[range intersection]

intersection.ts

/**
 * 传入两个范围字符串，返回交集；无交集或异常情况返回 null。
 * - 如果要考虑整行整列，通过解析为 Range 对象来处理会更清晰。
 */
function intersection(rangeA: string, rangeB: string): string | null {
  const splitedA = splitRangeStr(rangeA)
  const splitedB = splitRangeStr(rangeB)
  if (!splitedA || !splitedB) {
    return null
  }

  const [startColA, startRowA, endColA, endRowA] = splitedA
  const [startColB, startRowB, endColB, endRowB] = splitedB

  const notSec = endRowA < startRowB || startRowA > endRowB || endColA < startColB || startColA > endColB
  if (notSec) {
    return null
  }

  const startCol = startColA > startColB ? startColA : startColB
  const startRow = startRowA > startRowB ? startRowA : startRowB
  const endCol = endColA < endColB ? endColA : endColB
  const endRow = endRowA < endRowB ? endRowA : endRowB
  return `${startCol}${startRow}:${endCol}${endRow}`
}

/**
 * 'A1:B2' => ['A', 1, 'B', 2]
 */
function splitRangeStr(rangeStr: string): [string, number, string, number] | null {
  if (!rangeStr || typeof rangeStr !== 'string') {
    return null
  }
  const [startCellStr, endCellStr] = rangeStr.split(':')
  const splitedStart = splitCellStr(startCellStr)
  const splitedEnd = splitCellStr(endCellStr)
  if (splitedStart && splitedEnd) {
    const [startCol, startRow] = splitedStart
    const [endCol, endRow] = splitedEnd
    return [startCol, startRow, endCol, endRow]
  }
  return null
}

const regCell = /^([A-Za-z]*)([0-9]*)$/
/**
 * 'A1' => ['A', 1]
 */
function splitCellStr(cellStr: string): [string, number] | null {
  const matched = cellStr && regCell.exec(cellStr)
  if (matched) {
    return [matched[1], parseInt(matched[2])]
  }
  return null
}

/////////

test('intersection', () => {
  expect(splitRangeStr('A1:B5')).toEqual(['A', 1, 'B', 5])
  expect(splitRangeStr('AA10:BB50')).toEqual(['AA', 10, 'BB', 50])

  expect(intersection('A1:C3', 'B2:D4')).toBe('B2:C3')
  expect(intersection('C1:F4', 'A3:D6')).toBe('C3:D4')
  expect(intersection('AA100:CC200', 'BB150:DD250')).toBe('BB150:CC200')

  expect(intersection('A1:A2', 'A3:A4')).toBe(null)
  expect(intersection('AA', 'B1:BB')).toBe(null)
})