import {
  closestCenter, DndContext, KeyboardSensor, PointerSensor, useSensor, useSensors,
  type DragEndEvent,
} from '@dnd-kit/core';
import {
  SortableContext, sortableKeyboardCoordinates, useSortable, verticalListSortingStrategy,
} from '@dnd-kit/sortable';
import {CSS} from '@dnd-kit/utilities';
import type {SectionItem} from '@o2o/shared';
import {GripVertical, Layers, Lock, Shapes} from 'lucide-react';
import {Switch} from '@/components/ui/switch';
import {cn} from '@/lib/utils';
import {useBuilderStore} from '@/stores/builder';
import {resolveVariant} from './canvas/registry';

interface SectionListPanelProps {
  onAfterSelect?: () => void;
}

interface SortableSectionProps extends SectionListPanelProps {
  section: SectionItem;
  index: number;
}

function SortableSection({section, index, onAfterSelect}: SortableSectionProps) {
  const industry = useBuilderStore((s) => s.industry);
  const setRightTab = useBuilderStore((s) => s.setRightTab);
  const isSelected = useBuilderStore((s) => s.selectedSectionId === section.id);
  const selectSection = useBuilderStore((s) => s.selectSection);
  const toggleSection = useBuilderStore((s) => s.toggleSection);
  const variant = resolveVariant(section, industry);
  const {attributes, listeners, setNodeRef, transform, transition, isDragging} = useSortable({
    id: section.id,
  });

  const select = () => {
    selectSection(section.id);
    setRightTab('content');
    onAfterSelect?.();
    if (!section.isEnabled) return;

    // 좁은 화면에서는 onAfterSelect가 캔버스 탭을 먼저 연다. 다음 페인트가 끝난 뒤
    // 실제 섹션으로 이동해야 display:none 상태의 위치를 잘못 읽지 않는다.
    requestAnimationFrame(() => {
      requestAnimationFrame(() => {
        document
          .getElementById(`canvas-section-${section.id}`)
          ?.scrollIntoView({behavior: 'smooth', block: 'start'});
      });
    });
  };

  return (
    <li
      ref={setNodeRef}
      style={{transform: CSS.Transform.toString(transform), transition}}
      className={cn('relative', isDragging && 'z-10')}
    >
      <div
        role="button"
        tabIndex={0}
        onClick={select}
        onKeyDown={(event) => {
          if (event.key === 'Enter' || event.key === ' ') {
            event.preventDefault();
            select();
          }
        }}
        className={cn(
          'group flex cursor-pointer items-center justify-between rounded-md border p-2 text-xs transition-[background-color,border-color,opacity,box-shadow]',
          isDragging && 'cursor-grabbing opacity-70 shadow-lg',
          isSelected
            ? 'border-primary bg-primary/8 font-semibold text-foreground'
            : section.isEnabled
              ? 'border-border bg-card hover:bg-muted/60'
              : 'border-border bg-muted/40 text-muted-foreground',
        )}
      >
        <div className="flex min-w-0 items-center gap-2 pr-1">
          <button
            type="button"
            title={`${section.name} 드래그하여 순서 변경`}
            aria-label={`${section.name} 드래그하여 순서 변경`}
            onClick={(event) => event.stopPropagation()}
            className="-mr-1 touch-none cursor-grab rounded p-0.5 text-muted-foreground hover:bg-accent hover:text-foreground active:cursor-grabbing"
            {...attributes}
            {...listeners}
          >
            <GripVertical className="size-3.5" />
          </button>
          <span className="w-3 text-right font-mono text-[10px] text-muted-foreground">
            {index + 1}
          </span>
          <div className="min-w-0 truncate">
            <span className={cn('block truncate', !section.isEnabled && 'line-through')}>
              {section.name}
            </span>

            {variant && (
              <span
                role="button"
                tabIndex={0}
                title={`${variant.name} — 눌러서 레이아웃 바꾸기`}
                onClick={(event) => {
                  event.stopPropagation();
                  selectSection(section.id);
                  setRightTab('design');
                  onAfterSelect?.();
                }}
                onKeyDown={(event) => {
                  if (event.key !== 'Enter' && event.key !== ' ') return;
                  event.preventDefault();
                  event.stopPropagation();
                  selectSection(section.id);
                  setRightTab('design');
                  onAfterSelect?.();
                }}
                className="flex cursor-pointer items-center gap-0.5 truncate text-[9px] font-normal text-muted-foreground hover:text-foreground"
              >
                <Shapes className="size-2.5 shrink-0" />
                <span className="truncate">{variant.name}</span>
              </span>
            )}

            {section.isLocked && (
              <span className="flex items-center gap-0.5 text-[9px] font-normal text-muted-foreground">
                <Lock className="size-2.5" /> 필수 고정
              </span>
            )}
          </div>
        </div>

        <div className="flex shrink-0 items-center gap-1" onClick={(event) => event.stopPropagation()} role="presentation">
          {section.isLocked ? (
            <span title="SEO·필수 마크업이 달린 섹션이라 끌 수 없습니다." className="p-1 text-muted-foreground">
              <Lock className="size-4" />
            </span>
          ) : (
            <Switch checked={section.isEnabled} onCheckedChange={() => toggleSection(section.id)} aria-label={`${section.name} 섹션 표시 여부`} />
          )}
        </div>
      </div>
    </li>
  );
}

export function SectionListPanel({onAfterSelect}: SectionListPanelProps) {
  const sections = useBuilderStore((s) => s.sections);
  const reorderSection = useBuilderStore((s) => s.reorderSection);
  const sensors = useSensors(
    useSensor(PointerSensor, {activationConstraint: {distance: 6}}),
    useSensor(KeyboardSensor, {coordinateGetter: sortableKeyboardCoordinates}),
  );
  const activeCount = sections.filter((section) => section.isEnabled).length;

  const handleDragEnd = ({active, over}: DragEndEvent) => {
    if (!over || active.id === over.id) return;
    const fromIndex = sections.findIndex((section) => section.id === active.id);
    const toIndex = sections.findIndex((section) => section.id === over.id);
    reorderSection(fromIndex, toIndex);
  };

  return (
    <div className="flex h-full w-full shrink-0 select-none flex-col overflow-hidden border-r border-border bg-card lg:w-[250px]">
      <div className="flex items-center justify-between border-b border-border bg-muted/50 p-3.5">
        <div className="flex items-center gap-1.5">
          <Layers className="size-4" />
          <span className="text-xs font-bold">섹션 관리</span>
        </div>
        <span className="rounded border border-border bg-card px-2 py-0.5 font-mono text-[11px] text-muted-foreground">
          {activeCount} / {sections.length} 활성
        </span>
      </div>

      <p className="border-b border-border bg-muted/30 px-3.5 py-2 text-[11px] text-muted-foreground">
        핸들을 드래그해 순서를 바꾸고, 레이아웃 이름을 누르면 모양을 바꿉니다.
      </p>

      <DndContext sensors={sensors} collisionDetection={closestCenter} onDragEnd={handleDragEnd}>
        <SortableContext items={sections.map((section) => section.id)} strategy={verticalListSortingStrategy}>
          <ul className="flex-1 space-y-1.5 overflow-y-auto p-2">
            {sections.map((section, index) => (
              <SortableSection
                key={section.id}
                section={section}
                index={index}
                onAfterSelect={onAfterSelect}
              />
            ))}
          </ul>
        </SortableContext>
      </DndContext>

      <p className="border-t border-border bg-muted/30 p-2.5 text-center text-[10px] text-muted-foreground">
        * 자물쇠 항목은 검색·AI 노출에 필요한 마크업이 달려 있어 고정입니다.
      </p>
    </div>
  );
}