const digits = ['', '일', '이', '삼', '사', '오', '육', '칠', '팔', '구']
const units = ['', '십', '백', '천']
const higherUnits = ['', '만', '억', '조', '경', '해']

// 숫자를 한글 표기로 (예: 12000 → 일만이천)
export function numberToKorean(num: number): string {
  if (num === 0) return '영'

  const groups: number[] = []
  let numStr = num.toString()
  while (numStr.length > 0) {
    groups.unshift(parseInt(numStr.slice(-4)))
    numStr = numStr.slice(0, -4)
  }

  let result = ''
  const groupLen = groups.length
  for (let idx = 0; idx < groupLen; idx++) {
    const group = groups[idx]
    if (group === 0) continue
    const groupStr = processGroup(group, idx === 0)
    result += groupStr + higherUnits[groupLen - idx - 1]
  }
  return result
}

function processGroup(num: number, isFirstGroup = false): string {
  const numStr = num.toString().padStart(4, '0')
  let result = ''
  for (let idx = 0; idx < numStr.length; idx++) {
    const digit = parseInt(numStr[idx])
    const unit = units[3 - idx]
    if (digit === 0) continue
    if (digit === 1) {
      if (unit !== '') {
        result += isFirstGroup && unit === '천' ? digits[digit] + unit : unit
      } else {
        result += '일'
      }
    } else {
      result += digits[digit] + unit
    }
  }
  return result
}