"""Track up/down transitions for any subject (Sparks AND services) and cache MACs.

Persisted to /data/connectivity.json. Schema:

    {
      "macs": { "spark1": "aa:bb:..", "spark2": "11:22:.." },
      "current": { "spark1": "up", "parakeet": "up", "kokoro": "up", ... },
      "last_change": { ... },
      "events": [
        # Active-probe transition (logged when state flips during polling)
        { "subject": "spark2", "at": "...", "kind": "transition",
          "transition": "down" },
        { "subject": "spark2", "at": "...", "kind": "transition",
          "transition": "up", "down_seconds": 4500 },

        # Passive report (logged whenever an external app POSTs to
        # /api/health-event regardless of state change)
        { "subject": "parakeet", "at": "...", "kind": "report",
          "ok": false, "source": "open-webui",
          "detail": "Connection refused", "latency_ms": 320 },
      ]
    }

Legacy events from v0.5 with `spark` instead of `subject` and no `kind` field
are read transparently as kind="transition".
"""
from __future__ import annotations
import json
import os
import threading
from datetime import datetime, timezone
from pathlib import Path
from typing import Optional


MAX_EVENTS = 200  # rolling window — plenty for showing recent history


def _path() -> str:
    return os.environ.get("CONNECTIVITY_LOG", "/data/connectivity.json")


_lock = threading.Lock()


def _read() -> dict:
    try:
        with open(_path()) as f:
            return json.load(f) or {}
    except (FileNotFoundError, json.JSONDecodeError):
        return {}


def _write(data: dict) -> None:
    p = _path()
    Path(p).parent.mkdir(parents=True, exist_ok=True)
    tmp = p + ".tmp"
    with open(tmp, "w") as f:
        json.dump(data, f, indent=2, sort_keys=False)
    os.replace(tmp, p)


def load() -> dict:
    with _lock:
        d = _read()
        d.setdefault("macs", {})
        d.setdefault("current", {})
        d.setdefault("last_change", {})
        d.setdefault("events", [])
        return d


def record_mac(subject: str, mac: Optional[str]) -> None:
    if not mac:
        return
    with _lock:
        d = _read()
        d.setdefault("macs", {})
        if d["macs"].get(subject) != mac:
            d["macs"][subject] = mac
            _write(d)


def record_state(subject: str, reachable: bool) -> Optional[dict]:
    """Update current state for `subject`. If it differs from the last seen
    state, append a transition event. Returns the event dict if a transition
    was recorded, else None.

    `subject` can be a Spark host key (spark1/spark2) or a service name
    (parakeet/kokoro/vllm).
    """
    new_state = "up" if reachable else "down"
    now = datetime.now(timezone.utc).isoformat().replace("+00:00", "Z")
    with _lock:
        d = _read()
        d.setdefault("macs", {})
        d.setdefault("current", {})
        d.setdefault("last_change", {})
        d.setdefault("events", [])
        prev = d["current"].get(subject)
        if prev == new_state:
            return None
        event: dict = {
            "subject": subject,
            "at": now,
            "kind": "transition",
            "transition": new_state,
        }
        # When we have a previous state and timestamp, compute duration
        last_change = d["last_change"].get(subject)
        if prev and last_change:
            try:
                prev_dt = datetime.fromisoformat(last_change.replace("Z", "+00:00"))
                duration = (datetime.now(timezone.utc) - prev_dt).total_seconds()
                if prev == "down" and new_state == "up":
                    event["down_seconds"] = round(duration)
                if prev == "up" and new_state == "down":
                    event["up_seconds"] = round(duration)
            except ValueError:
                pass
        d["current"][subject] = new_state
        d["last_change"][subject] = now
        d["events"].append(event)
        if len(d["events"]) > MAX_EVENTS:
            d["events"] = d["events"][-MAX_EVENTS:]
        _write(d)
        return event


def record_report(
    subject: str,
    *,
    ok: bool,
    source: str = "external",
    detail: str = "",
    latency_ms: Optional[int] = None,
) -> dict:
    """Record a passive report from an external caller (e.g. Open WebUI got a
    503 calling Parakeet). Always appended to the events list; does NOT change
    the active-probe state (which only the polling probe is authoritative on).
    """
    now = datetime.now(timezone.utc).isoformat().replace("+00:00", "Z")
    with _lock:
        d = _read()
        d.setdefault("events", [])
        event: dict = {
            "subject": subject,
            "at": now,
            "kind": "report",
            "ok": bool(ok),
            "source": source or "external",
        }
        if detail:
            event["detail"] = detail
        if latency_ms is not None:
            event["latency_ms"] = int(latency_ms)
        d["events"].append(event)
        if len(d["events"]) > MAX_EVENTS:
            d["events"] = d["events"][-MAX_EVENTS:]
        _write(d)
        return event


def get_mac(subject: str) -> Optional[str]:
    d = load()
    return d.get("macs", {}).get(subject)


def _normalize_event(e: dict) -> dict:
    """Promote legacy v0.5 events to the v0.6 shape so the UI sees one schema."""
    if "subject" in e:
        e.setdefault("kind", "transition")
        return e
    # Legacy: had "spark" + "transition" only
    if "spark" in e:
        e["subject"] = e.pop("spark")
        e.setdefault("kind", "transition")
    return e


def summary() -> dict:
    """Compact summary for the UI: known MACs, current state, recent events."""
    d = load()
    events = [_normalize_event(dict(e)) for e in d.get("events", [])]
    return {
        "macs": d.get("macs", {}),
        "current": d.get("current", {}),
        "last_change": d.get("last_change", {}),
        "events": events[-80:],
    }