"""Daily activity-digest scheduler (Phase B).

Co-located with the Gmail sync scheduler (it shares the same conn-factory and
daemon-thread idiom). One daemon thread wakes every 60s and fires the daily
activity digest once per local day, at/after the configured send hour.

Control lives in the DB, set from Settings -> Admin (digest_builder.load_digest_policy
-> app_settings 'digest_policy'): {enabled, send_hour}. The thread always runs and
re-reads the policy each cycle, so toggling the digest on/off or changing the time
takes effect on the next loop — no restart. CRM_DIGEST_ENABLED/SEND_HOUR only seed
the first-boot default before an admin sets the policy.

The send is an internal ops email to the team's own admins — exempt from the
"agents draft, humans send" rule (which governs outward LP/prospect contact).
Digest content is summarized on Spark (local), never Claude — see digest_builder.

Window: the content covers (last successful send, now]. Tracked in app_settings
so a missed day's activity rolls into the next digest rather than being dropped;
the first-ever run covers the prior 24h. The once-per-day guard is a separate
local-date key. The transport (Gmail-DWD -> SMTP) is digest_mailer's job.
"""
import json
import logging
import sqlite3
import threading
from datetime import datetime, timedelta, timezone

from .scheduler import _conn_factory_from_env


log = logging.getLogger("email_integration.digest_scheduler")

_LAST_DATE_KEY = "digest_last_sent_date"   # local YYYY-MM-DD — once-per-day guard
_LAST_AT_KEY = "digest_last_sent_at"       # UTC ISO — content-window cursor

_state: dict[str, object] = {"thread": None, "stop": threading.Event()}


def _utc_iso(dt: datetime) -> str:
    return dt.astimezone(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")


# app_settings access kept local (no server.py import — avoid the startup cycle);
# the value_json/JSON encoding matches server.get/set_app_setting exactly.
def _get_setting(conn, key):
    try:
        row = conn.execute("SELECT value_json FROM app_settings WHERE key = ?", (key,)).fetchone()
    except sqlite3.OperationalError:
        return None
    if not row:
        return None
    try:
        return json.loads(row["value_json"])
    except Exception:
        return None


def _set_setting(conn, key, value) -> None:
    conn.execute(
        "INSERT INTO app_settings (key, value_json, updated_at) VALUES (?, ?, ?) "
        "ON CONFLICT(key) DO UPDATE SET value_json = excluded.value_json, "
        "updated_at = excluded.updated_at",
        (key, json.dumps(value), _utc_iso(datetime.now(timezone.utc))),
    )


def _admin_recipients(conn) -> list[str]:
    rows = conn.execute(
        "SELECT email FROM users WHERE role = 'admin' AND is_active = 1 "
        "AND email IS NOT NULL AND TRIM(email) != ''"
    ).fetchall()
    return [str(r["email"]).strip() for r in rows if str(r["email"]).strip()]


def _build_and_send(conn, since_iso, until_iso, *, build_fn=None, send_fn=None):
    """Build the digest and hand it to the transport. Raises digest_mailer.NoTransport
    (no transport / no recipient) — callers map that to a clear 400; the daily loop
    logs it. build_fn/send_fn are injectable for tests."""
    import digest_builder
    import digest_mailer

    bf = build_fn or digest_builder.build_digest
    sf = send_fn or digest_mailer.send_digest

    recipients = _admin_recipients(conn)
    if not recipients:
        raise digest_mailer.NoTransport(
            "No active admin has an email address — give one an address to receive the digest.")

    digest = bf(conn, since_iso, until_iso)
    result = sf(conn, recipients, digest["subject"], digest["body"])
    return {
        "recipients": recipients,
        "transport": (result or {}).get("transport"),
        "has_activity": digest["has_activity"],
        "user_count": digest["user_count"],
        "email_count": digest["email_count"],
        "investor_count": digest.get("investor_count"),
        "window": [since_iso, until_iso],
    }


def maybe_send_digest(conn_factory=None, *, force=False,
                      now_local=None, now_utc=None, build_fn=None, send_fn=None):
    """Send the daily digest if it is due (or unconditionally when force=True).

    Daily path: skips before the send hour and if already sent today; content
    window runs from the last send to now and the cursor advances on success.
    force path (the admin 'send now' endpoint): ignores the policy and the guards,
    uses a fixed last-24h window, and does NOT advance the daily cursor — so an
    on-demand preview never suppresses the scheduled send."""
    import digest_builder

    factory = conn_factory or _conn_factory_from_env()
    conn = factory()
    try:
        policy = digest_builder.load_digest_policy(conn)
        if not force and not policy["enabled"]:
            return {"status": "disabled"}

        nl = now_local or datetime.now()
        nu = now_utc or datetime.now(timezone.utc)

        if not force:
            today = nl.strftime("%Y-%m-%d")
            if nl.hour < policy["send_hour"]:
                return {"status": "before_send_hour", "send_hour": policy["send_hour"]}
            if _get_setting(conn, _LAST_DATE_KEY) == today:
                return {"status": "already_sent_today"}

        until_iso = _utc_iso(nu)
        last_at = None if force else _get_setting(conn, _LAST_AT_KEY)
        since_iso = last_at or _utc_iso(nu - timedelta(hours=24))

        result = _build_and_send(conn, since_iso, until_iso, build_fn=build_fn, send_fn=send_fn)

        if not force:
            _set_setting(conn, _LAST_DATE_KEY, nl.strftime("%Y-%m-%d"))
            _set_setting(conn, _LAST_AT_KEY, until_iso)
            conn.commit()
        return {"status": "sent", **result}
    finally:
        conn.close()


def start_digest_scheduler(conn_factory=None) -> None:
    """Start the daily digest loop (idempotent). The thread always runs and reads
    the DB policy each cycle (admin-panel control), so it sends only when the policy
    is enabled — no env gate, no restart needed to toggle."""
    if _state["thread"] is not None:
        return

    factory = conn_factory or _conn_factory_from_env()
    stop = threading.Event()
    _state["stop"] = stop

    def _loop():
        log.info("digest scheduler started (policy-controlled via Settings -> Admin)")
        if stop.wait(15):   # let server finish startup
            return
        while not stop.is_set():
            try:
                res = maybe_send_digest(factory)
                if res.get("status") == "sent":
                    log.info("daily digest sent: %s", res)
            except Exception:
                log.exception("digest send failed; will retry next cycle")
            if stop.wait(60):
                return

    t = threading.Thread(target=_loop, name="digest", daemon=True)
    t.start()
    _state["thread"] = t


def stop_digest_scheduler() -> None:
    ev: threading.Event = _state["stop"]  # type: ignore
    ev.set()
    t = _state.get("thread")
    if t:
        try:
            t.join(timeout=5)  # type: ignore
        except Exception:
            pass
    _state["thread"] = None