from datetime import datetime, timedelta
import sys
from PyQt6.QtWidgets import (
    QApplication,
    QWidget,
    QVBoxLayout,
    QDateEdit,
    QGridLayout,
    QHBoxLayout,
    QPushButton,
    QLabel,
    QListWidget,
    QListWidgetItem,
    QFrame,
    QFileDialog,
    QMessageBox
)
from database import init_database, get_database, close_database
from models.station import Station
from models.rental import Rental
from peewee import fn, SQL

DATA_ROLE = 1001


LABELS = [
            "Avg. rent duration when starting there",
            "Avg. rent duration when stopping there",
            "Count of different bikes stopped there",
            "Most popular destination from there"
    ]

class DatabaseViewer(QWidget):
    def __init__(self):
        self.value_labels = {}
        super().__init__()
        self.init()
        self.stations = []

    def init(self):
        self.setWindowTitle("Database stats")
        self.setGeometry(100, 100, 900, 500)

        mainLayout = QVBoxLayout()

        topLayout = QHBoxLayout()
        self.pathLabel = QLabel("Select database file...")
        self.openButton = QPushButton("Open")
        self.openButton.clicked.connect(self.open_file_dialog)


        topLayout.addWidget(self.pathLabel)
        topLayout.addWidget(self.openButton)



        middleLayout = QHBoxLayout()
        self.stationsListWidget = QListWidget()
        self.stationsListWidget.itemClicked.connect(self.select_station)
        middleLayout.addWidget(self.stationsListWidget, 2)

        self.statsFrame = QFrame()
        statsLayout = QVBoxLayout(self.statsFrame)
        self.create_stats_widget(statsLayout)
        middleLayout.addWidget(self.statsFrame, 2)

        mainLayout.addLayout(topLayout)
        mainLayout.addLayout(middleLayout)

        self.setLayout(mainLayout)

    def reset_ui(self):
        self.pathLabel.setText("Select database file...")

        self.stationsListWidget.clear()

        for label in LABELS:
            self.value_labels[label].setText("")
            
        

    def select_station(self, item):
        station_id = item.data(DATA_ROLE)

        try:
            avg_time_start = (Rental
                .select(fn.AVG(Rental.duration))
                .where(Rental.rent_station == station_id)
                .scalar()
            ) or 0.0

            avg_time_stopped = (Rental
                .select(fn.AVG(Rental.duration))
                .where(Rental.ret_station == station_id)
                .scalar()
            ) or 0.0

            bikes_count = (Rental
                .select(fn.COUNT(fn.DISTINCT(Rental.bike_id)))
                .where(Rental.ret_station == station_id)
                .scalar()
            ) or 0

            (most_popular, count) = (Rental
                .select(Rental.ret_station, fn.COUNT(Rental.ret_station).alias("count"))
                .where(Rental.rent_station == station_id)
                .group_by(Rental.ret_station)
                .order_by(SQL("count").desc())
                .scalar(as_tuple=True)
            ) or (0,0)

            most_popular_station = (Station
                .select()
                .where(Station.id == most_popular)
                .get()
            ) if count != 0 else None


            self.value_labels[LABELS[0]].setText(f"{avg_time_start:.2f} minutes")
            self.value_labels[LABELS[1]].setText(f"{avg_time_stopped:.2f} minutes")
            self.value_labels[LABELS[2]].setText(str(bikes_count)) 
            self.value_labels[LABELS[3]].setText(f"{most_popular_station.name if most_popular_station is not None else '-'} ({count} trips)")
        except Exception as ex:
            self.show_error(f"Failed when executing database queries: {str(ex)}")


    def create_stats_widget(self, layout):
        gridLayout = QGridLayout()


        for index, label in enumerate(LABELS):
            labelWidget = QLabel(f"{label}:")
            valueLabel = QLabel()
            gridLayout.addWidget(labelWidget, index, 0)
            gridLayout.addWidget(valueLabel, index, 1)
            self.value_labels[label] = valueLabel

        layout.addLayout(gridLayout)

    def open_file_dialog(self):
        if len(self.stations) > 0:
            self.openButton.setText("Open")
            self.stations = []
            self.reset_ui()
            try:
                close_database()
            except:
                self.show_error("Failed to close database!")
        else:
            
            fileName, _ = QFileDialog.getOpenFileName(
                self,
                "Open Database File",
                "",
                "Sqlite Files (*.sqlite3);;All Files (*)",
            )
            if fileName:
                self.load_database(fileName)

    def load_database(self, file_path):

        self.reset_ui()

        self.openButton.setText("Close")
        self.pathLabel.setText(file_path)

        try:
            init_database(file_path)
            self.stations = Station.select().order_by(Station.name)

            self.update_list()
        except:
            self.show_error("Failed to load database!")


    def update_list(self):
        self.stationsListWidget.clear()

        for station in self.stations:
            
            item = QListWidgetItem(station.name)
            item.setData(DATA_ROLE, station.id)
            self.stationsListWidget.addItem(item)
            


    def show_error(self, text):
        message_box = QMessageBox()
        message_box.setIcon(QMessageBox.Icon.Critical)
        message_box.setText("Error")
        message_box.setWindowTitle("Error")
        message_box.setInformativeText(text)
        message_box.exec()


def main():
    app = QApplication(sys.argv)
    ex = DatabaseViewer()
    ex.show()
    sys.exit(app.exec())


if __name__ == "__main__":
    main()