feat: implement Theme Builder concept and Display Conditions resolver system

src/utils/conditionResolver.ts

@@ -0,0 +1,67 @@
+export interface DisplayCondition {
+  type: 'include' | 'exclude';
+  scope: 'entire_site' | 'singular' | 'archive' | 'page_404';
+  entity?: 'page' | 'post' | 'category';
+  entityId?: string;
+}
+
+export interface TemplateMeta {
+  id: string;
+  name: string;
+  type: 'header' | 'footer' | 'single' | 'archive' | '404';
+  status: 'draft' | 'published';
+  priority: number;
+  conditions: DisplayCondition[];
+  createdAt?: string;
+  updatedAt?: string;
+}
+
+/**
+ * Resolves which template to use based on target type and request context conditions.
+ * Specific matches (singular/page_404) take precedence over general 'entire_site' matches.
+ */
+export function resolveTemplate(
+  templates: TemplateMeta[],
+  targetType: TemplateMeta['type'],
+  context: { url: string; routeType: 'singular' | 'archive' | '404' | 'home'; entityId?: string }
+): TemplateMeta | null {
+  const candidates = templates.filter(t => t.type === targetType && t.status === 'published');
+  let bestMatch: TemplateMeta | null = null;
+  let highestScore = -1;
+
+  for (const tpl of candidates) {
+    let isIncluded = false;
+    let isExcluded = false;
+    let score = 0;
+
+    for (const cond of tpl.conditions) {
+      if (cond.type === 'exclude') {
+        if (cond.scope === 'entire_site') isExcluded = true;
+        if (cond.scope === 'singular' && context.routeType === 'singular' && (!cond.entityId || cond.entityId === context.entityId)) {
+          isExcluded = true;
+        }
+        if (cond.scope === 'page_404' && context.routeType === '404') isExcluded = true;
+      } else if (cond.type === 'include') {
+        if (cond.scope === 'entire_site') {
+          isIncluded = true;
+          score = Math.max(score, tpl.priority || 1);
+        } else if (cond.scope === 'singular' && context.routeType === 'singular') {
+          if (!cond.entityId || cond.entityId === context.entityId) {
+            isIncluded = true;
+            score = Math.max(score, (tpl.priority || 1) + 10);
+          }
+        } else if (cond.scope === 'page_404' && context.routeType === '404') {
+          isIncluded = true;
+          score = Math.max(score, (tpl.priority || 1) + 10);
+        }
+      }
+    }
+
+    if (isIncluded && !isExcluded && score > highestScore) {
+      highestScore = score;
+      bestMatch = tpl;
+    }
+  }
+
+  return bestMatch;
+}