import { useEffect, useMemo, useRef, useState } from "react";
import {
  useFloating,
  autoUpdate,
  offset as offsetMiddleware,
  flip,
  shift,
  size,
  hide,
  useClick,
  useHover,
  useFocus,
  useDismiss,
  useRole,
  useListNavigation,
  useTypeahead,
  useInteractions,
  useFloatingNodeId,
  safePolygon,
  type Placement,
  type UseRoleProps,
} from "@floating-ui/react";
import { useLayer } from "../../lib/layerStack";
import { pageStep, pageTarget, scrollParent } from "../../lib/listPaging";

// The non-component half of the R8 popover platform: the `useAnchoredPopover` engine hook and the
// `closeThenAct` row helper. The surfaces it drives (PopoverSurface / PopoverItem) and the platform's
// design notes live in AnchoredPopover.tsx; the split keeps that file components-only (Fast Refresh).

// Internal to the platform; call sites pass the string literal via `mode`, they don't name the type.
type PopoverMode = "menu" | "listbox" | "hover" | "dialog" | "combobox";

export interface AnchoredPopoverOptions {
  open: boolean;
  onOpenChange: (open: boolean, event?: Event) => void;
  /** "menu"/"listbox"/"dialog" open on click; "hover" opens on hover+focus (tooltips, hover cards);
   *  "combobox" is a typeable input + listbox where focus stays in the field (use via <Combobox>). */
  mode?: PopoverMode;
  placement?: Placement;
  /** Gap between trigger and panel, px. Default 4. */
  offset?: number;
  /** Hover mode only: open/close intent delays, ms. */
  hoverDelay?: number | { open?: number; close?: number };
  /** ARIA role for the panel; defaults to "tooltip" in hover mode, else "menu". */
  role?: UseRoleProps["role"];
  /** Cap the panel height to the available space (adds the `size` middleware). Off by default so a
   *  caller's own max-height class wins; turn on for long lists that should shrink to fit. */
  fitHeight?: boolean;
  /** Type-to-focus a matching item by label (menu/listbox only). Default on; turn OFF for menus that
   *  contain a free-text input, where character keys belong to the text field. */
  typeahead?: boolean;
  /** This menu hosts a free-text input (an inline "create" field). Turns off BOTH typeahead AND
   *  focus-item-on-hover, so neither typed characters nor a pointer passing over a list item steals
   *  focus/keystrokes from the field. Set it instead of `typeahead:false` for such menus. */
  hostsInput?: boolean;
  /** Menu mode only: ALSO open on mouse hover, keeping the click/tap toggle. The submenu idiom —
   *  a mouse expects a submenu to fall open under the pointer, a finger has no hover at all and
   *  must tap. `mouseOnly` is forced on so a tap's synthetic mouseenter can't open the panel a
   *  hair before the click handler toggles it shut again. */
  hoverAlso?: boolean;
  /** Hover mode only: a MOUSE affordance and nothing else — no focus-open, no touch. A media card's
   *  preview (ui/MediaPreview): a keyboard walk down a grid would otherwise pop a panel at every stop,
   *  and a tap is the card's play. */
  pointerOnly?: boolean;
  /** Index of the item that is currently CHOSEN, for a single-choice menu/listbox. Opening then
   *  lands the roving focus on it instead of the first item — the behaviour a "pick one of these
   *  modes" menu needs. Leave unset for action menus and multi-select toggle lists. */
  selectedIndex?: number | null;
  /** Close when a scroll container under the panel scrolls. Off by default, because a panel anchored
   *  to a real trigger element simply MOVES with it. Turn it on when the anchor is a fixed point
   *  rather than an element — a right-click menu, which otherwise stays parked over whatever row
   *  scrolls under it while its actions still target the row you opened it on (E10 review round 1).
   *  This is also what a native context menu does. */
  dismissOnScroll?: boolean;
}

export function useAnchoredPopover(opts: AnchoredPopoverOptions) {
  const mode = opts.mode ?? "menu";
  const isHover = mode === "hover";
  const isCombobox = mode === "combobox";
  // Roving-keyboard list surfaces: a menu of actions or a listbox of options. A "dialog" popover holds
  // arbitrary focusable content (its own Tab order), and "hover" is a passive tooltip — neither roves.
  const isNav = mode === "menu" || mode === "listbox";
  // Surfaces that host a navigable item list (registry + list-navigation): the roving menu/listbox AND
  // the virtual-nav combobox. The combobox navigates WITHOUT moving DOM focus (see below), so it is kept
  // out of `isNav` (which also gates the focus trap + typeahead + roving tabindex) and folded in here.
  const roves = isNav || isCombobox;
  // null when not inside a <FloatingTree> — the hook still works, just without nested-layer awareness.
  const nodeId = useFloatingNodeId();

  // Item registry for list navigation + typeahead, populated by <PopoverItem> via useListItem.
  const elementsRef = useRef<Array<HTMLElement | null>>([]);
  const labelsRef = useRef<Array<string | null>>([]);
  const [activeIndex, setActiveIndex] = useState<number | null>(null);
  // Pointer-hover highlight, kept SEPARATE from floating-ui's activeIndex on purpose: useListNavigation
  // syncs DOM focus to activeIndex, so setting activeIndex on hover would blur a menu's free-text input
  // (the create-tag field) mid-typing. hoverIndex drives only the VISUAL highlight; DOM focus never
  // follows it. The highlighted row = hoverIndex ?? activeIndex, so there is exactly one highlight that
  // tracks the pointer when hovering and the keyboard otherwise.
  const [hoverIndex, setHoverIndex] = useState<number | null>(null);

  const { refs, floatingStyles, context, middlewareData, isPositioned } = useFloating({
    nodeId,
    open: opts.open,
    onOpenChange: opts.onOpenChange,
    placement: opts.placement ?? "bottom-start",
    whileElementsMounted: autoUpdate,
    middleware: [
      offsetMiddleware(opts.offset ?? 4),
      flip({ padding: 8 }),
      shift({ padding: 8 }),
      ...(opts.fitHeight
        ? [
            size({
              padding: 8,
              apply({ availableHeight, elements }) {
                // Cap the positioned element, AND publish the available space as a custom property so
                // the INNER styled/scroll wrapper (PopoverSurface renders `className` on a child, not on
                // the floating element) can cap itself too — e.g. `maxHeight: min(28rem, var(--fit-max-h))`
                // keeps a caller's design cap while still shrinking to fit at high zoom / short viewports.
                // Capping only the outer element would leave the inner overflow-y-auto box at its fixed
                // height, spilling its top off-screen (the whole point of fitHeight).
                elements.floating.style.maxHeight = `${availableHeight}px`;
                elements.floating.style.setProperty("--fit-max-h", `${availableHeight}px`);
              },
            }),
          ]
        : []),
      // A combobox panel matches the field's width (with a sane floor for a very narrow rail); its inner
      // scroll box owns the height cap. `rects.reference` is the POSITION reference — the whole chips+input
      // field box (the caller mounts it via setPositionReference), not the bare input.
      ...(isCombobox
        ? [
            size({
              padding: 8,
              apply({ rects, elements }) {
                elements.floating.style.width = `${Math.max(rects.reference.width, 192)}px`;
              },
            }),
          ]
        : []),
      hide({ padding: 8 }),
    ],
  });

  // A stale active item would highlight (and steal the next open's initial focus) the second time a
  // menu opens; clear it whenever the surface closes.
  useEffect(() => {
    if (!opts.open) {
      // eslint-disable-next-line react-hooks/set-state-in-effect -- both indices are also floating-ui's list-navigation state (passed to useListNavigation below), so they cannot be derived from `open` without lying to the library about where the cursor is. Clearing on close is what stops a stale row stealing the next open's initial focus.
      setActiveIndex(null);
      setHoverIndex(null);
    }
  }, [opts.open]);

  // A combobox opens from the field's own focus/typing (wired by <Combobox>), never a click-to-toggle —
  // a click on the input must place the caret, not close the just-opened list.
  const click = useClick(context, { enabled: !isHover && !isCombobox });
  const hover = useHover(context, {
    enabled: isHover || !!opts.hoverAlso,
    move: false,
    // A hover-card is a pointer affordance either way; a hover-ALSO menu must ignore touch, or the
    // synthetic mouseenter a tap emits would race the click toggle (open, then immediately shut).
    mouseOnly: !isHover || !!opts.pointerOnly,
    // A submenu wants a shorter intent delay than a hover card: the pointer is already inside a
    // menu, so the "did they mean it" question is mostly answered.
    delay: opts.hoverDelay ?? (isHover ? { open: 120, close: 140 } : { open: 90, close: 120 }),
    handleClose: safePolygon(),
  });
  const focus = useFocus(context, { enabled: isHover && !opts.pointerOnly });
  // Escape for EVERY mode (hover included) is dispatched through the shared `layerStack` below, so it
  // is strictly topmost-only across popovers, Modals and players — so turn floating-ui's own Escape
  // off entirely. (Leaving it on for hover made an open tooltip's document-level handler either
  // stopPropagation the Escape away from a Modal/player underneath, or double-close both.) Outside-
  // press stays with floating-ui (tree-aware).
  const dismiss = useDismiss(context, {
    escapeKey: false,
    ancestorScroll: opts.dismissOnScroll ?? false,
  });
  // `role:"combobox"` makes Floating UI wire the whole typeable-combobox ARIA tree: the reference input
  // → role=combobox + aria-expanded/controls/autocomplete + aria-activedescendant (from the virtual nav),
  // the surface → role=listbox, the items → role=option + their option ids. (`combobox` maps to the
  // `listbox` aria-role internally.) So <Combobox> sets NO aria-* by hand.
  const role = useRole(context, {
    role: opts.role ?? (isHover ? "tooltip" : isCombobox ? "combobox" : "menu"),
  });
  const listNav = useListNavigation(context, {
    enabled: roves,
    // Virtual navigation for a combobox: DOM focus stays on the text input while ↑/↓ move an
    // `aria-activedescendant` pointer over the options (the handler rides on getReferenceProps → the
    // input). A menu/listbox uses real roving focus instead.
    virtual: isCombobox,
    listRef: elementsRef,
    activeIndex,
    // Keyboard (and pointer, when floating-ui owns it) navigation takes the visual highlight back from
    // a stale pointer-hover position.
    onNavigate: (i) => {
      setActiveIndex(i);
      setHoverIndex(null);
    },
    selectedIndex: opts.selectedIndex ?? null,
    // Disabled items are skipped automatically: with no `disabledIndices`, useListNavigation reads
    // each item's DOM `disabled`/`aria-disabled` (PopoverItem always renders native `disabled`), so a
    // pending/inert item is never a roving target. (Verified against @floating-ui/react 0.27
    // `isListIndexDisabled`.) No explicit index list needed.
    loop: true,
    // Focus the first item on open for BOTH click and keyboard (the default 'auto' skips pointer-opens,
    // which strands focus on the menu container — arrows then can't enter the roving list at all). A
    // combobox opens with NO active item — the caret is in the input, and the first ↓ lands on the first
    // option; auto-highlighting item 0 on open would fight the typed query.
    focusItemOnOpen: isCombobox ? false : true,
    // A menu that hosts a free-text input, and every combobox, must NOT pull focus onto a list item when
    // the pointer merely passes over it (the library default) — that blurs the input mid-typing and
    // mis-routes the next Enter to the hovered item. The visual hover highlight is driven off hoverIndex
    // instead (see PopoverItem), so the pointer still highlights without stealing the caret.
    focusItemOnHover: isCombobox ? false : !opts.hostsInput,
  });
  const typeahead = useTypeahead(context, {
    enabled: isNav && (opts.typeahead ?? true) && !opts.hostsInput,
    listRef: labelsRef,
    activeIndex,
    onMatch: (i) => {
      setActiveIndex(i);
      setHoverIndex(null);
    },
  });

  // PageUp/PageDown: a page of rows at a time (lib/listPaging, shared with the palette). floating-ui's
  // list navigation knows only the arrows and Home/End, and the arrows alone crawl through the sidebar's
  // channel filter or a Plex studio list. On BOTH elements: a combobox's keys arrive on its input, a
  // menu's on the focused row inside the surface. Last in the list, so floating-ui's own keydown has
  // already switched to keyboard modality — which is what makes it scroll the new row into view. A
  // nested menu's surface bubbles through its parent's in the React tree; the inner one handles the
  // key first and marks it, so the outer one stands down.
  const onPageKey = (e: React.KeyboardEvent) => {
    if ((e.key !== "PageDown" && e.key !== "PageUp") || e.defaultPrevented) return;
    const rows = elementsRef.current;
    const live = rows.filter((el): el is HTMLElement => el != null);
    // No mounted rows — a closed surface, a hover card, a dialog — and the key keeps its own meaning.
    if (!live.length) return;
    e.preventDefault();
    const step = pageStep(scrollParent(live[0]!), live);
    const to = pageTarget(
      activeIndex ?? 0,
      e.key === "PageDown" ? step : -step,
      rows.length,
      (i) => !!rows[i] && !rows[i]!.hasAttribute("disabled"),
    );
    if (to === null) return;
    setActiveIndex(to);
    setHoverIndex(null);
  };
  const pageKeyRef = useRef(onPageKey);
  pageKeyRef.current = onPageKey;
  const paging = useMemo(() => {
    const onKeyDown = (e: React.KeyboardEvent) => pageKeyRef.current(e);
    return { reference: { onKeyDown }, floating: { onKeyDown } };
  }, []);

  const interactions = useInteractions([
    click,
    hover,
    focus,
    dismiss,
    role,
    listNav,
    typeahead,
    paging,
  ]);

  // `hide()` flips this true once the trigger is scrolled out of its clipping scroller; the surface is
  // then painted invisible (PopoverSurface) but stays open so it can reappear on scroll-back.
  const referenceHidden = middlewareData.hide?.referenceHidden ?? false;

  // Register the open popover as a dismissable layer so Escape is topmost-only and a player/modal
  // underneath defers to it. Hover popovers register too (an open tooltip/hover-card should take
  // Escape before the surface beneath it — and, when it is a player's own overlay card, keep the
  // player alive). An invisible (referenceHidden) surface is NOT a layer: it must not silently eat
  // an Escape the user aimed at whatever is actually on screen. A hover surface is a PASSIVE layer:
  // it does not own the keyboard, so the page's own keys keep working under a resting pointer.
  useLayer(opts.open && !referenceHidden, () => opts.onOpenChange(false), { passive: isHover });

  return {
    nodeId,
    mode,
    isNav,
    isCombobox,
    roves,
    open: opts.open,
    selectedIndex: opts.selectedIndex ?? null,
    refs,
    floatingStyles,
    context,
    isPositioned,
    referenceHidden,
    elementsRef,
    labelsRef,
    activeIndex,
    highlightIndex: hoverIndex ?? activeIndex,
    setHoverIndex,
    ...interactions,
  };
}

/** A menu row whose action opens a dialog or moves the focus: close the menu FIRST and act once it
 *  has handed the focus back. floating-ui returns the focus to the trigger from a microtask queued as
 *  the menu unmounts, so an action run in the same batch had its focus taken back by it: measured in
 *  Chrome (E11 S2), a confirm dialog opened from the rail's menu landed its focus on Cancel and lost it
 *  7 ms later to the row BEHIND its scrim, where Enter activated the row. A fresh task runs after that
 *  microtask — and a dialog opened there captures the trigger, not a dying menu item, as the element
 *  to restore the focus to. Every such row goes through here (`ActionMenu`, "Manage views…"). */
export function closeThenAct(close: () => void, act: () => void): void {
  close();
  setTimeout(act, 0);
}