feat: add skip & take

Author: rokashkovvd

src/skip/index.ts

@@ -0,0 +1,55 @@
+import {
+  Event,
+  Store,
+  Unit,
+  combine,
+  createEvent,
+  createStore,
+  is,
+  sample,
+} from 'effector';
+
+export function skip<T>({
+  clock,
+  count,
+  reset,
+}: {
+  clock?: Unit<T>;
+  count: Store<number> | number;
+  reset?: Unit<T>;
+}): Event<T> {
+  const $count = is.store(count) ? count : createStore(count);
+
+  const $skipped = createStore(0);
+
+  const $canTrigger = combine(
+    [$skipped, $count],
+    ([skipped, count]) => skipped >= count,
+  );
+
+  clock = is.unit(clock) ? clock : createEvent();
+
+  reset = is.unit(reset) ? reset : createEvent();
+
+  const event = sample({
+    clock,
+    source: $skipped,
+    filter: $canTrigger,
+    fn: (_, params) => params,
+  });
+
+  sample({
+    clock,
+    source: $skipped,
+    filter: $canTrigger.map((canTrigger) => !canTrigger),
+    fn: (skipped) => skipped + 1,
+    target: $skipped,
+  });
+
+  sample({
+    clock: [$count, reset],
+    target: $skipped.reinit,
+  });
+
+  return event;
+}

src/take/index.ts

@@ -0,0 +1,52 @@
+import {
+  Event,
+  Store,
+  Unit,
+  combine,
+  createEvent,
+  createStore,
+  is,
+  sample,
+} from 'effector';
+
+export function skip<T>({
+  clock,
+  count,
+  reset,
+}: {
+  clock: Unit<T>;
+  count: Store<number> | number;
+  reset?: Unit<T>;
+}): Event<T> {
+  const $count = is.store(count) ? count : createStore(count);
+
+  const $taken = createStore(0);
+
+  const $canTrigger = combine([$taken, $count], ([taken, count]) => taken >= count);
+
+  clock = is.unit(clock) ? clock : createEvent();
+
+  reset = is.unit(reset) ? reset : createEvent();
+
+  const event = sample({
+    clock,
+    source: $taken,
+    filter: $canTrigger,
+    fn: (_, params) => params,
+  });
+
+  sample({
+    clock,
+    source: $taken,
+    filter: $canTrigger.map((canTrigger) => !canTrigger),
+    fn: (taken) => taken + 1,
+    target: $taken,
+  });
+
+  sample({
+    clock: [$count, reset],
+    target: $taken.reinit,
+  });
+
+  return event;
+}