#!/usr/bin/python3
# felhom-os-apply — the ROOT half of the agent's operating-system update leg (`11-os-updates.md` §5.4.1, §8.1–8.2).
#
# Install as /usr/local/sbin/felhom-os-apply (0755 root:root). The non-root agent invokes it via `sudo -n`
# (FELHOM_OSAPPLY alias) with EXACTLY:   felhom-os-apply --plan /var/lib/felhom-agent/os/plan-<id>.json
# Nothing else on the command line is accepted. Python 3, standard library only (a JSON plan cannot be parsed
# safely in sh). Tests: configs/test_felhom_os_apply.py (a fake runner; nothing real is executed).
#
# THE TRUST MODEL. The plan is written by the agent, so a broken-into agent writes whatever plan it likes. The
# protection is therefore what this file REFUSES, not where the plan came from: no removal, no downgrade, no new
# package, no package outside the plan, only Debian origin in the fast lane, no kernel / boot package on the host,
# only the box's own customer guest, and the host layer only on a box whose ROOT-OWNED install record says
# "appliance" (a BYO host belongs to its owner, `11` §1). Package signatures stay Debian's: apt checks every Release
# file, including the snapshot.debian.org fallback (decision 79). Nothing here is overridable from the environment.
#
# LAYERS (agent v0.141.0): "guest" (the customer LXC, entered with `pct exec`) and "host" (this Proxmox host, run
# directly). LANE: "fast" only — the slow lane (kernel, Proxmox, Docker) is REFUSED (R3, R14) until `11` §8 steps 5–6.
#
# Modes (plan field "mode"):
#   inventory   `apt-get update`, then report what is installed (with origin), what is pending, and health.
#   apply       repair first, pick the packages (select "listed": the plan's name=version list; "pending-fast": every
#               pending Debian / Debian-Security upgrade, for ring 0), check every refusal on an `apt-get -s`
#               simulation of EXACTLY name=version, install, clean, scan for restart-needed, report as inventory.
#   health      report health only (the agent polls it after a run).
# Output: log lines on stderr and the journal (tag felhom-os-apply); the LAST stdout line is
#   OSAPPLY-REPORT <one JSON object>
# which is what the agent parses. Exit 0 = done; 2 = refused (nothing changed); 3 = failed during install.
#
# SPEED (R-845, agent v0.141.0). Every `pct exec` costs ~0.9 s (measured on demo-hp), and v0.140.0 made one per
# package for version comparisons — 272 packages ≈ 4 minutes. Versions are now compared with the HOST's dpkg (the same
# Debian algorithm), madison/policy run once per pass for all packages, the restart scan runs only after an install,
# and one wrapper call does the whole pass (no separate inventory call before an apply).
import json
import os
import re
import stat
import subprocess
import sys
import time

PLAN_DIR = "/var/lib/felhom-agent/os"
PLAN_RE = re.compile(r"^plan-[A-Za-z0-9._-]{1,80}\.json$")
AGENT_USER = "felhom-agent"
FAST_ORIGINS = ("Debian", "Debian-Security")
# Debian package name and version grammar (Debian policy §5.6.1, §5.6.12).
NAME_RE = re.compile(r"^[a-z0-9][a-z0-9+.-]+$")
VERSION_RE = re.compile(r"^(?:[0-9]+:)?[0-9][A-Za-z0-9.+~-]*$")
SNAP_RE = re.compile(r"^[0-9]{8}T[0-9]{6}Z$")
RESERVED_VMIDS = set(range(990000, 990010)) | {9999}
DRIVES_PARENT = "/mnt/felhom-drives"
SNAPSHOT_LIST = "/etc/apt/sources.list.d/felhom-os-snapshot.list"
APT_ENV = ["env", "DEBIAN_FRONTEND=noninteractive", "APT_LISTCHANGES_FRONTEND=none", "NEEDRESTART_MODE=l", "LC_ALL=C"]
DPKG_OPTS = ["-o", "Dpkg::Options::=--force-confold", "-o", "Dpkg::Options::=--force-confdef"]
MIN_FREE = 500 * 1024 * 1024
# The installer's ROOT-OWNED record (felhom-host-install.sh `state_set mode`); the agent cannot write it.
INSTALL_STATE = "/var/lib/felhom-install/state.json"
# Kernel, boot and firmware packages are the SLOW lane on the host whatever their origin (`11` C3, §5.2): a host
# reboot is needed for them to take effect, and a bad one can stop the box from booting.
HOST_SLOW_RE = re.compile(r"^(linux-(image|headers|kbuild|modules|base)|proxmox-kernel|proxmox-default-kernel|pve-kernel|"
                          r"pve-firmware|firmware-|grub|shim|systemd-boot|intel-microcode|amd64-microcode|efibootmgr)")
# restart_needed() leaves out processes whose cgroup line matches (grep basic regex). Host: the LXC guests' own
# processes (`0::/lxc/<vmid>/...`) -- NOT lxc-start itself, whose cgroup is `0::/lxc.monitor/<vmid>` (measured
# 2026-10-04 on demo-felhom: the old pattern "lxc" hid lxc-start with 20 deleted maps, so "reboot needed" stayed false
# after a libc6 update). Pinned by test_restart_skip_patterns_against_real_cgroups.
RESTART_SKIP_CGROUP = {"guest": "docker", "host": ":/lxc/"}
HOST_SERVICES = ["pveproxy", "pvedaemon", "pvestatd", "pve-cluster", "felhom-agent"]


class Refused(Exception):
    def __init__(self, code, reason):
        super().__init__(f"{code} {reason}")
        self.code, self.reason = code, reason


class Runner:
    """Runs commands for real. Tests replace it with a fake. `guest` runs inside the container via pct exec."""

    def host(self, argv, timeout=600, stdin=None):
        p = subprocess.run(argv, capture_output=True, text=True, timeout=timeout, input=stdin)
        return p.returncode, p.stdout, p.stderr

    def guest(self, vmid, argv, timeout=1800):
        return self.host(["/usr/sbin/pct", "exec", str(vmid), "--"] + argv, timeout)

    def read_file(self, path):
        with open(path) as f:
            return f.read()

    def stat(self, path):
        return os.lstat(path)

    def agent_uid(self):
        import pwd
        return pwd.getpwnam(AGENT_USER).pw_uid

    def write_file(self, layer, vmid, path, body):
        """Write a small text file in the target layer — never via a shell string."""
        if layer == "host":
            with open(path, "w") as f:
                f.write(body)
            return
        rc, _, _ = self.host(["/usr/sbin/pct", "exec", str(vmid), "--", "tee", path], 60, stdin=body)
        if rc != 0:
            raise Refused("R7", f"could not write {path} in the guest")

    def log(self, line):
        print(line, file=sys.stderr, flush=True)
        try:
            subprocess.run(["logger", "-t", "felhom-os-apply", line], timeout=10)
        except Exception:
            pass


class Apply:
    def __init__(self, runner, plan_path):
        self.r = runner
        self.plan_path = plan_path
        self.report = {"refused": None, "mode": None}

    # ---------- checks ----------
    def load_plan(self):
        p = self.plan_path
        d, base = os.path.dirname(p), os.path.basename(p)
        if d != PLAN_DIR or not PLAN_RE.match(base) or ".." in p:
            raise Refused("R1", f"the plan must be {PLAN_DIR}/plan-<id>.json, got {p!r}")
        try:
            st = self.r.stat(p)
        except OSError as e:
            raise Refused("R1", f"cannot stat the plan: {e}")
        if not stat.S_ISREG(st.st_mode):
            raise Refused("R1", "the plan is not a regular file (a symlink or a device is refused)")
        if st.st_uid != self.r.agent_uid():
            raise Refused("R1", f"the plan is not owned by {AGENT_USER}")
        if st.st_size > 2 * 1024 * 1024:
            raise Refused("R1", "the plan is larger than 2 MB")
        try:
            plan = json.loads(self.r.read_file(p))
        except (OSError, ValueError) as e:
            raise Refused("R1", f"the plan is not valid JSON: {e}")
        if not isinstance(plan, dict):
            raise Refused("R1", "the plan is not a JSON object")
        return plan

    def check_plan(self, plan):
        mode = plan.get("mode", "apply")
        if mode not in ("apply", "inventory", "health"):
            raise Refused("R11", f"unknown mode {mode!r}")
        layer = plan.get("layer")
        if layer not in ("guest", "host"):
            raise Refused("R12", f"layer {layer!r} is not guest or host")
        if plan.get("lane", "fast") != "fast":
            raise Refused("R3", "the slow lane is refused in this release")
        vmid = plan.get("vmid")
        if not isinstance(vmid, int) or isinstance(vmid, bool) or vmid <= 0:
            raise Refused("R11", f"vmid must be a positive integer, got {vmid!r}")
        rid = plan.get("release_id", "")
        if not isinstance(rid, str) or not re.match(r"^[A-Za-z0-9._:-]{1,80}$", rid):
            raise Refused("R11", f"release_id {rid!r} is not a plain id")
        if plan.get("allow_new"):
            raise Refused("R6", "allow_new is a slow-lane field; the fast lane never adds a package")
        select = plan.get("select", "listed")
        if select not in ("listed", "pending-fast"):
            raise Refused("R11", f"unknown select {select!r}")
        pk = plan.get("packages", [])
        if not isinstance(pk, list):
            raise Refused("R11", "packages must be a list")
        if mode == "apply" and select == "listed" and not pk:
            raise Refused("R11", "packages must be a non-empty list in apply mode (select listed)")
        if select == "pending-fast" and pk:
            raise Refused("R11", "select pending-fast takes no package list")
        seen = set()
        for e in pk:
            if not isinstance(e, dict):
                raise Refused("R11", "every package entry must be an object")
            n, v, o = e.get("name"), e.get("version"), e.get("origin")
            if not isinstance(n, str) or not NAME_RE.match(n):
                raise Refused("R11", f"package name {n!r} is not a Debian package name")
            if not isinstance(v, str) or not VERSION_RE.match(v):
                raise Refused("R11", f"version {v!r} of {n} is not a Debian version string")
            if n in seen:
                raise Refused("R11", f"package {n} is named twice")
            seen.add(n)
            if o not in FAST_ORIGINS:
                raise Refused("R2", f"{n}: origin {o!r} is not Debian / Debian-Security (the fast lane, `11` C3)")
            if layer == "host" and HOST_SLOW_RE.match(n):
                raise Refused("R14", f"{n} is a kernel / boot / firmware package — the host's slow lane")
        snap = plan.get("snapshot", "")
        if snap and not SNAP_RE.match(snap):
            raise Refused("R11", f"snapshot {snap!r} is not YYYYMMDDTHHMMSSZ")
        return mode, layer, vmid, select

    def check_appliance(self):
        """R12: the host layer only on a box whose ROOT-OWNED install record says appliance (`11` §1: never BYO)."""
        try:
            st = self.r.stat(INSTALL_STATE)
        except OSError:
            raise Refused("R12", f"no install record ({INSTALL_STATE}) — this box cannot prove it is an appliance")
        if st.st_uid != 0 or (st.st_mode & 0o022):
            raise Refused("R12", f"{INSTALL_STATE} is not root-owned and root-only-writable — it proves nothing")
        try:
            mode = json.loads(self.r.read_file(INSTALL_STATE)).get("mode")
        except (OSError, ValueError, AttributeError):
            raise Refused("R12", f"{INSTALL_STATE} is unreadable — this box cannot prove it is an appliance")
        if mode != "appliance":
            raise Refused("R12", f"this box was installed as {mode!r}, not appliance — its host belongs to its owner")

    def check_guest(self, vmid):
        if vmid in RESERVED_VMIDS:
            raise Refused("R10", f"vmid {vmid} is a reserved scratch vmid")
        try:
            conf = self.r.read_file(f"/etc/pve/lxc/{vmid}.conf")
        except OSError:
            raise Refused("R10", f"vmid {vmid} is not a container on this host")
        cur = conf.split("\n[", 1)[0]  # the current config, not a snapshot section
        binds = [l for l in cur.splitlines() if re.match(r"^mp[0-9]+: " + re.escape(DRIVES_PARENT) + r",", l)]
        if not binds:
            raise Refused("R10", f"vmid {vmid} does not bind {DRIVES_PARENT} — it is not this box's customer guest")
        lock = [l for l in cur.splitlines() if l.startswith("lock:")]
        if lock:
            raise Refused("R9", f"vmid {vmid} is locked ({lock[0].split(':', 1)[1].strip()}) — a backup or restore is running")
        rc, out, _ = self.r.host(["/usr/sbin/pct", "status", str(vmid)])
        if rc != 0 or "running" not in out:
            raise Refused("R10", f"vmid {vmid} is not running")

    # ---------- target helpers ----------
    def x(self, argv, timeout=1800):
        """Run in the TARGET layer: the guest via pct exec, or the host directly."""
        if self.layer == "host":
            return self.r.host(argv, timeout)
        return self.r.guest(self.vmid, argv, timeout)

    def g(self, argv, timeout=1800):
        """Run in the customer GUEST whatever the layer (its health)."""
        return self.r.guest(self.vmid, argv, timeout)

    def dpkg_cmp(self, a, op, b):
        # The HOST's dpkg: the same Debian version algorithm, and no `pct exec` (0.9 s) per comparison (R-845).
        rc, _, _ = self.r.host(["dpkg", "--compare-versions", a, op, b], 30)
        return rc == 0

    def installed(self):
        rc, out, _ = self.x(["dpkg-query", "-W", "-f", "${Package}\t${Version}\t${db:Status-Abbrev}\n"])
        res = {}
        for l in out.splitlines():
            parts = l.split("\t")
            if len(parts) == 3 and parts[2].startswith("ii"):
                res[parts[0]] = parts[1]
        return res

    def madison_all(self, names):
        """name -> set of downloadable versions, ONE call for all names."""
        res = {n: set() for n in names}
        if not names:
            return res
        rc, out, _ = self.x(["apt-cache", "madison"] + sorted(names))
        for l in out.splitlines():
            f = [x.strip() for x in l.split("|")]
            if len(f) >= 3 and f[0] in res:
                res[f[0]].add(f[1])
        return res

    def simulate(self, args):
        rc, out, err = self.x(APT_ENV + ["apt-get", "-s", "-q"] + args)
        inst, remv = [], []
        for l in out.splitlines():
            m = re.match(r"^Inst (\S+) (?:\[([^]]*)\] )?\((\S+) (.*?) \[[a-z0-9]+\]\)", l)
            if m:
                inst.append({"name": m.group(1), "from": m.group(2), "to": m.group(3), "origin": m.group(4)})
            m = re.match(r"^Remv (\S+)", l)
            if m:
                remv.append(m.group(1))
        return rc, inst, remv, out + err

    @staticmethod
    def origin_name(origin):
        # "Debian:13.7/stable, Debian-Security:13/stable-security" -> {"Debian", "Debian-Security"}
        return {o.strip().split(":")[0] for o in origin.split(",") if o.strip()}

    def free_bytes(self):
        rc, out, _ = self.x(["df", "-B1", "--output=avail", "/"])
        try:
            return int(out.strip().splitlines()[-1])
        except (ValueError, IndexError):
            return -1

    def apt_lock_held(self):
        rc, out, _ = self.x(["fuser", "/var/lib/dpkg/lock-frontend", "/var/lib/dpkg/lock"])
        return rc == 0 and out.strip() != ""

    def guest_health(self):
        """The guest's signals: every container's state + health, the controller's own health, the network."""
        rc, out, _ = self.g(["docker", "ps", "-a", "--format", "{{.Names}}\t{{.State}}\t{{.Status}}"], timeout=60)
        cont = {}
        for l in out.splitlines():
            p = l.split("\t")
            if len(p) == 3:
                h = "healthy" if "(healthy)" in p[2] else "unhealthy" if "(unhealthy)" in p[2] else \
                    "starting" if "(health: starting)" in p[2] else "none"
                cont[p[0]] = {"state": p[1], "health": h}
        nrc, _, _ = self.g(["getent", "hosts", "deb.debian.org"], timeout=30)
        return {"docker_ok": rc == 0, "containers": cont,
                "controller": cont.get("felhom-controller", {}).get("health", "absent"),
                "network_ok": nrc == 0}

    def health(self):
        if self.layer == "guest":
            return self.guest_health()
        rc, out, _ = self.r.host(["systemctl", "is-active"] + HOST_SERVICES, 30)
        states = out.split()
        svc = {s: (states[i] if i < len(states) else "unknown") for i, s in enumerate(HOST_SERVICES)}
        src, sout, _ = self.r.host(["/usr/sbin/pct", "status", str(self.vmid)], 30)
        running = src == 0 and "running" in sout
        return {"host_services": svc, "guest_running": running, "guest": self.guest_health() if running else None}

    def restart_needed(self):
        """Processes still mapping deleted files, OUTSIDE containers (C11). Guest: outside docker; host: outside the
        LXC guests (the host's /proc shows guest processes too)."""
        skip = RESTART_SKIP_CGROUP[self.layer]
        script = ('for p in /proc/[0-9]*; do grep -q "(deleted)" $p/maps 2>/dev/null || continue; '
                  'grep -q "%s" $p/cgroup 2>/dev/null && continue; echo "${p#/proc/} $(cat $p/comm 2>/dev/null)"; done' % skip)
        rc, out, _ = self.x(["sh", "-c", script], timeout=120)
        lines = [l for l in out.splitlines() if " " in l]
        procs = sorted({l.split(" ", 1)[1] for l in lines})
        pid1 = any(l.split(" ", 1)[0] == "1" for l in lines)
        return procs, pid1 or "lxc-start" in procs

    def inventory(self, inst=None):
        inst = inst if inst is not None else self.installed()
        names = sorted(inst)
        origins = {}
        if names:
            rc, out, _ = self.x(["apt-cache", "policy"] + names)  # ONE call (R-845)
            cur, star = None, False
            for l in out.splitlines():
                if not l.startswith(" "):
                    cur, star = l.rstrip(":"), False
                    continue
                s = l.strip()
                if s.startswith("*** "):
                    star = True
                    continue
                if star and cur and re.match(r"^[0-9-]+ ", s):
                    if "/var/lib/dpkg/status" in s:
                        origins.setdefault(cur, "local")
                    else:
                        origins[cur] = s
                    continue
                if star and not re.match(r"^[0-9-]+ ", s):
                    star = False

        def oname(src):
            if src in (None, "local"):
                return "unknown"
            if "proxmox" in src:
                return "Proxmox"
            if "security" in src and "debian" in src:
                return "Debian-Security"
            if "docker.com" in src:
                return "Docker"
            if "debian" in src:
                return "Debian"
            return "other"
        rc, pend, remv, _ = self.simulate(["dist-upgrade"])
        self._pending = pend
        return {
            "installed": [{"name": n, "version": inst[n], "origin": oname(origins.get(n))} for n in names],
            "pending": [{"name": p["name"], "from": p["from"], "to": p["to"],
                         "origin": sorted(self.origin_name(p["origin"]))} for p in pend],
        }

    # ---------- the run ----------
    def run(self):
        plan = self.load_plan()
        self.mode, self.layer, self.vmid, self.select = self.check_plan(plan)
        self.report.update(mode=self.mode, layer=self.layer, release_id=plan.get("release_id"), vmid=self.vmid)
        if self.layer == "host":
            self.check_appliance()
        self.check_guest(self.vmid)
        log = self.r.log
        if self.mode == "health":
            self.report["health"] = self.health()
            return 0
        log(f"os-apply: START release={plan.get('release_id')} layer={self.layer}" +
            (f":{self.vmid}" if self.layer == "guest" else "") +
            f" lane=fast mode={self.mode} select={self.select} packages={len(plan.get('packages', []))}")
        if self.apt_lock_held():
            raise Refused("R9", f"another apt/dpkg holds the lock on the {self.layer}")
        self.report["health_before"] = self.health()
        if self.mode == "apply":
            self.repair()
        rc, out, err = self.x(APT_ENV + ["apt-get", "-q", "update"], timeout=600)
        if rc != 0:
            raise Refused("R7", f"apt-get update failed on the {self.layer}: {(out + err).strip().splitlines()[-1:]}")
        installed_after = None
        if self.mode == "apply":
            rc, installed_after = self.apply(plan)
            if rc:
                return rc
        self.report.update(self.inventory(installed_after))
        if self.layer == "host" and "reboot_needed" not in self.report:
            # The host is scanned on EVERY pass (local, no pct exec): a reboot must CLEAR "reboot needed", or the hub's
            # 14-day alarm fires on a host that was rebooted long ago. The guest still scans only after an install
            # (R-845; one pct exec, and no alarm reads it). Pinned by test_host_scans_every_pass_guest_only_after_install.
            self.report["restart_needed"], self.report["reboot_needed"] = self.restart_needed()
        self.report["reboot_scanned"] = "reboot_needed" in self.report
        self.report["health_after"] = self.health()
        return 0

    def repair(self):
        rc, before, _ = self.x(["dpkg", "--audit"])
        configured = len([l for l in before.splitlines() if l.startswith(" ")])
        fixed = 0
        after = ""
        if before.strip():  # nothing half-done → nothing to run (R-845: two calls saved on every clean pass)
            self.x(APT_ENV + ["dpkg", "--configure", "-a", "--force-confold"])
            rc2, out, err = self.x(APT_ENV + ["apt-get", "-f", "install", "-y", "-q"] + DPKG_OPTS)
            _, after, _ = self.x(["dpkg", "--audit"])
            fixed = len(re.findall(r"^Setting up ", out, re.M))
        self.report["repair"] = {"half_configured_before": configured, "fixed": fixed, "clean_after": after.strip() == ""}
        self.r.log(f"os-apply: REPAIR configured={configured} fixed={fixed}")
        if after.strip():
            raise Refused("R13", "dpkg is still broken after the repair: " + after.strip().splitlines()[0])

    def pending_fast(self):
        """Ring 0 (select pending-fast): every pending upgrade of an INSTALLED package whose every origin is Debian /
        Debian-Security — and, on the host, not a kernel / boot / firmware package."""
        rc, pend, remv, _ = self.simulate(["dist-upgrade"])
        out = []
        for p in pend:
            o = self.origin_name(p["origin"])
            if p["from"] is None or not o or not o <= set(FAST_ORIGINS):
                continue
            if self.layer == "host" and HOST_SLOW_RE.match(p["name"]):
                continue
            out.append({"name": p["name"], "version": p["to"], "origin": "Debian-Security" if "Debian-Security" in o else "Debian"})
        return out

    def apply(self, plan):
        log = self.r.log
        packages = plan["packages"] if self.select == "listed" else self.pending_fast()
        inst = self.installed()
        upgrade, already, notinst = [], 0, 0
        for e in packages:
            n, v = e["name"], e["version"]
            if n not in inst:
                notinst += 1
                continue
            if not self.dpkg_cmp(v, "gt", inst[n]):
                already += 1
                continue
            upgrade.append((n, v))
        from_snap = 0
        if upgrade:
            avail = self.madison_all([n for n, _ in upgrade])
            missing = [(n, v) for n, v in upgrade if v not in avail[n]]
        else:
            missing = []
        if missing:
            snap = plan.get("snapshot", "")
            if not snap:
                raise Refused("R7", f"{missing[0][0]}={missing[0][1]} is not downloadable and the plan names no snapshot")
            self.add_snapshot_sources(snap)
            avail = self.madison_all([n for n, _ in missing])
            still = [(n, v) for n, v in missing if v not in avail[n]]
            if still:
                self.remove_snapshot_sources()
                raise Refused("R7", f"{still[0][0]}={still[0][1]} is not downloadable, not even from snapshot {snap}")
            from_snap = len(missing)
        try:
            log(f"os-apply: PLAN upgrade={len(upgrade)} already={already} not-installed={notinst} from-snapshot={from_snap}")
            self.report["plan"] = {"upgrade": len(upgrade), "already": already, "not_installed": notinst, "from_snapshot": from_snap}
            if not upgrade:
                self.report["upgraded"] = []
                log("os-apply: DONE rc=0 seconds=0 upgraded=0 (nothing to do)")
                return 0, inst
            args = ["install", "--only-upgrade", "--no-install-recommends"] + [f"{n}={v}" for n, v in upgrade]
            rc, sim, remv, text = self.simulate(args)
            if rc != 0:
                tail = text.strip().splitlines()[-1] if text.strip() else ""
                raise Refused("R7", "the simulation failed: " + tail)
            if remv:
                raise Refused("R4", f"the plan would remove {', '.join(remv[:5])}")
            want = dict(upgrade)
            for p in sim:
                if p["from"] is None:
                    raise Refused("R6", f"the plan would add a package that is not installed: {p['name']}")
                if p["name"] not in want:
                    raise Refused("R6", f"the plan would touch {p['name']}, which is not in the plan")
                if p["to"] != want[p["name"]]:
                    raise Refused("R6", f"{p['name']} would go to {p['to']}, not the approved {want[p['name']]}")
                if not self.dpkg_cmp(p["to"], "gt", p["from"]):
                    raise Refused("R5", f"{p['name']} would be downgraded {p['from']} -> {p['to']}")
                if not self.origin_name(p["origin"]) & set(FAST_ORIGINS):
                    raise Refused("R2", f"{p['name']} would come from {p['origin']}, not Debian")
                if self.layer == "host" and HOST_SLOW_RE.match(p["name"]):
                    raise Refused("R14", f"{p['name']} is a kernel / boot / firmware package — the host's slow lane")
            need = self.download_bytes(args)
            free = self.free_bytes()
            if free >= 0 and free < max(MIN_FREE, 3 * need):
                raise Refused("R8", f"free space {free} B is below max(500 MB, 3 x download {need} B)")
            t0 = time.time()
            rc, out, err = self.x(APT_ENV + ["apt-get", "-y", "-q"] + DPKG_OPTS + args)
            secs = time.time() - t0
            # dpkg says "Installing new version of config file X" when X was NOT changed locally (the package's new
            # version is taken), and "Configuration file 'X'" + "Keeping old config file" when it was (--force-confold
            # keeps the local one; the package's version lands as X.dpkg-dist). Measured live 2026-10-04 (debian_version).
            conflict = None
            for l in (out + err).splitlines():
                m = re.search(r"Installing new version of config file (\S+?)\s*\.\.\.", l)
                if m:
                    log(f"os-apply: CONFFILE updated {m.group(1)} (it was not changed locally)")
                m = re.search(r"Configuration file '([^']+)'", l)
                if m:
                    conflict = m.group(1)
                if conflict and "Keeping old config file" in l:
                    log(f"os-apply: CONFFILE kept {conflict} (changed locally; the package's version is {conflict}.dpkg-dist)")
                    self.report.setdefault("conffiles_kept", []).append(conflict)
                    conflict = None
            self.x(["apt-get", "clean"])
            if rc != 0:
                _, aud, _ = self.x(["dpkg", "--audit"])
                first = aud.strip().splitlines()[0] if aud.strip() else "clean"
                log(f"os-apply: FAILED rc={rc} step=install — dpkg state: {first}")
                self.report["failed"] = {"rc": rc, "dpkg_audit": first, "tail": (out + err).strip().splitlines()[-3:]}
                return 3, None
            self.report["upgraded"] = [{"name": n, "version": v} for n, v in upgrade]
            self.report["seconds"] = round(secs, 1)
            procs, reboot = self.restart_needed()  # only after an install (R-845)
            self.report["restart_needed"] = procs
            self.report["docker_restart_needed"] = any(p in ("dockerd", "containerd") for p in procs)
            self.report["reboot_needed"] = reboot
            log(f"os-apply: DONE rc=0 seconds={secs:.1f} upgraded={len(upgrade)} restart-needed={','.join(procs) or '-'} reboot-needed={'yes' if reboot else 'no'}")
            return 0, None
        finally:
            if from_snap:
                self.remove_snapshot_sources()

    def download_bytes(self, args):
        rc, out, _ = self.x(APT_ENV + ["apt-get", "-s", "-o", "Debug::NoLocking=1", "--print-uris", "-q"] + args)
        total = 0
        for l in out.splitlines():
            m = re.match(r"^'[^']+' \S+ ([0-9]+) ", l)
            if m:
                total += int(m.group(1))
        return total

    def add_snapshot_sources(self, snap):
        rc, out, _ = self.x(["sh", "-c", ". /etc/os-release && echo $VERSION_CODENAME"])
        code = out.strip()
        if not re.match(r"^[a-z]+$", code):
            raise Refused("R7", f"cannot read the {self.layer}'s Debian codename ({code!r})")
        body = (f"deb [check-valid-until=no] http://snapshot.debian.org/archive/debian/{snap} {code} main\n"
                f"deb [check-valid-until=no] http://snapshot.debian.org/archive/debian-security/{snap} {code}-security main\n")
        self.r.write_file(self.layer, self.vmid, SNAPSHOT_LIST, body)
        self.r.log(f"os-apply: SNAPSHOT using snapshot.debian.org/{snap} for versions no longer published (decision 79)")
        rc, out, err = self.x(APT_ENV + ["apt-get", "-q", "update"], timeout=600)
        if rc != 0:
            self.remove_snapshot_sources()
            raise Refused("R7", "apt-get update against snapshot.debian.org failed")

    def remove_snapshot_sources(self):
        self.x(["rm", "-f", SNAPSHOT_LIST])
        self.x(APT_ENV + ["apt-get", "-q", "update"], timeout=600)


def main(argv, runner=None):
    r = runner or Runner()
    if len(argv) != 3 or argv[1] != "--plan":
        r.log("os-apply: REFUSED: R1 usage: felhom-os-apply --plan /var/lib/felhom-agent/os/plan-<id>.json")
        print("OSAPPLY-REPORT " + json.dumps({"refused": {"code": "R1", "reason": "usage"}}))
        return 2
    a = Apply(r, argv[2])
    t0 = time.time()
    try:
        rc = a.run()
    except Refused as e:
        r.log(f"os-apply: REFUSED: {e.code} {e.reason}")
        a.report["refused"] = {"code": e.code, "reason": e.reason}
        rc = 2
    except subprocess.TimeoutExpired as e:
        r.log(f"os-apply: FAILED rc=124 step=timeout — {e.cmd}")
        a.report["failed"] = {"rc": 124, "timeout": str(e.cmd)[:200]}
        rc = 3
    a.report["pass_seconds"] = round(time.time() - t0, 1)
    print("OSAPPLY-REPORT " + json.dumps(a.report, sort_keys=True))
    return rc


if __name__ == "__main__":
    if os.geteuid() != 0:
        print("felhom-os-apply: must run as root (via sudo)", file=sys.stderr)
        sys.exit(2)
    sys.exit(main(sys.argv))