cka-sim/exam

#!/usr/bin/env python3
"""exam - Kubernetes certification exam simulator (CKA / CKAD / CKS tracks).
Hands-on tasks graded per-check against the live cluster, exam clock, attempt history,
weak-spot log, drill mode, and a browser front end modelled on the real exam."""
import http.server
import importlib
import json
import os
import shutil
import signal
import subprocess
import sys
import threading
import time
import urllib.parse
from collections.abc import Callable
from datetime import datetime
from typing import Any

VERSION = "2026.09.07.1"
ROOT = os.path.dirname(os.path.abspath(__file__))
sys.path.insert(0, ROOT)

# ------------------------------------------------------------ track ----
ARGV = sys.argv[1:]
TRACKS = ["cka", "ckad", "cks"]
TRACK_ID = ""
TRACK = {}
QUESTIONS = []
DOMAINS = {}
QUOTA = {}
QUOTA_HARD = {}
QBYID = {}
SETS = {}
POOL = []
EXAM_SECONDS = 0
PASS_PCT = 0
STATE_FILE = ""
HISTORY_FILE = ""
WEAK_FILE = ""


def load_track(track_id):
    """Bind every track-dependent global. Called at startup and when the UI switches track."""
    try:
        mod = importlib.import_module(f"tracks.{track_id}.questions")
    except ModuleNotFoundError:
        print(f"unknown track '{track_id}' (no tracks/{track_id}/questions.py)"); sys.exit(1)
    importlib.reload(mod)
    track, questions = mod.TRACK, list(mod.QUESTIONS)
    for q in questions:
        q["weight"] = sum(c["pts"] for c in q["checks"])
        q.setdefault("difficulty", "normal")
        q.setdefault("set", None)
    g = globals()
    g.update(
        TRACK_ID=track_id, TRACK=track, QUESTIONS=questions, DOMAINS=track["domains"],
        QUOTA=track.get("quota", {}), QUOTA_HARD=track.get("quota_hard", track.get("quota", {})),
        QBYID={q["id"]: q for q in questions},
        SETS=track.get("sets", {}),
        POOL=[q for q in questions if not q.get("set")],
        EXAM_SECONDS=track["minutes"] * 60, PASS_PCT=track["pass_pct"],
        STATE_FILE=os.path.join(ROOT, ".state", f"state-{track_id}.json"),
        HISTORY_FILE=os.path.join(ROOT, f"history-{track_id}.jsonl"),
        WEAK_FILE=os.path.join(ROOT, f"weak-spots-{track_id}.md"),
    )


def set_questions(name):
    return [q for q in QUESTIONS if q.get("set") == name]


STATE_DIR = os.path.join(ROOT, ".state")
WORKSPACE = os.path.join(ROOT, "workspace")
# How {WS} is shown in task text and solutions. Relative to the repo root by default, since that
# is where you are working; graders always use the absolute $WS internally.
WS_DISPLAY = os.environ.get("CKA_WS_DISPLAY") or os.path.relpath(WORKSPACE, ROOT)
DRILL_SECONDS_PER_TASK = 6 * 60
DRILL_SECONDS_PER_TASK_HARD = 5 * 60
DRILL_SIZE = 5
import random
NAMESPACES_TO_SETTLE = ["apps", "netpol", "svc", "ingress-app", "dns-check", "storage"]

# --- cluster targeting (override with env vars to use a non-kind cluster) ---
CONTEXT = os.environ.get("CKA_CONTEXT", "kind-cka-sim")
def _default_access():
    try:
        return open(os.path.join(STATE_DIR, "runtime")).read().strip()  # written by setup.sh
    except OSError:
        return "podman"
NODE_ACCESS = os.environ.get("CKA_NODE_ACCESS", _default_access())  # podman | docker | ssh | vagrant
NODES = {
    "CP": os.environ.get("CKA_CP", "cka-sim-control-plane"),
    "W1": os.environ.get("CKA_W1", "cka-sim-worker"),
    "W2": os.environ.get("CKA_W2", "cka-sim-worker2"),
    "W3": os.environ.get("CKA_W3", "cka-sim-worker3"),
}
def shell_hint(node):
    return {"podman": f"podman exec -it {node} bash",
            "docker": f"docker exec -it {node} bash",
            "ssh": f"ssh {node}",
            "vagrant": f"vagrant ssh {node}"}.get(NODE_ACCESS, f"ssh {node}")

PRELUDE = r"""
set -uo pipefail
K="kubectl --context ${CKA_CONTEXT:-kind-cka-sim}"     # grading never depends on the candidate's current context
WS="$WORKSPACE"
# j [kubectl get args...] '{jsonpath}'  -> prints the jsonpath result ("" on error)
j() { local n=$#; local path="${!n}"; $K get "${@:1:n-1}" -o "jsonpath=$path" 2>/dev/null; }
eq() { [ "$1" = "$2" ]; }
CP="${CKA_CP:-cka-sim-control-plane}"; W1="${CKA_W1:-cka-sim-worker}"
W2="${CKA_W2:-cka-sim-worker2}";       W3="${CKA_W3:-cka-sim-worker3}"
# nx NODE 'command' -> run a shell command on a node (stdin is forwarded)
nx() {
  local n="$1"; shift
  case "${CKA_NODE_ACCESS:-podman}" in
    ssh)     ssh -o BatchMode=yes -o StrictHostKeyChecking=accept-new "$n" "$@" ;;
    vagrant) vagrant ssh "$n" -c "$*" -- -o LogLevel=QUIET ;;
    docker)  docker exec -i "$n" sh -c "$*" ;;
    *)       podman exec -i "$n" sh -c "$*" ;;
  esac
}
# ensure_etcd_tools -> etcdctl and etcdutl on the control-plane node, as on the real exam.
# The etcd image is distroless, so they cannot be copied out of the pod; etcd-tools.sh takes
# them from the image in the node's containerd (and falls back to a download / apt).
ensure_etcd_tools() {
  nx "$CP" 'command -v etcdctl >/dev/null 2>&1 && command -v etcdutl >/dev/null 2>&1' </dev/null && return 0
  bash "${CKA_ROOT:-.}/etcd-tools.sh" --emit | nx "$CP" 'sh -s'
}
"""

def _pick_track_arg(argv):
    t = os.environ.get("CKA_TRACK", "cka")
    if "--track" in argv:
        i = argv.index("--track"); t = argv[i + 1]; del argv[i:i + 2]
    return t


load_track(_pick_track_arg(ARGV))

TTY = sys.stdout.isatty()
def c(code, s): return f"\033[{code}m{s}\033[0m" if TTY else s
def green(s): return c("32", s)
def red(s): return c("31", s)
def yellow(s): return c("33", s)
def bold(s): return c("1", s)
def dim(s): return c("2", s)
def die(msg, code=1):
    print(red(msg)); sys.exit(code)

# ------------------------------------------------------------- state ----
def load_state() -> dict[str, Any] | None:
    if not os.path.exists(STATE_FILE):
        return None
    with open(STATE_FILE) as f:
        return json.load(f)

def save_state(st: dict[str, Any]) -> None:
    os.makedirs(STATE_DIR, exist_ok=True)
    with open(STATE_FILE, "w") as f:
        json.dump(st, f, indent=2)

def paused_total(st: dict[str, Any] | None) -> float:
    """Seconds spent paused so far, including the current pause if any."""
    if not st:
        return 0.0
    t = float(st.get("paused_total", 0))
    if st.get("paused_at"):
        t += time.time() - float(st["paused_at"])
    return t

def untimed(st: dict[str, Any] | None) -> bool:
    return bool(st and st.get("untimed"))

def remaining(st: dict[str, Any] | None) -> float:
    if not st:
        return 0.0
    if untimed(st):
        return float("inf")
    return float(st.get("started_at", 0)) + float(st.get("duration", EXAM_SECONDS)) + paused_total(st) - time.time()

def set_paused(st: dict[str, Any], on: bool) -> None:
    if on and not st.get("paused_at"):
        st["paused_at"] = time.time(); st["pauses"] = int(st.get("pauses", 0)) + 1
    elif not on and st.get("paused_at"):
        st["paused_total"] = float(st.get("paused_total", 0)) + (time.time() - float(st["paused_at"])); st["paused_at"] = None
    save_state(st)

def fmt(secs: float | int) -> str:
    secs_int = max(0, int(secs))
    return f"{secs_int // 3600:02d}:{(secs_int % 3600) // 60:02d}:{secs_int % 60:02d}"

def require_started() -> dict[str, Any]:
    st = load_state()
    if not st:
        die("No session in progress. Run:  ./exam start   (or ./exam drill weak)")
    assert st is not None
    return st

def session_questions(st: dict[str, Any] | None) -> list[dict[str, Any]]:
    if not st:
        return list(QUESTIONS)
    ids = st.get("ids") or [q["id"] for q in QUESTIONS]
    # Preserve the session's own order. Filtering QUESTIONS (which is sorted by id) threw it away,
    # so compose_exam's rng.shuffle never reached the candidate and every exam arrived grouped by
    # domain and difficulty - base tasks first, then hard, then the sim sets. Real exams are not
    # ordered by difficulty, and practising triage on a sorted list teaches the wrong instinct.
    by_id = {q["id"]: q for q in QUESTIONS}
    return [by_id[i] for i in ids if i in by_id]

def q_by_id(n: int) -> dict[str, Any]:
    for q in QUESTIONS:
        if q["id"] == n:
            return q
    # ids are not contiguous (1-43 base, 101-124 hard, 201-217 / 301-317 sim sets), so print the
    # real ranges rather than "1-<count>", which named ids that do not exist.
    ids = sorted(q["id"] for q in QUESTIONS)
    ranges, start, prev = [], ids[0], ids[0]
    for i in ids[1:] + [None]:
        if i != prev + 1:
            ranges.append(str(start) if start == prev else f"{start}-{prev}")
            start = i
        prev = i
    die(f"No question {n}. Valid: {', '.join(ranges)}")
    return {}

def render(text, params):
    """Substitute %{param}, {WS}, {CP}.. and {SHELL_CP}.. placeholders."""
    t = text.replace("{WS}", WS_DISPLAY)
    for k, v in (params or {}).items():
        t = t.replace("%{" + k + "}", str(v))
    for k, v in NODES.items():
        t = t.replace("{" + k + "}", v).replace("{SHELL_" + k + "}", shell_hint(v))
    return t

def session_params(st, q):
    """Params drawn for this session; outside a session, a fixed sample so text still reads naturally."""
    p = (st or {}).get("params", {}).get(str(q["id"]))
    return p if p is not None else make_params(q, random.Random(q["id"]))

def task_text(q, params=None):
    return render(q["task"].strip(), params if params is not None else session_params(load_state(), q))

def make_params(q, rng):
    fn = q.get("params")
    return fn(rng) if fn else {}

# -------------------------------------------------------------- shell ----
def run(script, timeout=180, params=None):
    env = dict(os.environ, WORKSPACE=WORKSPACE, CKA_ROOT=ROOT, CKA_NODE_ACCESS=NODE_ACCESS, CKA_CONTEXT=CONTEXT,
               **{f"CKA_{k}": v for k, v in NODES.items()})
    p = subprocess.run(["bash", "-c", PRELUDE + render(script, params)], env=env, capture_output=True, text=True,
                       timeout=timeout, stdin=subprocess.DEVNULL)
    return p.returncode, (p.stdout + p.stderr).strip()

def kubectl_ok():
    try:
        return subprocess.run(["kubectl", "--context", CONTEXT, "get", "--raw=/version"],
                              capture_output=True, text=True, timeout=15).returncode == 0
    except Exception:
        return False

def grade_one(q, params=None):
    """Run every check independently. Returns a result dict with partial credit."""
    if params is None:
        params = session_params(load_state(), q)
    checks = []
    for ch in q["checks"]:
        try:
            rc, out = run(ch["script"], timeout=240, params=params)
        except subprocess.TimeoutExpired:
            rc, out = 1, "timed out"
        checks.append({"name": render(ch["name"], params), "pts": ch["pts"], "pass": rc == 0, "out": out[-400:]})
    earned = sum(ch["pts"] for ch in checks if ch["pass"])
    return {"pass": earned == q["weight"], "earned": earned, "total": q["weight"],
            "checks": checks, "at": time.time(), "difficulty": q["difficulty"]}

def result_detail(r):
    return "\n".join(("  ✓ " if ch["pass"] else "  ✗ ") + ch["name"] + f" ({ch['pts']} pt)" for ch in r["checks"])

def score(st, results=None):
    results = results if results is not None else st["results"]
    qs = session_questions(st)
    total = sum(q["weight"] for q in qs)
    earned = sum(results.get(str(q["id"]), {}).get("earned", 0) for q in qs)
    return earned, total, (round(100 * earned / total, 1) if total else 0)

# ----------------------------------------------------------- history ----
def load_history():
    if not os.path.exists(HISTORY_FILE):
        return []
    with open(HISTORY_FILE) as f:
        return [json.loads(l) for l in f if l.strip()]

def record_attempt(st):
    earned, total, pct = score(st)
    entry = {"at": datetime.now().isoformat(timespec="minutes"), "mode": st.get("mode", "exam"), "hard": st.get("hard", False),
             "ids": [q["id"] for q in session_questions(st)], "score_pct": pct, "earned": earned, "total": total,
             "time_used": int(st["ended_at"] - st["started_at"] - paused_total(st)),
             "pauses": st.get("pauses", 0), "paused_seconds": int(paused_total(st)),
             "results": {k: {"pass": v["pass"], "earned": v["earned"], "total": v["total"],
                             "failed": [ch["name"] for ch in v["checks"] if not ch["pass"]]}
                         for k, v in st["results"].items()}}
    with open(HISTORY_FILE, "a") as f:
        f.write(json.dumps(entry) + "\n")
    write_weak_spots()
    return entry

class AggEntry:
    def __init__(self) -> None:
        self.attempts: int = 0
        self.fails: int = 0
        self.last: Any = None
        self.last_fail_at: str = ""
        self.failed: list[str] = []
        self.last_earned: str = ""

    def __getitem__(self, item: str) -> Any:
        return getattr(self, item)

    def __setitem__(self, item: str, value: Any) -> None:
        setattr(self, item, value)

    def to_dict(self) -> dict[str, Any]:
        return {
            "attempts": self.attempts,
            "fails": self.fails,
            "last": self.last,
            "last_fail_at": self.last_fail_at,
            "failed": self.failed,
            "last_earned": self.last_earned,
        }


def stats() -> dict[int, AggEntry]:
    agg: dict[int, AggEntry] = {int(q["id"]): AggEntry() for q in QUESTIONS}
    for e in load_history():
        for k, r in e.get("results", {}).items():
            a = agg.get(int(k))
            if a is None:
                continue
            a.attempts += 1
            a.last = r.get("pass")
            a.last_earned = f"{r.get('earned', 0)}/{r.get('total', 0)}"
            if not r.get("pass"):
                a.fails += 1
                a.last_fail_at = str(e.get("at", ""))
                a.failed = list(r.get("failed", []))
    return agg

def last_seen():
    """question id -> index of the most recent session it appeared in (higher = more recent)."""
    seen = {}
    for i, e in enumerate(load_history()):
        for k in e["results"]:
            seen[int(k)] = i
    return seen

def drilled_domains():
    out = {d: 0 for d in DOMAINS}
    for e in load_history():
        if e["mode"] != "drill":
            continue
        for k in e["results"]:
            q = QBYID.get(int(k))
            if q:
                out[q["domain"]] += 1
    return out

def no_conflicts(cands, n, taken=()):
    """Take up to n tasks, never two that break the same thing (or clash with tasks already taken)."""
    used = {q.get("breaks") for q in taken if q.get("breaks")}
    out = []
    for q in cands:
        b = q.get("breaks")
        if b and b in used:
            continue
        out.append(q)
        if b:
            used.add(b)
        if len(out) == n:
            break
    return out

def pick(domain, n, hard, rng, exclude=(), taken=(), unseen_only=False):
    """n tasks from a domain: unseen first, then least recently seen; hard sessions prefer hard tasks."""
    seen = last_seen()

    def build(allow_hard):
        pool = [q for q in POOL if q["domain"] == domain and q["id"] not in exclude
                and (allow_hard or q["difficulty"] == "normal") and not (unseen_only and q["id"] in seen)]
        rng.shuffle(pool)
        pool.sort(key=lambda q: (0 if (hard and q["difficulty"] == "hard") else 1, seen.get(q["id"], -1)))
        return pool

    got = no_conflicts(build(hard), n, taken)
    if len(got) < n and not hard:
        # A domain whose only tasks are "hard" contributes NOTHING to a normal session and drops
        # out of the blueprint entirely - CKS SUPPLY and RUNTIME (20% each) were both unreachable
        # via ./exam start. Better to hand over a hard task than to silently skip the domain.
        got = no_conflicts(build(True), n, taken)
    return got

def compose_exam(hard, rng):
    quota = QUOTA_HARD if hard else QUOTA
    # Scarcest domain first. Two tasks that "breaks" the same thing can't share a session, so a
    # one-task domain loses every such tie to a bigger domain that claimed the shared slot earlier
    # and then contributes nothing: CKS RUNTIME (only Q9, apiserver-flag) was never drawn in ANY
    # mode because SETUP was iterated first and took that slot with Q2.
    order = sorted(quota, key=lambda d: len([q for q in POOL if q["domain"] == d]))
    qs, short = [], {}
    for d in order:
        got = pick(d, quota[d], hard, rng, taken=qs)
        if len(got) < quota[d]:
            short[d] = (len(got), quota[d])
        qs += got
    if short:
        # Never truncate in silence - a short session still gets scored out of its own total, so
        # the missing domains look like they were simply not on the blueprint.
        print(yellow("  warning: bank too small to fill the blueprint - "
                     + ", ".join(f"{d} {g}/{w}" for d, (g, w) in short.items())))
    rng.shuffle(qs)
    return qs

def campaign_batch(hard, rng):
    """'drill all': DRILL_SIZE tasks you have never attempted, round-robin across domains,
    hard tasks included when --hard. When everything has been seen once, falls back to weak tasks."""
    seen = last_seen()
    pool = [q for q in POOL if q["id"] not in seen and (hard or q["difficulty"] == "normal")]
    if not pool:
        return None, []
    qs, domains = [], list(DOMAINS)
    rng.shuffle(pool)
    pool.sort(key=lambda q: 0 if (hard and q["difficulty"] == "hard") else 1)
    while len(qs) < DRILL_SIZE and pool:
        progressed = False
        for d in domains:
            cand = [q for q in pool if q["domain"] == d and q not in qs]
            got = no_conflicts(cand, 1, qs)
            if got:
                qs += got; progressed = True
                if len(qs) == DRILL_SIZE:
                    break
        if not progressed:
            break
    total = len([q for q in POOL if hard or q["difficulty"] == "normal"])
    return f"{total - len(pool)}/{total} attempted", qs

def solution_allowed(st: dict[str, Any] | None, qid: int | str) -> bool:
    """Study: always. Drill: once the task has been graded. Exam: only after submit."""
    if not st or st.get("ended_at") or untimed(st):
        return True
    return bool(st.get("mode") == "drill" and str(qid) in st.get("results", {}))

def cmd_solution(args):
    if not args:
        die("usage: ./exam solution N   (drills: after grading the task; exams: after submit; --force to peek anyway)")
    force = "--force" in args; args = [a for a in args if a != "--force"]
    q = q_by_id(int(args[0])); st = load_state()
    if not solution_allowed(st, int(q["id"])) and not force:
        die("Not yet: in a drill, grade the task first (./exam grade N); in an exam, submit first. --force overrides.")
    print(bold(f"Solution - Q{q['id']} {q['title']}")); print("-" * 64)
    sol = str(q.get("solution", ""))
    print(render(sol, session_params(st, q))); print("-" * 64)
    print(dim(f"One correct way, not the only one. $do = --dry-run=client -o yaml, k = kubectl. Paths are relative to {ROOT}"))

def cmd_progress(args):
    seen = last_seen(); agg = stats()
    print(bold(f"{'Domain':<8}{'attempted':>11}{'passed':>9}   {'hard attempted':>15}{'hard passed':>13}"))
    for d in DOMAINS:
        dq = [q for q in QUESTIONS if q["domain"] == d]
        n = [q for q in dq if q["difficulty"] == "normal"]; h = [q for q in dq if q["difficulty"] == "hard"]
        att = lambda L: sum(1 for q in L if q["id"] in seen); ok = lambda L: sum(1 for q in L if agg.get(int(q["id"])) and agg[int(q["id"])].last is True)
        print(f"{d:<8}{att(n):>6}/{len(n):<4}{ok(n):>6}/{len(n):<4}   {att(h):>9}/{len(h):<4}{ok(h):>8}/{len(h):<4}")
    left = [q["id"] for q in QUESTIONS if q["id"] not in seen]
    print(dim(f"\n{len(QUESTIONS) - len(left)}/{len(QUESTIONS)} tasks attempted at least once." + (f"  Never seen: Q{', Q'.join(map(str, left))}" if left and len(left) <= 25 else "")))
    print(dim("passed = latest attempt was a full pass.  ./exam drill all [--hard] works through what's left."))

def weak_ids(agg=None):
    agg = agg or stats()
    return [q["id"] for q in QUESTIONS
            if (agg[q["id"]]["last"] is False or agg[q["id"]]["fails"] >= 2)
            or (agg[q["id"]]["attempts"] == 0 and not q.get("set"))]

def write_weak_spots():
    agg = stats(); hist = load_history()
    L = [f"# {TRACK_ID.upper()} weak spots", "", f"_Generated by exam from {len(hist)} attempt(s); regenerated on every `end`._", ""]
    exams = [e for e in hist if e["mode"] == "exam"]
    if exams:
        e = exams[-1]
        L += [f"## Domain scores (latest full exam, {e['at']}, {e['score_pct']}%)", ""]
        for d, name in DOMAINS.items():
            dq = [q for q in QUESTIONS if q["domain"] == d]
            dt = sum(q["weight"] for q in dq); de = sum(e["results"].get(str(q["id"]), {}).get("earned", 0) for q in dq)
            L.append(f"- **{d}** {de}/{dt} — {name}")
        L.append("")
    L += ["## Drill next  (`./exam drill weak`)", ""]
    weak = [q for q in QUESTIONS if q["id"] in weak_ids(agg) and agg[q["id"]]["attempts"] > 0]
    if not weak:
        L.append("Nothing failing right now.")
    for q in weak:
        a = agg[q["id"]]
        L.append(f"### Q{q['id']:02d} · {q['domain']} · {q['title']}  ({a['fails']}/{a['attempts']} failed, last {a['last_earned']} pts, {a['last_fail_at']})")
        failed_list = list(a["failed"]) if isinstance(a["failed"], (list, tuple)) else []
        L += [f"- ✗ {n}" for n in failed_list]
        L.append("")
    L += ["## Attempt matrix", "", "| Q | Domain | Title | " + " | ".join(f"{e['mode'][0].upper()}{i + 1}" for i, e in enumerate(hist)) + " |",
          "|---|---|---|" + "---|" * len(hist)]
    for q in QUESTIONS:
        cells = []
        for e in hist:
            r = e["results"].get(str(q["id"]))
            cells.append("·" if r is None else ("✓" if r["pass"] else f"{r['earned']}/{r['total']}"))
        L.append(f"| {q['id']} | {q['domain']} | {q['title']} | " + " | ".join(cells) + " |")
    L += ["", "_E = full exam, D = drill, · = not in that session, n/m = partial credit._", ""]
    with open(WEAK_FILE, "w") as f:
        f.write("\n".join(L))

# ------------------------------------------------------------ session ----
def preflight():
    out = subprocess.run(["kubectl", "get", "nodes", "-o", "jsonpath={.items[*].metadata.name}"],
                         capture_output=True, text=True).stdout.split()
    missing = [v for v in NODES.values() if v not in out]
    if missing:
        die(f"Nodes not found in cluster: {missing}\n  cluster has: {out}\n"
            "  Set CKA_CP, CKA_W1, CKA_W2, CKA_W3 to your node names (needs 1 control-plane + 3 workers).")
    rc, _ = run('nx "$CP" "true" </dev/null && nx "$W2" "true" </dev/null && nx "$W3" "true" </dev/null', timeout=60)
    if rc != 0:
        die(f"Cannot run commands on nodes with CKA_NODE_ACCESS={NODE_ACCESS}.\n"
            "  podman/docker -> node names must be kind container names (kind get nodes --name cka-sim)\n"
            "  ssh     -> passwordless ssh to each node name must work\n"
            "  vagrant -> run from the Vagrantfile directory; names are vagrant machine names")
    print(dim(f"  track: {TRACK_ID}  cluster: {CONTEXT}  node access: {NODE_ACCESS}  nodes: {', '.join(NODES.values())}"))
    for tool, why in (("helm", "Helm tasks (the real exam has helm on the terminal)"), ("openssl", "certificate tasks"), ("curl", "tasks that fetch manifests")):
        if not shutil.which(str(tool)):
            print(yellow(f"  warning: '{tool}' not found on this machine - needed for {why}"))

HARD_CONTEXTS = {"k8s-c1-H": "default", "k8s-c2-AC": "%{ns}", "k8s-c3-CCC": "kube-system"}

def context_namespace(ctx, template, params_by_id):
    """Default namespace for one exam context.

    Several tasks can name the same context while working in different namespaces, but a
    context has only one default namespace - so it belongs to whichever task actually reads it
    ("ctx_ns": True, i.e. the task says to work in the context's namespace without -n). Every
    other task states its namespace in its own text, so the value does not matter to them.
    """
    if "%{ns}" not in template:
        return template
    def ns_of(pred):
        return [p["ns"] for i, p in params_by_id.items()
                if p.get("ctx") == ctx and p.get("ns") and pred(QBYID.get(int(i)) or {})]
    return (ns_of(lambda q: q.get("ctx_ns")) or ns_of(lambda q: True)
            or [p["ns"] for p in params_by_id.values() if p.get("ns")] or ["default"])[0]

def setup_contexts(hard, params_by_id):
    """Exam-style contexts on the same cluster with different default namespaces.

    Created whenever a task in the session asks for one - 24 tasks open with
    `kubectl config use-context k8s-c?-?` and are unfollowable without it - not only when the
    whole session was started with --hard. A drill that names hard task ids explicitly
    ('./exam drill 121', './exam drill weak') pulls those tasks in with hard=False.
    """
    cluster = subprocess.run(["kubectl", "config", "view", "-o", f"jsonpath={{.contexts[?(@.name=='{CONTEXT}')].context.cluster}}"],
                             capture_output=True, text=True).stdout.strip()
    user = subprocess.run(["kubectl", "config", "view", "-o", f"jsonpath={{.contexts[?(@.name=='{CONTEXT}')].context.user}}"],
                          capture_output=True, text=True).stdout.strip()
    for name in HARD_CONTEXTS:
        subprocess.run(["kubectl", "config", "delete-context", name], capture_output=True)
    wanted = set(HARD_CONTEXTS) if hard else {p.get("ctx") for p in params_by_id.values()} & set(HARD_CONTEXTS)
    if not wanted:
        subprocess.run(["kubectl", "config", "use-context", CONTEXT], capture_output=True)
        return
    for name in sorted(wanted):
        subprocess.run(["kubectl", "config", "set-context", name, f"--cluster={cluster}", f"--user={user}",
                        f"--namespace={context_namespace(name, HARD_CONTEXTS[name], params_by_id)}"], capture_output=True)
    # Hard mode starts you in c1 like the real exam; a mixed drill stays on the normal context
    # so its non-hard tasks behave as usual and the hard ones still switch as instructed.
    start = "k8s-c1-H" if hard and "k8s-c1-H" in wanted else CONTEXT
    subprocess.run(["kubectl", "config", "use-context", start], capture_output=True)

def _log_msg(*args: Any, **kwargs: Any) -> None:
    print(*args, **kwargs)


# Disruptive tasks (see "breaks": ... in the question bank) corrupt shared control-plane /
# node state. A session's setup only touches the questions it actually contains, so damage
# from a task in an earlier session lingers if that task isn't picked again - e.g. Q39 wrecks
# W1's kubelet config, and a later session with different questions never undoes it. This
# restores every known "breaks" target to a good baseline before each session seeds, so
# leftover damage never leaks across sessions regardless of which questions get sampled.
RESTORE_BASELINE = r"""
# apiserver FIRST: Q123 renames the command to "kube-apiserverr", which takes the whole API
# down - every kubectl-based step below would fail until this is undone. The repair goes over
# podman/ssh (nx), not kubectl, so it works precisely when the cluster is unreachable.
if nx "$CP" 'grep -q "^ *- kube-apiserverr$" /etc/kubernetes/manifests/kube-apiserver.yaml' </dev/null 2>/dev/null; then
  nx "$CP" 'sed -i "s|^\( *\)- kube-apiserverr$|\1- kube-apiserver|" /etc/kubernetes/manifests/kube-apiserver.yaml' </dev/null
  # the kubelet re-reads the manifest on its own; wait for the API to answer again
  for _ in $(seq 1 30); do kubectl --context "${CKA_CONTEXT:-kind-cka-sim}" get --raw=/readyz >/dev/null 2>&1 && break; sleep 2; done
fi

# scheduler: undo the "kube-scheduler" -> "kube-schedulerr" command typo (Q20/Q118)
nx "$CP" '
f=/etc/kubernetes/manifests/kube-scheduler.yaml
sed -i "s|^\( *\)- kube-schedulerr$|\1- kube-scheduler|" $f 2>/dev/null
' </dev/null

# controller-manager: undo Q38's injected flag and Q118's broken image tag
nx "$CP" '
f=/etc/kubernetes/manifests/kube-controller-manager.yaml
sed -i "/--leader-elect-lease-duration=1s/d" $f 2>/dev/null
sed -i "s|\(image: registry.k8s.io/kube-controller-manager:v[0-9.]*\)-broken|\1|" $f 2>/dev/null
' </dev/null

# coredns: restore the default upstream forward (Q37/Q114 point it somewhere bogus)
cf=$($K -n kube-system get cm coredns -o jsonpath='{.data.Corefile}' 2>/dev/null)
if [ -n "$cf" ] && ! printf '%s' "$cf" | grep -Eq '^[[:space:]]*forward \. /etc/resolv\.conf'; then
  printf '%s' "$cf" | sed -E 's|^([[:space:]]*forward \. )[^[:space:]{]+|\1/etc/resolv.conf|' > /tmp/Corefile.restore
  $K -n kube-system create cm coredns --from-file=Corefile=/tmp/Corefile.restore --dry-run=client -o yaml | $K apply -f - >/dev/null 2>&1
  $K -n kube-system rollout restart deploy coredns >/dev/null 2>&1
fi

# w1/w2/w3 kubelet: undo Q17/Q39-style tampering, then make sure it's enabled and running.
# staticPodPath is normalised unconditionally: Q103 relocates it to /etc/kubernetes/static, and
# the config.yaml.orig copy below only helps if something made that backup first - nothing does,
# so a relocated path used to survive every later session and silently break Q05 (whose check
# looks in /etc/kubernetes/manifests). Only restart the kubelet if we actually changed the file.
for n in "$W1" "$W2" "$W3"; do
  nx "$n" '
    [ -f /var/lib/kubelet/config.yaml.orig ] && cp -f /var/lib/kubelet/config.yaml.orig /var/lib/kubelet/config.yaml
    if grep -q "^staticPodPath:" /var/lib/kubelet/config.yaml 2>/dev/null \
       && ! grep -q "^staticPodPath: /etc/kubernetes/manifests$" /var/lib/kubelet/config.yaml; then
      sed -i "s|^staticPodPath: .*|staticPodPath: /etc/kubernetes/manifests|" /var/lib/kubelet/config.yaml
      systemctl restart kubelet >/dev/null 2>&1
    fi
    systemctl enable kubelet >/dev/null 2>&1
    systemctl start kubelet  >/dev/null 2>&1
  ' </dev/null
done

# w1-taint: clear every randomized demo taint key the bank can apply. Q25 draws from
# dedicated/team/workload, Q107 from pool/lane, and Q307 pins maintenance=inprogress - miss one
# and that node silently stops accepting pods for every later session.
# One key per call: `kubectl taint node N a- b-` aborts on the first key that is not present and
# removes NOTHING, so the single taint that is actually set survives the "cleanup" and W1 keeps
# rejecting pods in every later session - the exact failure this block exists to prevent.
for _t in dedicated workload team pool lane maintenance; do
  $K taint node "$W1" "$_t-" >/dev/null 2>&1 || true
done

# metrics-server: Q23 seeds its scenario by stripping --kubelet-insecure-tls, and kind's kubelet
# serving certs have no IP SANs, so without that flag metrics-server never becomes Ready. Left
# broken it does far more than disable `kubectl top`: the v1beta1.metrics.k8s.io APIService has no
# endpoints, aggregated discovery goes stale, and then EVERY namespace deletion in the cluster
# hangs on NamespaceDeletionDiscoveryFailure. Baseline runs before seeding, so a session that
# actually contains Q23 re-breaks it a moment later, exactly as intended.
if $K -n kube-system get deploy metrics-server >/dev/null 2>&1 \
   && ! $K -n kube-system get deploy metrics-server -o jsonpath='{.spec.template.spec.containers[0].args}' | grep -q 'kubelet-insecure-tls'; then
  $K -n kube-system patch deploy metrics-server --type=json \
    -p '[{"op":"add","path":"/spec/template/spec/containers/0/args/-","value":"--kubelet-insecure-tls"}]' >/dev/null 2>&1 || true
fi

# w1-block/w2-drain/w3-drain: Q307 cordons W1 and Q117 cordons W2, and Q208/Q309 have the
# candidate drain W2/W3. A cordon left behind fails any later task that counts pods per node
# (Q26/Q211 DaemonSet coverage, Q212's one-pod-per-node spread).
for n in "$W1" "$W2" "$W3"; do $K uncordon "$n" >/dev/null 2>&1 || true; done

# Deliberately NOT restored, and why:
#   etcd (Q102) and certs (Q122). Neither setup damages anything - Q102 only takes a snapshot
#   and deletes a ConfigMap, Q122 only records the current notBefore. Any damage comes from a
#   half-finished candidate attempt (etcd.yaml left pointing at a restored data-dir, static pod
#   manifests moved to /tmp and never moved back), which is not deterministic: there is no way
#   to tell "mid-attempt" from "correctly completed" without guessing, and guessing wrong here
#   rewrites etcd's data-dir or re-issues certs on a healthy cluster. Re-run ./setup.sh (or
#   ./teardown.sh && ./setup.sh) if one of those leaves the control plane wedged.
#
#   proxy-rules (Q302) needs nothing: its setup only creates a namespace and deletes a pod and
#   service. The "breaks" key is there for no_conflicts() bookkeeping, not because it damages
#   shared state.
"""

def restore_baseline(log: Callable[..., Any] = _log_msg):
    log(dim("  resetting control-plane / node state to a clean baseline..."))
    rc, out = run(RESTORE_BASELINE, timeout=90)
    if rc != 0:
        log(yellow(f"  warning: baseline restore had issues (continuing anyway):\n{dim(out[-500:])}"))


def seed(qs, log: Callable[..., Any] = _log_msg, params_by_id=None):
    params_by_id = params_by_id or {}
    normal = [q for q in qs if not q.get("disruptive")]
    disruptive = [q for q in qs if q.get("disruptive")]
    def one(q):
        try:
            rc, out = run(q["setup"], params=params_by_id.get(str(q["id"])), timeout=240)
        except subprocess.TimeoutExpired:
            rc, out = 1, "setup timed out after 240s"
        log(f"  {'✓' if rc == 0 else '!'} Q{q['id']:02d} {q['title']}" + ("" if rc == 0 else f"\n{dim(out[-300:])}"))
    for q in normal:
        one(q)
    if disruptive:
        log(dim("  waiting up to 45s for seeded pods to be scheduled..."))
        for _ in range(15):
            pending = subprocess.run(["kubectl", "--context", CONTEXT, "get", "pods", "-A", "--field-selector=spec.nodeName=",
                                      "-o", "name"], capture_output=True, text=True).stdout.strip()
            if not pending:
                break
            time.sleep(3)
    for q in disruptive:
        one(q)

def begin_session(qs, mode, duration, force, log: Callable[..., Any] = _log_msg, hard=False, untimed_session=False):
    st = load_state()
    if st and not st.get("ended_at") and not force:
        die("A session is already in progress. './exam end' it first, or add --force.")
    if not kubectl_ok():
        die(f"Cannot reach the cluster through kubectl context '{CONTEXT}'. Run ./setup.sh (kind) or set CKA_CONTEXT for another cluster.")
    if not qs:
        die(f"Track '{TRACK_ID}' has no questions yet.")
    preflight()
    os.makedirs(WORKSPACE, exist_ok=True)
    rng = random.Random()
    params_by_id = {str(q["id"]): make_params(q, rng) for q in qs}
    setup_contexts(hard, params_by_id)
    restore_baseline(log)
    log(bold(f"Seeding {len(qs)} scenario(s){' [HARD]' if hard else ''}..."))
    seed(qs, log, params_by_id)
    st = {"mode": mode, "track": TRACK_ID, "hard": hard, "untimed": untimed_session, "ids": [q["id"] for q in qs],
          "params": params_by_id, "duration": duration, "started_at": time.time(), "ended_at": None,
          "results": {}, "flags": [], "notes": ""}
    save_state(st)
    log("")
    log(bold("=" * 64))
    log(bold(f"  {TRACK_ID.upper()} {'EXAM' if mode == 'exam' else 'DRILL'}{' · HARD' if hard else ''} - clock started"))
    if hard:
        log(yellow("  Contexts: k8s-c1-H (default) · k8s-c2-AC · k8s-c3-CCC  - each task tells you which to use; you are on k8s-c1-H now"))
    log(f"  Ends    : {datetime.fromtimestamp(st['started_at'] + duration).strftime('%H:%M:%S')}  ({duration // 60} min)")
    log(f"  Tasks   : {', '.join('Q%02d' % q['id'] for q in qs) if mode == 'drill' else len(qs)}   Pass mark: {PASS_PCT}%")
    log(bold("=" * 64))
    log("  ./exam web         exam-style browser UI (task pane + terminal + clock)\n"
        "  ./exam list / show N / grade N / timer / end   terminal workflow\n"
        + ("  Tip: read ALL tasks first. Some are cluster-wide failures that block others.\n" if mode == "exam" else "")
        + f"  Files the tasks ask for go under {WS_DISPLAY}/ (relative to this directory)\n"
        + "  Your own terminal: source ./examrc   (fish: source ./examrc.fish)  -> k, $do, $now, completion")
    return st

def finish_session(st, log: Callable[..., Any] = _log_msg):
    qs = session_questions(st)
    over = remaining(st) <= 0
    set_paused(st, False)
    log(bold(f"Submitting - grading {len(qs)} task(s)..."))
    for q in qs:
        r = grade_one(q)
        st["results"][str(q["id"])] = r
        tag = green("PASS") if r["pass"] else (yellow(f"{r['earned']}/{r['total']}") if r["earned"] else red("FAIL"))
        log(f"Q{q['id']:02d} {tag}  {q['title']}" + ("" if r["pass"] else f"\n{dim(result_detail(r))}"))
    st["ended_at"] = time.time()
    st["over_time"] = over
    save_state(st)
    setup_contexts(False, {})
    if untimed(st):
        return None
    return record_attempt(st)

# ----------------------------------------------------------- commands ----
def cmd_start(args):
    hard = "--hard" in args; force = "--force" in args
    undrilled = [d for d, n in drilled_domains().items() if n == 0]
    if undrilled and not force:
        die("Drill every domain at least once before a full exam (that is the point of the drills).\n"
            f"  Not yet drilled: {', '.join(undrilled)}\n  Run:  ./exam drill      (picks the next domain)\n"
            "  or:   ./exam start --force   to skip the gate.")
    begin_session(compose_exam(hard, random.Random()), "exam", EXAM_SECONDS, force, hard=hard)

def next_drill(hard, rng):
    """No-arg drill: the least-drilled domain, DRILL_SIZE tasks, least-recently-seen first."""
    cov = drilled_domains()
    domain = min(DOMAINS, key=lambda d: (cov[d], list(DOMAINS).index(d)))
    return domain, pick(domain, DRILL_SIZE, hard, rng)

def cmd_drill(args):
    force = "--force" in args; hard = "--hard" in args
    args = [a for a in args if a not in ("--force", "--hard")]
    minutes = None
    if "--time" in args:
        i = args.index("--time"); minutes = int(args[i + 1]); del args[i:i + 2]
    per_task = DRILL_SECONDS_PER_TASK_HARD if hard else DRILL_SECONDS_PER_TASK
    if not args:
        domain, qs = next_drill(hard, random.Random())
        cov = drilled_domains()
        print(bold(f"Drill: {DOMAINS[domain]}") + dim(f"  ({sum(1 for v in cov.values() if v)}/{len(DOMAINS)} domains drilled so far)"))
        begin_session(qs, "drill", (minutes * 60) if minutes else per_task * len(qs), force, hard=hard)
        return
    if args[0] == "all":
        label, qs = campaign_batch(hard, random.Random())
        if not qs:
            print(bold("Every task in the bank has been attempted." ) + " Switching to weak tasks.")
            qs = [q for q in QUESTIONS if q["id"] in weak_ids()]
            qs = no_conflicts(qs, DRILL_SIZE)
            if not qs:
                die("Nothing weak either - you have passed everything on its latest attempt. Time for ./exam start --hard.")
        else:
            print(bold(f"Campaign: {label}") + dim(f"  this batch: Q{', Q'.join(str(q['id']) for q in qs)}"))
        begin_session(qs, "drill", (minutes * 60) if minutes else per_task * len(qs), force, hard=hard)
        return
    if args[0] == "weak":
        ids = weak_ids()
        if not ids:
            die("Nothing marked weak - finish a session with './exam end' first, or name tasks: ./exam drill 2 17")
    else:
        ids = []
        for a in args:
            if a.lower().replace("set", "") in SETS and a.lower().startswith("set"):
                ids += [q["id"] for q in set_questions(a.lower().replace("set", ""))]
            elif a.upper() in DOMAINS:
                ids += [q["id"] for q in QUESTIONS if q["domain"] == a.upper()]
            else:
                ids.append(q_by_id(int(a))["id"])
    ids = sorted(set(ids))
    qs = [q for q in QUESTIONS if q["id"] in ids]
    kept = no_conflicts(qs, len(qs))
    if len(kept) < len(qs):
        dropped = [q["id"] for q in qs if q not in kept]
        print(yellow(f"Dropped Q{', Q'.join(map(str, dropped))}: they break the same thing as another task in this set. Drill them separately."))
    # Shuffle AFTER resolving conflicts, so which task gets dropped stays deterministic while the
    # order you meet them in does not. A drill listed by id walks you from easy to hard in
    # lockstep, which is the one ordering the real exam will never give you.
    random.Random().shuffle(kept)
    begin_session(kept, "drill", (minutes * 60) if minutes else per_task * len(kept), force, hard=hard)

def cmd_study(args):
    """No clock, solutions unlocked from the start, nothing written to history."""
    hard = "--hard" in args; force = "--force" in args
    rest = [a for a in args if not a.startswith("--")]
    n = DRILL_SIZE
    if "--count" in args:
        n = int(args[args.index("--count") + 1]); rest = [a for a in rest if a != str(n)]
    rng = random.Random()
    if rest and rest[0].upper() in DOMAINS:
        domain = rest[0].upper()
        qs = pick(domain, n, hard, rng)
        print(bold(f"Study: {DOMAINS[domain]}"))
    elif rest and rest[0] == "weak":
        qs = no_conflicts([q for q in QUESTIONS if q["id"] in weak_ids()], n)
        print(bold("Study: tasks you have been failing"))
    elif rest:
        qs = no_conflicts([q_by_id(int(a)) for a in rest], len(rest))
        print(bold("Study: " + ", ".join(f"Q{q['id']}" for q in qs)))
    else:
        domain, qs = next_drill(hard, rng)
        print(bold(f"Study: {DOMAINS[domain]}"))
    begin_session(qs, "drill", EXAM_SECONDS, force, hard=hard, untimed_session=True)

def cmd_sim(args):
    """Fixed 17-task simulator set, full exam rules and clock."""
    force = "--force" in args
    names = [a.lower() for a in args if not a.startswith("--")]
    if not names or names[0] not in SETS:
        die(f"usage: ./exam sim {'|'.join(SETS) or '<set>'} [--force]\n  "
            + "\n  ".join(f"{k}: {v} ({len(set_questions(k))} tasks)" for k, v in SETS.items()))
    name = names[0]
    qs = set_questions(name)
    print(bold(f"{SETS[name]} - {len(qs)} tasks, {TRACK['minutes']} minutes, exam rules (no feedback until you submit)"))
    begin_session(qs, "exam", EXAM_SECONDS, force, hard=True)

def cmd_list(args):
    st = load_state()
    results = st["results"] if st and "results" in st else {}
    qs = session_questions(st) if st and not st.get("ended_at") else list(QUESTIONS)
    agg = stats()
    print(bold(f"{'#':>3}  {'Domain':<8}{'Pts':>4}  {'Now':<8} {'History':<9} Title"))
    for q in qs:
        r = results.get(str(q["id"]))
        now = "-" if r is None else (green("PASS") if r.get("pass") else yellow(f"{r.get('earned')}/{r.get('total')}"))
        a = agg.get(int(q["id"])) or AggEntry()
        hist = "" if a.attempts == 0 else f"{a.attempts - a.fails}/{a.attempts}"
        if a.attempts and a.last is False:
            hist = red(hist + " ✗")
        print(f"{q['id']:>3}  {q['domain']:<8}{q['weight']:>4}  {now:<17} {hist:<18} {q['title']}{'  [hard]' if q['difficulty'] == 'hard' else ''}")
    print(dim("\nHistory = full passes/attempts across sessions, ✗ = failed most recently."))
    if st and not st.get("ended_at"):
        print(status_line(st))

def cmd_show(args):
    if not args:
        die("usage: ./exam show N")
    q = q_by_id(int(args[0]))
    st0 = load_state()
    sq = session_questions(st0) if st0 and not st0.get("ended_at") else []
    pos = f"{sq.index(q) + 1} of {len(sq)}  |  " if q in sq else ""
    print(bold(f"{pos}Q{q['id']}  |  {DOMAINS[q['domain']]}  |  {q['weight']} pts{'  |  HARD' if q['difficulty'] == 'hard' else ''}"))
    print(bold(q["title"])); print("-" * 64); print(task_text(q)); print("-" * 64)
    st = load_state()
    if st and not st.get("ended_at"):
        print(status_line(st))

def cmd_grade(args):
    st = require_started()
    if not args:
        die("usage: ./exam grade N | all")
    ids = [q["id"] for q in session_questions(st)] if args[0] == "all" else [int(a) for a in args]
    for n in ids:
        q = q_by_id(n); r = grade_one(q)
        st["results"][str(n)] = r
        tag = green("PASS") if r.get("pass") else yellow(f"{r.get('earned')}/{r.get('total')}")
        print(f"Q{n:02d} {tag}  {q['title']}"); print(dim(result_detail(r)))
    save_state(st)
    if args[0] == "all":
        print_score(st)

def print_score(st):
    qs = session_questions(st)
    earned, total, pct = score(st)
    print(); print(bold("Per-domain:"))
    for d, name in DOMAINS.items():
        dq = [q for q in qs if q["domain"] == d]
        if not dq:
            continue
        dt = sum(q["weight"] for q in dq); de = sum(st["results"].get(str(q["id"]), {}).get("earned", 0) for q in dq)
        n = int(20 * de / dt)
        print(f"  {d:<7} {'█' * n}{'░' * (20 - n)} {de:>3}/{dt:<3} {dim(name)}")
    verdict = green("PASS") if pct >= PASS_PCT else red("FAIL")
    print(f"\n{bold('Score:')} {earned}/{total} = {pct}%  ->  {verdict} (pass mark {PASS_PCT}%)")

def status_line(st):
    if untimed(st):
        return green("study mode - no clock") + dim(f"  [{len(session_questions(st))} tasks, nothing recorded]")
    r = remaining(st)
    if st.get("paused_at"):
        return yellow(f"⏸  PAUSED - {fmt(r)} remaining") + dim("  ./exam resume")
    if r <= 0:
        return red("⏰ TIME IS UP - run ./exam end")
    col = green if r > 30 * 60 else (yellow if r > 10 * 60 else red)
    return col(f"⏱  {fmt(r)} remaining") + dim(f"  [{st.get('mode', 'exam')}]")

def cmd_status(args):
    st = require_started()
    if st.get("ended_at"):
        print("Session ended."); print_score(st); return
    print(status_line(st))
    print(dim(f"{sum(1 for v in st['results'].values() if v['pass'])} passed / {len(st['results'])} graded / {len(session_questions(st))} in session"))

def cmd_timer(args):
    st = require_started()
    if st.get("ended_at"):
        die("Session already ended.")
    if untimed(st):
        die("This is a study session - there is no clock.")
    try:
        while True:
            st = load_state(); r = remaining(st)
            if st.get("paused_at"):
                sys.stdout.write("\r" + yellow(bold(f"⏸  {fmt(r)} PAUSED   ")) + dim("   ./exam resume        ")); sys.stdout.flush(); time.sleep(1); continue
            if r <= 0:
                print("\r" + red(bold("⏰  00:00:00  TIME IS UP - run ./exam end       "))); break
            col = green if r > 30 * 60 else (yellow if r > 10 * 60 else red)
            sys.stdout.write("\r" + col(bold(f"⏱  {fmt(r)} remaining")) + dim("   (Ctrl-C to hide)")); sys.stdout.flush()
            if int(r) in (30 * 60, 15 * 60, 5 * 60) and TTY:
                sys.stdout.write("\a")
            time.sleep(1)
    except KeyboardInterrupt:
        print()

def cmd_pause(args):
    st = require_started()
    if st.get("ended_at"):
        die("Session already ended.")
    set_paused(st, True); print(status_line(st))

def cmd_resume(args):
    st = require_started()
    set_paused(st, False); print(status_line(st))

def cmd_end(args):
    st = require_started()
    if st.get("ended_at"):
        die("Session already ended and recorded.")
    if remaining(st) <= 0:
        print(yellow("Note: time expired before submission."))
    entry = finish_session(st)
    print_score(st)
    if entry is None:
        print(dim("Study session - not added to history or weak-spots.")); return
    print(dim(f"Time used: {fmt(st['ended_at'] - st['started_at'])}" + ("  (over time)" if st.get("over_time") else "")))
    failed = sorted(int(k) for k, v in entry["results"].items() if not v["pass"])
    print(dim(f"Attempt #{len(load_history())} logged to {os.path.basename(HISTORY_FILE)}; {os.path.basename(WEAK_FILE)} updated."))
    if failed:
        print(bold("\nTo drill what you missed:  ./exam drill weak") + dim(f"   (Q{', Q'.join(map(str, failed))})"))

def cmd_abort(args):
    """End a session without grading it and restore the kubectl context."""
    st = load_state()
    if not st or st.get("ended_at"):
        die("No session in progress.")
    assert st is not None
    if "--yes" not in args:
        die(f"This discards the {st.get('mode', 'exam')} in progress without grading or recording it.\n"
            "  Confirm:  ./exam abort --yes        (to grade and keep it instead: ./exam end)")
    st["ended_at"] = time.time(); st["aborted"] = True
    save_state(st)
    setup_contexts(False, {})
    print(yellow("Session discarded. Nothing was graded or written to history."))
    print(dim(f"  kubectl context restored to {CONTEXT}. Seeded objects are still on the cluster;"))
    print(dim("  './exam drill ...' or './exam start' re-seeds, './teardown.sh' removes the cluster."))

def cmd_weak(args):
    agg = stats(); hist = load_history()
    if not hist:
        die("No history yet - finish a session with './exam end'.")
    ids = [i for i in weak_ids(agg) if agg[i]["attempts"] > 0]
    print(bold(f"Weak spots after {len(hist)} attempt(s):"))
    if not ids:
        print(green("  none - everything attempted has passed on its latest try"))
    for i in ids:
        q = q_by_id(i); a = agg[i]
        print(f"\n{red('Q%02d' % i)} {q['domain']:<7} {q['title']}  " + dim(f"{a['fails']}/{a['attempts']} failed, last {a['last_earned']} pts, {a['last_fail_at']}"))
        for n in a["failed"]:
            print(dim("    ✗ " + n))
    never = [q["id"] for q in QUESTIONS if agg[q["id"]]["attempts"] == 0]
    if never:
        print(dim(f"\nNever attempted: Q{', Q'.join(map(str, never))}"))
    print(dim(f"\nFull log: {WEAK_FILE}     Drill them: ./exam drill weak"))

def cmd_history(args):
    hist = load_history()
    if not hist:
        die("No history yet.")
    print(bold(f"{'#':>3}  {'when':<17}{'mode':<7}{'score':>7}  {'time':<9} tasks"))
    for i, e in enumerate(hist, 1):
        col = green if e["score_pct"] >= PASS_PCT else red
        tasks = f"all {len(QUESTIONS)}" if len(e["ids"]) == len(QUESTIONS) else "Q" + ",".join(map(str, e["ids"]))
        print(f"{i:>3}  {e['at']:<17}{(e['mode'] + ('*' if e.get('hard') else '')):<7}{col('%5.1f%%' % e['score_pct']):>16}  {fmt(e['time_used']):<9} {tasks}")
    exams = [e for e in hist if e["mode"] == "exam"]
    print(dim("* = hard"))
    if len(exams) >= 2:
        print(bold("\nDomain trend (full exams, % of points):"))
        for d in DOMAINS:
            dq = [q for q in QUESTIONS if q["domain"] == d]; dt = sum(q["weight"] for q in dq)
            pts = [round(100 * sum(e["results"].get(str(q["id"]), {}).get("earned", 0) for q in dq) / dt) for e in exams]
            print(f"  {d:<7} " + " → ".join(f"{p:>3}%" for p in pts))

def cmd_reset(args):
    if not args:
        die("usage: ./exam reset N   (re-seed one task's scenario)")
    q = q_by_id(int(args[0])); rc, out = run(str(q.get("setup", "")), params=session_params(load_state(), q))
    print(("re-seeded " if rc == 0 else "problem re-seeding ") + f"Q{q['id']:02d}: {q['title']}")
    if out:
        print(dim(out))

# --------------------------------------------------------------- web ----
class Api(http.server.BaseHTTPRequestHandler):
    """Serves web/index.html plus a small JSON API. State lives in the same files the CLI uses."""
    lock = threading.Lock()
    log_lines = []
    seeding = False
    seed_error = None
    ttyd_port = 7681
    shell = "bash"

    def log_message(self, format: str, *args: Any) -> None:  # quiet
        pass

    def _json(self, obj, code=200):
        body = json.dumps(obj).encode()
        self.send_response(code); self.send_header("Content-Type", "application/json")
        self.send_header("Content-Length", str(len(body))); self.end_headers(); self.wfile.write(body)

    def _read_json(self):
        n = int(self.headers.get("Content-Length") or 0)
        return json.loads(self.rfile.read(n) or b"{}")

    def do_GET(self):
        p = urllib.parse.urlparse(self.path)
        if p.path in ("/", "/index.html"):
            with open(os.path.join(ROOT, "web", "index.html"), "rb") as f:
                body = f.read()
            self.send_response(200); self.send_header("Content-Type", "text/html; charset=utf-8")
            self.send_header("Content-Length", str(len(body))); self.end_headers(); self.wfile.write(body); return
        if p.path == "/api/session":
            with Api.lock:
                return self._json(self.session_payload())
        if p.path == "/api/history":
            return self._json({"history": load_history(), "weak": weak_ids(), "stats": {str(k): v.to_dict() for k, v in stats().items()}})
        self._json({"error": "not found"}, 404)

    def do_POST(self):
        p = urllib.parse.urlparse(self.path); body = self._read_json()
        with Api.lock:
            st = load_state()
            if p.path == "/api/track":
                t = body.get("track")
                if t not in TRACKS:
                    return self._json({"error": f"unknown track {t}"}, 400)
                if Api.seeding:
                    return self._json({"error": "a session is being seeded"}, 409)
                load_track(t)
                Api.log_lines = []
                return self._json(self.session_payload())
            if p.path == "/api/start":
                if Api.seeding:
                    return self._json({"error": "already seeding"}, 409)
                mode = body.get("mode", "exam"); hard = bool(body.get("hard")); rng = random.Random()
                Api.log_lines = []; Api.seed_error = None; Api.seeding = True
                ansi = __import__("re").compile(r"\x1b\[[0-9;]*m")
                ulog = lambda line: Api.log_lines.append(ansi.sub("", line))
                def work():
                    try:
                        if body.get("sim") in SETS:
                            begin_session(set_questions(body["sim"]), "exam", EXAM_SECONDS, True, log=ulog, hard=True)
                        elif mode == "exam":
                            begin_session(compose_exam(hard, rng), "exam", EXAM_SECONDS, True, log=ulog, hard=hard)
                        else:
                            if body.get("domain") in DOMAINS:
                                qs = pick(body["domain"], DRILL_SIZE, hard, rng)
                            elif body.get("campaign"):
                                _, qs = campaign_batch(hard, rng)
                                if not qs:
                                    qs = no_conflicts([q for q in QUESTIONS if q["id"] in weak_ids()], DRILL_SIZE)
                            elif body.get("next"):
                                _, qs = next_drill(hard, rng)
                            else:
                                ids = body.get("ids") or weak_ids()
                                qs = no_conflicts([q for q in QUESTIONS if q["id"] in ids], len(ids))
                            per = DRILL_SECONDS_PER_TASK_HARD if hard else DRILL_SECONDS_PER_TASK
                            begin_session(qs, "drill", per * len(qs), True, log=ulog, hard=hard,
                                          untimed_session=bool(body.get("study")))
                    except SystemExit:
                        Api.seed_error = "\n".join(l for l in Api.log_lines if l.strip()) or "start failed - see the terminal running ./exam web"
                    except Exception as e:  # noqa: BLE001
                        Api.seed_error = f"{type(e).__name__}: {e}"
                    finally:
                        Api.seeding = False
                threading.Thread(target=work, daemon=True).start()
                return self._json({"seeding": True})
            if not st:
                return self._json({"error": "no session"}, 400)
            if p.path == "/api/flag":
                qid = int(body["id"]); flags = set(st.get("flags", []))
                flags.symmetric_difference_update({qid}); st["flags"] = sorted(flags); save_state(st)
            elif p.path == "/api/pause":
                set_paused(st, bool(body.get("paused", True)))
            elif p.path == "/api/notes":
                st["notes"] = body.get("notes", ""); save_state(st)
            elif p.path == "/api/grade":
                if st.get("mode") != "drill" and not st.get("ended_at"):
                    return self._json({"error": "No feedback during an exam. Submit to see results."}, 403)
                q = q_by_id(int(body["id"]))
                if "results" not in st or not isinstance(st["results"], dict):
                    st["results"] = {}
                st["results"][str(q["id"])] = grade_one(q, session_params(st, q)); save_state(st)
            elif p.path == "/api/end":
                if not st.get("ended_at"):
                    finish_session(st, log=lambda *_: None)
            elif p.path == "/api/reset":
                q = q_by_id(int(body["id"])); run(str(q.get("setup", "")), params=session_params(st, q))
            else:
                return self._json({"error": "not found"}, 404)
            return self._json(self.session_payload())

    def session_payload(self) -> dict[str, Any]:
        st = load_state()
        qs = session_questions(st) if st else QUESTIONS
        payload: dict[str, Any] = {
            "track": TRACK, "track_id": TRACK_ID, "workspace": WS_DISPLAY, "version": VERSION, "ttyd_port": Api.ttyd_port,
            "ttyd": shutil.which("ttyd") is not None, "shell": Api.shell, "setup_log": Api.log_lines,
            "questions": [{"id": q["id"], "domain": q["domain"], "title": q["title"], "weight": q["weight"], "difficulty": q["difficulty"],
                           "task": task_text(q, session_params(st, q)), "checks": [{"name": c["name"], "pts": c["pts"]} for c in q["checks"]],
                           "solution": render(str(q.get("solution", "")), session_params(st, q)) if solution_allowed(st, int(q["id"])) else None}
                          for q in qs],
            "bank": [{"id": q["id"], "domain": q["domain"], "title": q["title"], "difficulty": q["difficulty"]} for q in QUESTIONS],
            "tracks": TRACKS, "drilled": drilled_domains(), "sets": {k: {"name": v, "count": len(set_questions(k))} for k, v in SETS.items()},
            "seen": sorted(last_seen()),
            "seeding": Api.seeding, "seed_error": Api.seed_error,
            "session": None,
        }
        if st:
            earned, total, pct = score(st)
            payload["session"] = {"mode": st.get("mode"), "hard": st.get("hard", False), "started_at": st["started_at"], "duration": st.get("duration", EXAM_SECONDS),
                                  "ends_at": st["started_at"] + st.get("duration", EXAM_SECONDS), "ended_at": st.get("ended_at"),
                                  "over_time": st.get("over_time", False), "flags": st.get("flags", []),
                                  "paused": bool(st.get("paused_at")), "paused_total": paused_total(st), "pauses": st.get("pauses", 0),
                                  "untimed": untimed(st), "notes": st.get("notes", ""),
                                  "results": st["results"], "score": {"earned": earned, "total": total, "pct": pct, "pass_pct": PASS_PCT},
                                  "domains": self.domain_scores(st), "server_time": time.time()}
        return payload

    def domain_scores(self, st: dict[str, Any]) -> dict[str, Any]:
        qs = session_questions(st); out = {}
        st_results: dict[str, Any] = st.get("results", {})
        for d in DOMAINS:
            dq = [q for q in qs if q["domain"] == d]
            if dq:
                out[d] = {"earned": sum(st_results.get(str(q["id"]), {}).get("earned", 0) for q in dq),
                          "total": sum(q["weight"] for q in dq)}
        return out

def cmd_web(args):
    port = 8080
    if "--port" in args:
        port = int(args[args.index("--port") + 1])
    Api.shell = os.environ.get("CKA_SHELL", "bash")
    if "--shell" in args:
        Api.shell = args[args.index("--shell") + 1]
    os.makedirs(WORKSPACE, exist_ok=True)
    import socket
    def port_free(pt):
        with socket.socket() as sk:
            sk.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            try:
                sk.bind(("127.0.0.1", pt)); return True
            except OSError:
                return False
    if not port_free(port):
        die(f"Port {port} is already in use - probably another './exam web' still running.\n"
            f"  Find it:  ss -ltnp | grep :{port}      or start on another port:  ./exam web --port {port + 10}")
    if shutil.which("ttyd") and not port_free(Api.ttyd_port):
        print(yellow(f"  ttyd port {Api.ttyd_port} already in use - reusing the existing terminal server."))
    ttyd = None
    if shutil.which("ttyd") and port_free(Api.ttyd_port):
        env = dict(os.environ, WORKSPACE=WORKSPACE, KUBECONFIG=os.environ.get("KUBECONFIG", os.path.expanduser("~/.kube/config")))
        rc = os.path.join(ROOT, "examrc.fish" if "fish" in Api.shell else "examrc")
        if "fish" in Api.shell:
            shell_cmd = [Api.shell, "-C", f"source {rc}"]
        else:
            shell_cmd = [Api.shell, "--rcfile", rc, "-i"]
        # -W makes the terminal writable, so it must never be reachable off this machine: it is an
        # unauthenticated root-equivalent shell with the cluster kubeconfig. ttyd binds every
        # interface by default, so pin it to loopback (macOS needs lo0; override if yours differs).
        iface = os.environ.get("CKA_TTYD_INTERFACE", "lo")
        ttyd = subprocess.Popen(["ttyd", "-p", str(Api.ttyd_port), "-i", iface, "-W",
                                 "-t", "fontSize=14", "-t", "theme={\"background\":\"#1a1b1e\"}",
                                 "--cwd", ROOT] + shell_cmd, env=env,
                                stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
        print(dim(f"  terminal: ttyd on {iface}:{Api.ttyd_port} running {Api.shell} in {ROOT} with k=kubectl, $do and $now preset"))
    else:
        print(yellow("  ttyd not found - the terminal pane will show install instructions.\n"
                     "  (dnf/apt/pacman/brew install ttyd, or https://github.com/tsl0922/ttyd/releases)"))
    http.server.ThreadingHTTPServer.allow_reuse_address = True
    srv = http.server.ThreadingHTTPServer(("127.0.0.1", port), Api)  # type: ignore[arg-type]
    print(bold(f"\n  {TRACK_ID.upper()} exam UI:  http://127.0.0.1:{port}   (exam {VERSION})\n") + dim("  Ctrl-C stops the UI (not the exam clock)."))
    def stop(*_):
        if ttyd:
            ttyd.terminate()
        srv.shutdown()
    signal.signal(signal.SIGINT, lambda *_: threading.Thread(target=stop).start())
    signal.signal(signal.SIGTERM, lambda *_: threading.Thread(target=stop).start())
    try:
        srv.serve_forever()
    finally:
        if ttyd:
            ttyd.terminate()

def cmd_version(args):
    print(f"exam {VERSION}  track={TRACK_ID}  bank={len(QUESTIONS)} tasks  python={sys.version.split()[0]}")

def cmd_help(args):
    print(__doc__ + f"\nversion {VERSION}")
    print(f"""usage: ./exam [--track cka|ckad|cks] <command>        (current track: {TRACK_ID}, {len(QUESTIONS)} tasks)

  web [--port 8080] [--shell bash]   exam-style browser UI: tasks, terminal, clock, submit
  study [DOMAIN|weak|N..]  no clock, solutions unlocked, nothing recorded  (--count N, default {DRILL_SIZE})
  drill                    next domain you have drilled least: {DRILL_SIZE} tasks, 6 min each  (--hard: 5 min, hard tasks)
  drill all [--hard]       campaign: {DRILL_SIZE} never-attempted tasks per session until the bank is done, then weak ones
  drill weak|N..|DOMAIN..  chosen tasks  (--time MIN, --force, --hard)
  progress                 attempted/passed per domain, normal and hard
  solution N               reference solution (drills: after grading N; exams: after submit)
  sim {'|'.join(SETS) or '<set>'}{' ' * max(1, 20 - len('|'.join(SETS)))}fixed simulator set, exam rules, {TRACK['minutes']} min
  start [--hard]           full exam: {sum(QUOTA.values()) or '?'} tasks sampled by domain ({sum(QUOTA_HARD.values()) or '?'} in hard mode), {TRACK['minutes']} min.
                           Requires every domain drilled once first (--force skips). Hard mode adds traps,
                           exact-output tasks, compound failures, collateral checks and exam-style contexts.
  list                     tasks in this session, with current + historical results
  show N                   display task N
  grade N|all              grade one task (or all) per check - drills only, in the UI
  status / timer           time remaining (timer = live countdown)
  pause / resume           stop the clock (recorded on the attempt - the real exam has no pause)
  end                      submit: grade per check, score, log attempt, update weak-spots
  weak                     what you keep getting wrong, with the failing checks
  history                  every attempt, scores, and per-domain trend
  reset N                  re-seed the scenario for task N
""")

COMMANDS = {"start": cmd_start, "drill": cmd_drill, "list": cmd_list, "show": cmd_show, "grade": cmd_grade,
            "status": cmd_status, "timer": cmd_timer, "pause": cmd_pause, "resume": cmd_resume, "end": cmd_end, "weak": cmd_weak, "history": cmd_history,
            "reset": cmd_reset, "web": cmd_web, "abort": cmd_abort, "progress": cmd_progress, "solution": cmd_solution, "sim": cmd_sim, "study": cmd_study, "version": cmd_version, "help": cmd_help}

if __name__ == "__main__":
    cmd = ARGV[0] if ARGV else "help"
    COMMANDS.get(cmd, cmd_help)(ARGV[1:])