"""Canonical topic hierarchy for the DECNET ServiceBus.

Locked early so consumers can subscribe with stable wildcard patterns.
Adding new topic families is fine; **renaming** existing ones is a breaking
change for every subscriber and requires a coordinated rollout.

Token structure (NATS-style, dot-separated):

    topology.{topology_id}.mutation.{state}
    topology.{topology_id}.status
    decky.{decky_id}.state
    decky.{decky_id}.traffic
    attacker.observed
    attacker.scored
    attacker.session.started
    attacker.session.ended
    system.log
    system.bus.health
    system.{worker}.health

Wildcards (per :func:`decnet.bus.base.matches`):

* ``*`` matches exactly one token.
* ``>`` matches one-or-more trailing tokens (so ``topology.>`` matches
  ``topology.abc.status`` but not the bare root ``topology``).
"""
from __future__ import annotations

# ─── Root prefixes ───────────────────────────────────────────────────────────

TOPOLOGY = "topology"
DECKY = "decky"
ATTACKER = "attacker"
SYSTEM = "system"


# ─── Leaf event-type constants (the last segment of each topic) ──────────────

# Topology mutation lifecycle states — keep in sync with TopologyMutation.state
# in decnet/web/db/models.py; the bus topic mirrors the DB state machine.
MUTATION_ENQUEUED = "enqueued"
MUTATION_APPLYING = "applying"
MUTATION_APPLIED = "applied"
MUTATION_FAILED = "failed"

# Topology-level status transitions (topology.{id}.status): fires when the
# topology row's status column changes (pending/deploying/active/degraded/failed).
TOPOLOGY_STATUS = "status"

# Decky-level event types (second token).
DECKY_STATE = "state"
DECKY_TRAFFIC = "traffic"
# On-demand mutation request — published by the API/CLI/UI, consumed by
# the mutator's watch loop to force an immediate mutation of one decky
# without waiting for its scheduled interval.  Underscored (not dotted)
# to stay a single NATS token so the builder's validator accepts it.
DECKY_MUTATE_REQUEST = "mutate_request"
# Mutation transition event — distinct from DECKY_STATE ("current
# shape") because a mutation is a *transition* that carries old/new
# services + trigger + timing.  Correlator consumes these (via the
# syslog sidechannel too) to interleave substrate-change markers into
# attacker traversals.
DECKY_MUTATION = "mutation"

# Attacker event types (second token under the ``attacker`` root).  First
# sighting, session boundary transitions, and score-threshold crossings
# published by correlator + profiler.  Consumers typically subscribe to
# the wildcard ``attacker.>``.
ATTACKER_OBSERVED = "observed"
ATTACKER_SCORED = "scored"
# Published once per successful active probe result (JARM/HASSH/TCPfp).
# Distinct from ``observed`` which is the correlator's first-sight signal —
# a fingerprint is additional evidence about an already-observed attacker.
ATTACKER_FINGERPRINTED = "fingerprinted"
ATTACKER_SESSION_STARTED = "session.started"
ATTACKER_SESSION_ENDED = "session.ended"

# System event types.
SYSTEM_LOG = "log"
SYSTEM_BUS_HEALTH = "bus.health"
# Worker-health leaf — built per-worker as ``system.<worker>.health`` via
# :func:`system_health`.  The leaf constant stays the same across workers;
# the worker name goes in the middle token.
SYSTEM_HEALTH = "health"
# Worker-control leaf — built per-worker as ``system.<worker>.control`` via
# :func:`system_control`.  Admin-originated stop intents travel on this
# topic; each worker subscribes to its own.
SYSTEM_CONTROL = "control"

# Control payload ``action`` values — the wire vocabulary.  Only ``stop`` is
# handled in v1; ``start`` is reserved because a stopped worker has no
# subscriber, so starting requires external supervision (systemd).
WORKER_CONTROL_STOP = "stop"
WORKER_CONTROL_START = "start"


# ─── Builders ────────────────────────────────────────────────────────────────

def topology_mutation(topology_id: str, state: str) -> str:
    """Build ``topology.<id>.mutation.<state>``.

    *state* should be one of the ``MUTATION_*`` constants.
    """
    _reject_tokens(topology_id, state)
    return f"{TOPOLOGY}.{topology_id}.mutation.{state}"


def topology_status(topology_id: str) -> str:
    """Build ``topology.<id>.status``."""
    _reject_tokens(topology_id)
    return f"{TOPOLOGY}.{topology_id}.{TOPOLOGY_STATUS}"


def decky(decky_id: str, event_type: str) -> str:
    """Build ``decky.<id>.<event_type>``.

    *event_type* is typically one of ``DECKY_STATE`` or ``DECKY_TRAFFIC``.
    """
    _reject_tokens(decky_id, event_type)
    return f"{DECKY}.{decky_id}.{event_type}"


def decky_mutation(decky_id: str) -> str:
    """Build ``decky.<id>.mutation``."""
    _reject_tokens(decky_id)
    return f"{DECKY}.{decky_id}.{DECKY_MUTATION}"


def system(event_type: str) -> str:
    """Build ``system.<event_type>``.

    *event_type* may itself contain dots (e.g. ``bus.health``) — we don't
    re-validate the already-constant leaves; this just prefixes.
    """
    if not event_type:
        raise ValueError("system topic requires a non-empty event_type")
    return f"{SYSTEM}.{event_type}"


def attacker(event_type: str) -> str:
    """Build ``attacker.<event_type>``.

    *event_type* is typically one of ``ATTACKER_OBSERVED``,
    ``ATTACKER_SCORED``, ``ATTACKER_SESSION_STARTED``,
    ``ATTACKER_SESSION_ENDED``.  Dotted leaves (``session.started``) are
    permitted — same rationale as :func:`system`.
    """
    if not event_type:
        raise ValueError("attacker topic requires a non-empty event_type")
    return f"{ATTACKER}.{event_type}"


def system_health(worker: str) -> str:
    """Build ``system.<worker>.health``.

    Worker-health heartbeats live as a nested leaf under ``system`` so
    consumers can subscribe to ``system.*.health`` for every worker at
    once, or to ``system.mutator.health`` for a single one.  *worker* is
    validated as a regular segment — no dots, wildcards, or whitespace.
    """
    _reject_tokens(worker)
    return f"{SYSTEM}.{worker}.{SYSTEM_HEALTH}"


def system_control(worker: str) -> str:
    """Build ``system.<worker>.control``.

    Admin-originated stop (and, eventually, start) intents are published
    here; the worker in question subscribes to its own address and reacts.
    Payload shape::

        {"action": "stop", "requested_by": "<username>", "ts": <unix>}

    *action* must be one of :data:`WORKER_CONTROL_STOP` /
    :data:`WORKER_CONTROL_START`; any other value is ignored by the
    listener.  Same segment rules as :func:`system_health`.
    """
    _reject_tokens(worker)
    return f"{SYSTEM}.{worker}.{SYSTEM_CONTROL}"


def _reject_tokens(*parts: str) -> None:
    """Reject topic segments that would break NATS-style tokenization.

    Dots, wildcards, whitespace, and empty strings in a *segment* would
    silently corrupt the hierarchy (e.g. ``topology.a.b.status`` for a
    ``topology_id`` of ``"a.b"``).  Raise early at the builder instead of
    shipping a malformed topic to the wire.
    """
    for p in parts:
        if not p:
            raise ValueError("topic segment must not be empty")
        if "." in p or "*" in p or ">" in p or any(c.isspace() for c in p):
            raise ValueError(
                f"topic segment {p!r} may not contain '.', '*', '>', or whitespace"
            )