feat: add item input now doubles as search bar for the list

src/utils/__tests__/fuzzyMatch.spec.ts

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest'
+import { fuzzyMatch } from '../fuzzyMatch'
+
+describe('fuzzyMatch', () => {
+  it('matches an empty query against anything', () => {
+    expect(fuzzyMatch('', 'Groceries')).toBe(true)
+    expect(fuzzyMatch('   ', 'Groceries')).toBe(true)
+  })
+
+  it('matches an exact substring, case-insensitively', () => {
+    expect(fuzzyMatch('milk', 'Buy milk and eggs')).toBe(true)
+    expect(fuzzyMatch('MILK', 'buy milk and eggs')).toBe(true)
+  })
+
+  it('tolerates a couple of off characters', () => {
+    expect(fuzzyMatch('mikl', 'Buy milk and eggs')).toBe(true)
+    expect(fuzzyMatch('grocries', 'Groceries')).toBe(true)
+  })
+
+  it('does not match unrelated text', () => {
+    expect(fuzzyMatch('xyz', 'Groceries')).toBe(false)
+    expect(fuzzyMatch('banana', 'Groceries')).toBe(false)
+  })
+})

src/utils/fuzzyMatch.ts

@@ -0,0 +1,45 @@
+function levenshtein(a: string, b: string): number {
+  const rows = a.length + 1
+  const cols = b.length + 1
+  let prev: number[] = Array.from({ length: cols }, (_, j) => j)
+
+  for (let i = 1; i < rows; i++) {
+    const curr: number[] = [i]
+    for (let j = 1; j < cols; j++) {
+      const cost = a[i - 1] === b[j - 1] ? 0 : 1
+      curr.push(Math.min((curr[j - 1] ?? 0) + 1, (prev[j] ?? 0) + 1, (prev[j - 1] ?? 0) + cost))
+    }
+    prev = curr
+  }
+
+  return prev[cols - 1] ?? 0
+}
+
+function maxDistanceFor(queryLength: number): number {
+  if (queryLength <= 4) return 1
+  return 2
+}
+
+/**
+ * Cheap, local fuzzy substring match: true if `text` contains a run of
+ * characters within edit-distance of `query` (tolerating ~1-2 typos).
+ */
+export function fuzzyMatch(query: string, text: string): boolean {
+  const q = query.trim().toLowerCase()
+  if (!q) return true
+
+  const t = text.toLowerCase()
+  if (t.includes(q)) return true
+
+  const maxDistance = maxDistanceFor(q.length)
+  const minLen = Math.max(1, q.length - maxDistance)
+  const maxLen = q.length + maxDistance
+
+  for (let len = minLen; len <= maxLen; len++) {
+    for (let start = 0; start + len <= t.length; start++) {
+      if (levenshtein(q, t.substring(start, start + len)) <= maxDistance) return true
+    }
+  }
+
+  return false
+}