#!/usr/bin/env python3
"""
WZDX Field Device Monitor
=========================

Polls a WZDX field-device feed on a fixed interval, detects field devices that
are no longer communicating, and emails an alert to one or more recipients.

A device is considered NOT COMMUNICATING when EITHER of these is true:
  * its `device_status` is one of DOWN_STATUSES (e.g. "error" / "unknown"), OR
  * its `update_date` (last report time) is older than STALE_THRESHOLD_MINUTES.

Behavior:
  * One alert email per poll cycle listing every device that has *newly* gone
    down since the previous cycle (no repeated spam while a device stays down).
  * A recovery email when a previously-down device starts reporting normally
    again.

Only dependency beyond the standard library is `requests`:
    pip install requests
"""

import sys
import time
import smtplib
import logging
from datetime import datetime, timezone
from email.message import EmailMessage

import requests
from requests.auth import HTTPBasicAuth

# ============================ CONFIGURATION ============================
# --- WZDX feed ---
WZDX_FEED_URL = "https://projects.slndrtech.com/Salander/api/wzdx/v42/deviceFeed/5tjm0tva5is76sd33mp85gpj4s"
FEED_USERNAME = "JP Story"
FEED_PASSWORD = "l3tmeslndr"
FEED_TIMEOUT_SECONDS = 30

# --- Alert recipients ---
ALERT_RECIPIENTS = ["jp@slndrtech.com"]

# --- Outbound email (SMTP) ---
SMTP_HOST = "smtp-relay.brevo.com"
SMTP_PORT = 587
SMTP_USERNAME = "a7bfc2001@smtp-brevo.com"
SMTP_PASSWORD = "bskWFnIXIvjIr67"
SMTP_USE_TLS = True                       # True for STARTTLS (port 587)
EMAIL_FROM = "wzdx-monitor@example.com"

# --- Detection settings ---
POLL_INTERVAL_SECONDS = 60                # how often to poll the feed
STALE_THRESHOLD_MINUTES = 5               # no update in this many minutes = down
DOWN_STATUSES = {"error", "unknown"}      # device_status values treated as down
SEND_RECOVERY_ALERTS = True

# Alert if the feed itself becomes unreachable (won't repeat while it stays down)
ALERT_ON_FEED_FAILURE = True
# ======================================================================


logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s  %(levelname)-7s  %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
)
log = logging.getLogger("wzdx-monitor")


# ---------------------------------------------------------------------------
# Feed fetching
# ---------------------------------------------------------------------------
def fetch_feed():
    """Fetch and JSON-decode the WZDX feed. Returns a dict, or raises on error."""
    auth = None
    if FEED_USERNAME or FEED_PASSWORD:
        auth = HTTPBasicAuth(FEED_USERNAME, FEED_PASSWORD)
    resp = requests.get(WZDX_FEED_URL, auth=auth, timeout=FEED_TIMEOUT_SECONDS)
    resp.raise_for_status()
    return resp.json()


# ---------------------------------------------------------------------------
# Feed parsing
# ---------------------------------------------------------------------------
def _first(props, *keys):
    """Return the first present, non-None value among the given keys."""
    for k in keys:
        if isinstance(props, dict) and props.get(k) is not None:
            return props[k]
    return None


def extract_devices(feed):
    """
    Normalize the WZDX FeatureCollection into a list of simple device dicts:
        {id, name, type, status, update_date (datetime|None)}

    Field-device details usually live under properties.core_details, but this
    reads flexibly so it also works if the producer flattens them.
    """
    devices = []
    for feature in feed.get("features", []) or []:
        props = feature.get("properties", {}) or {}
        core = props.get("core_details", props)  # fall back to flat properties

        device_id = (
            feature.get("id")
            or _first(core, "id", "name")
            or _first(props, "id", "name")
        )
        name = _first(core, "name", "description") or device_id or "(unnamed device)"
        dev_type = _first(core, "device_type") or _first(props, "device_type")
        status = _first(core, "device_status", "status") or _first(props, "device_status", "status")
        raw_update = _first(core, "update_date", "updated_timestamp") or _first(
            props, "update_date", "updated_timestamp"
        )

        devices.append(
            {
                "id": str(device_id) if device_id is not None else name,
                "name": name,
                "type": dev_type,
                "status": (status or "").lower() if isinstance(status, str) else status,
                "update_date": _parse_timestamp(raw_update),
                "raw_update": raw_update,
            }
        )
    return devices


def _parse_timestamp(value):
    """Parse an ISO-8601 timestamp (WZDX style) into an aware UTC datetime."""
    if not value or not isinstance(value, str):
        return None
    text = value.strip().replace("Z", "+00:00")
    try:
        dt = datetime.fromisoformat(text)
    except ValueError:
        return None
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    return dt.astimezone(timezone.utc)


# ---------------------------------------------------------------------------
# Detection
# ---------------------------------------------------------------------------
def evaluate_devices(devices, now=None):
    """
    Return {device_id: {"device": <device>, "reason": <str>}} for every device
    currently considered NOT communicating.
    """
    now = now or datetime.now(timezone.utc)
    down = {}
    for d in devices:
        reason = None

        if d["status"] in DOWN_STATUSES:
            reason = f"device_status = '{d['status']}'"

        elif d["update_date"] is not None:
            age_min = (now - d["update_date"]).total_seconds() / 60.0
            if age_min > STALE_THRESHOLD_MINUTES:
                reason = (
                    f"no update in {age_min:.1f} min "
                    f"(last update {d['raw_update']}, threshold "
                    f"{STALE_THRESHOLD_MINUTES} min)"
                )

        if reason:
            down[d["id"]] = {"device": d, "reason": reason}
    return down


# ---------------------------------------------------------------------------
# Email
# ---------------------------------------------------------------------------
def send_email(subject, body):
    msg = EmailMessage()
    msg["Subject"] = subject
    msg["From"] = EMAIL_FROM
    msg["To"] = ", ".join(ALERT_RECIPIENTS)
    msg.set_content(body)

    with smtplib.SMTP(SMTP_HOST, SMTP_PORT, timeout=30) as server:
        if SMTP_USE_TLS:
            server.starttls()
        if SMTP_USERNAME or SMTP_PASSWORD:
            server.login(SMTP_USERNAME, SMTP_PASSWORD)
        server.send_message(msg)
    log.info("Alert email sent to %s | %s", ", ".join(ALERT_RECIPIENTS), subject)


def _device_line(entry):
    d = entry["device"]
    dtype = f" [{d['type']}]" if d.get("type") else ""
    return f"  - {d['name']}{dtype} (id: {d['id']})\n      reason: {entry['reason']}"


def send_down_alert(newly_down):
    ts = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M:%S UTC")
    count = len(newly_down)
    subject = f"[WZDX ALERT] {count} device(s) not communicating"
    lines = [
        f"{count} WZDX field device(s) stopped communicating as of {ts}.",
        f"Feed: {WZDX_FEED_URL}",
        "",
        "Affected devices:",
    ]
    lines += [_device_line(e) for e in newly_down.values()]
    send_email(subject, "\n".join(lines))


def send_recovery_alert(recovered):
    ts = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M:%S UTC")
    count = len(recovered)
    subject = f"[WZDX RECOVERED] {count} device(s) communicating again"
    lines = [
        f"{count} WZDX field device(s) resumed communicating as of {ts}.",
        f"Feed: {WZDX_FEED_URL}",
        "",
        "Recovered devices:",
    ]
    for d in recovered.values():
        dtype = f" [{d['type']}]" if d.get("type") else ""
        lines.append(f"  - {d['name']}{dtype} (id: {d['id']})")
    send_email(subject, "\n".join(lines))


def send_feed_failure_alert(error):
    subject = "[WZDX ALERT] Feed unreachable"
    body = (
        f"The WZDX monitor could not retrieve the feed as of "
        f"{datetime.now(timezone.utc).strftime('%Y-%m-%d %H:%M:%S UTC')}.\n\n"
        f"Feed: {WZDX_FEED_URL}\nError: {error}"
    )
    send_email(subject, body)


# ---------------------------------------------------------------------------
# Main loop
# ---------------------------------------------------------------------------
def run_once(state):
    """
    Execute a single poll cycle, mutating `state` in place.

    state = {
        "down": {id: {"device", "reason"}},  # devices currently considered down
        "feed_failed": bool,                 # whether last cycle failed to fetch
    }
    """
    try:
        feed = fetch_feed()
    except Exception as exc:  # network / auth / decode errors
        log.error("Failed to fetch feed: %s", exc)
        if ALERT_ON_FEED_FAILURE and not state["feed_failed"]:
            try:
                send_feed_failure_alert(exc)
            except Exception as mail_exc:
                log.error("Could not send feed-failure email: %s", mail_exc)
        state["feed_failed"] = True
        return

    if state["feed_failed"]:
        log.info("Feed reachable again.")
    state["feed_failed"] = False

    devices = extract_devices(feed)
    present_ids = {d["id"] for d in devices}
    down_now = evaluate_devices(devices)
    down_before = state["down"]

    # Newly down = down now but not previously flagged.
    newly_down = {k: v for k, v in down_now.items() if k not in down_before}

    # Recovered = was down, is still present in the feed, and is now healthy.
    recovered = {
        k: v["device"]
        for k, v in down_before.items()
        if k in present_ids and k not in down_now
    }
    # Devices that were down and have vanished from the feed are dropped quietly
    # (a work zone ending legitimately removes its devices).
    vanished = [k for k in down_before if k not in present_ids and k not in down_now]

    log.info(
        "Polled %d device(s): %d down (%d new), %d recovered, %d vanished.",
        len(devices), len(down_now), len(newly_down), len(recovered), len(vanished),
    )

    if newly_down:
        try:
            send_down_alert(newly_down)
        except Exception as exc:
            log.error("Could not send down alert: %s", exc)

    if recovered and SEND_RECOVERY_ALERTS:
        try:
            send_recovery_alert(recovered)
        except Exception as exc:
            log.error("Could not send recovery alert: %s", exc)

    state["down"] = down_now


def main():
    log.info("Starting WZDX device monitor (poll every %ss).", POLL_INTERVAL_SECONDS)
    log.info("Feed: %s", WZDX_FEED_URL)
    state = {"down": {}, "feed_failed": False}
    while True:
        start = time.monotonic()
        try:
            run_once(state)
        except Exception as exc:  # never let the loop die
            log.exception("Unexpected error in poll cycle: %s", exc)
        elapsed = time.monotonic() - start
        time.sleep(max(0, POLL_INTERVAL_SECONDS - elapsed))


if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        log.info("Stopped by user.")
        sys.exit(0)