feat: use flexsearch for all local searches (#997)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/997
Reviewed-by: dpschen <dpschen@noreply.kolaente.de>
Co-authored-by: konrad <k@knt.li>
Co-committed-by: konrad <k@knt.li>

src/indexes/index.ts

@@ -0,0 +1,52 @@
+import {Document, SimpleDocumentSearchResultSetUnit} from 'flexsearch'
+
+export interface withId {
+	id: number,
+}
+
+const indexes: { [k: string]: Document<withId> } = {}
+
+export const createNewIndexer = (name: string, fieldsToIndex: string[]) => {
+	if (typeof indexes[name] === 'undefined') {
+		indexes[name] = new Document<withId>({
+			tokenize: 'full',
+			document: {
+				id: 'id',
+				index: fieldsToIndex,
+			},
+		})
+	}
+
+	const index = indexes[name]
+
+	function add(item: withId) {
+		return index.add(item.id, item)
+	}
+
+	function remove(item: withId) {
+		return index.remove(item.id)
+	}
+
+	function update(item: withId) {
+		return index.update(item.id, item)
+	}
+
+	function search(query: string | null): number[] | null {
+		if (query === '' || query === null) {
+			return null
+		}
+
+		// @ts-ignore
+		return index.search(query)
+				?.flatMap(r => r.result)
+				.filter((value, index, self) => self.indexOf(value) === index)
+			|| null
+	}
+
+	return {
+		add,
+		remove,
+		update,
+		search,
+	}
+}