"""WhatsApp ingestion — the Python-side consumer of the whatsapp-bridge sidecar.

The bridge (digest-engine/whatsapp-bridge/) runs a real, headful Chromium logged
into web.whatsapp.com and appends one JSON object per received message to a
shared file on a Docker volume. This module drains that file each run.

A file on a shared volume beats an HTTP call to the bridge here: a digest run
fires on a systemd timer with no regard for whether the bridge container happens
to be restarting, re-authenticating, or mid-Chromium-crash. Messages the bridge
already wrote are still on disk and still get read; there is no liveness or
retry/backoff coordination problem to solve.

Draining is a rename-then-read, not a truncate-in-place: the bridge appends with
an open-write-close per message, so renaming the file out from under it is atomic
from the reader's side and the bridge simply recreates the original path on its
next append. A read-then-truncate would silently drop anything written in between.

This is opt-in and off by default — see the ban-risk warning in README.md.
"""

import json
import logging
import os
from datetime import datetime, timedelta, timezone

LOG = logging.getLogger(__name__)

DEFAULT_MESSAGES_PATH = "/data/whatsapp-bridge/messages.jsonl"
MAX_BODY_CHARS = 2000


def fetch(lookback_hours):
    messages_path = os.environ.get("WHATSAPP_MESSAGES_PATH", DEFAULT_MESSAGES_PATH)
    drained_path = messages_path + ".draining"

    if not os.path.exists(messages_path):
        LOG.warning(
            "whatsapp: no message file at %s (is whatsapp-bridge running and logged in?), skipping",
            messages_path,
        )
        return []

    try:
        os.replace(messages_path, drained_path)
    except OSError:
        LOG.warning("whatsapp: could not claim %s for reading, skipping", messages_path, exc_info=True)
        return []

    since = datetime.now(timezone.utc) - timedelta(hours=lookback_hours)
    messages = []

    try:
        with open(drained_path, "r", encoding="utf-8") as handle:
            for line in handle:
                line = line.strip()
                if not line:
                    continue
                try:
                    record = json.loads(line)
                    timestamp = record.get("timestamp")
                    sent_at = (
                        datetime.fromtimestamp(timestamp, tz=timezone.utc) if timestamp else None
                    )
                    if sent_at and sent_at < since:
                        continue
                    messages.append(
                        {
                            "source": "whatsapp",
                            "from": record.get("from_name") or record.get("from"),
                            "chat": record.get("chat"),
                            "timestamp": sent_at.isoformat() if sent_at else None,
                            "body": (record.get("body") or "")[:MAX_BODY_CHARS],
                        }
                    )
                except Exception:
                    LOG.warning("whatsapp: could not parse a bridge line, skipping", exc_info=True)
    except Exception:
        LOG.warning("whatsapp: could not read %s, returning nothing", drained_path, exc_info=True)
        return []
    finally:
        try:
            os.remove(drained_path)
        except OSError:
            LOG.warning("whatsapp: could not remove %s", drained_path, exc_info=True)

    LOG.info("whatsapp: %d message(s) in the last %sh", len(messages), lookback_hours)
    return messages