// std/collections — Collection utilities.
/**
* Options for `pick_keys`.
*
* `drop_nil` removes selected keys whose value is `nil` from the result;
* defaults to `false`.
*/
type PickKeysOptions = {drop_nil?: bool}
/**
* Remove entries from a dict where the value is nil, an empty string, or the
* literal "null" string. Generic over the value type so a typed input
* (`dict<string, V>` or a structural shape) projects back to a dict with the
* same value contract instead of collapsing to untyped `dict`.
*
* @effects: []
* @allocation: heap
* @errors: []
* @api_stability: stable
* @example: filter_nil(d)
*/
pub fn filter_nil<V>(d: dict<string, V>) -> dict<string, V> {
return __dict_filter_nil(d ?? {})
}
/**
* Project a dict onto an explicit list of keys, preserving the original value
* contract. Pass `{drop_nil: true}` to omit keys whose value resolves to nil
* after lookup. Missing keys are silently dropped.
*
* @effects: []
* @allocation: heap
* @errors: []
* @api_stability: stable
* @example: pick_keys(d, selected_keys, options)
*/
pub fn pick_keys<V>(d: dict<string, V>, selected_keys: list<string>, options: PickKeysOptions = {}) -> dict<string, V> {
if type_of(d) != "dict" {
return {}
}
let drop_nil = options.drop_nil ?? false
return __dict_pick_keys(d, selected_keys, drop_nil)
}
// Check if a store key is stale (older than max_age_seconds).
// Uses store_get/store_set convention: timestamps stored as key + "_ts".
/**
* store_stale.
*
* @effects: [time, store.read]
* @allocation: heap
* @errors: []
* @api_stability: stable
* @example: store_stale(key, max_age_seconds)
*/
pub fn store_stale(key, max_age_seconds) {
let ts = store_get(key + "_ts")
if ts == nil {
return true
}
return timestamp() - ts > max_age_seconds
}
// Refresh a store key's timestamp to now.
/**
* store_refresh.
*
* @effects: [time, store.write]
* @allocation: heap
* @errors: []
* @api_stability: stable
* @example: store_refresh(key)
*/
pub fn store_refresh(key) {
store_set(key + "_ts", timestamp())
}