Implement create custom recommendations

lib/server/ruleTemplates.ts

@@ -1,6 +1,27 @@
 import type { RuleTemplateDto } from "../create/fetchTemplates";
 import { prisma } from "./db";
 import { isDatabaseConfigured } from "./env";
+import { scoreTemplatesByFacets } from "./methodRecommendations";
+import { templateMethodsFromBody } from "./templateMethods";
+import type { RequestedFacets } from "./validation/methodFacetsSchemas";
+import { flattenRequestedFacets } from "./validation/methodFacetsSchemas";
+
+const TEMPLATE_SELECT = {
+  id: true,
+  slug: true,
+  title: true,
+  category: true,
+  description: true,
+  body: true,
+  sortOrder: true,
+  featured: true,
+} as const;
+
+const CURATED_ORDER_BY = [
+  { featured: "desc" as const },
+  { sortOrder: "asc" as const },
+  { title: "asc" as const },
+];
 
 /**
  * Curated templates for public list UIs (same query as GET /api/templates).
@@ -12,19 +33,82 @@ export async function listRuleTemplatesFromDb(): Promise<RuleTemplateDto[]> {
   }
   try {
     return await prisma.ruleTemplate.findMany({
-      orderBy: [{ featured: "desc" }, { sortOrder: "asc" }, { title: "asc" }],
-      select: {
-        id: true,
-        slug: true,
-        title: true,
-        category: true,
-        description: true,
-        body: true,
-        sortOrder: true,
-        featured: true,
-      },
+      orderBy: CURATED_ORDER_BY,
+      select: TEMPLATE_SELECT,
     });
   } catch {
     return [];
   }
 }
+
+export type TemplateScore = {
+  score: number;
+  matchedFacets: string[];
+};
+
+export type RankedTemplatesResult = {
+  templates: RuleTemplateDto[];
+  /** Per-template-slug score map; absent slugs scored `0`. */
+  scores: Record<string, TemplateScore>;
+};
+
+/**
+ * Curated templates ranked by how many of `facets` each composed method
+ * matches (§9.1). When `facets` is empty, returns the curated ordering with
+ * an empty `scores` map (caller can omit it from the API response).
+ *
+ * Ties (and zero-score templates) fall back to the curated
+ * `(featured, sortOrder, title)` order so no-facets and zero-match cases
+ * produce identical output to `listRuleTemplatesFromDb`.
+ */
+export async function listRankedRuleTemplatesFromDb(
+  facets: RequestedFacets,
+): Promise<RankedTemplatesResult> {
+  if (!isDatabaseConfigured()) {
+    return { templates: [], scores: {} };
+  }
+  const requested = flattenRequestedFacets(facets);
+  if (requested.length === 0) {
+    const templates = await listRuleTemplatesFromDb();
+    return { templates, scores: {} };
+  }
+
+  let templates: RuleTemplateDto[];
+  try {
+    templates = await prisma.ruleTemplate.findMany({
+      orderBy: CURATED_ORDER_BY,
+      select: TEMPLATE_SELECT,
+    });
+  } catch {
+    return { templates: [], scores: {} };
+  }
+
+  const templateMethods = templates.map((t) => ({
+    templateSlug: t.slug,
+    methods: templateMethodsFromBody(t.body),
+  }));
+
+  const ranked = await scoreTemplatesByFacets({ templateMethods, facets });
+  if (!ranked) {
+    return { templates, scores: {} };
+  }
+
+  const scores: Record<string, TemplateScore> = {};
+  for (const r of ranked) {
+    scores[r.templateSlug] = {
+      score: r.score,
+      matchedFacets: r.matchedFacets,
+    };
+  }
+
+  // Stable sort: scoreDesc, then preserve curated index order.
+  const indexBySlug = new Map(templates.map((t, i) => [t.slug, i]));
+  const sorted = [...templates].sort((a, b) => {
+    const sa = scores[a.slug]?.score ?? 0;
+    const sb = scores[b.slug]?.score ?? 0;
+    if (sa !== sb) return sb - sa;
+    return (indexBySlug.get(a.slug) ?? 0) - (indexBySlug.get(b.slug) ?? 0);
+  });
+
+  return { templates: sorted, scores };
+}