import psycopg2
from psycopg2 import sql
from psycopg2.errors import DuplicateDatabase
from PyQt5.QtWidgets import QApplication, QMainWindow, QGridLayout, QWidget, QTableWidget, QTableWidgetItem, QHeaderView
from PyQt5.QtCore import QSize, Qt


def connect(config):
    """ Connect to the PostgreSQL database server """
    try:
        # connecting to the PostgreSQL server
        with psycopg2.connect(**config) as conn:
            print('Connected to the PostgreSQL server.')
            return conn
    except (psycopg2.DatabaseError, Exception) as error:
        print(error)


def createUsersDB(config):
    """ Connect to the PostgreSQL database server """
    try:
        # connecting to the PostgreSQL server
        conn.autocommit = True
        cur = conn.cursor()
        cur.execute(sql.SQL("CREATE DATABASE {}").format(
            sql.Identifier('university'))
        )
        print('db created')
    except DuplicateDatabase:
            print('db already exists')
            pass


def createuUiversityDB(config):
    """ Connect to the PostgreSQL database server """
    try:
        # connecting to the PostgreSQL server
        conn.autocommit = True
        cur = conn.cursor()
        cur.execute(sql.SQL("CREATE DATABASE {}").format(
            sql.Identifier('university'))
        )
        print('db created')
    except DuplicateDatabase:
            print('db already exists')
            pass


def createUsersTable(config):
    """ Connect to the PostgreSQL database server """
    try:
        # connecting to the PostgreSQL server
        conn.autocommit = True
        cur = conn.cursor()
        cur.execute(sql.SQL("CREATE TABLE IF NOT EXISTS users(id int, name varchar(255), age int)"))
        print('table created')
    except (psycopg2.DatabaseError, Exception) as error:
        print(error)


def selectUsers(config):
    try:
        cur = conn.cursor()
        cur.execute(sql.SQL("SELECT * FROM users"))
        return cur.fetchall()
    except (psycopg2.DatabaseError, Exception) as error:
        print(error)
        return []


def insertUsersData(config, values):
    """ Connect to the PostgreSQL database server """
    try:
        conn.autocommit = True
        cur = conn.cursor()

        users = selectUsers(conn)

        if len(users) == 0:
            args = ','.join(cur.mogrify("(%s,%s,%s)", i).decode('utf-8')
                            for i in values)

            # executing the sql statement
            cur.execute("INSERT INTO users VALUES " + (args))
            print('inserted')
        else:
            print('already inserted')
            print(users)
    except (psycopg2.DatabaseError, Exception) as error:
        print(error)


class MainWindow(QMainWindow):
    # Override class constructor
    def __init__(self):
        # You must call the super class method
        QMainWindow.__init__(self)

        self.setMinimumSize(QSize(480, 80))  # Set sizes
        self.setWindowTitle("DB example")  # Set the window title
        central_widget = QWidget(self)  # Create a central widget
        self.setCentralWidget(central_widget)  # Install the central widget

        grid_layout = QGridLayout(self)  # Create QGridLayout
        central_widget.setLayout(grid_layout)  # Set this layout in central widget

        self.table = QTableWidget(self)  # Create a table
        self.table.setColumnCount(3)  # Set three columns
        self.table.setRowCount(1)  # and one row
        self.table.horizontalHeader().setSectionResizeMode(1, QHeaderView.Stretch)
        # Set the table headers
        self.table.setHorizontalHeaderLabels(["ID", "Name", "Age"])

        # Set the tooltips to headings
        self.table.horizontalHeaderItem(0).setToolTip("ID ")
        self.table.horizontalHeaderItem(1).setToolTip("Name ")
        self.table.horizontalHeaderItem(2).setToolTip("Age ")

        # Set the alignment to the headers
        self.table.horizontalHeaderItem(0).setTextAlignment(Qt.AlignHCenter)
        self.table.horizontalHeaderItem(1).setTextAlignment(Qt.AlignHCenter)
        self.table.horizontalHeaderItem(2).setTextAlignment(Qt.AlignHCenter)

        # Do the resize of the columns by content
        self.table.resizeColumnsToContents()

        grid_layout.addWidget(self.table, 0, 0)  # Adding the table to the grid

    def load_data(self, users_data):
        for i, user in enumerate(users_data):
            row_number = self.table.rowCount()-1
            if len(users_data) != self.table.rowCount():
                self.table.insertRow(row_number)
            self.table.setItem(row_number, 0, QTableWidgetItem(str(user[0])))
            self.table.setItem(row_number, 1, QTableWidgetItem(str(user[1])))
            self.table.setItem(row_number, 2, QTableWidgetItem(str(user[2])))


if __name__ == "__main__":
    import sys

    conn = psycopg2.connect("user=postgres password=456 host=localhost port=5432")

    createuUiversityDB(conn)

    conn = psycopg2.connect("user=postgres dbname=university password=456 host=localhost port=5432")

    createUsersTable(conn)

    values = [(1, 'Ivan', 15), (2, 'Igor', 22), (3, 'Alex', 16), (4, 'Anna', 40), (5, 'Inna', 30)]

    insertUsersData(conn, values)

    users = selectUsers(conn)

    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.load_data(users)
    mw.show()
    sys.exit(app.exec())