+    # Get the rowid just inserted
+    %{rows: [[rowid]]} =
+      Repo.query!(
+        "SELECT rowid FROM products_search_map WHERE product_id = ?1",
+        [product.id]
+      )
+
+    # Build index content
+    variant_info = build_variant_info(product.variants || [])
+    description = strip_html(product.description || "")
+
+    Repo.query!(
+      """
+      INSERT INTO products_search (rowid, title, category, variant_info, description)
+      VALUES (?1, ?2, ?3, ?4, ?5)
+      """,
+      [rowid, product.title || "", product.category || "", variant_info, description]
+    )
+  end
+
+  defp remove_from_index(product_id) do
+    # Get the rowid for this product (if indexed)
+    case Repo.query!(
+           "SELECT rowid FROM products_search_map WHERE product_id = ?1",
+           [product_id]
+         ) do
+      %{rows: [[rowid]]} ->
+        Repo.query!("DELETE FROM products_search WHERE rowid = ?1", [rowid])
+        Repo.query!("DELETE FROM products_search_map WHERE rowid = ?1", [rowid])
+
+      _ ->
+        :ok
+    end
+  end
+
+  # Build searchable variant text from enabled variants
+  defp build_variant_info(variants) do
+    variants
+    |> Enum.filter(& &1.is_enabled)
+    |> Enum.flat_map(fn v -> [v.title | Map.values(v.options || %{})] end)
+    |> Enum.uniq()
+    |> Enum.join(" ")
+  end
+
+  # Strip HTML tags and decode common entities
+  defp strip_html(html) do
+    html
+    |> String.replace(~r/<[^>]+>/, " ")
+    |> String.replace("&amp;", "&")
+    |> String.replace("&lt;", "<")
+    |> String.replace("&gt;", ">")
+    |> String.replace("&quot;", "\"")
+    |> String.replace("&#39;", "'")
+    |> String.replace("&nbsp;", " ")
+    |> String.replace(~r/\s+/, " ")
+    |> String.trim()
+  end
+end

lib/simpleshop_theme/sync/product_sync_worker.ex

@@ -99,6 +99,10 @@ defmodule SimpleshopTheme.Sync.ProductSyncWorker do
       Products.update_sync_status(conn, "completed", DateTime.utc_now())
       product_count = Products.count_products_for_connection(conn.id)
       broadcast_sync(conn.id, {:sync_status, "completed", product_count})
+
+      # Rebuild search index after successful sync
+      SimpleshopTheme.Search.rebuild_index()
+
       :ok
     else
       {:error, reason} = error ->