void StandardCalculatorViewModel::HandleUpdatedOperandData()

in src/CalcViewModel/StandardCalculatorViewModel.cpp [444:578]
129 lines of code
27 McCabe index (conditional complexity)

void StandardCalculatorViewModel::HandleUpdatedOperandData(Command cmdenum)
{
    DisplayExpressionToken ^ displayExpressionToken = ExpressionTokens->GetAt(m_TokenPosition);
    if (displayExpressionToken == nullptr)
    {
        return;
    }
    if ((displayExpressionToken->Token == nullptr) || (displayExpressionToken->Token->Length() == 0))
    {
        displayExpressionToken->CommandIndex = 0;
    }

    wchar_t ch = 0;
    if ((cmdenum >= Command::Command0) && (cmdenum <= Command::Command9))
    {
        switch (cmdenum)
        {
        case Command::Command0:
            ch = L'0';
            break;
        case Command::Command1:
            ch = L'1';
            break;
        case Command::Command2:
            ch = L'2';
            break;
        case Command::Command3:
            ch = L'3';
            break;
        case Command::Command4:
            ch = L'4';
            break;
        case Command::Command5:
            ch = L'5';
            break;
        case Command::Command6:
            ch = L'6';
            break;
        case Command::Command7:
            ch = L'7';
            break;
        case Command::Command8:
            ch = L'8';
            break;
        case Command::Command9:
            ch = L'9';
            break;
        }
    }
    else if (cmdenum == Command::CommandPNT)
    {
        ch = L'.';
    }
    else if (cmdenum == Command::CommandBACK)
    {
        ch = L'x';
    }
    else
    {
        return;
    }

    int length = 0;
    wchar_t* temp = new wchar_t[100];
    const wchar_t* data = m_selectedExpressionLastData->Data();
    int i = 0, j = 0;
    int commandIndex = displayExpressionToken->CommandIndex;

    if (IsOperandTextCompletelySelected)
    {
        // Clear older text;
        m_selectedExpressionLastData = L"";
        if (ch == L'x')
        {
            temp[0] = L'\0';
            commandIndex = 0;
        }
        else
        {
            temp[0] = ch;
            temp[1] = L'\0';
            commandIndex = 1;
        }
        IsOperandTextCompletelySelected = false;
    }
    else
    {
        if (ch == L'x')
        {
            if (commandIndex == 0)
            {
                delete[] temp;
                return;
            }

            length = m_selectedExpressionLastData->Length();
            for (; j < length; ++j)
            {
                if (j == commandIndex - 1)
                {
                    continue;
                }
                temp[i++] = data[j];
            }
            temp[i] = L'\0';
            commandIndex -= 1;
        }
        else
        {
            length = m_selectedExpressionLastData->Length() + 1;
            if (length > 50)
            {
                delete[] temp;
                return;
            }
            for (; i < length; ++i)
            {
                if (i == commandIndex)
                {
                    temp[i] = ch;
                    continue;
                }
                temp[i] = data[j++];
            }
            temp[i] = L'\0';
            commandIndex += 1;
        }
    }

    String ^ updatedData = ref new String(temp);
    UpdateOperand(m_TokenPosition, updatedData);
    displayExpressionToken->Token = updatedData;
    IsOperandUpdatedUsingViewModel = true;
    displayExpressionToken->CommandIndex = commandIndex;
}