"use client";

/**
 * SmartSelect
 *
 * 옵션 개수에 따라 자동으로 검색 기능을 제공하는 셀렉트 컴포넌트.
 * - 옵션 5개 미만: 기본 Select
 * - 옵션 5개 이상: 검색 + 가상 스크롤 Combobox (대용량 옵션도 빠르게 처리)
 */

import React, { useState, useMemo, useEffect, useRef } from "react";
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select";
import { Popover, PopoverContent, PopoverTrigger } from "@/components/ui/popover";
import { Input } from "@/components/ui/input";
import { Button } from "@/components/ui/button";
import { Check, ChevronsUpDown, Search as SearchIcon } from "lucide-react";
import { cn } from "@/lib/utils";
import { useVirtualizer } from "@tanstack/react-virtual";

const SEARCH_THRESHOLD = 5;
const ITEM_HEIGHT = 36;
const LIST_HEIGHT = 280;

export interface SmartSelectOption {
  code: string;
  label: string;
}

interface SmartSelectProps {
  options: SmartSelectOption[];
  value: string;
  onValueChange: (value: string) => void;
  placeholder?: string;
  disabled?: boolean;
  className?: string;
}

export function SmartSelect({
  options,
  value,
  onValueChange,
  placeholder = "선택",
  disabled = false,
  className,
}: SmartSelectProps) {
  const [open, setOpen] = useState(false);
  const [search, setSearch] = useState("");
  const scrollRef = useRef<HTMLDivElement | null>(null);

  // code가 비어있는 옵션은 자동 제외 (Radix Select value 제약 + key 중복 방지)
  const safeOptions = useMemo(
    () => options.filter((o) => o.code !== null && o.code !== undefined && o.code !== ""),
    [options],
  );

  const selectedLabel = useMemo(
    () => safeOptions.find((o) => o.code === value)?.label,
    [safeOptions, value],
  );

  // 팝오버 닫힐 때 검색어 리셋
  useEffect(() => {
    if (!open) setSearch("");
  }, [open]);

  // 검색어로 옵션 필터 (대소문자 무시)
  const filtered = useMemo(() => {
    const q = search.trim().toLowerCase();
    if (!q) return safeOptions;
    return safeOptions.filter((o) => o.label.toLowerCase().includes(q));
  }, [safeOptions, search]);

  const virtualizer = useVirtualizer({
    count: filtered.length,
    getScrollElement: () => scrollRef.current,
    estimateSize: () => ITEM_HEIGHT,
    overscan: 10,
  });

  // 팝오버 열릴 때 측정 강제 (Portal 렌더 타이밍 대응)
  useEffect(() => {
    if (!open) return;
    const id = requestAnimationFrame(() => virtualizer.measure());
    return () => cancelAnimationFrame(id);
  }, [open, virtualizer, filtered.length]);

  if (safeOptions.length < SEARCH_THRESHOLD) {
    return (
      <Select value={value} onValueChange={onValueChange} disabled={disabled}>
        <SelectTrigger className={cn("h-9", className)}>
          <SelectValue placeholder={placeholder} />
        </SelectTrigger>
        <SelectContent>
          {safeOptions.map((o, idx) => (
            <SelectItem key={`${o.code}-${idx}`} value={o.code}>
              {o.label}
            </SelectItem>
          ))}
        </SelectContent>
      </Select>
    );
  }

  return (
    <Popover open={open} onOpenChange={setOpen}>
      <PopoverTrigger asChild>
        <Button
          variant="outline"
          role="combobox"
          aria-expanded={open}
          disabled={disabled}
          className={cn("h-9 w-full justify-between font-normal", className)}
        >
          <span className="truncate">
            {selectedLabel || <span className="text-muted-foreground">{placeholder}</span>}
          </span>
          <ChevronsUpDown className="ml-2 h-4 w-4 shrink-0 opacity-50" />
        </Button>
      </PopoverTrigger>
      <PopoverContent
        className="p-0"
        style={{ width: "var(--radix-popover-trigger-width)" }}
        align="start"
      >
        <div className="flex items-center border-b px-2">
          <SearchIcon className="h-4 w-4 text-muted-foreground mr-1 shrink-0" />
          <Input
            autoFocus
            placeholder="검색..."
            value={search}
            onChange={(e) => setSearch(e.target.value)}
            className="h-9 border-0 px-1 shadow-none focus-visible:ring-0 focus-visible:ring-offset-0"
          />
        </div>
        {filtered.length === 0 ? (
          <div className="py-6 text-center text-sm text-muted-foreground">검색 결과가 없습니다.</div>
        ) : (
          <div
            ref={scrollRef}
            className="overflow-auto py-1"
            style={{ height: LIST_HEIGHT }}
          >
            <div
              style={{
                height: `${virtualizer.getTotalSize()}px`,
                width: "100%",
                position: "relative",
              }}
            >
              {virtualizer.getVirtualItems().map((vItem) => {
                const o = filtered[vItem.index];
                const isSelected = value === o.code;
                return (
                  <button
                    key={`${o.code}-${vItem.index}`}
                    type="button"
                    onClick={() => {
                      onValueChange(o.code);
                      setOpen(false);
                    }}
                    className={cn(
                      "absolute left-0 top-0 w-full flex items-center px-2 text-sm text-left hover:bg-accent",
                      isSelected && "bg-accent/60",
                    )}
                    style={{
                      height: `${vItem.size}px`,
                      transform: `translateY(${vItem.start}px)`,
                    }}
                  >
                    <Check className={cn("mr-2 h-4 w-4 shrink-0", isSelected ? "opacity-100" : "opacity-0")} />
                    <span className="truncate">{o.label}</span>
                  </button>
                );
              })}
            </div>
          </div>
        )}
      </PopoverContent>
    </Popover>
  );
}