chore: refactoring and tests (#12468)

2 files changed, 173 insertions, 0 deletions

diff --git a/packages/app/src/utils/scoped-cache.test.ts b/packages/app/src/utils/scoped-cache.test.ts
new file mode 100644
index 000000000..0c6189daf
--- /dev/null
+++ b/packages/app/src/utils/scoped-cache.test.ts
@@ -0,0 +1,69 @@
+import { describe, expect, test } from "bun:test"
+import { createScopedCache } from "./scoped-cache"
+
+describe("createScopedCache", () => {
+  test("evicts least-recently-used entry when max is reached", () => {
+    const disposed: string[] = []
+    const cache = createScopedCache((key) => ({ key }), {
+      maxEntries: 2,
+      dispose: (value) => disposed.push(value.key),
+    })
+
+    const a = cache.get("a")
+    const b = cache.get("b")
+    expect(a.key).toBe("a")
+    expect(b.key).toBe("b")
+
+    cache.get("a")
+    const c = cache.get("c")
+
+    expect(c.key).toBe("c")
+    expect(cache.peek("a")?.key).toBe("a")
+    expect(cache.peek("b")).toBeUndefined()
+    expect(cache.peek("c")?.key).toBe("c")
+    expect(disposed).toEqual(["b"])
+  })
+
+  test("disposes entries on delete and clear", () => {
+    const disposed: string[] = []
+    const cache = createScopedCache((key) => ({ key }), {
+      dispose: (value) => disposed.push(value.key),
+    })
+
+    cache.get("a")
+    cache.get("b")
+
+    const removed = cache.delete("a")
+    expect(removed?.key).toBe("a")
+    expect(cache.peek("a")).toBeUndefined()
+
+    cache.clear()
+    expect(cache.peek("b")).toBeUndefined()
+    expect(disposed).toEqual(["a", "b"])
+  })
+
+  test("expires stale entries with ttl and recreates on get", () => {
+    let clock = 0
+    let count = 0
+    const disposed: string[] = []
+    const cache = createScopedCache((key) => ({ key, count: ++count }), {
+      ttlMs: 10,
+      now: () => clock,
+      dispose: (value) => disposed.push(`${value.key}:${value.count}`),
+    })
+
+    const first = cache.get("a")
+    expect(first.count).toBe(1)
+
+    clock = 9
+    expect(cache.peek("a")?.count).toBe(1)
+
+    clock = 11
+    expect(cache.peek("a")).toBeUndefined()
+    expect(disposed).toEqual(["a:1"])
+
+    const second = cache.get("a")
+    expect(second.count).toBe(2)
+    expect(disposed).toEqual(["a:1"])
+  })
+})
diff --git a/packages/app/src/utils/scoped-cache.ts b/packages/app/src/utils/scoped-cache.ts
new file mode 100644
index 000000000..224c363c1
--- /dev/null
+++ b/packages/app/src/utils/scoped-cache.ts
@@ -0,0 +1,104 @@
+type ScopedCacheOptions<T> = {
+  maxEntries?: number
+  ttlMs?: number
+  dispose?: (value: T, key: string) => void
+  now?: () => number
+}
+
+type Entry<T> = {
+  value: T
+  touchedAt: number
+}
+
+export function createScopedCache<T>(createValue: (key: string) => T, options: ScopedCacheOptions<T> = {}) {
+  const store = new Map<string, Entry<T>>()
+  const now = options.now ?? Date.now
+
+  const dispose = (key: string, entry: Entry<T>) => {
+    options.dispose?.(entry.value, key)
+  }
+
+  const expired = (entry: Entry<T>) => {
+    if (options.ttlMs === undefined) return false
+    return now() - entry.touchedAt >= options.ttlMs
+  }
+
+  const sweep = () => {
+    if (options.ttlMs === undefined) return
+    for (const [key, entry] of store) {
+      if (!expired(entry)) continue
+      store.delete(key)
+      dispose(key, entry)
+    }
+  }
+
+  const touch = (key: string, entry: Entry<T>) => {
+    entry.touchedAt = now()
+    store.delete(key)
+    store.set(key, entry)
+  }
+
+  const prune = () => {
+    if (options.maxEntries === undefined) return
+    while (store.size > options.maxEntries) {
+      const key = store.keys().next().value
+      if (!key) return
+      const entry = store.get(key)
+      store.delete(key)
+      if (!entry) continue
+      dispose(key, entry)
+    }
+  }
+
+  const remove = (key: string) => {
+    const entry = store.get(key)
+    if (!entry) return
+    store.delete(key)
+    dispose(key, entry)
+    return entry.value
+  }
+
+  const peek = (key: string) => {
+    sweep()
+    const entry = store.get(key)
+    if (!entry) return
+    if (!expired(entry)) return entry.value
+    store.delete(key)
+    dispose(key, entry)
+  }
+
+  const get = (key: string) => {
+    sweep()
+    const entry = store.get(key)
+    if (entry && !expired(entry)) {
+      touch(key, entry)
+      return entry.value
+    }
+    if (entry) {
+      store.delete(key)
+      dispose(key, entry)
+    }
+
+    const created = {
+      value: createValue(key),
+      touchedAt: now(),
+    }
+    store.set(key, created)
+    prune()
+    return created.value
+  }
+
+  const clear = () => {
+    for (const [key, entry] of store) {
+      dispose(key, entry)
+    }
+    store.clear()
+  }
+
+  return {
+    get,
+    peek,
+    delete: remove,
+    clear,
+  }
+}