"""Gateway lifecycle ledger — durable termination-reason evidence.

Graceful shutdowns leave forensics (``gateway-exit-diag.log``); an unclean
death (SIGKILL, kernel OOM, VM death) runs no handler.  A sentinel at
``<HERMES_HOME>/state/gateway.lifecycle.json`` closes the gap:
:func:`record_startup` finds ``phase == "running"`` from the previous life →
unclean death, appended to the exit-diag log as ``gateway.previous_unclean_exit``
and logged at WARNING; :func:`mark_exited` rewrites ``phase=exited`` on every
clean exit path.  Best-effort: forensics must never affect the lifecycle.
"""

from __future__ import annotations

import json
import logging
import os
import sqlite3
import time
from contextlib import closing
from datetime import datetime, timezone
from pathlib import Path
from typing import Any, Dict, Optional

logger = logging.getLogger(__name__)


def _process_hermes_home() -> Path:
    """HERMES_HOME for process-level identity files (ignore task overrides)."""
    from hermes_constants import get_hermes_home

    val = os.environ.get("HERMES_HOME", "").strip()
    return Path(val) if val else get_hermes_home()


def _home_path(home: Optional[Path], *relative: str) -> Path:
    return (_process_hermes_home() if home is None else home).joinpath(*relative)


def get_lifecycle_sentinel_path(home: Optional[Path] = None) -> Path:
    """Return ``<HERMES_HOME>/state/gateway.lifecycle.json``."""
    return _home_path(home, "state", "gateway.lifecycle.json")


def _now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


def _proc_fields(path: str, wanted: Dict[str, str]) -> Dict[str, int]:
    """``{dst: int}`` for each ``src: dst`` key found in a ``Key: value`` /proc file."""
    found: Dict[str, int] = {}
    try:
        with open(path, encoding="utf-8") as fh:
            for line in fh:
                key = line.split(":", 1)[0]
                if key in wanted:
                    found[wanted[key]] = int(line.split()[1])
                    if len(found) == len(wanted):
                        break
    except (OSError, ValueError, IndexError):
        return {}
    return found


def sample_memory() -> Dict[str, Any]:
    """Cheap /proc snapshot (KiB): own RSS + MemTotal/MemAvailable + swap used.  Linux-only
    (``{}`` elsewhere), never raises; the 30s heartbeat embeds it so OOM cycles are classifiable."""
    sample = _proc_fields("/proc/self/status", {"VmRSS": "rss_kib"})
    mem = _proc_fields("/proc/meminfo", {"MemTotal": "mem_total_kib", "MemAvailable": "mem_available_kib",
                                         "SwapTotal": "SwapTotal", "SwapFree": "SwapFree"})
    swap_total, swap_free = mem.pop("SwapTotal", None), mem.pop("SwapFree", None)
    sample.update(mem)
    if swap_total is not None and swap_free is not None:
        sample["swap_used_kib"] = swap_total - swap_free
    return sample


def _read_json(path: Path) -> Optional[Dict[str, Any]]:
    try:
        data = json.loads(path.read_text(encoding="utf-8"))
    except (OSError, ValueError):
        return None
    return data if isinstance(data, dict) else None


def _write_sentinel(payload: Dict[str, Any], home: Optional[Path]) -> None:
    try:
        from utils import atomic_json_write

        path = get_lifecycle_sentinel_path(home)
        from hermes_constants import mkdir_under_hermes_home

        mkdir_under_hermes_home(path.parent)
        atomic_json_write(path, payload, indent=None)
    except Exception:
        logger.debug("Failed to write lifecycle sentinel", exc_info=True)


def _append_exit_diag(record: Dict[str, Any], home: Optional[Path]) -> None:
    """Append a JSON line to gateway-exit-diag.log (same format as the CLI's ``_exit_diag``)."""
    try:
        path = _home_path(home, "logs", "gateway-exit-diag.log")
        from hermes_constants import mkdir_under_hermes_home

        mkdir_under_hermes_home(path.parent)
        with path.open("a", encoding="utf-8") as fh:
            fh.write(json.dumps(record, default=str) + "\n")
    except OSError:
        logger.debug("Failed to append unclean-exit record", exc_info=True)


def _pid_is_sentinel_owner(pid: Any, start_time: Any, create_time: Any) -> bool:
    """True when ``pid`` is a live process that is the sentinel's incarnation — guards the
    ``--replace`` race: a live matching owner mid-teardown is a handover, not a death.

    Identity is the psutil ``create_time`` the sentinel stamps at claim (epoch seconds, same
    producer on both sides). The sentinel's ``start_time`` is the ledger claim time and is NOT
    comparable with ``gateway.status.get_process_start_time`` (proc ticks on Linux, centiseconds
    elsewhere) — the old comparison never matched, so every ``--replace`` handover read as an
    unclean death. A pre-stamp sentinel (no ``create_time``) still has ``start_time`` in epoch
    seconds: the owner was born BEFORE it claimed, a PID reuser AFTER the owner died, so a birth
    later than the claim is a reuser."""
    try:
        pid_int = int(pid)
        # NOT os.kill(pid, 0): on Windows that sends CTRL_C_EVENT to the target's console group.
        from gateway.status import _pid_exists

        if pid_int <= 0 or not _pid_exists(pid_int):
            return False
    except Exception:
        return False
    from hermes_cli.process_identity import _process_create_time

    actual = _process_create_time(pid_int)
    if actual is None:
        return True  # can't disambiguate PID reuse
    if type(create_time) in (int, float):
        return abs(actual - float(create_time)) <= 2.0
    if type(start_time) in (int, float):
        return actual <= float(start_time) + 2.0
    return True


def _suspected_oom(mem: Dict[str, Any]) -> bool:
    """Heuristic only (classification stays with the reader); thresholds are
    memory_status' "critical" tier so a live warning and a post-mortem verdict agree."""
    from gateway.memory_status import _CRITICAL_AVAILABLE_FRACTION, _CRITICAL_AVAILABLE_KIB

    total, avail = mem.get("mem_total_kib"), mem.get("mem_available_kib")
    if not isinstance(avail, int):
        return False
    return avail < _CRITICAL_AVAILABLE_KIB or (
        isinstance(total, int) and total > 0 and avail / total < _CRITICAL_AVAILABLE_FRACTION
    )


def detect_unclean_exit(home: Optional[Path] = None) -> Optional[Dict[str, Any]]:
    """Evidence dict when the previous life died uncleanly, else ``None``. Read-only."""
    sentinel = _read_json(get_lifecycle_sentinel_path(home))
    if not sentinel or sentinel.get("phase") != "running":
        return None
    if _pid_is_sentinel_owner(sentinel.get("pid"), sentinel.get("start_time"), sentinel.get("create_time")):
        return None  # live owner — planned takeover in flight, not a death
    evidence: Dict[str, Any] = {
        "prior_pid": sentinel.get("pid"), "prior_started_at": sentinel.get("started_at"),
        "prior_start_time": sentinel.get("start_time"),
    }
    # Enrich with the last heartbeat: last proven liveness and memory at that moment.
    try:
        from gateway.shutdown_watchdog import get_loop_heartbeat_path

        hb = _read_json(get_loop_heartbeat_path(home)) or {}
    except Exception:
        hb = {}
    if hb:
        evidence["last_heartbeat_at"] = hb.get("updated_at")
    mem = hb.get("mem")
    if isinstance(mem, dict):
        evidence["last_heartbeat_mem"] = mem
        if _suspected_oom(mem):
            evidence["suspected_oom"] = True
    return evidence


def check_state_db_integrity(home: Optional[Path] = None) -> str:
    """``"ok"``, ``"absent"``, or the first ``quick_check`` complaint.  Never raises.

    Only after an unclean death — SIGKILL mid-WAL-checkpoint can leave half-written
    b-tree pages.  ``quick_check(1)`` stops at the first problem (~2s on a healthy
    500MB store): cheap once per unclean boot, too costly every boot.  Opened
    normally: a WAL store needs its -shm sidecar for read-only, and the PRAGMA writes nothing.
    """
    path = _home_path(home, "state.db")
    if not path.exists():
        return "absent"
    try:
        with closing(sqlite3.connect(str(path))) as conn:
            row = conn.execute("PRAGMA quick_check(1)").fetchone()
    except Exception as exc:
        return f"check-failed: {exc}"
    return "check-failed: no result" if not row or row[0] is None else str(row[0])


def _report_unclean_exit(evidence: Dict[str, Any], home: Optional[Path]) -> None:
    """Integrity-check the store, persist the exit-diag record, log at WARNING."""
    # The death may have torn the store; this is the only moment we know to look.
    verdict = evidence["state_db_integrity"] = check_state_db_integrity(home=home)
    if verdict not in ("ok", "absent"):
        logger.error(
            "state.db FAILED integrity check after an unclean gateway exit: %s — sessions may read as "
            "missing until it is repaired. Run `hermes doctor`.",
            verdict,
        )
    _append_exit_diag({"ts": _now_iso(), "tag": "gateway.previous_unclean_exit", "pid": os.getpid(), **evidence}, home)
    logger.warning(
        "Previous gateway life (pid=%s, started_at=%s) exited UNCLEANLY (no exit path ran — SIGKILL / OOM / "
        "VM death). last_heartbeat_at=%s last_mem=%s suspected_oom=%s",
        evidence.get("prior_pid"), evidence.get("prior_started_at"), evidence.get("last_heartbeat_at"),
        evidence.get("last_heartbeat_mem"), evidence.get("suspected_oom", False),
    )


def record_startup(home: Optional[Path] = None) -> Optional[Dict[str, Any]]:
    """Boot entry point: report any unclean previous exit (evidence dict, also persisted
    to ``gateway-exit-diag.log`` and logged at WARNING) then claim the sentinel.  Never raises."""
    evidence: Optional[Dict[str, Any]] = None
    try:
        evidence = detect_unclean_exit(home)
        if evidence is not None:
            _report_unclean_exit(evidence, home)
    except Exception:
        logger.debug("Unclean-exit detection failed", exc_info=True)
    try:
        claim: Dict[str, Any] = {"phase": "running", "pid": os.getpid(), "start_time": time.time(), "started_at": _now_iso()}
        # Process birth (psutil), distinct from ``start_time`` (the ledger claim, seconds later once
        # imports finish): the Windows start attestation binds PIDs to birth time (#110020 review).
        from hermes_cli.process_identity import _process_create_time

        create_time = _process_create_time(os.getpid())
        if create_time is not None:
            claim["create_time"] = create_time
        # Carry the verdict on the PREVIOUS life on the new sentinel: it is the only
        # machine-readable copy (/api/status reads it to report an OOM restart).
        # Scoped to this life — the next clean exit or boot rewrites the sentinel.
        if evidence is not None:
            claim["prior_unclean_exit"] = True
            if evidence.get("suspected_oom"):
                claim["prior_suspected_oom"] = True
        _write_sentinel(claim, home)
    except Exception:
        logger.debug("Failed to claim lifecycle sentinel", exc_info=True)
    return evidence


def mark_exited(exit_code: Optional[int] = None, reason: str = "graceful_shutdown", home: Optional[Path] = None) -> None:
    """Mark the current life as cleanly exited.  Idempotent, never raises.

    Only rewrites a sentinel provably owned by this process: during ``--replace``
    the replacement claims it before the old process finishes teardown and must not
    be clobbered.  ``pid=None`` / malformed sentinels have unknown ownership → left alone.
    """
    try:
        sentinel = _read_json(get_lifecycle_sentinel_path(home))
        if sentinel is not None and sentinel.get("pid") != os.getpid():
            return
        exited: Dict[str, Any] = {"phase": "exited", "pid": os.getpid(), "exit_code": exit_code, "exit_reason": reason,
                                  "exited_at": _now_iso()}
        # Carry the incarnation identity: the Windows start attestation matches a clean exit by
        # PID *and* start time so a reused PID's exit cannot vouch for a different life (#110020).
        for key in ("start_time", "create_time"):
            if sentinel is not None and sentinel.get(key) is not None:
                exited[key] = sentinel[key]
        _write_sentinel(exited, home)
    except Exception:
        logger.debug("Failed to mark lifecycle sentinel exited", exc_info=True)


def read_prior_exit_label(profile_home: Path) -> str:
    """``clean``/``unclean``/``unknown`` for the profile's last gateway life; annotates
    ``container-boot.log``.  ``running`` is unclean: the old PID namespace is gone at container boot."""
    try:
        phase = (_read_json(get_lifecycle_sentinel_path(profile_home)) or {}).get("phase")
        return {"exited": "clean", "running": "unclean"}.get(phase, "unknown")
    except Exception:
        return "unknown"