"use client";

import { useCallback, useEffect, useMemo, useState } from "react";

import { useBuilderSelectedScreen, useBuilderState } from "@/lib/admin/builder/context";
import { renderScreen } from "@/lib/funnel/screenRenderer";
import { mergeScreenWithOverrides } from "@/lib/admin/builder/variants";

export function BuilderPreview() {
  const selectedScreen = useBuilderSelectedScreen();
  const builderState = useBuilderState();
  const [selectedIds, setSelectedIds] = useState<string[]>([]);
  const [previewVariantIndex, setPreviewVariantIndex] = useState<number | null>(null);

  useEffect(() => {
    if (!selectedScreen) {
      setSelectedIds([]);
      setPreviewVariantIndex(null);
      return;
    }

    setSelectedIds((prev) => {
      if (prev.length === 0) {
        return prev;
      }
      return [];
    });
  }, [selectedScreen]);

  const handleSelectionChange = useCallback((ids: string[]) => {
    setSelectedIds((prev) => {
      if (prev.length === ids.length && prev.every((value, index) => value === ids[index])) {
        return prev;
      }
      return ids;
    });
  }, []);


  const variants = useMemo(() => selectedScreen?.variants ?? [], [selectedScreen]);

  useEffect(() => {
    setPreviewVariantIndex(null);
  }, [selectedScreen]);

  const previewScreen = useMemo(() => {
    if (!selectedScreen) {
      return null;
    }

    if (previewVariantIndex === null) {
      return selectedScreen;
    }

    const variant = variants[previewVariantIndex];
    if (!variant) {
      return selectedScreen;
    }

    return mergeScreenWithOverrides(selectedScreen, variant.overrides ?? {});
  }, [previewVariantIndex, selectedScreen, variants]);

  const renderScreenPreview = useCallback(() => {
    if (!previewScreen) return null;

    try {
      // Use the same renderer as FunnelRuntime for 1:1 accuracy
      return renderScreen({
        screen: previewScreen,
        selectedOptionIds: selectedIds,
        onSelectionChange: handleSelectionChange,
        onContinue: () => {}, // Mock continue handler for preview
        canGoBack: true, // Show back button in preview
        onBack: () => {}, // Mock back handler for preview  
        screenProgress: { current: 1, total: 10 }, // Mock progress for preview
        defaultTexts: builderState.defaultTexts, // Use real defaultTexts from builder
      });
    } catch (error) {
      console.error('Error rendering preview:', error);
      return (
        <div className="flex h-32 items-center justify-center rounded-lg border border-dashed border-border text-sm text-muted-foreground">
          Ошибка при отображении превью: {error instanceof Error ? error.message : 'Неизвестная ошибка'}
        </div>
      );
    }
  }, [previewScreen, selectedIds, handleSelectionChange, builderState.defaultTexts]);

  const preview = useMemo(() => {
    if (!previewScreen) {
      return (
        <div className="flex items-center justify-center mx-auto" style={{ height: '600px', width: '320px' }}>
          <div className="flex items-center justify-center rounded-lg border border-dashed border-border bg-muted/30 text-sm text-muted-foreground w-full h-full">
            Выберите экран для предпросмотра
          </div>
        </div>
      );
    }

    // Увеличим высоту чтобы кнопка поместилась полностью
    const PREVIEW_WIDTH = 320;
    const PREVIEW_HEIGHT = 750; // Увеличено с ~694px до 750px для BottomActionButton

    return (
      <div className="mx-auto space-y-3" style={{ width: PREVIEW_WIDTH }}>
        {variants.length > 0 && (
          <div className="rounded-lg border border-border/60 bg-background/90 p-2 text-xs text-muted-foreground">
            <div className="flex items-center justify-between gap-2">
              <span className="font-semibold uppercase tracking-wide text-muted-foreground/80">
                Превью варианта
              </span>
              <select
                className="rounded-md border border-border bg-background px-2 py-1 text-xs"
                value={previewVariantIndex === null ? "base" : String(previewVariantIndex)}
                onChange={(event) =>
                  setPreviewVariantIndex(event.target.value === "base" ? null : Number(event.target.value))
                }
              >
                <option value="base">Основной экран</option>
                {variants.map((variant, index) => (
                  <option key={index} value={index}>
                    Вариант {index + 1}
                  </option>
                ))}
              </select>
            </div>
            {previewVariantIndex !== null && (
              <div className="mt-2 rounded border border-blue-200 bg-blue-50 px-2 py-1 text-[11px] text-blue-700 dark:border-blue-800 dark:bg-blue-900/20 dark:text-blue-200">
                ⚠️ Превью принудительно показывает вариант. В реальной воронке он показывается только при выполнении условий.
              </div>
            )}
          </div>
        )}

        {/* Mobile Frame - Simple Border */}
        <div
          className="relative bg-white rounded-2xl border-4 border-gray-300 shadow-lg mx-auto"
          style={{
            height: PREVIEW_HEIGHT,
            width: PREVIEW_WIDTH,
            overflow: 'hidden', // Hide anything that goes outside
            contain: 'layout style paint', // CSS containment
            isolation: 'isolate', // Create new stacking context
            transform: 'translateZ(0)' // Force new layer
          }}
        >
          {/* Screen Content with scroll */}
          <div className="w-full h-full overflow-y-auto overflow-x-hidden [&::-webkit-scrollbar]:hidden [-ms-overflow-style:none] [scrollbar-width:none]">
            {renderScreenPreview()}
          </div>
        </div>
      </div>
    );
  }, [previewScreen, renderScreenPreview, variants, previewVariantIndex]);

  return preview;
}