intrn(query): sift tags by slug

Co-authored-by: Kenneth Trecy Tobias <19201.tobias.kennethtrecy.c@gmail.com>

database/queries/tag/sift_by_slug.ts

@@ -0,0 +1,43 @@
+import type { SlugFilter } from "$/types/query"
+import type { FindOptions } from "%/types/dependent"
+
+import Log from "$!/singletons/log"
+
+import Condition from "%/helpers/condition"
+import isUndefined from "$/type_guards/is_undefined"
+
+/**
+ * Sifts tag model which matches a certain name.
+ */
+export default function<T>(
+	currentState: FindOptions<T>,
+	constraints: SlugFilter
+): FindOptions<T> {
+	const newState = { ...currentState }
+
+	switch (constraints.filter.slug) {
+		case "":
+			// Do nothing
+			break
+		default: {
+			const condition = new Condition()
+			condition.or(
+				new Condition().search("name", constraints.filter.slug)
+			)
+
+			if (isUndefined(newState.where)) {
+				newState.where = {}
+			}
+
+			newState.where = {
+				...newState.where,
+				...condition.build()
+			}
+			break
+		}
+	}
+
+	Log.trace("pipeline", "sift by slug")
+
+	return newState
+}