import { useMemo, useState } from 'react';
import { createPortal } from 'react-dom';
import { Check, Star } from 'lucide-react';
import { favouritesFirst, groupByFamily, rotateToSelected } from 'theme';
import * as Dropdown from '@/components/ui/dropdown-menu';
import { useTheme, useThemeKeys } from '@/components/ui/ThemeProvider';
import { useThemeFavorites } from '@/state/useThemeFavorites';

const {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuItem,
  DropdownMenuLabel,
  DropdownMenuSeparator,
  DropdownMenuTrigger,
} = Dropdown;

/**
 * Themes, out of the avatar menu and into the header.
 *
 * They were buried under an avatar next to "Sign out", which is where a preference goes when nobody has
 * decided it matters. With fourteen of them it is a thing you use, so it gets its own control.
 *
 * ── The overlay ──
 *
 * `ctrl+shift+space` opens a list in the middle of the screen; `j`/`k` move through it and `l` applies the
 * focused theme to the app BEHIND it. That is the whole idea, and it is why this is a portal over a
 * translucent backdrop rather than a modal dialog: you are meant to watch the application change while
 * you browse, so as little of it as possible should be covered.
 *
 * Ported from the owner's `vimazing`, keys and all.
 */
export const ThemeSwitcher = () => {
  const { theme, themeId, setTheme, themes } = useTheme();
  const { favorites, isFavorite, toggle } = useThemeFavorites();
  // Declared before the key hook, which needs the toggle: `f` in the list and `ctrl+shift+f` from anywhere.
  const { open, setOpen, focused, setFocused } = useThemeKeys({ onToggleFavorite: toggle });
  const [onlyFavorites, setOnlyFavorites] = useState(false);

  /*
    One ordering, used by both lists.

    ROTATED to the theme you are wearing rather than sorted: with 200+ installed, the list's only structure
    is the registry order — families sit together in it — and lifting the selected theme out of its family
    would answer "which am I on" by destroying "what is next to it". A rotation answers both. See
    `theme/rotate.ts`.

    Then favourites first, which is a second rotation-preserving pass rather than a filter: each half keeps
    the order it was given, so the theme you are wearing still leads.
  */
  const ordered = useMemo(() => {
    const rotated = rotateToSelected(themes, themeId);
    const listed = onlyFavorites ? rotated.filter((t) => favorites.has(t.id)) : rotated;
    return favouritesFirst(listed, favorites);
    // `favorites` is a fresh Set each render; its CONTENTS are what matter, so key on those.
  }, [themes, themeId, onlyFavorites, [...favorites].sort().join(',')]);

  const families = useMemo(() => groupByFamily(ordered), [ordered]);

  return (
    <>
      <DropdownMenu>
        <DropdownMenuTrigger asChild>
          <button
            title={`Theme: ${theme.name}  ·  ctrl+shift+←/→ cycle · ctrl+shift+space browse · ctrl+shift+f ${
              isFavorite(themeId) ? 'unstar' : 'star'
            }`}
            aria-label={`Theme: ${theme.name}`}
            // Named rather than a palette glyph: with 227 themes the one you are wearing is worth
            // reading at a glance, and an icon cannot say which that is. Same pill as JobsIndicator so
            // the cluster stays one shape.
            className="flex h-8 cursor-pointer items-center rounded-full bg-black/25 px-2.5 text-xs font-semibold transition-colors hover:bg-black/35"
            style={{ color: 'var(--header-fg)' }}
          >
            {theme.name}
            {/* A star on the pill, so "is this one of mine" is answerable without opening anything. Only
                when true — a hollow star on every theme would be chrome that says nothing 200 times. */}
            {isFavorite(themeId) && <Star className="ml-1.5 h-3 w-3 fill-current opacity-80" />}
          </button>
        </DropdownMenuTrigger>
        {/*
          The CONTENT does not scroll — the list inside it does.

          It used to carry `overflow-y-auto` itself, which scrolled the instruction line away with the
          themes. Two hundred entries meant the one line telling you the keyboard shortcuts existed was
          visible for the first half-second and then gone for good, which is the same as not having written
          it. Header and footer are now siblings of a scroll box rather than passengers in one.
        */}
        <DropdownMenuContent align="end" className="z-50 flex max-h-[70vh] w-64 flex-col overflow-hidden p-0">
          <div className="shrink-0 border-b border-border px-2 py-1.5">
            <DropdownMenuLabel className="px-0 py-0 text-xs font-normal leading-relaxed text-muted-foreground">
              <span className="block">ctrl+shift+←/→ cycle · ctrl+shift+space browse</span>
              <span className="block">ctrl+? for every shortcut</span>
            </DropdownMenuLabel>
            <button
              type="button"
              onClick={(ev) => {
                // The dropdown closes on any item activation, and this is a filter rather than a choice.
                ev.preventDefault();
                ev.stopPropagation();
                setOnlyFavorites((was) => !was);
              }}
              className={`mt-1 inline-flex cursor-pointer items-center gap-1.5 rounded px-1.5 py-0.5 text-xs font-medium transition-colors ${
                onlyFavorites ? 'bg-primary/15 text-primary' : 'text-muted-foreground hover:text-foreground'
              }`}
            >
              <Star className={`h-3.5 w-3.5 ${onlyFavorites ? 'fill-current' : ''}`} />
              {onlyFavorites ? `Favourites only (${favorites.size})` : `Favourites (${favorites.size})`}
            </button>
          </div>

          <div className="min-h-0 flex-1 overflow-y-auto p-1">
            {ordered.length === 0 ? (
              <p className="px-2 py-6 text-center text-xs text-muted-foreground">
                No favourites yet — star one with the button on its row.
              </p>
            ) : (
              families.map(([family, entries]) => (
                <div key={family}>
                  {entries.map((t) => (
                    <DropdownMenuItem key={t.id} onClick={() => setTheme(t.id)} className="cursor-pointer pr-1">
                      <Check className={`mr-2 h-4 w-4 shrink-0 ${t.id === themeId ? 'opacity-100' : 'opacity-0'}`} />
                      <span className="min-w-0 flex-1 truncate">{t.name}</span>
                      {/* A sibling of the row's action, never nested inside it — starring is not choosing. */}
                      <button
                        type="button"
                        aria-label={isFavorite(t.id) ? `Unstar ${t.name}` : `Star ${t.name}`}
                        title={isFavorite(t.id) ? 'Remove from favourites' : 'Add to favourites'}
                        onClick={(ev) => {
                          ev.preventDefault();
                          ev.stopPropagation();
                          toggle(t.id);
                        }}
                        className="ml-1 shrink-0 rounded p-1 text-muted-foreground hover:text-primary"
                      >
                        <Star className={`h-3.5 w-3.5 ${isFavorite(t.id) ? 'fill-current text-primary' : ''}`} />
                      </button>
                    </DropdownMenuItem>
                  ))}
                </div>
              ))
            )}
          </div>
        </DropdownMenuContent>
      </DropdownMenu>

      {open &&
        createPortal(
          <div
            className="fixed inset-0 z-[900] flex items-center justify-center"
            // Deliberately light: the point is to see the app change behind it.
            style={{ backgroundColor: 'color-mix(in srgb, var(--background) 55%, transparent)' }}
            onClick={() => setOpen(false)}
          >
            <div
              className="rounded-2xl border px-10 py-8 shadow-2xl"
              style={{
                backgroundColor: 'var(--popover)',
                borderColor: 'var(--border)',
                color: 'var(--popover-foreground)',
              }}
              onClick={(ev) => ev.stopPropagation()}
            >
              {/* The SAME `ordered` list as the dropdown — rotated to what you are wearing, favourites
                  first. Both lists agreeing is the point: "the one below the one I have on" has to mean the
                  same thing in both, or the browse teaches you an order the menu then contradicts. */}
              <ul className="flex max-h-[70vh] flex-col gap-1 overflow-y-auto">
                {ordered.map((t) => {
                  const isFocused = t.id === focused;
                  return (
                    <li key={t.id}>
                      <button
                        onMouseEnter={() => setFocused(t.id)}
                        onClick={() => {
                          setTheme(t.id);
                          setOpen(false);
                        }}
                        className={`flex w-full items-center gap-2 rounded-md px-4 py-1 text-left transition-all cursor-pointer ${
                          isFocused ? 'text-2xl font-extrabold' : 'text-lg opacity-60 hover:opacity-100'
                        }`}
                      >
                        <span className="min-w-0 flex-1 truncate">{t.name}</span>
                        {t.id === themeId && <span className="shrink-0 text-xs opacity-70">active</span>}
                        {/*
                          A span, not a button: this sits inside the row's own <button>, and a button inside
                          a button is invalid HTML that browsers resolve by dropping one of them. The click
                          handler and the role are set explicitly instead, and `f` does the same thing from
                          the keyboard.
                        */}
                        <span
                          role="button"
                          tabIndex={-1}
                          aria-label={isFavorite(t.id) ? `Unstar ${t.name}` : `Star ${t.name}`}
                          title={isFavorite(t.id) ? 'Remove from favourites (f)' : 'Add to favourites (f)'}
                          onClick={(ev) => {
                            // Or the row's own onClick applies the theme and closes the overlay, which is
                            // the opposite of what starring is for.
                            ev.preventDefault();
                            ev.stopPropagation();
                            toggle(t.id);
                          }}
                          className="shrink-0 rounded p-1 opacity-70 hover:opacity-100"
                        >
                          <Star className={`h-4 w-4 ${isFavorite(t.id) ? 'fill-current' : ''}`} />
                        </span>
                      </button>
                    </li>
                  );
                })}
              </ul>
              {/* Always visible: it sits outside the scroll box above, for the same reason the dropdown's
                  header does. */}
              <p className="mt-6 text-center text-xs opacity-60">
                j/k or ↑/↓ move · l or → preview · f star · h or ← reset · enter keep · esc cancel
              </p>
            </div>
          </div>,
          document.body,
        )}
    </>
  );
};