app/backend/fluksio/flow/panels.py

"""Panels: which dashboards a given device shows.

A wall tablet in the hall and one in the workshop want different dashboards,
and the same dashboard may hang on both. Rather than nesting pages inside a
dashboard, a panel names an ordered set of whole dashboards — each keeps its
own canvas, its own draft and its own version, and the device switches between
them through a rail.

Stored beside the flows rather than in them, like the alerting configuration:
which screen hangs where is the deployment's concern, not any one dashboard's.
"""

from __future__ import annotations

import re
import threading
from pathlib import Path
from typing import Any, Literal

from pydantic import BaseModel, Field, field_validator

from fluksio.core.config import settings
from fluksio.flow.dashboards import DashboardDef, DashboardNotFound, DashboardStore
from fluksio.flow.schemas import _validate_name

#: Free text the device interprets: ``gpio.4``, ``backlight``, ``mic``.
PORT_PATTERN = re.compile(r"^[a-z0-9_.]+$")


class PanelPort(BaseModel):
    """One piece of the device's own hardware, wired to a message.

    A wall panel is a node as well as a screen: a button on its GPIO, a
    microphone, a speaker. Which ports exist is the device's business, so the
    name is free text and ``config`` is passed through to it unread.
    """

    port: str
    #: Qualified, ``flow.name`` — a flow still has to declare it, as for any
    #: widget, before a publish to it lands.
    message: str
    #: ``in`` is the device publishing into fluksio; ``out`` is the device
    #: following the message.
    direction: Literal["in", "out"]
    config: dict[str, Any] = Field(default_factory=dict)

    @field_validator("port")
    @classmethod
    def _check_port(cls, value: str) -> str:
        if not PORT_PATTERN.fullmatch(value):
            raise ValueError("Use lowercase letters, digits, underscores and dots")
        return value

    @field_validator("message")
    @classmethod
    def _check_message(cls, value: str) -> str:
        flow, _, name = value.partition(".")
        if not name:
            raise ValueError("Name the message with its flow, as flow.name")
        _validate_name(flow)
        return value


class PanelDef(BaseModel):
    """One device, and what it shows."""

    id: str
    title: str = ""
    #: Ordered. The first one is what the device opens after pairing, and the
    #: rail follows this order. A name that no longer resolves is simply a
    #: dashboard someone deleted; the panel skips it.
    dashboards: list[str] = Field(default_factory=list)
    #: Bigger controls, a bigger rail and no hover states, for a screen that is
    #: touched rather than pointed at. It belongs to the device rather than to
    #: any dashboard: the same dashboard may hang on a hallway tablet and on a
    #: desk browser, and only one of them has fingers on it.
    touch: bool = False
    #: The device's own inputs and outputs. An ``in`` port may publish whether
    #: or not a dashboard is locked — a lock covers the controls on a
    #: dashboard, not the sensors on the wall — and an ``out`` port only reads.
    io: list[PanelPort] = Field(default_factory=list)
    #: Which generation of credential this panel honours. A token names the
    #: nonce it was minted at, so bumping this refuses the screen currently
    #: hanging here and leaves the panel, its dashboards and their arrangement
    #: exactly as they are — re-pairing one device without deleting anything.
    #: Not settable from outside: a save carries the stored value forward.
    nonce: int = 0

    @field_validator("id")
    @classmethod
    def _check_id(cls, value: str) -> str:
        return _validate_name(value)


class PanelsConfig(BaseModel):
    """Every panel this instance knows about."""

    panels: list[PanelDef] = Field(default_factory=list)


#: Held across a read-modify-write of the panels file.
#:
#: Both `save_panels` and `unpair_panel` are one of those, and interleaving
#: them silently undid a revocation: a save that read the file before an
#: unpair wrote it put the old nonce back, and the screen that had just been
#: unpaired kept working. The nonce carry-forward in the save handler was
#: written to make that impossible, and the window between its read and its
#: write is where it happened anyway.
edit_lock = threading.Lock()


def _path() -> Path:
    return settings.PANELS_FILE


def read_config() -> PanelsConfig:
    """The stored panels, or none. Blocking."""
    path = _path()
    if not path.exists():
        return PanelsConfig()
    try:
        return PanelsConfig.model_validate_json(path.read_text())
    except Exception:
        # A hand-edited file that no longer parses must not lock everyone out.
        return PanelsConfig()


def write_config(config: PanelsConfig) -> None:
    """Blocking."""
    path = _path()
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(config.model_dump_json(indent=2))


def find(panel_id: str) -> PanelDef | None:
    """The panel by that id, or None if it was removed.

    Read from disk on every call: this is what makes deleting a panel revoke
    its credential, so it has to see the current file rather than a cache.
    """
    for panel in read_config().panels:
        if panel.id == panel_id:
            return panel
    return None


def dashboards_for(panel_id: str, store: DashboardStore) -> list[DashboardDef]:
    """The published documents this panel shows, in rail order.

    Published, since that is what a panel draws. A name that no longer
    resolves is a dashboard someone deleted and is skipped, and a panel that
    is gone shows nothing.

    Handed back whole rather than walked here, because what a panel may do
    with a message depends on the document it came from — a dashboard that
    says it is locked entitles a screen to read it and not to touch it.
    """
    panel = find(panel_id)
    if panel is None:
        return []
    found: list[DashboardDef] = []
    for name in panel.dashboards:
        try:
            found.append(store.read(name))
        except DashboardNotFound:
            continue
    return found


def messages_of(defn: DashboardDef) -> set[str]:
    """Every message one dashboard reads or writes.

    A dashboard's own bound settings count, not only its widgets': the theme a
    panel is driven to is a message no tile on it draws, and a wall panel
    refused its own theme message is the one surface the setting exists for.
    """
    names = set(defn.setting_messages)
    for widget in defn.widgets:
        names.update(widget.messages)
        if widget.target:
            names.add(widget.target)
    return names


def requests_of(defn: DashboardDef) -> set[str]:
    """The publishes this dashboard makes in order to read.

    A querying chart asks a flow for the series it draws by publishing a
    request, so that publish is how the tile reads rather than something
    anyone touched. Every other message a dashboard sends comes from a
    control, which is what marking it read-only turns off — so this is what a
    locked dashboard is still entitled to send.
    """
    return {w.target for w in defn.widgets if w.type == "chart" and w.target}


def io_in(panel_id: str) -> set[str]:
    """The messages this panel's own hardware publishes to."""
    panel = find(panel_id)
    if panel is None:
        return set()
    return {port.message for port in panel.io if port.direction == "in"}


def messages_for(panel_id: str, store: DashboardStore) -> set[str]:
    """Every message this panel's dashboards and its own I/O read or write.

    What a screen is entitled to see, as its dashboards and ports define it,
    and empty for a panel that is gone — which is the same answer as "nothing".
    """
    panel = find(panel_id)
    own = {port.message for port in panel.io} if panel else set()
    return own | {
        name for defn in dashboards_for(panel_id, store) for name in messages_of(defn)
    }