ERP-node/frontend/components/dashboard/widgets/CalculatorWidget.tsx

'use client';

/**
 * 계산기 위젯 컴포넌트
 * - 기본 사칙연산 지원
 * - 실시간 계산
 * - 대시보드 위젯으로 사용 가능
 */

import React, { useState } from 'react';
import { Button } from '@/components/ui/button';

interface CalculatorWidgetProps {
  className?: string;
}

export default function CalculatorWidget({ className = '' }: CalculatorWidgetProps) {
  const [display, setDisplay] = useState<string>('0');
  const [previousValue, setPreviousValue] = useState<number | null>(null);
  const [operation, setOperation] = useState<string | null>(null);
  const [waitingForOperand, setWaitingForOperand] = useState<boolean>(false);

  // 숫자 입력 처리
  const handleNumber = (num: string) => {
    if (waitingForOperand) {
      setDisplay(num);
      setWaitingForOperand(false);
    } else {
      setDisplay(display === '0' ? num : display + num);
    }
  };

  // 소수점 입력
  const handleDecimal = () => {
    if (waitingForOperand) {
      setDisplay('0.');
      setWaitingForOperand(false);
    } else if (display.indexOf('.') === -1) {
      setDisplay(display + '.');
    }
  };

  // 연산자 입력
  const handleOperation = (nextOperation: string) => {
    const inputValue = parseFloat(display);

    if (previousValue === null) {
      setPreviousValue(inputValue);
    } else if (operation) {
      const currentValue = previousValue || 0;
      const newValue = calculate(currentValue, inputValue, operation);
      
      setDisplay(String(newValue));
      setPreviousValue(newValue);
    }

    setWaitingForOperand(true);
    setOperation(nextOperation);
  };

  // 계산 수행
  const calculate = (firstValue: number, secondValue: number, operation: string): number => {
    switch (operation) {
      case '+':
        return firstValue + secondValue;
      case '-':
        return firstValue - secondValue;
      case '×':
        return firstValue * secondValue;
      case '÷':
        return secondValue !== 0 ? firstValue / secondValue : 0;
      default:
        return secondValue;
    }
  };

  // 등호 처리
  const handleEquals = () => {
    const inputValue = parseFloat(display);

    if (previousValue !== null && operation) {
      const newValue = calculate(previousValue, inputValue, operation);
      setDisplay(String(newValue));
      setPreviousValue(null);
      setOperation(null);
      setWaitingForOperand(true);
    }
  };

  // 초기화
  const handleClear = () => {
    setDisplay('0');
    setPreviousValue(null);
    setOperation(null);
    setWaitingForOperand(false);
  };

  // 백스페이스
  const handleBackspace = () => {
    if (!waitingForOperand) {
      const newDisplay = display.slice(0, -1);
      setDisplay(newDisplay || '0');
    }
  };

  // 부호 변경
  const handleSign = () => {
    const value = parseFloat(display);
    setDisplay(String(value * -1));
  };

  // 퍼센트
  const handlePercent = () => {
    const value = parseFloat(display);
    setDisplay(String(value / 100));
  };

  return (
    <div className={`h-full w-full p-3 bg-gradient-to-br from-slate-50 to-gray-100 ${className}`}>
      <div className="h-full flex flex-col justify-center gap-2">
        {/* 디스플레이 */}
        <div className="bg-white border-2 border-gray-200 rounded-lg p-4 shadow-inner min-h-[80px]">
          <div className="text-right h-full flex flex-col justify-center">
            <div className="h-4 mb-1">
              {operation && previousValue !== null && (
                <div className="text-xs text-gray-400">
                  {previousValue} {operation}
                </div>
              )}
            </div>
            <div className="text-2xl font-bold text-gray-900 truncate">
              {display}
            </div>
          </div>
        </div>

        {/* 버튼 그리드 */}
        <div className="flex-1 grid grid-cols-4 gap-2">
          {/* 첫 번째 줄 */}
          <Button
            variant="outline"
            onClick={handleClear}
            className="h-full text-red-600 hover:bg-red-50 hover:text-red-700 font-semibold select-none"
          >
            AC
          </Button>
          <Button
            variant="outline"
            onClick={handleSign}
            className="h-full text-gray-600 hover:bg-gray-100 font-semibold select-none"
          >
            +/-
          </Button>
          <Button
            variant="outline"
            onClick={handlePercent}
            className="h-full text-gray-600 hover:bg-gray-100 font-semibold select-none"
          >
            %
          </Button>
          <Button
            variant="default"
            onClick={() => handleOperation('÷')}
            className="h-full bg-blue-500 hover:bg-blue-600 text-white font-semibold select-none"
          >
            ÷
          </Button>

          {/* 두 번째 줄 */}
          <Button
            variant="outline"
            onClick={() => handleNumber('7')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            7
          </Button>
          <Button
            variant="outline"
            onClick={() => handleNumber('8')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            8
          </Button>
          <Button
            variant="outline"
            onClick={() => handleNumber('9')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            9
          </Button>
          <Button
            variant="default"
            onClick={() => handleOperation('×')}
            className="h-full bg-blue-500 hover:bg-blue-600 text-white font-semibold select-none"
          >
            ×
          </Button>

          {/* 세 번째 줄 */}
          <Button
            variant="outline"
            onClick={() => handleNumber('4')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            4
          </Button>
          <Button
            variant="outline"
            onClick={() => handleNumber('5')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            5
          </Button>
          <Button
            variant="outline"
            onClick={() => handleNumber('6')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            6
          </Button>
          <Button
            variant="default"
            onClick={() => handleOperation('-')}
            className="h-full bg-blue-500 hover:bg-blue-600 text-white font-semibold select-none"
          >
            -
          </Button>

          {/* 네 번째 줄 */}
          <Button
            variant="outline"
            onClick={() => handleNumber('1')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            1
          </Button>
          <Button
            variant="outline"
            onClick={() => handleNumber('2')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            2
          </Button>
          <Button
            variant="outline"
            onClick={() => handleNumber('3')}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            3
          </Button>
          <Button
            variant="default"
            onClick={() => handleOperation('+')}
            className="h-full bg-blue-500 hover:bg-blue-600 text-white font-semibold select-none"
          >
            +
          </Button>

          {/* 다섯 번째 줄 */}
          <Button
            variant="outline"
            onClick={() => handleNumber('0')}
            className="h-full col-span-2 hover:bg-gray-100 font-semibold text-lg select-none"
          >
            0
          </Button>
          <Button
            variant="outline"
            onClick={handleDecimal}
            className="h-full hover:bg-gray-100 font-semibold text-lg select-none"
          >
            .
          </Button>
          <Button
            variant="default"
            onClick={handleEquals}
            className="h-full bg-green-500 hover:bg-green-600 text-white font-semibold select-none"
          >
            =
          </Button>
        </div>
      </div>
    </div>
  );
}