format-formula.ts

export function formatFormula(formula: string): string {
  const INDENT = '  ' // 2 spaces
  let out = ''
  let depth = 0

  /** Stack of the current call-chain. */
  const stack: Array<{ fn: string; argCount: number }> = []

  /** Helper → current indentation string */
  const indent = () => INDENT.repeat(depth)

  /** Is char inside quotes right now? */
  let inString: false | '"' | "'" = false

  for (let i = 0; i < formula.length; i++) {
    const ch = formula[i]

    /* ────────── Handle string literals ────────── */
    if (inString) {
      out += ch
      // spreadsheet strings escape quotes by doubling them ( "")
      if (ch === inString && formula[i + 1] !== inString) {
        inString = false
      } else if (ch === inString && formula[i + 1] === inString) {
        // skip the escaped quote partner, copy it too
        out += formula[++i]
      }
      continue
    }
    if (ch === '"' || ch === "'") {
      inString = ch
      out += ch
      continue
    }

    /* ────────── Open-parenthesis: new function level ────────── */
    if (ch === '(') {
      // look backwards to fetch the function/token name
      let j = out.length - 1
      while (j >= 0 && /\s/.test(out[j])) j--
      const end = j
      while (j >= 0 && /[\w.|$]/.test(out[j])) j-- // include sheet names “.” “|” “$”
      const fn = out.slice(j + 1, end + 1).toUpperCase()

      stack.push({ fn, argCount: 0 })

      out += '('
      depth++
      out += '\n' + indent()
      continue
    }

    /* ────────── Comma: argument separator ────────── */
    if (ch === ',') {
      if (stack.length) {
        const top = stack[stack.length - 1]
        top.argCount += 1

        // Inside PAIR2JSON we keep first comma of each pair inline
        if (top.fn === 'PAIR2JSON' && top.argCount % 2 === 1) {
          out += ', '
          continue
        }
      }
      out += ',\n' + indent()
      continue
    }

    /* ────────── Close-parenthesis: end function level ────────── */
    if (ch === ')') {
      depth--
      out += '\n' + indent() + ')'
      stack.pop()
      // if next char is another “)” or “,” we’ll let loop handle it
      continue
    }

    /* ────────── Any other char ────────── */
    out += ch
  }

  return out.trim()
}

// TESTS
// =============================================================================

const tests = [
  {
    name: 'Função simples com 2 args',
    input: '=SOMA(1,2)',
    expected: `=SOMA(
  1,
  2
)`,
  },
  {
    name: 'Aninhamento profundo',
    input: '=IF(AND(A1>0,B1<5),SUM(A1,B1),IF(C1>10,MAX(A1,C1),0))',
    expected: `=IF(
  AND(
    A1>0,
    B1<5
  ),
  SUM(
    A1,
    B1
  ),
  IF(
    C1>10,
    MAX(
      A1,
      C1
    ),
    0
  )
)`,
  },
  {
    name: 'PAIR2JSON especial com pares na mesma linha',
    input: '=PAIR2JSON("a",1,"b",2,"c",FUNC(3,4))',
    expected: `=PAIR2JSON(
  "a", 1,
  "b", 2,
  "c", FUNC(
    3,
    4
  )
)`,
  },
]

for (const { name, input, expected } of tests) {
  const result = formatFormula(input)
  const passed = result === expected
  console.log(`Test: ${name}`)
  console.log(passed ? '✅ Passed' : '❌ Failed')
  if (!passed) {
    console.log('--- Expected:\n' + expected)
    console.log('--- Received:\n' + result)
  }
  console.log()
}