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openchamber/packages/web/server/lib/path-realpath-cache.js
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export const createRealpathCache = ({
realpath,
successTtlMs = 600_000,
failureTtlMs = 60_000,
maxEntries = 256,
fallbackOnError = false,
now = () => Date.now(),
} = {}) => {
const cache = new Map();
const resolveRealpath = typeof realpath === 'function' ? realpath : null;
const prune = () => {
while (cache.size > maxEntries) {
const oldestKey = cache.keys().next().value;
if (oldestKey === undefined) {
return;
}
cache.delete(oldestKey);
}
};
const remember = (key, entry, ttlMs) => {
if (!Number.isFinite(maxEntries) || maxEntries <= 0) {
return;
}
cache.delete(key);
cache.set(key, { ...entry, expiresAt: now() + Math.max(0, ttlMs) });
prune();
};
const resolve = async (value) => {
if (typeof value !== 'string' || value.length === 0 || !resolveRealpath) {
return value;
}
const cached = cache.get(value);
const currentTime = now();
if (cached?.promise) {
return cached.promise;
}
if (cached && cached.expiresAt > currentTime) {
cache.delete(value);
cache.set(value, cached);
if (cached.error) {
if (fallbackOnError) {
return value;
}
throw cached.error;
}
return cached.value;
}
if (cached) {
cache.delete(value);
}
const promise = Promise.resolve()
.then(() => resolveRealpath(value))
.then((resolved) => {
const next = typeof resolved === 'string' && resolved.length > 0 ? resolved : value;
remember(value, { value: next }, successTtlMs);
return next;
})
.catch((error) => {
remember(value, { value, error }, failureTtlMs);
if (!fallbackOnError) {
throw error;
}
return value;
});
if (Number.isFinite(maxEntries) && maxEntries > 0) {
cache.delete(value);
cache.set(value, { value, expiresAt: 0, promise });
prune();
}
return promise;
};
return {
resolve,
clear: () => cache.clear(),
size: () => cache.size,
};
};