import { useSearchParams } from 'react-router';
import { Check, Eye, Loader2, Monitor, Pencil, Smartphone, Tablet } from 'lucide-react';
import { Button } from '@/components/ui/button';
import { DEFAULT_SECTION, isSectionKey, sectionFor, sectionOpen, type SectionKey } from './sections';
import { AdministrationPanel } from './AdministrationPanel';
import { MediaPanel } from './MediaPanel';
import { GalleriesPanel } from './sections/GalleriesPanel';
import { LayoutPanel } from './sections/LayoutPanel';
import { PagesPanel } from './sections/PagesPanel';
import { PageBuilderPanel } from './sections/PageBuilderPanel';
import { PublishButton } from './PublishButton';
import { SaveTargetProvider, useSaveButton } from './SaveTarget';
import { DEVICES, ViewModeProvider, useViewMode, type DeviceName, type Mode } from './ViewMode';
import { MessagesPanel } from './MessagesPanel';
import { PlannedSection } from './PlannedSection';
import { useReady } from './useReady';

/**
 * The right column: whichever section the nav has selected.
 *
 * It reads `?section=` from the URL rather than being handed it — the two panels are siblings in a
 * workspace and neither owns the other.
 *
 * ── There used to be a `?config=1` ──
 *
 * The connection form was an overlay reached from a link in this header, because it was not one of the
 * sections. Now it IS one — Administration — so the overlay is gone and so is the link. A second route
 * to the same screen is a second thing to keep correct, and the two disagreed the moment a section was
 * selected underneath a form that covered it.
 *
 * ── Not ready means Administration, whatever the URL says ──
 *
 * The gate is `useReady`, shared with the nav so the two cannot disagree. Enforced HERE and not only
 * there, because the nav can only decline to offer a link — `?section=gallery` typed into the address
 * bar, or a bookmark from before the connection was forgotten, arrives without going through it. A
 * nav that hides a door is a courtesy; this is the lock.
 */

/**
 * Which component renders which section.
 *
 * A map rather than a conditional on `built`. The version of this that read
 * `built ? <MessagesPanel/> : <Planned/>` was correct only while exactly one section existed — the
 * second one to be finished would have rendered Messages under its own name, which is the kind of bug
 * that looks like a data problem for an hour. A key with no entry here falls through to Planned, so
 * marking a section `built` in sections.ts without writing its panel fails visibly rather than
 * silently showing somebody else's.
 */
const PANELS: Partial<Record<SectionKey, () => React.JSX.Element>> = {
  layout: LayoutPanel,
  pages: PagesPanel,
  galleries: GalleriesPanel,
  messages: MessagesPanel,
  administration: AdministrationPanel,
  media: MediaPanel,
};

/**
 * The one Save, driven by whichever section is open.
 *
 * Renders nothing at all when the section offers none — Media, Administration and Messages have
 * nothing to save, and a permanently dead button is worse than no button: it invites a press and
 * teaches that pressing does nothing.
 */
const SaveButton = () => {
  const target = useSaveButton();
  if (!target) return null;

  return (
    <Button
      size="sm"
      variant="outline"
      className="h-6 gap-1.5 px-2 text-xs"
      onClick={() => void target.save()}
      // Dead until there is something to write. The whole value of one Save is that its state answers
      // "have I saved?" — a button that looks the same either way answers nothing.
      disabled={!target.dirty || target.busy}
      title={target.dirty ? 'Save your changes' : 'Nothing to save'}
    >
      {target.busy ? <Loader2 className="size-3 animate-spin" /> : <Check className="size-3" />}
      {target.busy ? 'Saving…' : 'Save'}
    </Button>
  );
};

/**
 * Editing, or just looking.
 *
 * Two buttons rather than one that toggles, so the current state is readable without knowing what the
 * label means. A single button saying "View" has to be interpreted — is that what it is, or what it
 * would become? — and that question is asked every time.
 */
const ModeToggle = () => {
  const { previewable, mode, setMode } = useViewMode();
  if (!previewable) return null;

  const options: { value: Mode; label: string; Icon: typeof Pencil }[] = [
    { value: 'edit', label: 'Edit', Icon: Pencil },
    { value: 'view', label: 'View', Icon: Eye },
  ];

  return (
    <div className="flex items-center gap-0.5 rounded-md border border-border p-0.5">
      {options.map(({ value, label, Icon }) => (
        <Button
          key={value}
          size="sm"
          variant={mode === value ? 'secondary' : 'ghost'}
          className="h-5 gap-1 px-2 text-xs"
          onClick={() => setMode(value)}
        >
          <Icon className="size-3" />
          {label}
        </Button>
      ))}
    </div>
  );
};

/** The width the preview is rendered at. See DEVICES for why these three and not others. */
const DeviceToggle = () => {
  const { previewable, device, setDevice } = useViewMode();
  if (!previewable) return null;

  const options: { value: DeviceName; Icon: typeof Monitor }[] = [
    { value: 'desktop', Icon: Monitor },
    { value: 'tablet', Icon: Tablet },
    { value: 'mobile', Icon: Smartphone },
  ];

  return (
    <div className="flex items-center gap-0.5 rounded-md border border-border p-0.5">
      {options.map(({ value, Icon }) => (
        <Button
          key={value}
          size="sm"
          variant={device === value ? 'secondary' : 'ghost'}
          className="h-5 gap-1 px-2 text-xs"
          onClick={() => setDevice(value)}
          // The width is in the tooltip rather than the label. It is the thing somebody occasionally
          // needs and never needs three of at once, and three widths in a row is a row of numbers.
          title={`${DEVICES[value].label} — ${DEVICES[value].width}px`}
        >
          <Icon className="size-3" />
          <span className="sr-only">{DEVICES[value].label}</span>
        </Button>
      ))}
    </div>
  );
};

export const DetailPanel = () => {
  const [params] = useSearchParams();
  const raw = params.get('section');
  /*
    A page selected inside Pages opens the BUILDER, not the list with a row lit up. By SLUG, so the URL
    says which page rather than which row — see pageParam in usePages.

    The nav says the same thing — Pages is a section and the pages are rows under it — so the detail
    panel follows it. `?page=` is what distinguishes the two, which keeps both addressable.
  */
  const selectedPage = params.get('page');
  const selected: SectionKey = isSectionKey(raw) ? raw : DEFAULT_SECTION;

  const { ready, rootSet, loading } = useReady();

  if (loading) {
    return <div className="flex size-full items-center justify-center p-6 text-sm text-muted-foreground">Loading…</div>;
  }

  /*
    Not ready, so Administration regardless of what the URL asked for. The header then NAMES it, which
    is the part the old overlay could not do: the form used to appear under whichever row happened to
    be highlighted, so it read as that section being broken rather than as one step not done yet.
  */
  /*
    A section that cannot be opened sends you to Administration, because that is where every requirement
    is satisfied. Asked per section rather than by one flag: Media is reachable the moment a root
    location exists, long before fofos is connected.
  */
  const wanted = sectionFor(selected);
  const current = sectionOpen(wanted, { ready, rootSet }) ? wanted : sectionFor('administration');

  const Panel =
    current.key === 'pages' && selectedPage ? PageBuilderPanel : current.built ? PANELS[current.key] : undefined;

  return (
    <div className="flex size-full flex-col overflow-hidden">
      {/*
        The site's own actions, pinned above whatever the section is showing.

        OUTSIDE the scroll area on purpose. Every panel scrolls its own contents, so anything drawn
        inside one leaves the screen as soon as somebody reads to the bottom — and Publish is what you
        reach for AFTER reading to the bottom. It sits here instead, as a sibling of the scrolling
        region rather than the first thing inside it.

        Not in the workspace's chrome header either, where it lived for an afternoon. That header is
        shared furniture drawn the same way by every panel in the app; these two buttons belong to this
        plugin and to the site it administers.
      */}
      <SaveTargetProvider>
        <ViewModeProvider>
          {/*
            Three groups: how you are looking at it, at what width, and what to do with it.

            The middle one is centred against the BAR rather than against what is beside it — the two
            outer groups change width as sections come and go, and a middle that drifted with them
            would never be in the same place twice.
          */}
          <div className="flex shrink-0 items-center gap-2 border-b border-border px-4 py-2">
            <div className="flex flex-1 justify-start">
              <ModeToggle />
            </div>

            <div className="flex justify-center">
              <DeviceToggle />
            </div>

            <div className="flex flex-1 items-center justify-end gap-2">
              {/* Left of Publish, and in that order for a reason: save what you wrote, then make it
                  public. A row that put them the other way round would read as the sequence backwards. */}
              <SaveButton />
              <PublishButton />
            </div>
          </div>

          <div className="min-h-0 flex-1">{Panel ? <Panel /> : <PlannedSection section={current} />}</div>
        </ViewModeProvider>
      </SaveTargetProvider>
    </div>
  );
};