"""Helpery do znajdowania kandydatów scen w bazie (paths 1-4 resolvera)."""
from __future__ import annotations

import uuid
from datetime import date, timedelta

from sqlalchemy import and_, or_, select, text
from sqlalchemy.orm import Session

from app.config import get_settings
from app.models.scene import Scene, SceneExternalRef, SceneFingerprint
from app.models.source import Source
from app.resolve.scoring import hamming_distance_hex


def find_by_external_ref(
    session: Session, *, source_id: uuid.UUID, external_id: str
) -> Scene | None:
    """Path 1: ten sam (source, external_id) widziany już wcześniej."""
    ref = session.execute(
        select(SceneExternalRef).where(
            SceneExternalRef.source_id == source_id,
            SceneExternalRef.external_id == external_id,
        )
    ).scalar_one_or_none()
    if ref is None:
        return None
    return session.get(Scene, ref.scene_id)


def find_by_cross_source_refs(
    session: Session, *, refs: dict[str, str]
) -> tuple[Scene, str] | None:
    """Path 2: cross-source UUID. `refs` = {source_name: external_id}.

    Zwraca (Scene, source_name_via_which_matched). Pierwszy match wygrywa.
    """
    if not refs:
        return None
    sources = (
        session.execute(select(Source).where(Source.name.in_(list(refs))))
        .scalars()
        .all()
    )
    by_name = {s.name: s for s in sources}
    for source_name, external_id in refs.items():
        src = by_name.get(source_name)
        if src is None:
            continue
        ref = session.execute(
            select(SceneExternalRef).where(
                SceneExternalRef.source_id == src.id,
                SceneExternalRef.external_id == external_id,
            )
        ).scalar_one_or_none()
        if ref is not None:
            scene = session.get(Scene, ref.scene_id)
            if scene is not None:
                return scene, source_name
    return None


def find_by_fingerprint_exact(
    session: Session, *, kind: str, value: str
) -> Scene | None:
    """Path 3a: oshash / md5 — exact match."""
    row = session.execute(
        select(SceneFingerprint.scene_id)
        .where(SceneFingerprint.kind == kind, SceneFingerprint.value == value)
        .limit(1)
    ).scalar_one_or_none()
    if row is None:
        return None
    return session.get(Scene, row)


def find_by_phash_within(
    session: Session,
    *,
    phash: str,
    max_hamming: int | None = None,
) -> tuple[Scene, int] | None:
    """Path 3b: pHash w obrębie max_hamming (Hamming distance bitów hex).

    Hamming liczony server-side: `bit_count(a # b)` na 64-bitowych bit-stringach
    (`('x'||hex)::bit(64)`), ORDER BY dist LIMIT 1 → najbliższy match. Postgres robi
    popcount w C nad całym zbiorem phashy (~10⁵-10⁶) w kilkadziesiąt ms zamiast
    Python-loop ~6s/scenę (był bottleneck zabijający długie ingest-runy: każda scena
    z phashem skanowała wszystkie 277k fingerprintów po stronie aplikacji).

    Wymaga 64-bit (16 hex) phasha — `imagehash.phash(hash_size=8)` zawsze taki jest.
    Dla nietypowej długości fallback do Python-loop (rzadkie, np. legacy/uszkodzone).
    Zwraca (Scene, distance) dla najbliższego matcha ≤ max_hamming, albo None.
    """
    if max_hamming is None:
        max_hamming = get_settings().fingerprint_hamming_max

    if len(phash) == 16:
        row = session.execute(
            text(
                "SELECT scene_id, "
                "bit_count(('x'||value)::bit(64) # ('x'||:phash)::bit(64)) AS dist "
                "FROM scene_fingerprints "
                "WHERE kind = 'phash' AND length(value) = 16 "
                "ORDER BY dist ASC LIMIT 1"
            ),
            {"phash": phash},
        ).first()
        if row is None or row.dist > max_hamming:
            return None
        scene = session.get(Scene, row.scene_id)
        if scene is None:
            return None
        return scene, int(row.dist)

    # Fallback dla phashy o nietypowej długości — Python-loop nad zgodnymi długościami.
    rows = session.execute(
        select(SceneFingerprint.scene_id, SceneFingerprint.value).where(
            SceneFingerprint.kind == "phash"
        )
    ).all()
    best: tuple[uuid.UUID, int] | None = None
    target_len = len(phash)
    for scene_id, value in rows:
        if len(value) != target_len:
            continue
        try:
            d = hamming_distance_hex(phash, value)
        except ValueError:
            continue
        if d <= max_hamming and (best is None or d < best[1]):
            best = (scene_id, d)
            if d == 0:
                break
    if best is None:
        return None
    scene = session.get(Scene, best[0])
    if scene is None:
        return None
    return scene, best[1]


def find_blocking_candidates(
    session: Session,
    *,
    studio_id: uuid.UUID | None,
    release_date: date | None,
    window_days: int | None = None,
    title_normalized: str | None = None,
    limit: int = 50,
) -> list[Scene]:
    """Path 4 blocking: zawęża space scen do potencjalnych kandydatów.

    Reguły:
      - jeśli mamy studio + date → studio_id == X AND date BETWEEN ±window_days
      - jeśli mamy tylko date → date BETWEEN ±window_days
      - jeśli mamy tylko studio → studio_id == X
      - dodatkowo, jeśli `title_normalized` podany, OR-uj exact title match
        (przydaje się gdy date/studio brakuje)
    """
    if window_days is None:
        window_days = get_settings().date_window_days

    conds = []
    if studio_id is not None and release_date is not None:
        conds.append(
            and_(
                Scene.studio_id == studio_id,
                Scene.release_date.is_not(None),
                Scene.release_date >= release_date - timedelta(days=window_days),
                Scene.release_date <= release_date + timedelta(days=window_days),
            )
        )
    elif release_date is not None:
        conds.append(
            and_(
                Scene.release_date >= release_date - timedelta(days=window_days),
                Scene.release_date <= release_date + timedelta(days=window_days),
            )
        )
    elif studio_id is not None:
        conds.append(Scene.studio_id == studio_id)

    if title_normalized:
        conds.append(Scene.title_normalized == title_normalized)

    if not conds:
        return []

    stmt = select(Scene).where(or_(*conds)).limit(limit)
    return list(session.execute(stmt).scalars().all())