append method

TSimpleOperation append(String char)

Appends a given character to the current operation.

Implementation

TSimpleOperation append(String char) {
  // Create a copy of the current operands list
  final List<String> updatedOperands = List<String>.from(operands);

  // Get the index of the last element in the updated operands list
  final int lastIndex = updatedOperands.length - 1;

  // If the last operand is '0' and the character to be appended is also '0',
  // return the current object without any changes
  if (lastOperand == '0' && char == '0') return this;

  // Prevent adding a new operator or operand if the current operand
  // has no digit
  if (lastOperand == '-' && isOperator(char)) return this;

  // If the last operand is not empty and the new character is an operator
  if (isOperator(char) && operands.length < 2) {
    if (lastOperand.isNotEmpty || hasOperator) return _updateOperator(char);
  } else if (isOperator(char) && operands.length == 2) {
    return this;
  }

  // If the new character is a '.', handle it
  if (char == '.') return _updateDecimal(updatedOperands);

  // Prevent multiple negative signs in an operand
  if (char == '-' && lastOperand.startsWith('-')) return this;

  // If the current operation has an operator and only one operand,
  // add the new character to the operands list
  if (hasOperator && lastIndex == 0) {
    updatedOperands.add(char);
  } else if (lastOperand.isEmpty) {
    // If the new character is an operator that is not '-',
    // return the current object
    if (isOperator(char) && char != '-') return this;

    // Otherwise, add the new character to the operands list
    updatedOperands.add(char);
  } else if (lastOperand.isNotEmpty) {
    // If the last operand is not empty, append the new character
    updatedOperands[lastIndex] = lastOperand + char;
  }

  // Return a copy of the current object with the updated operands
  return copyWith(operands: updatedOperands);
}