"""Which drawings the drawing job looks up this run, in order.

Over live packets made from VISUAL that are not filed, have a drawing number, and sit in a department in scope
(feed setting `departments`; empty = every department). One item per drawing number (trimmed), the best priority
winning:

1. the VISUAL rev changed since the last lookup (`drawing_lookups.visual_rev_seen`), or a pending feed change
   order waits for a drawing (the item is the CO's target drawing and rev; at most every 15 minutes);
2. drafts still needing a drawing (`drawing_state = 'needed'`, or never looked up), unless a failed fetch set a
   later `next_check_at`;
3. failed lookups whose backoff ran out (`ok = false and next_check_at <= now`);
4. rechecks due (`checked_at` older than `drawing_recheck_hours`).

A packet with a hand drawing joins only through (1) or (4) once the feed has taken the hand drawing off; while
`drawing_state = 'hand'` it is skipped.
"""

from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime, timedelta
from typing import Any

BACKOFF_FIRST = timedelta(minutes=15)
BACKOFF_MAX = timedelta(hours=24)
CO_RECHECK = timedelta(minutes=15)  # a change order's target drawing is looked up at most this often

QUEUE_SQL = """
WITH own AS (
    SELECT p.id AS packet_id, btrim(p.drawing) AS dwg, coalesce(btrim(p.rev), '') AS visual_rev, NULL::bigint AS co_id,
        CASE
            WHEN d.dwg IS NOT NULL AND d.checked_at IS NOT NULL
                 AND d.visual_rev_seen IS DISTINCT FROM coalesce(btrim(p.rev), '') THEN 1
            WHEN p.status = 'draft' AND (d.dwg IS NULL OR p.drawing_state = 'needed')
                 AND (d.next_check_at IS NULL OR d.next_check_at <= %(now)s) THEN 2
            WHEN d.ok = false AND (d.next_check_at IS NULL OR d.next_check_at <= %(now)s) THEN 3
            WHEN d.checked_at IS NULL OR d.checked_at < %(recheck_before)s THEN 4
        END AS priority,
        d.checked_at
    FROM packets p
    LEFT JOIN drawing_lookups d ON d.dwg = btrim(p.drawing)
    WHERE p.removed_at IS NULL AND p.source_kind = 'visual' AND p.status <> 'filed'
      AND coalesce(btrim(p.drawing), '') <> '' AND p.drawing_state <> 'hand'
      AND (cardinality(%(depts)s::text[]) = 0 OR p.dept_code = ANY(%(depts)s::text[]))
),
co AS (
    SELECT p.id AS packet_id, btrim(c.waiting->>'dwg') AS dwg, coalesce(btrim(c.waiting->>'rev'), '') AS visual_rev,
        c.id AS co_id, 1 AS priority, d.checked_at
    FROM change_orders c
    JOIN packets p ON p.id = c.packet_id
    LEFT JOIN drawing_lookups d ON d.dwg = btrim(c.waiting->>'dwg')
    WHERE c.review = 'pending' AND c.origin IN ('visual', 'drawing') AND c.waiting IS NOT NULL
      AND jsonb_typeof(c.waiting) = 'object' AND coalesce(btrim(c.waiting->>'dwg'), '') <> ''
      AND p.removed_at IS NULL AND p.status NOT IN ('draft', 'filed')
      AND (d.checked_at IS NULL OR d.checked_at < %(co_before)s)
      AND (d.ok IS NOT false OR d.next_check_at IS NULL OR d.next_check_at <= %(now)s)
      AND (cardinality(%(depts)s::text[]) = 0 OR p.dept_code = ANY(%(depts)s::text[]))
),
items AS (
    SELECT * FROM own WHERE priority IS NOT NULL
    UNION ALL
    SELECT * FROM co
),
best AS (
    SELECT DISTINCT ON (dwg) packet_id, dwg, visual_rev, priority, co_id, checked_at
    FROM items
    ORDER BY dwg, priority, co_id NULLS LAST, packet_id
)
SELECT packet_id, dwg, visual_rev, priority, co_id
FROM best
ORDER BY priority, checked_at NULLS FIRST, dwg
"""


@dataclass(frozen=True, slots=True)
class QueueItem:
    packet_id: int
    dwg: str
    visual_rev: str
    priority: int
    co_id: int | None


def backoff(fail_count: int) -> timedelta:
    """15 minutes x 2^(fail_count - 1), at most 24 hours. fail_count counts this failure (1 = first)."""
    n = max(0, int(fail_count) - 1)
    if n >= 10:
        return BACKOFF_MAX
    return min(BACKOFF_FIRST * (2**n), BACKOFF_MAX)


def params(feed_settings: Any, now: datetime) -> dict[str, Any]:
    hours = int(getattr(feed_settings, "drawing_recheck_hours", 4))
    depts = [str(d) for d in (getattr(feed_settings, "departments", None) or [])]
    return {
        "now": now,
        "recheck_before": now - timedelta(hours=hours),
        "co_before": now - CO_RECHECK,
        "depts": depts,
    }


def queue(conn: Any, feed_settings: Any, now: datetime, *, limit: int | None = None) -> list[QueueItem]:
    """The ordered lookup list. `limit` cuts it (the job passes the budget)."""
    sql = QUEUE_SQL
    p = params(feed_settings, now)
    if limit is not None:
        sql += " LIMIT %(limit)s"
        p["limit"] = max(0, int(limit))
    rows = conn.execute(sql, p).fetchall()
    return [
        QueueItem(int(r[0]), str(r[1]), str(r[2] or ""), int(r[3]), None if r[4] is None else int(r[4])) for r in rows
    ]