rss-news/backend/app/scheduler.py

"""Smart publishing scheduler.

Calculates suggested publish slots for new WordPress drafts.
Rules:
- Maximum N drafts per day (configurable, default 2)
- Preferred slots: configurable hours (default 09:00 and 14:00 CET)
- New articles queue up after the last already-scheduled article
- Checks both local DB AND WordPress future posts to avoid double-booking
"""
from __future__ import annotations

import base64
import json
import urllib.request
from datetime import date, datetime, timedelta, timezone
from typing import Any

from .config import get_settings
from .db import get_conn


# CET offset (UTC+1 winter / UTC+2 summer – fixed +1 for simplicity)
_CET_OFFSET = timedelta(hours=1)


def _today_cet() -> date:
    return (datetime.now(timezone.utc) + _CET_OFFSET).date()


def _preferred_hours() -> list[int]:
    settings = get_settings()
    try:
        return [int(h.strip()) for h in settings.pipeline_publish_hours.split(",") if h.strip()]
    except Exception:
        return [9, 14]


def _fetch_wp_occupied_slots() -> set[tuple[str, int]]:
    """Fetch all future-scheduled WordPress posts and return occupied (date_iso, hour) pairs.

    This prevents the scheduler from assigning a slot that is already taken
    by a WP post that was not created via this pipeline (e.g. manually or via recovery scripts).
    Returns an empty set on any error so the scheduler degrades gracefully.
    """
    settings = get_settings()
    try:
        auth = base64.b64encode(
            f"{settings.wordpress_username}:{settings.wordpress_app_password}".encode()
        ).decode()
        url = (
            f"{settings.wordpress_base_url}/wp-json/wp/v2/posts"
            f"?status=future&per_page=100&orderby=date&order=asc&_fields=id,date"
        )
        req = urllib.request.Request(url, headers={"Authorization": f"Basic {auth}"})
        with urllib.request.urlopen(req, timeout=10) as resp:
            posts = json.loads(resp.read())
        occupied: set[tuple[str, int]] = set()
        for p in posts:
            try:
                dt = datetime.fromisoformat(p["date"])
                occupied.add((dt.date().isoformat(), dt.hour))
            except Exception:
                pass
        return occupied
    except Exception:
        return set()


def _get_last_future_scheduled_date(wp_occupied: set[tuple[str, int]]) -> date | None:
    """Return the date of the latest already-scheduled slot (DB + WP)."""
    today = _today_cet()

    # Latest from local DB
    with get_conn() as conn:
        row = conn.execute(
            """
            SELECT MAX(scheduled_publish_at) AS last_slot
            FROM articles
            WHERE scheduled_publish_at IS NOT NULL
            AND scheduled_publish_at >= ?
            AND status NOT IN ('error', 'no_image')
            """,
            (today.isoformat() + "T00:00:00",),
        ).fetchone()
    db_last: date | None = None
    if row and row["last_slot"]:
        try:
            db_last = datetime.fromisoformat(row["last_slot"]).date()
        except Exception:
            pass

    # Latest from WP
    wp_last: date | None = None
    for d_str, _ in wp_occupied:
        try:
            d = date.fromisoformat(d_str)
            if d >= today and (wp_last is None or d > wp_last):
                wp_last = d
        except Exception:
            pass

    if db_last and wp_last:
        return max(db_last, wp_last)
    return db_last or wp_last


def _next_free_hour(target_date: date, wp_occupied: set[tuple[str, int]]) -> int | None:
    """Return first preferred hour not yet used on target_date (DB + WP), or None if day is full."""
    hours = _preferred_hours()
    date_str = target_date.isoformat()

    # Hours used in local DB
    with get_conn() as conn:
        rows = conn.execute(
            """
            SELECT scheduled_publish_at FROM articles
            WHERE scheduled_publish_at >= ? AND scheduled_publish_at < ?
            AND status NOT IN ('error', 'no_image')
            """,
            (date_str + "T00:00:00", date_str + "T23:59:59"),
        ).fetchall()

    used_hours: set[int] = set()
    for row in rows:
        ts = row["scheduled_publish_at"] or ""
        try:
            used_hours.add(datetime.fromisoformat(ts).hour)
        except Exception:
            pass

    # Hours used in WordPress
    for d_str, h in wp_occupied:
        if d_str == date_str:
            used_hours.add(h)

    for h in hours:
        if h not in used_hours:
            return h
    return None


def _format_slot(d: date, hour: int) -> str:
    weekday_names = ["Mo", "Di", "Mi", "Do", "Fr", "Sa", "So"]
    wd = weekday_names[d.weekday()]
    return f"{wd}, {d.strftime('%d.%m.%Y')} um {hour:02d}:00 Uhr"


def _find_next_free_slot(
    wp_occupied: set[tuple[str, int]], lookahead_days: int = 60
) -> tuple[date, int] | None:
    """Find the next free (date, hour) slot.

    Starts from tomorrow and scans forward, filling any gaps in the schedule
    rather than always appending after the last existing post.
    """
    today = _today_cet()
    tomorrow = today + timedelta(days=1)

    for offset in range(0, lookahead_days + 1):
        candidate = tomorrow + timedelta(days=offset)
        hour = _next_free_hour(candidate, wp_occupied)
        if hour is not None:
            return candidate, hour

    return tomorrow, _preferred_hours()[0] if _preferred_hours() else 9


def release_publish_slot(article_id: int) -> None:
    """Clear a previously reserved slot (e.g. when article is rejected after slot assignment)."""
    with get_conn() as conn:
        conn.execute(
            "UPDATE articles SET scheduled_publish_at = NULL WHERE id = ?",
            (article_id,),
        )


def suggest_publish_slot() -> str:
    """Return a suggested publish datetime string (CET) for the next free slot."""
    wp_occupied = _fetch_wp_occupied_slots()
    result = _find_next_free_slot(wp_occupied)
    if result:
        d, hour = result
        return _format_slot(d, hour)
    tomorrow = _today_cet() + timedelta(days=1)
    return _format_slot(tomorrow, _preferred_hours()[0] if _preferred_hours() else 9)


def reserve_publish_slot(article_id: int) -> str:
    """Reserve a publish slot for an article and persist it in the DB.

    If the article already has a scheduled_publish_at, keep it unchanged.
    Returns the formatted publish datetime string.
    """
    # Check if already has a slot
    with get_conn() as conn:
        row = conn.execute(
            "SELECT scheduled_publish_at FROM articles WHERE id = ?",
            (article_id,),
        ).fetchone()
    existing_slot = row["scheduled_publish_at"] if row else None
    if existing_slot:
        try:
            dt = datetime.fromisoformat(existing_slot)
            return _format_slot(dt.date(), dt.hour)
        except Exception:
            pass  # invalid slot, re-assign below

    wp_occupied = _fetch_wp_occupied_slots()
    result = _find_next_free_slot(wp_occupied, lookahead_days=30)
    if result:
        candidate, hour = result
    else:
        candidate = _today_cet() + timedelta(days=1)
        hours = _preferred_hours()
        hour = hours[0] if hours else 9

    iso_ts = f"{candidate.isoformat()}T{hour:02d}:00:00"
    with get_conn() as conn:
        conn.execute(
            "UPDATE articles SET scheduled_publish_at = ? WHERE id = ?",
            (iso_ts, article_id),
        )
    return _format_slot(candidate, hour)