textual_terminal.py

from __future__ import annotations
import asyncio
from textual.app import App, ComposeResult
from textual import events
from textual.widgets import Header, Footer, Input, TextLog


class Prompt(Input):
    app: 'Terminal'

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._history = []
        self._history_pointer = None

    def on_key(self, event: events.Key) -> None:
        if event.key == "enter" and self.value:
            self.app.append(self.value)
            if not self._history or self._history[-1] != self.value:
                self._history.append(self.value)
            self._history_pointer = None
            self.value = ""
        elif event.key == 'up' and self._history:
            if self._history_pointer is None:
                self._history_pointer = len(self._history) - 1
            else:
                self._history_pointer = max(0, self._history_pointer - 1)

            self.value = self._history[self._history_pointer]
            self.cursor_position = len(self.value)
        elif event.key == 'down' and self._history:
            if self._history_pointer is None:
                return

            self._history_pointer = min(len(self._history), self._history_pointer + 1)
            if self._history_pointer == len(self._history):
                self.value = ""
            else:
                self.value = self._history[self._history_pointer]
            self.cursor_position = len(self.value)


class OutputWidget(TextLog):
    pass


class Terminal(App):
    textlog: OutputWidget
    prompt: Prompt
    network_task: asyncio.Task

    CSS_PATH = "vertical_layout.css"

    BINDINGS = [
        ("d", "toggle_dark", "Toggle dark mode"),
        ("q", "quit", "Quit"),
        ("escape", "quit", "Quit"),
    ]

    def compose(self) -> ComposeResult:
        """Create child widgets for the app."""
        self.textlog = OutputWidget(classes='output')
        self.prompt = Prompt(classes='input')
        yield Header()
        yield self.textlog
        yield self.prompt
        yield Footer()

    def on_mount(self) -> None:
        self.network_task = asyncio.create_task(fake_network_task(self))
        self.network_task.add_done_callback(self.network_task_done)
        self.query_one(Prompt).focus()

    def network_task_done(self, task: asyncio.Task) -> None:
        try:
            task.result()
        except asyncio.CancelledError:
            pass
        except Exception as e:
            self.append(f"Network task failed: {e}. Restarting")
            self.network_task = asyncio.create_task(fake_network_task(self))

    def action_toggle_dark(self) -> None:
        """An action to toggle dark mode."""
        self.dark = not self.dark

    def append(self, text: str):
        self.textlog.write(text)


async def fake_network_task(app: Terminal) -> None:
    """A fake network task."""
    for _ in range(3):
        await asyncio.sleep(1)
        app.append("Hello world")
    raise RuntimeError("Something went wrong")


async def main():
    app = Terminal()

    await app.run_async()
    app.network_task.cancel()
    try:
        await app.network_task
    except asyncio.CancelledError:
        pass


if __name__ == "__main__":
    asyncio.run(main())

vertical_layout.css

Screen {
    layout: vertical;
}

.output {
    height: 1fr;
    border: solid green;
}

.input {

}