import glob
import re
import shutil
import socket
import subprocess
import time
from typing import Any

import psutil

_wifi_cache: dict[str, tuple[float, str | None]] = {}
_WIFI_TTL = 15.0
_SSID_RE = re.compile(r"SSID:\s+(\S.*)")


def _wifi_ifaces() -> set[str]:
    """Return the names of interfaces that are wireless.

    Returns:
        Interface names having a /sys/class/net/<name>/wireless entry.
    """
    return {p.split("/")[-2] for p in glob.glob("/sys/class/net/*/wireless")}


def _ssid(iface: str) -> str | None:
    r"""Get the SSID currently associated on a wifi interface.

    Shells out to `iw dev <iface> link` and matches the unquoted
    `SSID: name` line; the working regex is `SSID:\s+(\S.*)` (a `$` anchor
    would only match the final line of the output without MULTILINE). The
    result is
    cached per interface for 15 s so the 2 s poll doesn't spawn a
    subprocess every cycle.

    Args:
        iface: network interface name.

    Returns:
        The SSID, or None if not associated or `iw` is unavailable.
    """
    hit = _wifi_cache.get(iface)
    now = time.monotonic()
    if hit is not None and now - hit[0] < _WIFI_TTL:
        return hit[1]
    ssid: str | None = None
    if shutil.which("iw"):
        try:
            out = subprocess.run(
                ["iw", "dev", iface, "link"], capture_output=True, text=True, timeout=3, check=False
            ).stdout
            m = _SSID_RE.search(out)
            if m:
                ssid = m.group(1).strip().strip('"') or None
        except (OSError, subprocess.SubprocessError):
            pass
    _wifi_cache[iface] = (now, ssid)
    return ssid


def sample() -> dict[str, Any | None]:
    """Collect interface list and wifi association for the overview page.

    Only interfaces that are up and are not the loopback are included;
    each entry carries its IPv4 addresses. The first up wifi interface
    (alphabetical order) provides the displayed SSID.

    Returns:
        A dict with "net_ifaces" (list of {name, ipv4}) and "net_wifi"
        ({iface, ssid} or None).
    """
    addrs = psutil.net_if_addrs()
    stats = psutil.net_if_stats()
    wifi_set = _wifi_ifaces()
    ifaces: list[dict[str, Any]] = []
    wifi: dict[str, Any] | None = None
    for name in sorted(addrs):
        if name == "lo":
            continue
        st = stats.get(name)
        if st is None or not bool(st.isup):
            continue
        ipv4 = [a.address for a in addrs[name] if a.family == socket.AF_INET]
        ifaces.append({"name": name, "ipv4": ipv4})
        if name in wifi_set and wifi is None:
            wifi = {"iface": name, "ssid": _ssid(name)}
    return {"net_ifaces": ifaces, "net_wifi": wifi}