"""Which session owns which virtual display, read from ``phone_vd.sh`` state.

``phone_vd.sh`` keeps one directory per session under
``$PHONE_VD_STATE_DIR/<serial>/<owner>/`` holding ``display`` (the logical id
``input -d`` takes), ``sf`` (the SurfaceFlinger id ``screencap -d`` takes) and
``package``. The owner directory name is the phone_lease owner id with
anything outside ``[A-Za-z0-9_.-]`` replaced by ``_``, exactly as the script
writes it.
"""

from __future__ import annotations

from dataclasses import dataclass
import os
from pathlib import Path
import re
import tempfile

_UNSAFE = re.compile(r"[^A-Za-z0-9_.-]")


def state_root() -> Path:
    """The directory ``phone_vd.sh`` keeps its per-phone state in.

    ``$PHONE_VD_STATE_DIR``, else ``phone_vd`` under the temp dir -- the same
    ``${TMPDIR:-/tmp}`` rule the script applies, so both sides agree.
    """
    default = Path(tempfile.gettempdir()) / "phone_vd"
    return Path(os.environ.get("PHONE_VD_STATE_DIR", str(default)))


def owner_dir_name(owner: str) -> str:
    """``owner`` as ``phone_vd.sh`` names its state directory."""
    return _UNSAFE.sub("_", owner)


@dataclass(frozen=True)
class SessionDisplay:
    """One running virtual display and whose it is."""

    owner_dir: str
    display: int
    sf: str
    package: str


def _read(path: Path) -> str:
    try:
        return path.read_text(encoding="utf-8").strip()
    except OSError:
        return ""


def displays(serial: str) -> list[SessionDisplay]:
    """Every session's virtual display on ``serial``."""
    root = state_root() / serial
    found: list[SessionDisplay] = []
    if not root.is_dir():
        return found
    for entry in sorted(root.iterdir()):
        display = _read(entry / "display")
        if not display.isdigit():
            continue
        found.append(
            SessionDisplay(
                owner_dir=entry.name,
                display=int(display),
                sf=_read(entry / "sf"),
                package=_read(entry / "package"),
            )
        )
    return found


def own_display(serial: str, owner: str) -> SessionDisplay | None:
    """``owner``'s virtual display on ``serial``, if it has one running."""
    mine = owner_dir_name(owner)
    return next((d for d in displays(serial) if d.owner_dir == mine), None)


def display_owner(serial: str, display: int) -> SessionDisplay | None:
    """The session whose virtual display has logical id ``display``."""
    return next((d for d in displays(serial) if d.display == display), None)