mainwindow.cpp

#include "mainwindow.h"
#include "./ui_mainwindow.h"

#include <QDebug>

/**
 * @brief global variable section.
 */
double firstNum;
bool userIsTypingSecondNumber = false;

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // number buttons
    connect(ui->pushButton_0, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_1, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_2, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_3, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_4, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_5, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_6, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_7, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_8, SIGNAL(released()), this, SLOT(digit_pressed()));
    connect(ui->pushButton_9, SIGNAL(released()), this, SLOT(digit_pressed()));

    // unary operation buttons.
    connect(ui->pushButton_plusMinus, SIGNAL(released()), this, SLOT(unary_operation_pressed()));
    connect(ui->pushButton_percent, SIGNAL(released()), this, SLOT(unary_operation_pressed()));

    // binary operation buttons.
    connect(ui->pushButton_add, SIGNAL(released()), this, SLOT(binary_operation_pressed()));
    connect(ui->pushButton_subtrack, SIGNAL(released()), this, SLOT(binary_operation_pressed()));
    connect(ui->pushButton_multiply, SIGNAL(released()), this, SLOT(binary_operation_pressed()));
    connect(ui->pushButton_divide, SIGNAL(released()), this, SLOT(binary_operation_pressed()));

    // setting some properties.
    ui->pushButton_add->setCheckable(true);
    ui->pushButton_subtrack->setCheckable(true);
    ui->pushButton_multiply->setCheckable(true);
    ui->pushButton_divide->setCheckable(true);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::digit_pressed()
{
    QPushButton *button = (QPushButton *)sender();

    double labelNumber;
    QString newLabel;

    if( (ui->pushButton_add->isChecked() || ui->pushButton_subtrack->isChecked()
    || ui->pushButton_multiply->isChecked() || ui->pushButton_divide->isChecked() ) && (!userIsTypingSecondNumber))
    {
        labelNumber = (button->text()).toDouble();
        userIsTypingSecondNumber = true;
        newLabel = QString::number(labelNumber, 'g', 15);
    }
    else
    {
        if (ui->label->text().contains('.') && button->text() == "0")
        {
            newLabel = ui->label->text() + button->text();
        }
        else
        {
            labelNumber = (ui->label->text() + button->text()).toDouble();
            newLabel = QString::number(labelNumber, 'g', 15);
        }
    }
    ui->label->setText(newLabel);
}

void MainWindow::on_pushButton_decimal_released()
{
    ui->label->setText(ui->label->text() + ".");
}

void MainWindow::unary_operation_pressed()
{
    QPushButton *button = (QPushButton *)sender();
    QString newLabel;
    double labelNumber;

    if (button->text() == "+/-")
    {
        labelNumber = ui->label->text().toDouble();
        labelNumber = labelNumber * -1;
        newLabel = QString::number(labelNumber, 'g', 15);
        ui->label->setText(newLabel);
    }
    if (button->text() == "%")
    {
        labelNumber = ui->label->text().toDouble();
        labelNumber = labelNumber * 0.01;
        newLabel = QString::number(labelNumber, 'g', 15);
        ui->label->setText(newLabel);
    }
}

void MainWindow::on_pushButton_clear_released()
{
    ui->pushButton_add->setChecked(false);
    ui->pushButton_subtrack->setChecked(false);
    ui->pushButton_multiply->setChecked(false);
    ui->pushButton_divide->setChecked(false);

    userIsTypingSecondNumber = false;

    ui->label->setText("0");
}

void MainWindow::on_pushButton_equals_released()
{
    double labelNumber, secondNum;
    QString newLabel;

    secondNum = ui->label->text().toDouble();

    if (ui->pushButton_add->isChecked())
    {
        labelNumber = firstNum + secondNum;
        newLabel = QString::number(labelNumber, 'g', 15);
        ui->label->setText(newLabel);
        ui->pushButton_add->setChecked(false);
    }
    else if (ui->pushButton_subtrack->isChecked())
    {
        labelNumber = firstNum - secondNum;
        newLabel = QString::number(labelNumber, 'g', 15);
        ui->label->setText(newLabel);
        ui->pushButton_subtrack->setChecked(false);
    }
    else if (ui->pushButton_multiply->isChecked())
    {
        labelNumber = firstNum * secondNum;
        newLabel = QString::number(labelNumber, 'g', 15);
        ui->label->setText(newLabel);
        ui->pushButton_multiply->setChecked(false);
    }
    else if (ui->pushButton_divide->isChecked())
    {
        labelNumber = firstNum / secondNum;
        newLabel = QString::number(labelNumber, 'g', 15);
        ui->label->setText(newLabel);
        ui->pushButton_divide->setChecked(false);
    }

    userIsTypingSecondNumber = false;
}

void MainWindow::binary_operation_pressed()
{
    QPushButton *button = (QPushButton *)sender();

    firstNum = ui->label->text().toDouble();

    button->setChecked(true);

    ui->label->setText("");
}