feat : add fuzzy matching for searching

lib/search.test.ts

@@ -0,0 +1,58 @@
+import { describe, expect, it } from "vitest";
+import { searchItems } from "./search";
+
+const items = [
+  { name: "Mualani", aliases: ["Shark Surfer"], overview: "A hydro guide", key: "internal" },
+  { name: "Obsidian Codex", aliases: ["Codex"], overview: "An artifact", key: "obsidian" },
+];
+const search = (query: string) => searchItems(items, query,
+  (item) => `${item.name} ${item.aliases.join(" ")} ${item.overview} ${item.key}`,
+  (item) => [item.name, ...item.aliases]);
+const names = (items: string[], query: string) => searchItems(items, query, (item) => item, (item) => [item]);
+
+describe("fuzzy search fallback", () => {
+  it("preserves direct substring matches, case, whitespace, and empty queries", () => {
+    expect(search("  MUALA  ")).toEqual({ items: [items[0]], fuzzy: false });
+    expect(search("  ")).toEqual({ items, fuzzy: false });
+    expect(search("hydro").items).toEqual([items[0]]);
+  });
+
+  it("does not append typo matches when another item matches directly", () => {
+    expect(names(["Mualani", "Mulani Guide"], "mulani")).toEqual({ items: ["Mulani Guide"], fuzzy: false });
+  });
+
+  it.each(["mulani", "muallani", "mualoni", "mualnai"])("finds missing, extra, substituted, or swapped characters: %s", (query) => {
+    expect(search(query)).toEqual({ items: [items[0]], fuzzy: true });
+  });
+
+  it("matches aliases and individual words in multiword names", () => {
+    expect(search("surfre")).toEqual({ items: [items[0]], fuzzy: true });
+    expect(search("codxe")).toEqual({ items: [items[1]], fuzzy: true });
+    expect(search("obsidain codex")).toEqual({ items: [items[1]], fuzzy: true });
+  });
+
+  it("does not fuzzy match overview prose or internal keys", () => {
+    expect(search("hydor")).toEqual({ items: [], fuzzy: false });
+    expect(search("interanl")).toEqual({ items: [], fuzzy: false });
+  });
+
+  it("keeps short queries strict and enforces edit limits", () => {
+    expect(names(["Jean"], "jen")).toEqual({ items: [], fuzzy: false });
+    expect(names(["Mualani"], "muloni").items).toEqual([]);
+    expect(names(["abcdefgh"], "abxdxfgh")).toEqual({ items: ["abcdefgh"], fuzzy: true });
+    expect(names(["abcdefgh"], "abxdxygh").items).toEqual([]);
+    expect(search("unrelated").items).toEqual([]);
+  });
+
+  it("normalizes composed Unicode and handles Thai code points", () => {
+    expect(names(["Café"], "Cafe\u0301")).toEqual({ items: ["Café"], fuzzy: false });
+    expect(names(["ตัวละคร"], "ตัวลคร")).toEqual({ items: ["ตัวละคร"], fuzzy: true });
+    expect(names(["😀abcd"], "😀abdc")).toEqual({ items: ["😀abcd"], fuzzy: true });
+  });
+
+  it("ranks by distance with stable ties and retains item identities", () => {
+    expect(names(["abxdxfgh", "abcxefgh", "abcdxfgh"], "abcdefgh").items)
+      .toEqual(["abcxefgh", "abcdxfgh", "abxdxfgh"]);
+    expect(search("mulani").items[0]).toBe(items[0]);
+  });
+});