From 151a393fb5b3a7636af769bedb942b0545dedc5b Mon Sep 17 00:00:00 2001
From: Sebastian Malton <sebastian@malton.name>
Date: Tue, 23 May 2023 10:12:18 -0400
Subject: [PATCH] feat: Improve UX of namespace select filter

- Add better support for thousands of namespaces

- Add support for mouse only multi-selection

Signed-off-by: Sebastian Malton <sebastian@malton.name>
---
 .../namespace-select-filter-model.tsx         | 152 +++++------
 .../namespaces/namespace-select-filter.scss   | 129 +++++-----
 .../namespaces/namespace-select-filter.tsx    | 238 +++++++++++++-----
 .../renderer/components/namespaces/store.ts   |  14 ++
 .../window/event-listener.injectable.ts       |   4 +-
 .../utilities/src/type-narrowing.ts           |   3 +-
 6 files changed, 338 insertions(+), 202 deletions(-)

diff --git a/packages/core/src/renderer/components/namespaces/namespace-select-filter-model/namespace-select-filter-model.tsx b/packages/core/src/renderer/components/namespaces/namespace-select-filter-model/namespace-select-filter-model.tsx
index c0ad194dfb..8a3cac363c 100644
--- a/packages/core/src/renderer/components/namespaces/namespace-select-filter-model/namespace-select-filter-model.tsx
+++ b/packages/core/src/renderer/components/namespaces/namespace-select-filter-model/namespace-select-filter-model.tsx
@@ -2,16 +2,14 @@
  * Copyright (c) OpenLens Authors. All rights reserved.
  * Licensed under MIT License. See LICENSE in root directory for more information.
  */
-import React from "react";
-import type { IComputedValue } from "mobx";
+import type React from "react";
+import type { IComputedValue, IObservableValue } from "mobx";
 import { observable, action, computed, comparer } from "mobx";
 import type { NamespaceStore } from "../store";
-import type { ActionMeta, MultiValue } from "react-select";
-import { Icon } from "@k8slens/icon";
-import type { SelectOption } from "../../select";
 import { observableCrate } from "@k8slens/utilities";
 import type { IsMultiSelectionKey } from "./is-selection-key.injectable";
 import type { ClusterContext } from "../../../cluster-frame-context/cluster-frame-context";
+import GlobToRegExp from "glob-to-regexp";
 
 interface Dependencies {
   context: ClusterContext;
@@ -22,22 +20,31 @@ interface Dependencies {
 export const selectAllNamespaces = Symbol("all-namespaces-selected");
 
 export type SelectAllNamespaces = typeof selectAllNamespaces;
-export type NamespaceSelectFilterOption = SelectOption<string | SelectAllNamespaces>;
+export interface NamespaceSelectFilterOption {
+  value: string | SelectAllNamespaces;
+  label: string;
+  id: string | SelectAllNamespaces;
+}
 
 export interface NamespaceSelectFilterModel {
-  readonly options: IComputedValue<readonly NamespaceSelectFilterOption[]>;
+  readonly options: IComputedValue<NamespaceSelectFilterOption[]>;
+  readonly filteredOptions: IComputedValue<NamespaceSelectFilterOption[]>;
+  readonly selectedOptions: IComputedValue<NamespaceSelectFilterOption[]>;
   readonly menu: {
     open: () => void;
     close: () => void;
+    toggle: () => void;
     readonly isOpen: IComputedValue<boolean>;
+    readonly hasSelectedAll: IComputedValue<boolean>;
+    onKeyDown: React.KeyboardEventHandler;
+    onKeyUp: React.KeyboardEventHandler;
   };
-  onChange: (newValue: MultiValue<NamespaceSelectFilterOption>, actionMeta: ActionMeta<NamespaceSelectFilterOption>) => void;
-  onClick: () => void;
-  onKeyDown: React.KeyboardEventHandler;
-  onKeyUp: React.KeyboardEventHandler;
+  onClick: (options: NamespaceSelectFilterOption) => void;
+  deselect: (namespace: string) => void;
+  select: (namespace: string) => void;
+  readonly filterText: IObservableValue<string>;
   reset: () => void;
   isOptionSelected: (option: NamespaceSelectFilterOption) => boolean;
-  formatOptionLabel: (option: NamespaceSelectFilterOption) => JSX.Element;
 }
 
 enum SelectMenuState {
@@ -45,6 +52,18 @@ enum SelectMenuState {
   Open = "open",
 }
 
+const filterBasedOnText = (filterText: string) => {
+  const regexp = new RegExp(GlobToRegExp(filterText, { extended: true, flags: "gi" }));
+
+  return (options: NamespaceSelectFilterOption) => {
+    if (options.value === selectAllNamespaces) {
+      return true;
+    }
+
+    return Boolean(options.value.match(regexp));
+  };
+};
+
 export function namespaceSelectFilterModelFor(dependencies: Dependencies): NamespaceSelectFilterModel {
   const { isMultiSelectionKey, namespaceStore, context } = dependencies;
 
@@ -58,6 +77,7 @@ export function namespaceSelectFilterModelFor(dependencies: Dependencies): Names
       didToggle = false;
     },
   }]);
+  const filterText = observable.box("");
   const selectedNames = computed(() => new Set(context.contextNamespaces), {
     equals: comparer.structural,
   });
@@ -74,7 +94,7 @@ export function namespaceSelectFilterModelFor(dependencies: Dependencies): Names
       ? 1
       : -1;
   };
-  const options = computed((): readonly NamespaceSelectFilterOption[] => [
+  const options = computed((): NamespaceSelectFilterOption[] => [
     {
       value: selectAllNamespaces,
       label: "All Namespaces",
@@ -89,6 +109,8 @@ export function namespaceSelectFilterModelFor(dependencies: Dependencies): Names
         id: namespace,
       })),
   ]);
+  const filteredOptions = computed(() => options.get().filter(filterBasedOnText(filterText.get())));
+  const selectedOptions = computed(() => options.get().filter(model.isOptionSelected));
   const menuIsOpen = computed(() => menuState.get() === SelectMenuState.Open);
   const isOptionSelected: NamespaceSelectFilterModel["isOptionSelected"] = (option) => {
     if (option.value === selectAllNamespaces) {
@@ -100,82 +122,66 @@ export function namespaceSelectFilterModelFor(dependencies: Dependencies): Names
 
   const model: NamespaceSelectFilterModel = {
     options,
+    filteredOptions,
+    selectedOptions,
     menu: {
       close: action(() => {
         menuState.set(SelectMenuState.Close);
+        filterText.set("");
       }),
       open: action(() => {
         menuState.set(SelectMenuState.Open);
       }),
+      toggle: () => {
+        if (menuIsOpen.get()) {
+          model.menu.close();
+        } else {
+          model.menu.open();
+        }
+      },
       isOpen: menuIsOpen,
-    },
-    onChange: (_, action) => {
-      switch (action.action) {
-        case "clear":
-          namespaceStore.selectAll();
-          break;
-        case "deselect-option":
-        case "select-option":
-          if (action.option) {
-            didToggle = true;
-
-            if (action.option.value === selectAllNamespaces) {
-              namespaceStore.selectAll();
-            } else if (isMultiSelection) {
-              namespaceStore.toggleSingle(action.option.value);
-            } else {
-              namespaceStore.selectSingle(action.option.value);
-            }
-          }
-          break;
-      }
-    },
-    onClick: () => {
-      if (!menuIsOpen.get()) {
-        model.menu.open();
-      } else if (!isMultiSelection) {
-        model.menu.close();
-      }
-    },
-    onKeyDown: (event) => {
-      if (isMultiSelectionKey(event)) {
-        isMultiSelection = true;
-      }
-    },
-    onKeyUp: (event) => {
-      if (isMultiSelectionKey(event)) {
-        isMultiSelection = false;
-
-        if (didToggle) {
+      hasSelectedAll: computed(() => namespaceStore.areAllSelectedImplicitly),
+      onKeyDown: (event) => {
+        if (isMultiSelectionKey(event)) {
+          isMultiSelection = true;
+        } else if (event.key === "Escape") {
           model.menu.close();
         }
-      }
+      },
+      onKeyUp: (event) => {
+        if (isMultiSelectionKey(event)) {
+          isMultiSelection = false;
+
+          if (didToggle) {
+            model.menu.close();
+          }
+        }
+      },
     },
+    onClick: action((option) => {
+      if (option.value === selectAllNamespaces) {
+        namespaceStore.selectAll();
+        model.menu.close();
+      } else if (isMultiSelection) {
+        didToggle = true;
+        namespaceStore.toggleSingle(option.value);
+      } else {
+        namespaceStore.selectSingle(option.value);
+        model.menu.close();
+      }
+    }),
+    deselect: action((namespace) => {
+      namespaceStore.deselectSingle(namespace);
+    }),
+    select: action((namespace) => {
+      namespaceStore.includeSingle(namespace);
+    }),
+    filterText,
     reset: action(() => {
       isMultiSelection = false;
       model.menu.close();
     }),
     isOptionSelected,
-    formatOptionLabel: (option) => {
-      if (option.value === selectAllNamespaces) {
-        return <>All Namespaces</>;
-      }
-
-      return (
-        <div className="flex gaps align-center">
-          <Icon small material="layers" />
-          <span>{option.value}</span>
-          {isOptionSelected(option) && (
-            <Icon
-              small
-              material="check"
-              className="box right"
-              data-testid={`namespace-select-filter-option-${option.value}-selected`}
-            />
-          )}
-        </div>
-      );
-    },
   };
 
   return model;
diff --git a/packages/core/src/renderer/components/namespaces/namespace-select-filter.scss b/packages/core/src/renderer/components/namespaces/namespace-select-filter.scss
index f227976b46..2eead588e1 100644
--- a/packages/core/src/renderer/components/namespaces/namespace-select-filter.scss
+++ b/packages/core/src/renderer/components/namespaces/namespace-select-filter.scss
@@ -4,75 +4,86 @@
   }
 }
 
-.NamespaceSelectFilterParent {
-  max-width: 300px;
-}
+.namespace-select-filter {
+  width: 300px;
+  position: relative;
 
-.NamespaceSelectFilter {
-  --gradientColor: var(--select-menu-bgc);
+  .list-container {
+    position: absolute;
+    top: 30px;
+    z-index: 10;
+    background: var(--mainBackground);
+    border-radius: var(--border-radius);
 
-  .Select {
-    &__placeholder {
-      white-space: nowrap;
-      overflow: scroll hidden!important;
-      text-overflow: unset!important;
-      margin-left: -8px;
-      padding-left: 8px;
-      margin-right: -8px;
-      padding-right: 8px;
-      line-height: 1.1;
+    li.option {
+      cursor: pointer;
+      padding: calc(var(--padding) / 2) var(--padding);
+      list-style: none;
 
-      &::-webkit-scrollbar {
-        display: none;
+      &:hover {
+        color: white;
+      }
+
+      .selected-icon:hover {
+        color: var(--buttonAccentBackground);
+      }
+
+      .add-selection-icon:hover {
+        color: var(--colorSuccess);
       }
     }
+  }
 
-    &__value-container {
+  .menu {
+    width: 300px;
+    border-radius: var(--border-radius);
+    border: 1px solid;
+    border-color: var(--halfGray);
+    padding: calc(var(--padding) / 2) var(--padding);
+    display: flex;
+
+    .non-icon {
+      width: -webkit-fill-available;
       position: relative;
 
-      &::before, &::after {
-        content: ' ';
-        position: absolute;
-        z-index: 20;
-        display: block;
-        width: 8px;
-        height: var(--font-size);
-      }
-
-      &::before {
-        left: 0;
-        background: linear-gradient(to right, var(--gradientColor) 0px, transparent);
-      }
-
-      &::after {
-        right: 0;
-        background: linear-gradient(to left, var(--gradientColor) 0px, transparent);
-      }
-    }
-  }
-}
-
-.NamespaceSelectFilterMenu {
-  right: 0;
-
-  .Select {
-    &__menu-list {
-      max-width: 400px;
-    }
-
-    &__option {
-      white-space: normal;
-      word-break: break-all;
-      padding: 4px 8px;
-      border-radius: 3px;
-
-      &--is-selected:not(&--is-focused) {
+      input {
+        width: 100%;
         background: transparent;
       }
+
+      label {
+        white-space: nowrap;
+        overflow: scroll hidden!important;
+        text-overflow: unset!important;
+        margin-left: -16px;
+        padding-left: 8px;
+        padding-right: 8px;
+        width: calc(100% + 4px);
+        position: absolute;
+        left: 9px;
+
+        &::-webkit-scrollbar {
+          display: none;
+        }
+      }
+
+      .gradient {
+        position: absolute;
+        width: 10px;
+        top: 0;
+        height: 20px;
+        z-index: 21;
+
+        &.left {
+          left: -7px;
+          background: linear-gradient(to right, var(--contentColor) 0%, rgba(255, 255, 255, 0) 100%);
+        }
+
+        &.right {
+          right: 2px;
+          background: linear-gradient(to left, var(--contentColor) 0%, rgba(255, 255, 255, 0) 100%);
+        }
+      }
     }
   }
-
-  .Icon {
-    margin-right: $margin * 0.5;
-  }
 }
diff --git a/packages/core/src/renderer/components/namespaces/namespace-select-filter.tsx b/packages/core/src/renderer/components/namespaces/namespace-select-filter.tsx
index de1c2a8cd6..b22ba43114 100644
--- a/packages/core/src/renderer/components/namespaces/namespace-select-filter.tsx
+++ b/packages/core/src/renderer/components/namespaces/namespace-select-filter.tsx
@@ -5,16 +5,17 @@
 
 import "./namespace-select-filter.scss";
 
-import React from "react";
+import React, { useEffect, useRef } from "react";
 import { observer } from "mobx-react";
-import type { PlaceholderProps } from "react-select";
-import { components } from "react-select";
-import type { NamespaceStore } from "./store";
-import { Select } from "../select";
 import { withInjectables } from "@ogre-tools/injectable-react";
-import type { NamespaceSelectFilterModel, NamespaceSelectFilterOption, SelectAllNamespaces } from "./namespace-select-filter-model/namespace-select-filter-model";
+import type { NamespaceSelectFilterModel, NamespaceSelectFilterOption } from "./namespace-select-filter-model/namespace-select-filter-model";
+import { selectAllNamespaces } from "./namespace-select-filter-model/namespace-select-filter-model";
 import namespaceSelectFilterModelInjectable from "./namespace-select-filter-model/namespace-select-filter-model.injectable";
-import namespaceStoreInjectable from "./store.injectable";
+import { VariableSizeList } from "react-window";
+import { Icon } from "../icon";
+import { cssNames, prevDefault } from "@k8slens/utilities";
+import { addWindowEventListener } from "../../window/event-listener.injectable";
+import { TooltipPosition } from "@k8slens/tooltip";
 
 interface NamespaceSelectFilterProps {
   id: string;
@@ -24,33 +25,171 @@ interface Dependencies {
   model: NamespaceSelectFilterModel;
 }
 
-const NonInjectedNamespaceSelectFilter = observer(({ model, id }: Dependencies & NamespaceSelectFilterProps) => (
-  <div
-    onKeyUp={model.onKeyUp}
-    onKeyDown={model.onKeyDown}
-    onClick={model.onClick}
-    className="NamespaceSelectFilterParent"
-    data-testid="namespace-select-filter"
-  >
-    <Select<string | SelectAllNamespaces, NamespaceSelectFilterOption, true>
+const Gradient = ({ type }: { type: "left" | "right" }) => (
+  <div className={cssNames("gradient", type)} />
+);
+
+const NamespaceSelectFilterMenu = observer(({ id, model }: Dependencies & NamespaceSelectFilterProps) => {
+  const selectedOptions = model.selectedOptions.get();
+  const prefix = selectedOptions.length === 1
+    ? "Namespace"
+    : "Namespaces";
+
+  return (
+    <div className="menu">
+      <div className="non-icon">
+        <input
+          type="text"
+          id={`${id}-filter`}
+          value={model.filterText.get()}
+          onChange={(event) => model.filterText.set(event.target.value)}
+          onClick={model.menu.open}
+        />
+        <Gradient type="left" />
+        <label htmlFor={`${id}-filter`}>
+          {(
+            model.filterText.get() !== ""
+              ? model.filterText.get()
+              : (
+                model.menu.hasSelectedAll.get()
+                  ? "All namespaces"
+                  : `${prefix}: ${selectedOptions.map(option => option.value).join(", ")}`
+              )
+          )}
+        </label>
+        <Gradient type="right" />
+      </div>
+      <Icon
+        className="expand-icon"
+        material={model.menu.isOpen.get() ? "expand_less" : "expand_more"}
+        onClick={model.menu.toggle}
+      />
+    </div>
+  );
+});
+
+const rowHeight = 29;
+
+const NonInjectedNamespaceSelectFilter = observer(({ model, id }: Dependencies & NamespaceSelectFilterProps) => {
+  const divRef = useRef<HTMLDivElement | null>(null);
+
+  useEffect(() => {
+    return addWindowEventListener("click", (event) => {
+      if (!model.menu.isOpen.get()) {
+        return;
+      }
+
+      if (divRef.current?.contains(event.target as Node)) {
+        return;
+      }
+
+      model.menu.close();
+    });
+  }, []);
+
+  return (
+    <div
+      onKeyUp={model.menu.onKeyUp}
+      onKeyDown={model.menu.onKeyDown}
+      className="namespace-select-filter"
+      data-testid="namespace-select-filter"
       id={id}
-      isMulti={true}
-      isClearable={false}
-      menuIsOpen={model.menu.isOpen.get()}
-      components={{ Placeholder }}
-      closeMenuOnSelect={false}
-      controlShouldRenderValue={false}
-      onChange={model.onChange}
-      onBlur={model.reset}
-      formatOptionLabel={model.formatOptionLabel}
-      options={model.options.get()}
-      className="NamespaceSelect NamespaceSelectFilter"
-      menuClass="NamespaceSelectFilterMenu"
-      isOptionSelected={model.isOptionSelected}
-      hideSelectedOptions={false}
+      ref={divRef}
+      tabIndex={1}
+    >
+      <NamespaceSelectFilterMenu model={model} id={id} />
+      {model.menu.isOpen.get() && (
+        <div
+          className="list-container"
+        >
+          <VariableSizeList
+            className="list"
+            width={300}
+            height={Math.min(model.filteredOptions.get().length * rowHeight, 300)}
+            itemSize={() => rowHeight}
+            itemCount={model.filteredOptions.get().length}
+            itemData={{
+              items: model.filteredOptions.get(),
+              model,
+            }}
+            overscanCount={5}
+            innerElementType={"ul"}
+          >
+            {NamespaceSelectFilterRow}
+          </VariableSizeList>
+        </div>
+      )}
+    </div>
+  );
+});
+
+interface FilterRowProps {
+  index: number;
+  style: React.CSSProperties;
+  data: {
+    model: NamespaceSelectFilterModel;
+    items: NamespaceSelectFilterOption[];
+  };
+}
+
+const renderSingleOptionIcons = (namespace: string, option: NamespaceSelectFilterOption, model: NamespaceSelectFilterModel) => {
+  if (model.isOptionSelected(option)) {
+    return (
+      <Icon
+        small
+        material="check"
+        className="selected-icon box right"
+        data-testid={`namespace-select-filter-option-${namespace}-selected`}
+        tooltip={`Remove ${namespace} from selection`}
+        onClick={prevDefault(() => model.deselect(namespace))}
+      />
+    );
+  }
+
+  return (
+    <Icon
+      small
+      material="add_box"
+      className="add-selection-icon box right"
+      data-testid={`namespace-select-filter-option-${namespace}-add-to-selection`}
+      tooltip={`Add ${namespace} to selection`}
+      onClick={prevDefault(() => model.select(namespace))}
     />
-  </div>
-));
+  );
+};
+
+const NamespaceSelectFilterRow = observer(({ index, style, data: { model, items }}: FilterRowProps) => {
+  const option = items[index];
+
+  return (
+    <li
+      style={style}
+      className={cssNames("option", "flex gaps align-center", {
+        "all-namespaces": option.value === selectAllNamespaces,
+        "single-namespace": option.value !== selectAllNamespaces,
+      })}
+      onClick={() => model.onClick(option)}
+    >
+      {option.value === selectAllNamespaces
+        ? <span className="data">All Namespaces</span>
+        : (
+          <>
+            <Icon
+              small
+              material="layers"
+              onClick={prevDefault(() => model.onClick(option))}
+              tooltip={{
+                preferredPositions: TooltipPosition.LEFT,
+                children: `Select only ${option.value}`,
+              }}
+            />
+            <span className="data">{option.value}</span>
+            {renderSingleOptionIcons(option.value, option, model)}
+          </>
+        )}
+    </li>
+  );
+});
 
 export const NamespaceSelectFilter = withInjectables<Dependencies, NamespaceSelectFilterProps>(NonInjectedNamespaceSelectFilter, {
   getProps: (di, props) => ({
@@ -58,38 +197,3 @@ export const NamespaceSelectFilter = withInjectables<Dependencies, NamespaceSele
     ...props,
   }),
 });
-
-export interface CustomPlaceholderProps extends PlaceholderProps<NamespaceSelectFilterOption, true> {}
-
-interface PlaceholderDependencies {
-  namespaceStore: NamespaceStore;
-}
-
-const NonInjectedPlaceholder = observer(({ namespaceStore, ...props }: CustomPlaceholderProps & PlaceholderDependencies) => {
-  const getPlaceholder = () => {
-    const namespaces = namespaceStore.contextNamespaces;
-
-    if (namespaceStore.areAllSelectedImplicitly || namespaces.length === 0) {
-      return "All namespaces";
-    }
-
-    const prefix = namespaces.length === 1
-      ? "Namespace"
-      : "Namespaces";
-
-    return `${prefix}: ${namespaces.join(", ")}`;
-  };
-
-  return (
-    <components.Placeholder {...props}>
-      {getPlaceholder()}
-    </components.Placeholder>
-  );
-});
-
-const Placeholder = withInjectables<PlaceholderDependencies, CustomPlaceholderProps>( NonInjectedPlaceholder, {
-  getProps: (di, props) => ({
-    namespaceStore: di.inject(namespaceStoreInjectable),
-    ...props,
-  }),
-});
diff --git a/packages/core/src/renderer/components/namespaces/store.ts b/packages/core/src/renderer/components/namespaces/store.ts
index 1bbb4446dd..cce4a2e4c1 100644
--- a/packages/core/src/renderer/components/namespaces/store.ts
+++ b/packages/core/src/renderer/components/namespaces/store.ts
@@ -171,6 +171,20 @@ export class NamespaceStore extends KubeObjectStore<Namespace, NamespaceApi> {
     this.dependencies.storage.set([...nextState]);
   }
 
+  deselectSingle(namespace: string) {
+    const nextState = new Set(this.contextNamespaces);
+
+    nextState.delete(namespace);
+    this.dependencies.storage.set([...nextState]);
+  }
+
+  includeSingle(namespace: string) {
+    const nextState = new Set(this.contextNamespaces);
+
+    nextState.add(namespace);
+    this.dependencies.storage.set([...nextState]);
+  }
+
   /**
    * Makes the given namespace the sole selected namespace
    */
diff --git a/packages/core/src/renderer/window/event-listener.injectable.ts b/packages/core/src/renderer/window/event-listener.injectable.ts
index 631fec116e..4be1022424 100644
--- a/packages/core/src/renderer/window/event-listener.injectable.ts
+++ b/packages/core/src/renderer/window/event-listener.injectable.ts
@@ -9,10 +9,10 @@ import type { Disposer } from "@k8slens/utilities";
 export type AddWindowEventListener = typeof addWindowEventListener;
 export type WindowEventListener<K extends keyof WindowEventMap> = (this: Window, ev: WindowEventMap[K]) => any;
 
-function addWindowEventListener<K extends keyof WindowEventMap>(type: K, listener: WindowEventListener<K>, options?: boolean | AddEventListenerOptions): Disposer {
+export function addWindowEventListener<K extends keyof WindowEventMap>(type: K, listener: WindowEventListener<K>, options?: boolean | AddEventListenerOptions): Disposer {
   window.addEventListener(type, listener, options);
 
-  return () => void window.removeEventListener(type, listener);
+  return () => void window.removeEventListener(type, listener, options);
 }
 
 const windowAddEventListenerInjectable = getInjectable({
diff --git a/packages/utility-features/utilities/src/type-narrowing.ts b/packages/utility-features/utilities/src/type-narrowing.ts
index 68d5265237..8c545608df 100644
--- a/packages/utility-features/utilities/src/type-narrowing.ts
+++ b/packages/utility-features/utilities/src/type-narrowing.ts
@@ -123,7 +123,8 @@ export function isDefined<T>(val: T | undefined | null): val is T {
   return val != null;
 }
 
-export function isFunction(val: unknown): val is (...args: unknown[]) => unknown {
+// @ts-expect-error 2677
+export function isFunction<T>(val: T): val is Extract<T, Function>  extends never ? ((...args: unknown[]) => unknown) : Extract<T, Function> {
   return typeof val === "function";
 }