import { Fragment, useState, type ReactNode } from "react";
import { ChevronRight, MoreHorizontal } from "lucide-react";
import { PopoverItem, PopoverSurface } from "./AnchoredPopover";
import { closeThenAct, useAnchoredPopover } from "./anchoredPopoverHooks";
import { IconButton } from "./IconButton";
import { MenuCheck } from "./MenuCheck";
import { Pressable } from "./Pressable";
import { SURFACE } from "./surfaces";

// A reusable "⋯ more actions" overflow menu: a compact trigger that opens a list of one-shot actions.
// Built on the AnchoredPopover platform (arrows/typeahead/Escape/anchor-flip), same as ViewSwitcher
// and LanguageSwitcher. Use it to keep occasional actions out of a crowded toolbar. The items are
// fire-and-close (`onSelect`) — all but a `check: { kind: "many" }` row, which toggles in place; a
// `disabled` item (e.g. a mutation already in flight) is inert.
//
// The ITEM LIST is split out of the trigger (`MenuItemList`) so the ⋯ menu and the right-click
// context menu (`ContextMenu`) render the same rows from the same item type. That is the whole point
// of the split: a context menu that drifts from the overflow menu beside it is two menus, and the
// user has to learn both.

/** Shared surface paint for every menu built on this file — the ⋯ menu, its submenus, and
 *  `ContextMenu`. One constant so a context menu can never look like a different component. */
export const MENU_SURFACE = `${SURFACE.menu} min-w-52 animate-[popIn_0.16s_ease]`;
// No `disabled:opacity-50` on the row itself: a disabled row may carry a `note`, and opacity on the
// row would dim the one line that explains it. The icon and the label dim instead (`dim`).
const ROW =
  "flex w-full items-center gap-2.5 rounded-lg px-2 py-1.5 text-left text-sm outline-hidden transition";
const dim = (disabled: boolean | undefined) => (disabled ? " opacity-50" : "");

/** The label, and under it the row's note: why it is off, or the state of what it opens. */
function RowLabel({ item }: { item: MenuItemBase }) {
  return (
    <span className="min-w-0 flex-1">
      <span className={`block truncate${dim(item.disabled)}`}>{item.label}</span>
      {item.note && <span className="block text-2xs leading-snug text-muted">{item.note}</span>}
    </span>
  );
}

interface MenuItemBase {
  id: string;
  label: string;
  icon?: ReactNode; // an element (so a caller can swap in a spinning icon while pending)
  disabled?: boolean;
  /** Optional native tooltip (carries a longer hint the label alone can't) — for an ENABLED row. */
  title?: string;
  /** Why a DISABLED row is off, shown as a line under its label. Not a `title`: a disabled button
   *  fires no pointer events (no tooltip) and roving focus skips it, so a reason there reached
   *  nobody. An `aria-disabled` row was tried and reverted (floating-ui skips
   *  it identically, and the mouse got a highlight that then no-opped). Visible text is the one
   *  place a disabled row's reason can be: seen, and read in a screen reader's browse mode.
   *  On an ENABLED row it is the state of what the row opens ("Downloaded" under "Download…"),
   *  for the same reason: a `title` shows to a resting mouse only. */
  note?: string;
  /** Draw a divider above this item. Ignored on the first item — a menu never opens with a rule. */
  separatorBefore?: boolean;
}

interface ActionItem extends MenuItemBase {
  onSelect: () => void;
  /** Destructive action: painted in the danger colour, like the outline-danger buttons. */
  danger?: boolean;
  /** Run INSIDE the click, then close — for a clipboard write, which Safari allows only within the
   *  user's gesture (a task later, as `closeThenAct` runs every other row, it is refused). Only for
   *  an action that opens nothing and moves no focus: that is what the deferral exists for. */
  inGesture?: boolean;
  /** A checkable row, its state shown in the icon slot. `many`: one of a set that can all be on (a
   *  channel's tags) — a menuitemcheckbox that toggles IN PLACE: the menu stays open, so the next
   *  tag is one click away and the check just set is seen. `one`: one choice of several (a priority
   *  step) — a menuitemradio that picks and closes, like any other row. */
  check?: { kind: "many" | "one"; checked: boolean };
  items?: never;
}

interface SubmenuItem extends MenuItemBase {
  /** Non-empty → this row opens a submenu instead of firing. */
  items: readonly ActionMenuItem[];
  onSelect?: never;
}

// A discriminated union rather than "onSelect and items are both optional": the invariant is
// "a row either fires or it opens a submenu, never both and never neither", and this codebase's
// house rule is that such a rule lives in the type, not in a comment above it.
export type ActionMenuItem = ActionItem | SubmenuItem;

const isSubmenu = (it: ActionMenuItem): it is SubmenuItem => Array.isArray(it.items);

/** The rows of a menu: leaf actions, submenus and separators, from one item array. Rendered inside a
 *  `PopoverSurface` (which supplies the list registry) — see `ActionMenu` and `ContextMenu`.
 *  `onClose` closes the ROOT menu, so selecting deep inside a submenu dismisses the whole stack. */
export function MenuItemList({
  items,
  onClose,
}: {
  items: readonly ActionMenuItem[];
  onClose: () => void;
}) {
  return (
    <>
      {items.map((it, i) => (
        <Fragment key={it.id}>
          {it.separatorBefore && i > 0 && (
            <div role="separator" className="my-1 h-px bg-border" aria-hidden="true" />
          )}
          {isSubmenu(it) ? (
            <SubMenu item={it} onClose={onClose} />
          ) : (
            <PopoverItem
              role={
                it.check
                  ? it.check.kind === "many"
                    ? "menuitemcheckbox"
                    : "menuitemradio"
                  : "menuitem"
              }
              checked={it.check?.checked}
              disabled={it.disabled}
              label={it.label}
              title={it.title}
              // Any row may open a dialog (a confirm), so every row closes first — see closeThenAct.
              // A `many` row opens nothing and stays: the focus is still on it, nothing to hand back.
              onSelect={() => {
                if (it.check?.kind === "many") return it.onSelect();
                if (!it.inGesture) return closeThenAct(onClose, it.onSelect);
                it.onSelect();
                onClose();
              }}
              className={`${ROW}${it.danger ? " text-danger" : ""}`}
            >
              {it.check && <MenuCheck kind={it.check.kind} on={it.check.checked} />}
              {!it.check && it.icon && (
                <span
                  className={`shrink-0 ${it.danger ? "text-danger" : "text-muted"}${dim(it.disabled)}`}
                >
                  {it.icon}
                </span>
              )}
              <RowLabel item={it} />
            </PopoverItem>
          )}
        </Fragment>
      ))}
    </>
  );
}

/** One row that opens a nested menu. It is a real `PopoverItem`, so the parent's roving focus and
 *  typeahead reach it; the nested popover anchors to that same button.
 *
 *  Why it nests correctly with no extra wiring: this component renders INSIDE the parent's
 *  `PopoverSurface`, i.e. inside its `<FloatingNode>`, so `useFloatingNodeId()` picks the parent up
 *  as its tree parent. That is what makes Floating UI's outside-press tree-aware — a press inside
 *  the submenu is not "outside" the parent, and Escape closes the topmost layer only. */
function SubMenu({ item, onClose }: { item: SubmenuItem; onClose: () => void }) {
  const [open, setOpen] = useState(false);
  const pop = useAnchoredPopover({
    open,
    onOpenChange: setOpen,
    placement: "right-start",
    offset: 2,
    // A mouse expects the submenu to fall open under the pointer; a finger has no hover and taps.
    hoverAlso: true,
    // Target lists can be long (every playlist you own), so shrink to the viewport instead of
    // running off the bottom at 768px.
    fitHeight: true,
  });
  const { setReference } = pop.refs;
  return (
    <>
      <PopoverItem
        elementRef={setReference}
        {...pop.getReferenceProps()}
        role="menuitem"
        disabled={item.disabled}
        label={item.label}
        title={item.title}
        aria-haspopup="menu"
        aria-expanded={open}
        onKeyDown={(e) => {
          // The native-menu keys. Enter/Space already open it via useClick; ArrowRight is the one
          // the click handler doesn't cover.
          if (e.key === "ArrowRight") {
            e.preventDefault();
            setOpen(true);
          }
        }}
        className={ROW}
      >
        {item.icon && (
          <span className={`shrink-0 text-muted${dim(item.disabled)}`}>{item.icon}</span>
        )}
        <RowLabel item={item} />
        <ChevronRight className="h-4 w-4 shrink-0 text-muted" aria-hidden="true" />
      </PopoverItem>
      <PopoverSurface
        popover={pop}
        ariaLabel={item.label}
        className={`${MENU_SURFACE} overflow-y-auto`}
        style={{ maxHeight: "min(24rem, var(--fit-max-h))" }}
      >
        {/* ArrowLeft steps back out to the parent row — Escape would close the whole stack, and a
            submenu you can only leave by dismissing everything is not a submenu. Focus returns to
            the trigger via the surface's own returnFocus. */}
        <div
          onKeyDown={(e) => {
            if (e.key === "ArrowLeft") {
              e.preventDefault();
              e.stopPropagation();
              setOpen(false);
            }
          }}
        >
          <MenuItemList items={item.items} onClose={onClose} />
        </div>
      </PopoverSurface>
    </>
  );
}

export default function ActionMenu({
  items,
  ariaLabel,
  className,
  trigger,
}: {
  items: readonly ActionMenuItem[];
  /** Accessible name for the trigger (e.g. "Catalog actions"). */
  ariaLabel: string;
  /** Trigger className override; omit for the default glass ⋯ icon button. */
  className?: string;
  /** Custom trigger content; omit for the default ⋯ icon. */
  trigger?: ReactNode;
}) {
  const [open, setOpen] = useState(false);
  // A disabled item (a mutation already in flight) is skipped by roving keyboard nav automatically:
  // PopoverItem renders it as a native `disabled` button, which useListNavigation reads and never
  // focuses. No explicit disabledIndices needed. See ActionMenu.dom.test.tsx for the guard.
  const pop = useAnchoredPopover({ open, onOpenChange: setOpen, placement: "bottom-end" });
  const { setReference } = pop.refs;
  return (
    <>
      {/* A caller-shaped trigger (a labelled pill) is a surface; the default "…" is a glyph. */}
      {className ? (
        <Pressable
          ref={setReference}
          {...pop.getReferenceProps()}
          aria-label={ariaLabel}
          title={ariaLabel}
          className={className}
        >
          {trigger ?? <MoreHorizontal className="h-5 w-5" aria-hidden="true" />}
        </Pressable>
      ) : (
        <IconButton
          variant="glass"
          size="md"
          ref={setReference}
          {...pop.getReferenceProps()}
          label={ariaLabel}
        >
          {trigger ?? <MoreHorizontal aria-hidden="true" />}
        </IconButton>
      )}
      <PopoverSurface popover={pop} ariaLabel={ariaLabel} className={MENU_SURFACE}>
        <MenuItemList items={items} onClose={() => setOpen(false)} />
      </PopoverSurface>
    </>
  );
}