"""Global emergency stop (ESTOP) — a resumable pause for NEW work only.

``hermes pause`` writes a sentinel at ``$HERMES_HOME/ESTOP``; ``hermes resume``
removes it. While it exists the cron scheduler, kanban dispatcher and new
gateway turns skip work; in-flight work is never killed. The check is one or
two ``os.stat`` calls (process home + fleet root when they differ), uncached,
so engaging/disengaging binds on the next check. The sentinel body is optional
JSON ``{"reason", "engaged_at"}``; a corrupt/empty file still counts as engaged
(fail safe, e.g. ``touch ~/.hermes/ESTOP``). Ported from gastownhall/gastown
estop.go (MIT).
"""

from __future__ import annotations

import json
import logging
import threading
from datetime import datetime, timezone
from pathlib import Path
from typing import Optional

# Same profile-aware / fleet-root resolvers the file-safety guards use (fail-open to ~/.hermes).
from agent.file_safety import _hermes_home_path as _hermes_home, _hermes_root_path as _canonical_root

SENTINEL_NAME = "ESTOP"

# Per-component "logged already for this engagement" flags: log once per
# engagement, not once per tick.
_log_lock = threading.Lock()
_logged_components: set[str] = set()


def sentinel_path() -> Path:
    """Path of the ESTOP sentinel this process would write on `hermes pause`."""
    return _hermes_home() / SENTINEL_NAME


def _candidate_sentinel_paths() -> list:
    """Profile home first, then the fleet root if it is a different directory: a profile
    gateway (HERMES_HOME=~/.hermes/profiles/<n>) must still honor an operator's ~/.hermes/ESTOP."""
    primary = sentinel_path()
    paths = [primary]
    try:
        root = _canonical_root() / SENTINEL_NAME
    except Exception:
        return paths
    try:
        if root.resolve() != primary.resolve():
            paths.append(root)
    except Exception:
        # Non-Path test doubles fail .resolve(); plain equality still dedupes.
        if root != primary:
            paths.append(root)
    return paths


def is_engaged() -> bool:
    """True if ANY candidate sentinel exists; fail SAFE (True) on stat errors."""
    saw_stat_error = False
    for path in _candidate_sentinel_paths():
        try:
            if path.exists():
                return True
        except OSError:
            saw_stat_error = True
    return saw_stat_error


def engage(reason: Optional[str] = None) -> Path:
    """Create the ESTOP sentinel. Idempotent; re-engaging updates the file."""
    path = sentinel_path()
    payload = {"engaged_at": datetime.now(timezone.utc).isoformat(), "reason": reason or None}
    try:
        path.parent.mkdir(parents=True, exist_ok=True)
        path.write_text(json.dumps(payload, indent=2) + "\n", encoding="utf-8")
    except OSError:
        # Best effort: an empty/partial sentinel still pauses (fail safe).
        try:
            path.touch(exist_ok=True)
        except OSError:
            pass
    return path


def disengage() -> bool:
    """Remove every visible sentinel (process-local and fleet-root)."""
    lifted = False
    for path in _candidate_sentinel_paths():
        try:
            path.unlink()
            lifted = True
        except (OSError, AttributeError):
            continue
    return lifted


def get_state() -> Optional[dict]:
    """Return ``{"reason", "engaged_at"}`` or None when not engaged.

    An unreadable/corrupt body still reports engaged with both fields None.
    """
    if not is_engaged():
        return None
    reason = engaged_at = None
    found = False
    for path in _candidate_sentinel_paths():
        try:
            exists = path.exists()
        except OSError:
            return {"reason": None, "engaged_at": None}
        except AttributeError:
            continue
        if not exists:
            continue
        found = True
        try:
            raw = json.loads(path.read_text(encoding="utf-8"))
            if isinstance(raw, dict):
                reason = raw.get("reason") or None
                engaged_at = raw.get("engaged_at") or None
                break
        except (OSError, ValueError, AttributeError):
            continue
    if not found:
        return None
    return {"reason": reason, "engaged_at": engaged_at}


def paused_reply() -> Optional[str]:
    """Short user-facing notice for new gateway turns, or None if not paused."""
    state = get_state()
    if state is None:
        return None
    reason = state.get("reason")
    tag = f" ({reason})" if reason else ""
    return f"⏸️ Hermes is paused{tag}. New work is on hold; run `hermes resume` to pick things back up."


def check_paused(component: str, logger: logging.Logger) -> bool:
    """Return True when engaged, logging once per engagement per component
    (re-armed after a resume)."""
    if not is_engaged():
        with _log_lock:
            _logged_components.discard(component)
        return False
    with _log_lock:
        first = component not in _logged_components
        if first:
            _logged_components.add(component)
    if first:
        state = get_state() or {}
        reason = state.get("reason")
        suffix = f" (reason: {reason})" if reason else ""
        logger.info(
            "%s dispatch paused by global emergency stop%s — remove with "
            "`hermes resume` (%s)",
            component,
            suffix,
            sentinel_path(),
        )
    return True