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// memoize.ts (Bun-compatible, no Node Buffers)
import { mkdir } from "node:fs/promises";
import path from "node:path";
type MemoOpts<V> = {
ttlMs?: number; // time-to-live for entries
maxEntries?: number; // cap; oldest (LRU) evicted
persistDir?: string; // set to enable disk cache (e.g. ".cache/memo")
keyFn?: (...args: any[]) => string; // custom key if you need it
cacheErrors?: boolean; // default false
};
type Entry<V> = {
v: V;
exp: number | null;
at: number; // last hit (LRU)
};
const enc = new TextEncoder();
const dec = new TextDecoder();
const stableStringify = (x: any): string => {
const seen = new WeakSet();
const S = (v: any): any => {
if (v && typeof v === "object") {
if (seen.has(v)) return "[Circular]";
seen.add(v);
if (Array.isArray(v)) return v.map(S);
return Object.fromEntries(
Object.keys(v)
.sort()
.map((k) => [k, S(v[k])]),
);
}
if (typeof v === "function") return `[Function:${v.name || "anon"}]`;
if (typeof v === "undefined") return "__undefined__";
return v;
};
return JSON.stringify(S(x));
};
async function sha256Hex(s: string) {
const h = await crypto.subtle.digest("SHA-256", enc.encode(s));
return Array.from(new Uint8Array(h))
.map((b) => b.toString(16).padStart(2, "0"))
.join("");
}
function now() {
return Date.now();
}
export function memoize<
F extends (...args: any[]) => any,
V = Awaited<ReturnType<F>>,
>(fn: F, opts: MemoOpts<V> = {}): F {
const ttl = opts.ttlMs ?? 0;
const max = opts.maxEntries ?? 0;
const dir = opts.persistDir ? path.resolve(opts.persistDir) : null;
const mem = new Map<string, Entry<V>>();
const inflight = new Map<string, Promise<V>>();
async function keyOf(args: any[]): Promise<string> {
const base = opts.keyFn ? opts.keyFn(...args) : stableStringify(args);
return dir ? await sha256Hex(base) : base; // hash when persisting (safe filename)
}
async function readDisk(k: string): Promise<Entry<V> | null> {
if (!dir) throw new Error("no dir!");
const f = Bun.file(path.join(dir, `${k}.json`));
if (!(await f.exists())) return null;
try {
const obj = JSON.parse(await f.text());
return obj as Entry<V>;
} catch {
return null;
}
}
async function writeDisk(k: string, e: Entry<V>) {
if (!dir) throw new Error("no dir!");
await Bun.write(path.join(dir, `${k}.json`), JSON.stringify(e));
}
function evictLRU() {
if (!max || mem.size <= max) return;
const arr = [...mem.entries()].sort((a, b) => a[1].at - b[1].at);
for (let i = 0; i < mem.size - max; i++) mem.delete(arr[i][0]);
}
async function getOrCall(args: any[]): Promise<V> {
const k = await keyOf(args);
const t = now();
// in-flight coalescing
if (inflight.has(k)) return inflight.get(k)!;
// memory hit
const m = mem.get(k);
if (m && (!m.exp || t < m.exp)) {
m.at = t;
return m.v;
}
// disk hit
const d = await readDisk(k);
if (d && (!d.exp || t < d.exp)) {
d.at = t;
mem.set(k, d);
evictLRU();
return d.v;
}
// miss → call underlying
const call = (async () => {
try {
const r = fn.apply(undefined, args);
const v: V = r instanceof Promise ? await r : (r as V);
const e: Entry<V> = { v, exp: ttl ? t + ttl : null, at: t };
mem.set(k, e);
evictLRU();
await writeDisk(k, e);
return v;
} catch (err) {
if (opts.cacheErrors) {
const e: Entry<any> = { v: err, exp: ttl ? t + ttl : null, at: t };
mem.set(k, e);
await writeDisk(k, e as Entry<V>);
}
throw err;
} finally {
inflight.delete(k);
}
})();
inflight.set(k, call);
return call;
}
// Wrap preserving arity & `this` for methods
const wrapped = function (this: any, ...args: any[]) {
const maybe = getOrCall(args).then((v) => v);
// If original fn is sync (per your signature), unwrap to sync only when it's truly sync.
// We can detect by calling without awaiting once—dangerous—so be conservative:
return maybe as unknown as ReturnType<F>;
} as any as F;
return wrapped;
}
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