"""Bounded temporary work files on a private per-run tmpfs mount."""
from pathlib import Path
import re
import subprocess
from .catalog import safe_path


def mounts(settings):
    result = []
    for line in Path("/proc/mounts").read_text().splitlines():
        device, target, kind, *_ = line.split()
        if not device.startswith("xas-run-") or kind != "tmpfs":
            continue
        identity = device.removeprefix("xas-run-")
        if not re.fullmatch(r"[a-f0-9]{32}", identity):
            continue
        expected = settings.runs / identity / "work"
        if target != str(expected):
            continue
        result.append(safe_path(expected, settings.runs))
    return result


def create(settings, identity, uid):
    target = safe_path(settings.runs / identity / "work", settings.runs)
    if target in mounts(settings):
        raise ValueError("本次临时目录已经挂载，拒绝覆盖")
    subprocess.run(["mount", "-t", "tmpfs", "-o", f"size=134217728,nodev,nosuid,noexec,mode=0770,uid={uid},gid={uid}",
                    "xas-run-" + identity, str(target)], check=True, capture_output=True, timeout=10)


def remove(settings, target):
    if target not in mounts(settings):
        raise ValueError("临时挂载归属核验失败")
    subprocess.run(["umount", "--", str(target)], check=True, capture_output=True, timeout=10)