"""Textual app for managing Proxmox guests through cv4pve-cli."""

import subprocess
import sys
from datetime import datetime

from textual import work
from textual.app import App, ComposeResult, SuspendNotSupported
from textual.containers import Horizontal, Vertical
from textual.screen import ModalScreen
from textual.widgets import (
    Button,
    Checkbox,
    DataTable,
    Footer,
    Header,
    Input,
    OptionList,
    Select,
    Static,
)
from textual.widgets.option_list import Option

from cv4pve_tui import cli


def _message(exc: Exception) -> str:
    return (
        exc.summary if isinstance(exc, cli.CliError) else f"{type(exc).__name__}: {exc}"
    )


class ConfirmScreen(ModalScreen[bool]):
    BINDINGS = [("escape", "dismiss(False)", "No")]  # noqa: RUF012 - Textual idiom

    def __init__(self, message: str) -> None:
        super().__init__()
        self.message = message

    def compose(self) -> ComposeResult:
        with Vertical():
            yield Static(self.message)
            with Horizontal():
                yield Button("Yes", id="yes", variant="error")
                yield Button("No", id="no")

    def on_button_pressed(self, event: Button.Pressed) -> None:
        self.dismiss(event.button.id == "yes")


class EditScreen(ModalScreen):
    """Dismisses with a dict of validated values, or None when cancelled."""

    BINDINGS = [("escape", "dismiss(None)", "Cancel")]  # noqa: RUF012 - Textual idiom

    def __init__(self, guest: dict, config: dict, disks: dict[str, str]) -> None:
        super().__init__()
        self.guest, self.config, self.disks = guest, config, disks

    def compose(self) -> ComposeResult:
        with Vertical():
            yield Static(
                f"Edit {self.guest['name']} ({self.guest['vmid']}); empty = unchanged"
            )
            yield Input(
                placeholder=f"cores (now {self.config.get('cores', '?')})", id="cores"
            )
            yield Input(
                placeholder=f"memory MiB (now {self.config.get('memory', '?')})",
                id="memory",
            )
            yield Select(
                [(f"{k} ({v})", k) for k, v in self.disks.items()],
                prompt="disk",
                id="disk",
            )
            yield Input(placeholder="grow by GiB", id="grow")
            with Horizontal():
                yield Button("Apply", id="apply", variant="primary")
                yield Button("Cancel", id="cancel")

    def on_button_pressed(self, event: Button.Pressed) -> None:
        if event.button.id == "cancel":
            self.dismiss(None)
            return
        try:
            values = {name: self._number(name) for name in ("cores", "memory", "grow")}
        except ValueError as exc:
            self.app.notify(str(exc), severity="error")
            return
        disk = self.query_one("#disk", Select).value
        if values["grow"] is not None and disk is Select.NULL:
            self.app.notify("Choose a disk to grow", severity="error")
            return
        values["disk"] = None if disk is Select.NULL else disk
        self.dismiss(values)

    def _number(self, name: str) -> int | None:
        text = self.query_one(f"#{name}", Input).value.strip()
        if not text:
            return None
        if not text.isdecimal() or int(text) <= 0:
            raise ValueError(f"{name} must be a positive integer")
        return int(text)


class ContextScreen(ModalScreen[str | None]):
    """Dismisses with the chosen context name, or None when cancelled."""

    BINDINGS = [("escape", "dismiss(None)", "Cancel")]  # noqa: RUF012 - Textual idiom

    def __init__(self, contexts: list[dict]) -> None:
        super().__init__()
        self.contexts = contexts

    def compose(self) -> ComposeResult:
        with Vertical():
            yield OptionList(
                *(
                    Option(
                        f"{'*' if c['current'] else ' '} {c['name']}  {c['host']}",
                        id=c["name"],
                    )
                    for c in self.contexts
                ),
                id="contexts",
            )

    def on_option_list_option_selected(self, event: OptionList.OptionSelected) -> None:
        self.dismiss(event.option.id)


class BackupScreen(ModalScreen[str | None]):
    """Dismisses with the chosen storage, or None when cancelled."""

    BINDINGS = [("escape", "dismiss(None)", "Cancel")]  # noqa: RUF012 - Textual idiom

    def __init__(self, guest: dict, storages: list[str], chosen: str) -> None:
        super().__init__()
        self.guest, self.storages, self.chosen = guest, storages, chosen

    def compose(self) -> ComposeResult:
        with Vertical():
            yield Static(
                f"Back up {self.guest['name']} ({self.guest['vmid']}) now: mode snapshot, zstd"
            )
            yield Select(
                [(s, s) for s in self.storages],
                value=self.chosen,
                allow_blank=False,
                id="storage",
            )
            with Horizontal():
                yield Button("Yes", id="yes", variant="primary")
                yield Button("No", id="no")

    def on_button_pressed(self, event: Button.Pressed) -> None:
        if event.button.id == "yes":
            self.dismiss(self.query_one("#storage", Select).value)
        else:
            self.dismiss(None)


_IPV4_MODES = [("DHCP", "dhcp"), ("Static", "static"), ("None", "none")]
_IPV6_MODES = [("SLAAC", "auto"), *_IPV4_MODES]


class NetScreen(ModalScreen):
    """Edit bridge, VLAN, firewall and IP of one interface; confirms, then applies."""

    BINDINGS = [("escape", "dismiss", "Cancel")]  # noqa: RUF012 - Textual idiom
    DEFAULT_CSS = "NetScreen Horizontal { height: auto; }"

    def __init__(
        self, guest: dict, config: dict, bridges: list[str], running: bool
    ) -> None:
        super().__init__()
        self.guest, self.config, self.running = guest, config, running
        self.nets = cli.nets(config)
        self.is_vm = cli.kind(guest) == "vm"
        self.ip_enabled = not self.is_vm or cli.has_cloudinit(config)
        # a bridge the node no longer lists must stay selectable, or Select rejects the prefill
        used = {n.get("bridge") for n in self.nets.values()} - {None}
        self.bridges = sorted(set(bridges) | used)

    def compose(self) -> ComposeResult:
        with Vertical():
            yield Static(
                f"Network of {self.guest['name']} ({self.guest['vmid']})", markup=False
            )
            yield Select(
                [(k, k) for k in self.nets],
                value=next(iter(self.nets)),
                allow_blank=False,
                id="iface",
            )
            with Horizontal():
                yield Select(
                    [(b, b) for b in self.bridges], allow_blank=False, id="bridge"
                )
                yield Input(placeholder="VLAN tag (empty = none)", id="tag")
                yield Checkbox("Firewall", id="firewall")
            if not self.ip_enabled:
                yield Static(
                    "IP is configured inside the VM (no cloud-init drive)", id="ip_note"
                )
            for fam, modes in (("ipv4", _IPV4_MODES), ("ipv6", _IPV6_MODES)):
                with Horizontal():
                    yield Select(modes, allow_blank=False, id=fam)
                    yield Input(placeholder="address/prefix", id=f"{fam}_cidr")
                    yield Input(placeholder="gateway", id=f"{fam}_gw")
            with Horizontal():
                yield Button("Apply", id="apply", variant="primary")
                yield Button("Cancel", id="cancel")

    def on_mount(self) -> None:
        for wid in ("ipv4", "ipv4_cidr", "ipv4_gw", "ipv6", "ipv6_cidr", "ipv6_gw"):
            self.query_one(f"#{wid}").disabled = not self.ip_enabled
        self._prefill()

    def on_select_changed(self, event: Select.Changed) -> None:
        if event.select.id == "iface":
            self._prefill()

    def _ip_cfg(self, iface: str) -> dict:
        """The dict holding the IP keys: the VM's ipconfigN, or the LXC net itself."""
        if self.is_vm:
            return cli.parse_net(str(self.config.get(f"ipconfig{iface[3:]}", "")))
        return self.nets[iface]

    def _prefill(self) -> None:
        iface = self.query_one("#iface", Select).value
        net = self.nets[iface]
        self.query_one("#bridge", Select).value = net.get("bridge", self.bridges[0])
        self.query_one("#tag", Input).value = net.get("tag", "")
        self.query_one("#firewall", Checkbox).value = net.get("firewall") == "1"
        for fam, family in (("ipv4", 4), ("ipv6", 6)):
            mode, cidr, gw = cli.ip_mode(self._ip_cfg(iface), family)
            self.query_one(f"#{fam}", Select).value = mode
            self.query_one(f"#{fam}_cidr", Input).value = cidr
            self.query_one(f"#{fam}_gw", Input).value = gw

    def _changes(self) -> tuple[dict, dict]:
        """(changes, old) as raw netN/ipconfigN strings, None = absent; ValueError on bad input."""
        iface = self.query_one("#iface", Select).value
        text = self.query_one("#tag", Input).value.strip()
        if text and not text.isdecimal():
            raise ValueError("VLAN tag must be 1-4094")
        current = self.nets[iface]
        link = (
            self.query_one("#bridge", Select).value,
            int(text) if text else None,
            self.query_one("#firewall", Checkbox).value,
        )
        was = (current.get("bridge"), int(current["tag"]) if current.get("tag") else None,
               current.get("firewall") == "1")  # fmt: skip
        # untouched fields are not rewritten (e.g. firewall=0 stays as it is)
        net = cli.apply_link(current, *link) if link != was else dict(current)
        ip_key = f"ipconfig{iface[3:]}"
        ip_old = self._ip_cfg(iface) if self.is_vm else {}
        ip = ip_old if self.is_vm else net  # the dict that holds the IP keys
        if self.ip_enabled:
            for fam, family in (("ipv4", 4), ("ipv6", 6)):
                mode, cidr, gw = (
                    self.query_one(f"#{fam}{s}").value for s in ("", "_cidr", "_gw")
                )
                wanted = (mode, cidr.strip(), gw.strip())
                if wanted != cli.ip_mode(
                    ip, family
                ):  # untouched: e.g. ip6=manual stays
                    ip = cli.apply_ip(ip, family, *wanted)
        if not self.is_vm:
            net = ip
        changes, old = {}, {}
        if net != self.nets[iface]:
            changes[iface] = cli.format_net(net)
            old[iface] = str(self.config[iface])
        if self.is_vm and ip != ip_old:
            changes[ip_key] = cli.format_net(ip) or None
            old[ip_key] = self.config.get(ip_key)
        return changes, old

    def on_button_pressed(self, event: Button.Pressed) -> None:
        if event.button.id == "cancel":
            self.dismiss()
            return
        try:
            changes, old = self._changes()
        except ValueError as exc:
            self.app.notify(str(exc), severity="error")
            return
        if not changes:
            self.app.notify("No change")
            return
        lines = [
            f"{k}\n  from {old[k] or '(not set)'}\n  to   {v or '(removed)'}"
            for k, v in changes.items()
        ]
        notes = []
        if self.running and any(k.startswith("net") for k in changes):
            notes.append(
                "Link changes apply immediately and can cut the guest's network."
            )
        if (
            self.running
            and not self.is_vm
            and any(_ip_changed(old[k], v) for k, v in changes.items())
        ):  # seen live: static -> dhcp left the CT without IPv4 until it was rebooted
            notes.append(
                "IP changes on a running container may need a reboot of the container "
                "(e.g. DHCP is not restarted)."
            )
        if any(k.startswith("ipconfig") for k in changes):
            notes.append("IP settings (cloud-init) apply at next boot.")
        who = f"{self.guest['name']} ({self.guest['vmid']})"
        self.app.push_screen(
            ConfirmScreen("\n".join([f"Change network of {who}?", *lines, *notes])),
            lambda ok: (
                self.app.start_net_change(self.guest, changes, old, self)
                if ok
                else None
            ),
        )


class InfoScreen(ModalScreen):
    """Backups, backup job and network of one guest (read-only), plus backup now."""

    BINDINGS = [  # noqa: RUF012 - Textual idiom
        ("escape", "dismiss", "Close"),
        ("g", "reload", "Refresh"),
        ("b", "backup", "Backup now"),
        ("a", "toggle_all", "All backups"),
        ("n", "net", "Edit network"),
        ("u", "undo", "Undo network"),
    ]
    DEFAULT_CSS = "InfoScreen DataTable { height: auto; max-height: 12; }"

    def __init__(self, guest: dict) -> None:
        super().__init__()
        self.guest = guest
        self.storages: list[str] = []
        self.jobs: list[dict] = []
        self.backups: list[dict] = []
        self.show_all = False
        self.config: dict = {}
        self.running = False

    def compose(self) -> ComposeResult:
        with Vertical():
            yield Static(f"{self.guest['name']} ({self.guest['vmid']})", markup=False)
            yield Static("", id="jobs", markup=False)
            yield DataTable(id="backups")
            yield Static("", id="hidden", markup=False)
            yield DataTable(id="nets")
            yield Static("", id="unavailable", markup=False)
            yield DataTable(id="addresses")
            yield Footer()

    def on_mount(self) -> None:
        self.query_one("#backups", DataTable).add_columns(
            "Date", "Storage", "Size (GiB)", "Format", "Notes"
        )
        self.query_one("#nets", DataTable).add_columns(
            "Iface", "Bridge", "VLAN", "MAC", "IPv4", "IPv6", "Firewall"
        )
        self.query_one("#addresses", DataTable).add_columns(
            "Interface", "MAC", "IPv4", "IPv6"
        )
        self.action_reload()

    def action_reload(self) -> None:
        self._load_worker()

    @work(thread=True)
    def _load_worker(self) -> None:
        self.load()

    def load(self) -> None:
        """Runs in a worker thread."""
        guest = self.guest
        try:
            config = cli.guest_config(guest)
            nets = cli.nets(config)
            storages = cli.backup_storages(guest)
            jobs = cli.backup_jobs()
            backups = cli.backups(guest, storages)
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.app.call_from_thread(self.app.notify, _message(exc), severity="error")
            return
        addresses, unavailable = [], ""
        try:  # live status: the guest table's status may be stale
            running = cli.status(guest) == "running"
        except Exception as exc:  # noqa: BLE001 - shown inline, the rest of the screen still works
            running, unavailable = False, f"unavailable: {_message(exc)}"
        if running:
            try:
                addresses = cli.interfaces(guest)
            except Exception as exc:  # noqa: BLE001 - shown inline, the rest of the screen still works
                unavailable = f"unavailable: {_message(exc)}"
        self.running = running
        self.app.call_from_thread(
            self._show, config, nets, storages, jobs, backups, addresses, unavailable
        )

    def _show(
        self, config, nets, storages, jobs, backups, addresses, unavailable
    ) -> None:
        if not self.is_attached:  # closed while loading
            return
        try:
            self._fill_screen(
                config, nets, storages, jobs, backups, addresses, unavailable
            )
        except Exception as exc:  # noqa: BLE001 - odd API data must not kill the app
            self.app.notify(f"info: {_message(exc)}", severity="error")

    def _fill_screen(
        self, config, nets, storages, jobs, backups, addresses, unavailable
    ) -> None:
        self.storages, self.jobs, self.config = storages, jobs, config
        covering = cli.covering_jobs(jobs, self.guest)
        self.query_one("#jobs", Static).update(
            "; ".join(_job_text(j) for j in covering)
            or "No backup job covers this guest"
        )
        self.backups = backups
        self._show_backups()
        table = self.query_one("#nets", DataTable).clear()
        for name, net in nets.items():
            if cli.kind(self.guest) == "vm":  # IP settings are cloud-init's ipconfigN
                mac = next(iter(net.values()), "-")
                ip = cli.parse_net(str(config.get(f"ipconfig{name[3:]}", "")))
            else:
                mac, ip = net.get("hwaddr", "-"), net
            table.add_row(
                name,
                net.get("bridge", "-"),
                net.get("tag", "-"),
                mac,
                ip.get("ip", "-"),
                ip.get("ip6", "-"),
                "yes" if net.get("firewall") == "1" else "no",
            )
        self.query_one("#unavailable", Static).update(unavailable)
        table = self.query_one("#addresses", DataTable).clear()
        for i in addresses:
            table.add_row(
                i["name"], i["mac"] or "-", ", ".join(i["ipv4"]), ", ".join(i["ipv6"])
            )

    def _show_backups(self) -> None:
        name = self.guest["name"]
        shown = [
            b for b in self.backups if self.show_all or not _earlier_guest(b, name)
        ]
        table = self.query_one("#backups", DataTable).clear()
        for b in shown:
            table.add_row(
                datetime.fromtimestamp(b["ctime"]).strftime("%Y-%m-%d %H:%M")
                if b.get("ctime")
                else "-",
                b["storage"],
                f"{b['size'] / 2**30:.1f}" if b.get("size") is not None else "-",
                b.get("format") or "-",
                (b.get("notes") or "")
                + (" (earlier guest)" if _earlier_guest(b, name) else ""),
            )
        hidden = len(self.backups) - len(shown)
        self.query_one("#hidden", Static).update(
            f"{hidden} backup(s) of an earlier guest with this VMID hidden - press a to show"
            if hidden
            else ""
        )

    def action_toggle_all(self) -> None:
        self.show_all = not self.show_all
        self._show_backups()

    def _refuse_if_busy(self) -> bool:
        busy = self.guest["vmid"] in self.app.busy
        if busy:
            self.app.notify(
                f"{self.guest['name']} ({self.guest['vmid']}) is busy",
                severity="warning",
            )
        return busy

    def action_net(self) -> None:
        if cli.nets(self.config) and not self._refuse_if_busy():
            self._open_net()

    @work(thread=True)
    def _open_net(self) -> None:
        try:
            bridges = cli.bridges(self.guest)
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.app.call_from_thread(self.app.notify, _message(exc), severity="error")
            return
        self.app.call_from_thread(
            self.app.push_screen,
            NetScreen(self.guest, self.config, bridges, self.running),
        )

    def action_undo(self) -> None:
        old = self.app.undo.get(self.guest["vmid"])
        if old is None:
            self.app.notify("No network change to undo")
            return
        if self._refuse_if_busy():
            return
        lines = [f"{k} = {v or '(remove)'}" for k, v in old.items()]
        self.app.push_screen(
            ConfirmScreen(
                "\n".join(["Restore the previous network settings?", *lines])
            ),
            lambda ok: self.app.start_net_change(self.guest, old, None) if ok else None,
        )

    def action_backup(self) -> None:
        if not self.storages:
            self.app.notify("No backup storage available", severity="warning")
            return
        chosen = cli.job_storage(self.jobs, self.guest)
        if chosen not in self.storages:
            chosen = self.storages[0]
        self.app.push_screen(
            BackupScreen(self.guest, self.storages, chosen),
            lambda storage: (
                self.app.start_backup(self.guest, storage) if storage else None
            ),
        )


def _ip_changed(old: str | None, new: str | None) -> bool:
    before, after = cli.parse_net(old or ""), cli.parse_net(new or "")
    return any(before.get(k) != after.get(k) for k in ("ip", "gw", "ip6", "gw6"))


def _earlier_guest(backup: dict, name: str) -> bool:
    """VMIDs are reused: notes (the job's {{guestname}}) naming another guest mean a deleted one."""
    notes = backup.get("notes") or ""
    return bool(notes) and notes != name and not notes.startswith(f"{name} ")


def _job_text(job: dict) -> str:
    keep = (job.get("prune-backups") or {}).get("keep-last")
    return f"{job['schedule']} to {job['storage']}" + (
        f", keep-last {keep}" if keep else ""
    )


class GuestApp(App):
    BINDINGS = [  # noqa: RUF012 - Textual idiom
        ("s", "act('start')", "Start"),
        ("S", "act('shutdown')", "Shutdown"),
        ("x", "act('stop')", "Stop"),
        ("r", "act('reboot')", "Reboot"),
        ("e", "edit", "Edit"),
        ("i", "info", "Info"),
        ("t", "shell", "Shell"),
        ("g", "reload", "Refresh"),
        ("c", "context", "Context"),
        ("q", "quit", "Quit"),
    ]

    def __init__(self) -> None:
        super().__init__()
        self.guests: dict[str, dict] = {}
        self.busy: set[int] = set()
        self.undo: dict[int, dict] = {}  # vmid -> values before the last network change
        # bumped on every context switch; replies started earlier come from the old cluster
        self.generation = 0
        self.switching = False

    def compose(self) -> ComposeResult:
        yield Header()
        yield DataTable(id="guests", cursor_type="row")
        yield Footer()

    def on_mount(self) -> None:
        table = self.query_one("#guests", DataTable)
        table.add_columns(
            "VMID",
            "Name",
            "Type",
            "Node",
            "Status",
            "Cores",
            "Memory (MiB)",
            "Disk (GiB)",
        )
        self._show_context()
        self.action_reload()

    @work(thread=True)
    def _show_context(self) -> None:
        self._read_context()

    def _read_context(self) -> None:
        """Runs in a worker thread: show the CLI's current context in the Header."""
        gen = self.generation
        try:
            name = next(c["name"] for c in cli.contexts() if c["current"])
        except StopIteration:
            name = "?"
        except Exception as exc:  # noqa: BLE001 - any failure must reach the user, not kill the app
            self.call_from_thread(self.notify, _message(exc), severity="error")
            name = "?"
        self.call_from_thread(self._set_context_title, name, gen)

    def _set_context_title(self, name: str, gen: int) -> None:
        if gen == self.generation:
            self.sub_title = f"context: {name}"

    def _selected(self) -> dict | None:
        table = self.query_one("#guests", DataTable)
        if not table.row_count:
            return None
        return self.guests[
            table.coordinate_to_cell_key(table.cursor_coordinate).row_key.value
        ]

    def _fill(self, guests: list[dict], gen: int) -> None:
        if gen != self.generation:  # listed before a context switch: old cluster
            return
        table = self.query_one("#guests", DataTable)
        current = self._selected()
        table.clear()
        self.guests = {str(g["vmid"]): g for g in guests}
        for g in guests:
            table.add_row(
                g["vmid"], g["name"], g["type"], g["node"], g["status"],
                g.get("maxcpu", "-"), _scaled(g.get("maxmem"), 2**20), _scaled(g.get("maxdisk"), 2**30),
                key=str(g["vmid"]),
            )  # fmt: skip
        if current and str(current["vmid"]) in self.guests:
            table.move_cursor(row=table.get_row_index(str(current["vmid"])))

    def _reload(self, acted: dict | None = None) -> None:
        """Runs in a worker thread. `acted` gets its live status: the listing lags."""
        gen = self.generation
        try:
            guests = cli.list_guests()
            for g in guests:
                if acted and g["vmid"] == acted["vmid"]:
                    g["status"] = cli.status(g)
        except Exception as exc:  # noqa: BLE001 - any failure must reach the user, not kill the app
            self.call_from_thread(self.notify, _message(exc), severity="error")
            return
        self.call_from_thread(self._fill, guests, gen)

    def action_reload(self) -> None:
        if self.switching:
            self.notify("Switching context; refresh after it ends", severity="warning")
            return
        self._reload_worker()

    @work(thread=True)
    def _reload_worker(self) -> None:
        self._reload()

    def action_context(self) -> None:
        if self.busy or self.switching:
            self.notify(
                "Busy (guest action or context switch); try again when it ends",
                severity="warning",
            )
            return
        self._open_context()

    @work(thread=True)
    def _open_context(self) -> None:
        try:
            contexts = cli.contexts()
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.call_from_thread(self.notify, _message(exc), severity="error")
            return
        current = next((c["name"] for c in contexts if c["current"]), None)
        self.call_from_thread(
            self.push_screen,
            ContextScreen(contexts),
            lambda name: self._context_chosen(name, current),
        )

    def _context_chosen(self, name: str | None, current: str | None) -> None:
        if name is None or name == current:
            return
        self.query_one(
            "#guests", DataTable
        ).clear()  # old cluster's guests: not actionable
        self.guests = {}
        self.undo.clear()  # VMIDs repeat across clusters: never undo onto another cluster
        self.generation += 1
        self.switching = True
        self._switch_context(name)

    @work(thread=True)
    def _switch_context(self, name: str) -> None:
        try:
            try:
                cli.use_context(name)
            except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
                self.call_from_thread(self.notify, _message(exc), severity="error")
                self._read_context()
            else:
                self.call_from_thread(setattr, self, "sub_title", f"context: {name}")
            self._reload()
        finally:
            self.call_from_thread(setattr, self, "switching", False)

    def _start_job(self, guest: dict, label: str, job) -> None:
        if guest["vmid"] in self.busy:
            self.notify(
                f"{guest['name']} ({guest['vmid']}) is busy", severity="warning"
            )
            return
        self.busy.add(guest["vmid"])
        self.notify(f"{label} {guest['name']} ({guest['vmid']}) ...")
        self._run_job(guest, label, job)

    @work(thread=True)
    def _run_job(self, guest: dict, label: str, job) -> None:
        try:
            job()
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.call_from_thread(
                self.notify, f"{label} failed: {_message(exc)}", severity="error"
            )
        else:
            self.call_from_thread(
                self.notify, f"{label} done: {guest['name']} ({guest['vmid']})"
            )
        finally:
            self._reload(
                acted=guest
            )  # before un-busying, so no context switch can start mid-reload
            self.busy.discard(guest["vmid"])

    def action_act(self, name: str) -> None:
        guest = self._selected()
        if guest is None:
            return
        run = lambda: cli.action(name, guest)
        if name == "start":
            self._start_job(guest, name, run)
            return
        who = f"{guest['name']} ({guest['vmid']})"
        text = f"{name.capitalize()} {who}?"
        if name == "stop":
            text = f"Hard power-off {who}? The guest is killed without shutting down."
        self.push_screen(
            ConfirmScreen(text),
            lambda ok: self._start_job(guest, name, run) if ok else None,
        )

    def action_edit(self) -> None:
        guest = self._selected()
        if guest is None:
            return
        if guest["vmid"] in self.busy:
            self.notify(
                f"{guest['name']} ({guest['vmid']}) is busy", severity="warning"
            )
            return
        self._open_edit(guest)

    def action_info(self) -> None:
        guest = self._selected()
        if guest is not None:
            self.push_screen(InfoScreen(guest))

    def start_backup(self, guest: dict, storage: str) -> None:
        who = f"{guest['name']} ({guest['vmid']})"
        if guest["vmid"] in self.busy:
            self.notify(f"{who} is busy", severity="warning")
            return
        self.busy.add(guest["vmid"])
        self.notify(f"Backup started: {who} to {storage}")
        self._run_backup(guest, storage)

    @work(thread=True)
    def _run_backup(self, guest: dict, storage: str) -> None:
        who = f"{guest['name']} ({guest['vmid']})"
        try:
            cli.backup_now(guest, storage)
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.call_from_thread(
                self.notify, f"Backup failed: {_message(exc)}", severity="error"
            )
        else:
            self.call_from_thread(self.notify, f"Backup done: {who}")
        finally:
            self._reload_infos(guest)
            self.busy.discard(guest["vmid"])

    def _reload_infos(self, guest: dict) -> None:
        """Runs in a worker thread: reload the guest's open InfoScreens (call while still busy)."""
        for screen in list(self.screen_stack):
            if isinstance(screen, InfoScreen) and screen.guest["vmid"] == guest["vmid"]:
                screen.load()

    def start_net_change(
        self, guest: dict, changes: dict, entry: dict | None, screen=None
    ) -> None:
        """`entry` becomes the guest's undo entry on success (None clears it).

        `screen` (the NetScreen) is closed on success and stays open on failure.
        """
        who = f"{guest['name']} ({guest['vmid']})"
        if guest["vmid"] in self.busy:
            self.notify(f"{who} is busy", severity="warning")
            return
        self.busy.add(guest["vmid"])
        self.notify(f"Network change started: {who}")
        self._run_net(guest, changes, entry, screen)

    @work(thread=True)
    def _run_net(self, guest: dict, changes: dict, entry: dict | None, screen) -> None:
        who = f"{guest['name']} ({guest['vmid']})"
        done = False
        try:
            cli.set_net(guest, changes)
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.call_from_thread(
                self.notify, f"Network change failed: {_message(exc)}", severity="error"
            )
        else:
            done = True
            if entry is None:
                self.undo.pop(guest["vmid"], None)
            else:
                self.undo[guest["vmid"]] = entry
            self.call_from_thread(self.notify, f"Network change done: {who}")
        finally:
            self._reload_infos(guest)
            if done and screen is not None:
                self.call_from_thread(self._close_net, screen)
            self.busy.discard(guest["vmid"])

    def _close_net(self, screen) -> None:
        if self.screen is screen:  # the user may have left it already
            screen.dismiss()

    def action_shell(self) -> None:
        guest = self._selected()
        if guest is None:
            return
        who = f"{guest['name']} ({guest['vmid']})"
        if guest["type"] != "lxc":
            self.notify(f"{who} is not a container", severity="warning")
            return
        if guest["status"] != "running":
            self.notify(f"{who} is not running", severity="warning")
            return
        if guest["vmid"] in self.busy:
            self.notify(f"{who} is busy", severity="warning")
            return
        cmd = ["ssh", "-t", f"root@{guest['node']}", "pct", "enter", str(guest["vmid"])]
        error = None
        try:
            with self.suspend():
                try:  # inside: Textual's suspend() skips the resume if its body raises
                    _reset_terminal()
                    code = subprocess.run(cmd, check=False).returncode
                except OSError as exc:
                    error = _message(exc)
        except SuspendNotSupported as exc:
            error = _message(exc)
        else:
            if (
                error is None and code == 255
            ):  # other codes are the shell's own last status
                error = "ssh failed (exit 255)"
        if error:
            self.notify(f"Shell in {who} failed: {error}", severity="error")
        self.action_reload()

    @work(thread=True)
    def _open_edit(self, guest: dict) -> None:
        try:
            config = cli.guest_config(guest)
            disks = cli.disks(config, cli.kind(guest))
        except Exception as exc:  # noqa: BLE001 - surface every failure, never kill the app
            self.call_from_thread(self.notify, _message(exc), severity="error")
            return
        self.call_from_thread(
            self.push_screen,
            EditScreen(guest, config, disks),
            lambda v: self._edit_done(guest, v),
        )

    def _edit_done(self, guest: dict, values: dict | None) -> None:
        if not values or not any(values[k] for k in ("cores", "memory", "grow")):
            return
        if values["grow"]:
            who = f"{guest['name']} ({guest['vmid']})"
            self.push_screen(
                ConfirmScreen(
                    f"Grow {values['disk']} of {who} by {values['grow']} GiB? This cannot be undone."
                ),
                lambda ok: (
                    self._apply(guest, values) if ok else None
                ),  # "No" cancels the whole edit
            )
        else:
            self._apply(guest, values)

    def _apply(self, guest: dict, values: dict) -> None:
        cores, memory, grow = values["cores"], values["memory"], values["grow"]

        def job() -> None:
            if cores or memory:
                cli.set_resources(guest, cores=cores, memory_mb=memory)
            if grow:
                cli.resize_disk(guest, values["disk"], grow)
            if cores or memory:
                try:
                    pending = cli.pending_keys(guest)
                except Exception as exc:  # noqa: BLE001 - only a notice; the change itself succeeded
                    self.call_from_thread(
                        self.notify,
                        f"pending check failed: {_message(exc)}",
                        severity="warning",
                    )
                    return
                if {"cores", "memory"} & set(pending):
                    self.call_from_thread(self.notify, "Change applies at next reboot")

        self._start_job(guest, "edit", job)


def _reset_terminal() -> None:
    """Full terminal reset (ESC c, what `reset` sends): clean screen, no leftover TUI modes."""
    sys.stdout.write("\033c")
    sys.stdout.flush()


def _scaled(value, unit: int):
    return "-" if value is None else round(value / unit)


def main() -> None:
    GuestApp().run()