#!/usr/bin/env python3
"""Read-only readiness gate for an ops-bridge cert_command pilot (WARDEN-WP-0016 T1).

Before an operator migrates a tunnel from a static SSH key to a warden-signed
certificate (see ``wiki/playbooks/ops-bridge-tunnel-cert.md``), this script asserts the
**ops-warden side is ready** — *without signing anything*:

  * warden.yaml loads and names a known backend (local | vault),
  * the actor exists in the inventory with a valid type and resolvable TTL,
  * the public key file exists and is structurally a public key (no private key),
  * the actor has at least one principal,
  * (optional) the actor's principals are deployed in railiance-infra's
    ``ssh_principals.yaml`` (mirrors ``scripts/check_principals_drift.py``).

Exit 0 = ready, 1 = not ready (a check failed), 2 = bad input (missing/invalid files).
It never signs, reads a private key, or prints a secret. The actual cert_command smoke
is the opt-in ``--sign-smoke`` step (WP-0016 T2), kept separate because it issues a cert.

Usage:
  python scripts/check_tunnel_cert_readiness.py \\
    --actor agt-state-hub-bridge \\
    --pubkey ~/.ssh/agt-state-hub-bridge_ed25519.pub \\
    --config ~/.config/warden/warden.yaml \\
    [--infra ~/railiance-infra/ansible/inventory/ssh_principals.yaml]
"""
from __future__ import annotations

import argparse
import sys
from pathlib import Path
from typing import Any, List, Optional, Tuple

_SRC = Path(__file__).resolve().parent.parent / "src"
if _SRC.is_dir() and str(_SRC) not in sys.path:
    sys.path.insert(0, str(_SRC))

import yaml  # noqa: E402

from warden.config import ConfigError, WardenConfig, load_config  # noqa: E402
from warden.inventory import ActorEntry, InventoryError, load_inventory  # noqa: E402
from warden.models import MAX_TTL_HOURS, CertSpec  # noqa: E402

# A check result: status in {"ok", "fail", "skip"}, a short label, and a detail line.
Check = Tuple[str, str, str]

# Public-key prefixes we accept for a cert_command pubkey (never a private key).
_PUBKEY_PREFIXES = ("ssh-ed25519 ", "ssh-rsa ", "ecdsa-sha2-", "sk-ssh-", "ssh-dss ")


def build_cert_command(actor: str, pubkey: Path) -> str:
    """The cert_command an ops-bridge tunnel config would carry for this actor."""
    return f"warden sign {actor} --pubkey {pubkey}"


def check_pubkey(pubkey: Path) -> Check:
    if not pubkey.exists():
        return ("fail", "public key", f"{pubkey} does not exist")
    text = pubkey.read_text(errors="replace").strip()
    if "PRIVATE KEY" in text:
        return ("fail", "public key", f"{pubkey} looks like a PRIVATE key — use the .pub")
    if not text.startswith(_PUBKEY_PREFIXES):
        return ("fail", "public key", f"{pubkey} is not a recognized SSH public key")
    return ("ok", "public key", f"{pubkey} ({text.split()[0]})")


def check_actor(inventory_actors: dict, actor: str) -> Tuple[Check, Optional[ActorEntry]]:
    entry = inventory_actors.get(actor)
    if entry is None:
        return (("fail", "inventory", f"actor {actor!r} not in inventory"), None)
    max_ttl = MAX_TTL_HOURS.get(entry.actor_type)
    if not entry.ttl_hours or entry.ttl_hours <= 0:
        return (("fail", "inventory", f"actor {actor!r} has no resolvable TTL"), entry)
    if max_ttl and entry.ttl_hours > max_ttl:
        return (
            ("fail", "inventory", f"actor {actor!r} TTL {entry.ttl_hours}h exceeds "
             f"{entry.actor_type.value} max {max_ttl}h"),
            entry,
        )
    return (
        ("ok", "inventory", f"{actor} type={entry.actor_type.value} ttl={entry.ttl_hours}h"),
        entry,
    )


def check_principals(entry: ActorEntry) -> Check:
    if not entry.principals:
        return ("fail", "principals", f"actor {entry.name!r} has no principals")
    return ("ok", "principals", ", ".join(entry.principals))


def _infra_principals(infra: dict[str, Any]) -> set[str]:
    # Mirrors scripts/check_principals_drift.py._infra_principals.
    principals: set[str] = set()
    for host_data in (infra.get("ssh_principals") or {}).values():
        for user_principals in (host_data.get("users") or {}).values():
            principals.update(user_principals)
    return principals


def check_infra_principal(entry: ActorEntry, infra_path: Optional[Path]) -> Check:
    if infra_path is None:
        return ("skip", "infra principals", "no --infra given (host-side check skipped)")
    if not infra_path.exists():
        return ("fail", "infra principals", f"{infra_path} not found")
    infra = yaml.safe_load(infra_path.read_text()) or {}
    deployed = _infra_principals(infra)
    missing = [p for p in entry.principals if p not in deployed]
    if missing:
        return (
            "fail",
            "infra principals",
            f"not deployed in {infra_path.name}: {', '.join(missing)}",
        )
    return ("ok", "infra principals", f"all deployed in {infra_path.name}")


def run_checks(
    cfg: WardenConfig,
    actor: str,
    pubkey: Path,
    infra_path: Optional[Path],
) -> List[Check]:
    """Run every readiness check and return the result list (pure; no signing)."""
    checks: List[Check] = [
        ("ok", "config", f"backend={cfg.backend}, inventory={cfg.inventory_path}")
    ]
    inventory = load_inventory(cfg.inventory_path)
    actor_check, entry = check_actor(inventory.actors, actor)
    checks.append(actor_check)
    checks.append(check_pubkey(pubkey))
    if entry is not None:
        checks.append(check_principals(entry))
        checks.append(check_infra_principal(entry, infra_path))
    return checks


def sign_smoke(cfg: WardenConfig, actor: str, pubkey: Path) -> List[Check]:
    """Opt-in cert_command contract smoke against the LOCAL backend (WP-0016 T2).

    Actually runs the cert_command (issues a short-lived local cert) and validates the
    emitted certificate: identity matches the actor, principals match inventory, and the
    validity window is within the actor type's max TTL. Requires ``ssh-keygen`` and a
    local backend — it must not touch production OpenBao. Raises on misuse.
    """
    from warden.ca import CAError, LocalCA, parse_cert_metadata

    if cfg.backend != "local":
        raise ValueError(
            f"--sign-smoke runs offline against the local backend, but config backend is "
            f"{cfg.backend!r}. Point --config at a local warden.yaml for the smoke."
        )
    inventory = load_inventory(cfg.inventory_path)
    entry = inventory.actors.get(actor)
    if entry is None:
        return [("fail", "sign smoke", f"actor {actor!r} not in inventory")]

    spec = CertSpec(
        actor_name=actor,
        actor_type=entry.actor_type,
        pubkey_path=pubkey,
        ttl_hours=entry.ttl_hours,
        principals=entry.principals,
        identity=actor,
    )
    try:
        record = LocalCA(cfg.ca_key, cfg.state_dir).sign(spec)
    except CAError as e:
        return [("fail", "sign smoke", f"signing failed: {e}")]

    checks: List[Check] = []
    if record.identity == actor:
        checks.append(("ok", "cert identity", record.identity))
    else:
        checks.append(("fail", "cert identity", f"{record.identity!r} != {actor!r}"))

    if set(record.principals) == set(entry.principals):
        checks.append(("ok", "cert principals", ", ".join(record.principals)))
    else:
        checks.append(
            ("fail", "cert principals", f"{record.principals} != inventory {entry.principals}")
        )

    # Measure the validity window from the cert's own from→to so it is independent of
    # how ssh-keygen renders the timezone (parse_cert_metadata reads both the same way).
    max_ttl = MAX_TTL_HOURS.get(entry.actor_type)
    meta = parse_cert_metadata(record.cert_path)
    valid_from = meta.get("valid_from")
    if valid_from is None:
        window_h = (record.valid_before - record.signed_at).total_seconds() / 3600
    else:
        window_h = (meta["valid_before"] - valid_from).total_seconds() / 3600
    if max_ttl is None or window_h <= max_ttl + 0.1:
        checks.append(("ok", "cert validity", f"~{window_h:.1f}h (max {max_ttl}h)"))
    else:
        checks.append(("fail", "cert validity", f"~{window_h:.1f}h exceeds max {max_ttl}h"))
    return checks


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--actor", required=True)
    parser.add_argument("--pubkey", type=Path, required=True)
    parser.add_argument("--config", type=Path, default=None, help="warden.yaml (or WARDEN_CONFIG)")
    parser.add_argument("--infra", type=Path, default=None, help="railiance-infra ssh_principals.yaml")
    parser.add_argument(
        "--sign-smoke",
        action="store_true",
        help="Also run the cert_command against the local backend and validate the cert (WP-0016 T2)",
    )
    args = parser.parse_args()

    try:
        cfg = load_config(args.config)
    except ConfigError as e:
        print(f"config error: {e}", file=sys.stderr)
        return 2
    pubkey = args.pubkey.expanduser()
    try:
        checks = run_checks(cfg, args.actor, pubkey, args.infra)
        if args.sign_smoke:
            checks += sign_smoke(cfg, args.actor, pubkey)
    except (InventoryError, ValueError, yaml.YAMLError) as e:
        print(f"input error: {e}", file=sys.stderr)
        return 2

    glyph = {"ok": "✓", "fail": "✗", "skip": "·"}
    print(f"cert_command readiness — actor {args.actor!r}\n")
    for status, label, detail in checks:
        print(f"  {glyph[status]} {label}: {detail}")
    print(f"\n  cert_command: {build_cert_command(args.actor, args.pubkey)}")

    failed = [c for c in checks if c[0] == "fail"]
    if failed:
        print(f"\nNOT READY — {len(failed)} check(s) failed. See "
              "wiki/playbooks/ops-bridge-tunnel-cert.md")
        return 1
    print("\nREADY — ops-warden side is set. Next: cert_command smoke (--sign-smoke), "
          "then hand the cutover to ops-bridge.")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())