"""Helpers for reading/writing FCC filing state on telecom_entities.

The remediation handlers (RMD, CPNI, 499-A, BDC) all need to:
  1. Check whether the filing is already on record for the current cycle
     (idempotency — don't double-submit if the customer ordered twice).
  2. On success, persist the submission timestamp + confirmation number
     so the next compliance checkup flips the deficiency to green.

Columns added by migration 047:
  * rmd_last_cert_date / rmd_confirmation_number
  * cpni_last_cert_date / cpni_confirmation_number
  * form_499a_confirmation_number  (uses existing last_filing_year)
  * bdc_last_filing_date / bdc_confirmation_number
  * stir_shaken_cert_issued_at
"""

from __future__ import annotations

import logging
import os
from datetime import datetime, timedelta
from typing import Optional

logger = logging.getLogger(__name__)


def _connect():
    """Open a psycopg2 connection using DATABASE_URL. Returns None on failure."""
    try:
        import psycopg2

        return psycopg2.connect(os.environ.get("DATABASE_URL", ""))
    except Exception as exc:
        logger.error("filing_state: could not connect to PG: %s", exc)
        return None


def _get_entity_field(entity_id: int, field: str) -> Optional[object]:
    conn = _connect()
    if conn is None:
        return None
    try:
        with conn.cursor() as cur:
            # Column names come from the handlers, not user input — safe to
            # interpolate. psycopg2 does not parameterize identifiers.
            cur.execute(
                f"SELECT {field} FROM telecom_entities WHERE id = %s",  # noqa: S608
                (entity_id,),
            )
            row = cur.fetchone()
            return row[0] if row else None
    except Exception as exc:
        logger.warning("filing_state: read %s.%s failed: %s", entity_id, field, exc)
        return None
    finally:
        conn.close()


def _update_entity(entity_id: int, updates: dict[str, object]) -> bool:
    """UPDATE telecom_entities SET <updates> WHERE id = $id. Returns success."""
    if not updates:
        return True
    conn = _connect()
    if conn is None:
        return False
    try:
        set_clause = ", ".join(f"{k} = %s" for k in updates.keys())
        values = list(updates.values()) + [entity_id]
        with conn.cursor() as cur:
            cur.execute(
                f"UPDATE telecom_entities SET {set_clause} WHERE id = %s",  # noqa: S608
                values,
            )
        conn.commit()
        return True
    except Exception as exc:
        logger.warning("filing_state: update %s failed: %s", entity_id, exc)
        return False
    finally:
        conn.close()


# ── Idempotency windows ─────────────────────────────────────────────────────
#
# RMD recertification is annual; USAC 499-A is annual (due April 1); CPNI is
# annual (due March 1); BDC is twice-yearly (Dec 1 / Jun 1). "Already filed
# this cycle" roughly means the last filing was within the window below.

RMD_CYCLE_DAYS = 365
CPNI_CYCLE_DAYS = 365
FORM_499A_CYCLE_DAYS = 365
BDC_CYCLE_DAYS = 180


def already_filed(
    entity_id: int, filing_type: str, filing_year: Optional[int] = None,
) -> bool:
    """Return True if the filing is on record within its cycle window.

    ``filing_type`` is one of: "rmd", "cpni", "499a", "bdc".

    ``filing_year`` applies only to 499a — callers filing past-due should
    pass the target reporting year so we don't skip an older year just
    because a newer one was already filed. If not provided, defaults to
    the current year (preserving legacy behavior).
    """
    column, cycle_days = {
        "rmd": ("rmd_last_cert_date", RMD_CYCLE_DAYS),
        "cpni": ("cpni_last_cert_date", CPNI_CYCLE_DAYS),
        "499a": ("last_filing_year", None),  # year-based, handled separately
        "bdc": ("bdc_last_filing_date", BDC_CYCLE_DAYS),
    }.get(filing_type, (None, None))
    if column is None:
        return False

    value = _get_entity_field(entity_id, column)
    if value is None:
        return False

    if filing_type == "499a":
        try:
            last_year = int(value)
            check_year = filing_year if filing_year is not None else datetime.utcnow().year
            # "Already filed" means the entity's last_filing_year equals or
            # exceeds the year we're about to file. For past-due filings
            # targeting an older year, use that year explicitly.
            return last_year >= int(check_year)
        except (TypeError, ValueError):
            return False

    if isinstance(value, str):
        try:
            value = datetime.fromisoformat(value)
        except ValueError:
            return False
    if not isinstance(value, datetime):
        return False

    # psycopg2 returns tz-aware datetimes when the column is TIMESTAMPTZ; strip
    # tz for the arithmetic below.
    if value.tzinfo is not None:
        value = value.replace(tzinfo=None)
    return value >= datetime.utcnow() - timedelta(days=cycle_days or 0)


# ── Success writers ─────────────────────────────────────────────────────────

def record_rmd_filing(entity_id: int, confirmation_number: str = "") -> bool:
    return _update_entity(entity_id, {
        "rmd_last_cert_date": datetime.utcnow(),
        "rmd_confirmation_number": confirmation_number,
    })


def record_cpni_filing(entity_id: int, confirmation_number: str = "") -> bool:
    return _update_entity(entity_id, {
        "cpni_last_cert_date": datetime.utcnow(),
        "cpni_confirmation_number": confirmation_number,
    })


def record_form_499a_filing(entity_id: int, confirmation_number: str = "") -> bool:
    return _update_entity(entity_id, {
        "last_filing_year": datetime.utcnow().year,
        "form_499a_confirmation_number": confirmation_number,
    })


def record_bdc_filing(entity_id: int, confirmation_number: str = "") -> bool:
    return _update_entity(entity_id, {
        "bdc_last_filing_date": datetime.utcnow(),
        "bdc_confirmation_number": confirmation_number,
    })


def record_stir_shaken_cert(entity_id: int, issued_at: Optional[datetime] = None) -> bool:
    return _update_entity(entity_id, {
        "stir_shaken_cert_issued_at": issued_at or datetime.utcnow(),
    })