"""Title-based WIP auto-tagging (task #1458).

Deterministic heuristic: when a post's TITLE explicitly declares work-in-progress
(the artist's own "WIP" / "work in progress" label), the ``wip`` system tag is
applied to that post's images — a cheap, high-precision complement to the
image-based ML ``wip`` head. WIP images are excluded from the Explore/gallery
browse (see gallery_service ``excluded_system_tags``), so honouring the artist's
own label keeps unfinished pieces out of the main browse right at import.

Precision over recall — a false WIP tag HIDES a finished post — so matching is
token-anchored: ``swipe`` / ``wiped`` / ``wiping`` never trip it (a letter on the
boundary blocks the match).

Sync-only: both consumers (the importer and the backfill Celery task) run on a
sync Session. Application is idempotent-additive (ON CONFLICT DO NOTHING) and
stamps a distinct ``image_tag.source`` so a later pass can tell where a wip tag
came from — the "manual" / "head_auto" / "ccip_auto" / "ml_accepted" provenance
family gains one member.
"""
import re

from sqlalchemy import select
from sqlalchemy.dialects.postgresql import insert as pg_insert
from sqlalchemy.orm import Session

from ..models.tag import WIP_SYSTEM_TAG, Tag, image_tag

# image_tag.source stamped on title-heuristic WIP tags — distinct from the other
# apply sources so provenance stays legible and a future undo can target only these.
WIP_TITLE_SOURCE = "wip_title"

# A standalone "WIP" / "W.I.P" token, or the phrase "work in progress"
# (space/underscore/hyphen separated). The letter-boundary lookarounds are what
# make this precision-first: `s|wip|e`, `|wip|ed`, `|wip|ing` all have a letter
# abutting the token, so they're rejected. A trailing digit is allowed so
# "WIP2" (= WIP part 2) still matches.
_WIP_RE = re.compile(
    r"(?<![A-Za-z])(?:w\.?i\.?p\.?|work[\s_-]+in[\s_-]+progress)(?![A-Za-z])",
    re.IGNORECASE,
)

# Coarse SQL prefilter for the backfill sweep — narrows the post scan to rows that
# COULD match before the precise regex confirms. Case-insensitive ILIKE patterns.
# MUST stay a SUPERSET of _WIP_RE (every regex match contains "wip" or
# "work…progress") or the sweep would silently miss posts.
WIP_TITLE_SQL_PREFILTER = ("%wip%", "%work%progress%")

# Chunk bulk inserts so a large sweep can't blow past psycopg's 65535-parameter
# ceiling (3 params/row → ~21k rows max; 5k stays comfortably under).
_INSERT_CHUNK = 5000


def matches_wip_title(title: str | None) -> bool:
    """True when a post title explicitly marks it work-in-progress."""
    if not title:
        return False
    return _WIP_RE.search(title) is not None


def resolve_wip_tag_id(session: Session) -> int | None:
    """The seeded ``wip`` system tag's id (migration 0075), or None if absent."""
    return session.execute(
        select(Tag.id).where(Tag.name == WIP_SYSTEM_TAG, Tag.is_system.is_(True))
    ).scalar_one_or_none()


def apply_wip_image_tags(session: Session, image_ids, tag_id: int) -> int:
    """Attach ``tag_id`` (source='wip_title') to each image id, idempotently
    (ON CONFLICT DO NOTHING — never disturbs an existing tag or its source).
    Returns the number of image_tag rows newly inserted. Does NOT commit."""
    ids = list({int(i) for i in image_ids})
    if not ids:
        return 0
    inserted = 0
    for start in range(0, len(ids), _INSERT_CHUNK):
        chunk = ids[start:start + _INSERT_CHUNK]
        result = session.execute(
            pg_insert(image_tag)
            .values([
                {"image_record_id": iid, "tag_id": tag_id, "source": WIP_TITLE_SOURCE}
                for iid in chunk
            ])
            .on_conflict_do_nothing(index_elements=["image_record_id", "tag_id"])
        )
        inserted += result.rowcount or 0
    return inserted