import urwid
from concurrent.futures import ThreadPoolExecutor


class Items(urwid.ListBox):
    def __init__(self, items):
        super().__init__(self)
        walker = urwid.SimpleListWalker([urwid.AttrMap(item, None, 'reveal focus') for item in items])
        self.body = walker

    def keypress(self, size, key):
        if key in ("j", "down"):
            item_size = len(self.body)
            focus_widget, idx = self.get_focus()
            if idx < item_size - 1:
                idx = idx + 1
                self.set_focus(idx)
            return
        elif key in ("k", "up"):
            focus_widget, idx = self.get_focus()
            if idx > 0:
                idx = idx - 1
                self.set_focus(idx)
            return

        return super().keypress(size, key)


class TUI(urwid.Frame):

    @classmethod
    def create(cls):

        tui = cls()
        palette = [('header', 'white', 'black'), ('reveal focus', 'black', 'dark cyan', 'standout')]
        loop = urwid.MainLoop(
            tui,
            palette,
            event_loop=urwid.AsyncioEventLoop(),
            unhandled_input=tui.unhandled_input,
        )
        tui.loop = loop

        return tui

    def __init__(self):
        self.executor = ThreadPoolExecutor(max_workers=1)
        self.loop = None
        self.feedItems = [urwid.Text("Feed# " + str(i)) for i in range(0, 15)]
        self.articleItems = [urwid.Text("Article# " + str(i)) for i in range(0, 10)]
        self.feeds = Items(self.feedItems)
        self.articles = Items(self.articleItems)
        self.container = urwid.Columns([urwid.LineBox(self.feeds, title="Feeds"), urwid.LineBox(self.articles, title="Articles")])
        self.body = self.container

        super().__init__(self.body)

    def run(self):
        self.loop.run()
        self.executor.shutdown(wait=False)

    def unhandled_input(self, key):
        if key == "tab":
            self.container.set_focus(1)
        elif key == "q":
            raise urwid.ExitMainLoop()


tui = TUI.create()
tui.run()