chore: rename aelis to freya (#122)

apps/freya-backend/src/enhancement/merge.ts

@@ -0,0 +1,48 @@
+import type { FeedItem } from "@freya/core"
+
+import type { EnhancementResult } from "./schema.ts"
+
+const ENHANCEMENT_SOURCE_ID = "freya.enhancement"
+
+/**
+ * Merges an EnhancementResult into feed items.
+ *
+ * - Writes slot content from slotFills into matching items
+ * - Appends synthetic items to the list
+ * - Returns a new array (no mutation)
+ * - Ignores fills for items/slots that don't exist
+ */
+export function mergeEnhancement(
+	items: FeedItem[],
+	result: EnhancementResult,
+	currentTime: Date,
+): FeedItem[] {
+	const merged = items.map((item) => {
+		const fills = result.slotFills[item.id]
+		if (!fills || !item.slots) return item
+
+		const mergedSlots = { ...item.slots }
+		let changed = false
+
+		for (const [slotName, content] of Object.entries(fills)) {
+			if (slotName in mergedSlots && content !== null) {
+				mergedSlots[slotName] = { ...mergedSlots[slotName]!, content }
+				changed = true
+			}
+		}
+
+		return changed ? { ...item, slots: mergedSlots } : item
+	})
+
+	for (const synthetic of result.syntheticItems) {
+		merged.push({
+			id: synthetic.id,
+			sourceId: ENHANCEMENT_SOURCE_ID,
+			type: synthetic.type,
+			timestamp: currentTime,
+			data: { text: synthetic.text },
+		})
+	}
+
+	return merged
+}