"""Turn each question's image paths into labelled figure records.

Every figure is already a row in the image bank; what was missing was the link
that says *this question, this role, this label*. Without it a question could
hold one stem image and one explanation image, neither of which the prose could
refer to by name.

Titles are improved at the same time. A figure called
`page_339_img_0.png` tells you where it came from and nothing about what it
shows, so the provenance moves into the caption and the tags — where it is still
searchable — and the title becomes something a person can read.

    docker compose exec backend python -m scripts.backfill_question_figures
    docker compose exec backend python -m scripts.backfill_question_figures --apply
"""
import re
import sys

from sqlalchemy import text as sa_text

from app.database import SessionLocal
from app.models.media import MediaAsset
from app.models.question_media import QuestionMedia

ROLES = (("image_path", "stem"), ("explanation_image_path", "explanation"))


def readable_title(asset: MediaAsset, question_id: int, role: str, category: str | None) -> str:
    """A name a person can use, with the filename kept as provenance."""
    where = "Stem figure" if role == "stem" else "Explanation figure"
    subject = category or f"question #{question_id}"
    return f"{where} — {subject}"[:300]


def main():
    apply_changes = "--apply" in sys.argv
    db = SessionLocal()
    try:
        rows = db.execute(sa_text("""
            SELECT q.id, q.image_path, q.explanation_image_path, c.name
            FROM questions q
            LEFT JOIN question_categories c ON c.id = q.question_category_id
            WHERE (q.image_path IS NOT NULL AND q.image_path <> '')
               OR (q.explanation_image_path IS NOT NULL AND q.explanation_image_path <> '')
        """)).fetchall()
        assets = {a.path: a for a in db.query(MediaAsset).all()}
        existing = {(link.question_id, link.media_id, link.role)
                    for link in db.query(QuestionMedia).all()}

        planned, missing = [], []
        for question_id, stem_path, expl_path, category in rows:
            for column, role in ROLES:
                path = stem_path if column == "image_path" else expl_path
                if not path:
                    continue
                asset = assets.get(path)
                if asset is None:
                    missing.append((question_id, path))
                    continue
                if (question_id, asset.id, role) in existing:
                    continue
                planned.append((question_id, asset, role, category))

        print(f"  questions with a figure : {len(rows)}")
        print(f"  figure links to create  : {len(planned)}")
        if missing:
            print(f"  paths with no image record: {len(missing)} (left alone)")
        if not apply_changes:
            for question_id, asset, role, category in planned[:6]:
                print(f"    q#{question_id:<6} {role:<12} {asset.path}")
                print(f"              title -> {readable_title(asset, question_id, role, category)}")
            print("\n  Re-run with --apply.")
            return 0

        made = retitled = 0
        for question_id, asset, role, category in planned:
            position = db.query(QuestionMedia).filter_by(
                question_id=question_id, role=role).count()
            db.add(QuestionMedia(question_id=question_id, media_id=asset.id, role=role,
                                 label=f"Figure {position + 1}", position=position))
            made += 1
            # Keep the filename as provenance in the caption; it is the only
            # record of which page of which PDF this came from.
            if asset.title and re.match(r"^page_\d+_img", asset.title):
                asset.caption = (asset.caption or "") + f" (from {asset.path})"
                asset.title = readable_title(asset, question_id, role, category)
                retitled += 1
            if made % 200 == 0:
                db.commit()
        db.commit()
        print(f"\n  figure links created : {made}")
        print(f"  images retitled      : {retitled}")
    finally:
        db.close()
    return 0


if __name__ == "__main__":
    sys.exit(main())