"""CCIP few-shot character matcher (#114) — server-side, numpy on stored vectors.

CCIP is a FROZEN identity embedding; we don't train it. Instead the operator's
tagged characters become reference prototypes: a character tag's references are
the CCIP vectors of figure/face regions on images carrying that tag. To suggest
characters for a new image, we compare its figure-region CCIP vectors to every
character's references (multi-prototype: best match over a character's examples)
and surface the ones that clear a similarity threshold. No GPU here — the agent
already produced the vectors; this is cosine matching on what's stored.

v1 uses cosine similarity on the raw CCIP vectors with a tunable threshold; the
exact CCIP difference metric/threshold gets validated against the model during
the hands-on eval. numpy is imported lazily (API worker has it via pgvector).
"""

from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from ...models import (
    CcipPrototypeState,
    CharacterPrototype,
    ImageRegion,
    MLSettings,
    Tag,
    TagKind,
)
from ...models.tag import image_tag

# Cosine-similarity floor to call a figure the same character. The live setting
# (ml_settings.ccip_match_threshold) drives it; this is only the fallback when no
# threshold is supplied AND no settings row exists.
DEFAULT_SIM_THRESHOLD = 0.85
_FIGURE_KINDS = ("face", "figure")


async def _settings_threshold(session: AsyncSession) -> float:
    val = (
        await session.execute(
            select(MLSettings.ccip_match_threshold).where(MLSettings.id == 1)
        )
    ).scalar_one_or_none()
    return float(val) if val is not None else DEFAULT_SIM_THRESHOLD


def _l2norm(mat, np):
    n = np.linalg.norm(mat, axis=1, keepdims=True)
    n[n == 0] = 1.0
    return mat / n


# Single-shot cache of the (expensive) reference load, keyed on a cheap
# signature that changes exactly when references could: a character tag added/
# removed (n_char_tags) or a figure embedded (max/ n of ccip regions). Shared by
# the live matcher (every modal open) and the auto-apply sweep.
_REF_CACHE: dict = {"sig": None, "refs": None}


def _single_character_images():
    """Subquery of image ids carrying EXACTLY ONE character tag. References come
    only from these — on a multi-character image the tag is image-level, so every
    figure would otherwise pollute each character's prototype set (a 2-character
    image tagged 'Velma' would make Daphne's figure a Velma reference)."""
    return (
        select(image_tag.c.image_record_id)
        .join(Tag, Tag.id == image_tag.c.tag_id)
        .where(Tag.kind == TagKind.character)
        .group_by(image_tag.c.image_record_id)
        .having(func.count() == 1)
    )


def _hygiene_tagged_images():
    """Subquery of image ids carrying any SYSTEM tag (wip / banner / editor
    screenshot). Training hygiene (#128): such images never contribute
    reference prototypes — a faceless wip's figure region would otherwise
    become an identity reference for the character it's tagged with."""
    return (
        select(image_tag.c.image_record_id)
        .join(Tag, Tag.id == image_tag.c.tag_id)
        .where(Tag.is_system.is_(True))
    )


async def _ref_signature(session: AsyncSession) -> tuple:
    n_tags = (
        await session.execute(
            select(func.count())
            .select_from(image_tag)
            .join(Tag, Tag.id == image_tag.c.tag_id)
            .where(Tag.kind == TagKind.character)
        )
    ).scalar_one()
    n_regs, max_id = (
        await session.execute(
            select(func.count(), func.max(ImageRegion.id)).where(
                ImageRegion.kind.in_(_FIGURE_KINDS),
                ImageRegion.ccip_embedding.is_not(None),
            )
        )
    ).one()
    # Hygiene applications must invalidate too: tagging an image `wip` changes
    # the reference set without touching character-tag or region counts.
    n_hygiene = (
        await session.execute(
            select(func.count())
            .select_from(image_tag)
            .join(Tag, Tag.id == image_tag.c.tag_id)
            .where(Tag.is_system.is_(True))
        )
    ).scalar_one()
    return (n_tags, n_regs, max_id, n_hygiene)


async def character_references(session: AsyncSession) -> dict[int, list]:
    """Per character-tag CCIP reference vectors: figure/face-region CCIP
    embeddings on UNAMBIGUOUS (single-character) images carrying that tag.
    Multi-prototype — several vectors per character. Cached on a cheap signature."""
    sig = await _ref_signature(session)
    if _REF_CACHE["sig"] == sig and _REF_CACHE["refs"] is not None:
        return _REF_CACHE["refs"]
    rows = (
        await session.execute(
            select(image_tag.c.tag_id, ImageRegion.ccip_embedding)
            .select_from(ImageRegion)
            .join(
                image_tag,
                image_tag.c.image_record_id == ImageRegion.image_record_id,
            )
            .join(Tag, Tag.id == image_tag.c.tag_id)
            .where(Tag.kind == TagKind.character)
            .where(ImageRegion.kind.in_(_FIGURE_KINDS))
            .where(ImageRegion.ccip_embedding.is_not(None))
            .where(ImageRegion.image_record_id.in_(_single_character_images()))
            .where(
                ImageRegion.image_record_id.not_in(_hygiene_tagged_images())
            )
        )
    ).all()
    refs: dict[int, list] = {}
    for tag_id, vec in rows:
        refs.setdefault(tag_id, []).append(vec)
    _REF_CACHE.update(sig=sig, refs=refs)
    return refs


async def _tag_names(session: AsyncSession, tag_ids: list[int]) -> dict[int, str]:
    if not tag_ids:
        return {}
    return dict(
        (
            await session.execute(
                select(Tag.id, Tag.name).where(Tag.id.in_(tag_ids))
            )
        ).all()
    )


# Per-character normalized prototype matrices, cached per process and refreshed
# INCREMENTALLY: only characters whose ccip_prototype_state.updated_at advanced
# are reloaded. This replaces the request-path rebuild of the ENTIRE reference
# blob (the ~4s stall, #1317) — the prototypes are precomputed off the request
# path by services.ml.character_prototypes (a beat + after each retrain).
_PROTO_CACHE: dict = {"mats": {}, "ver": {}}


async def _load_prototypes(session: AsyncSession) -> dict:
    """{tag_id: (P, D) L2-normalized prototype matrix} from character_prototype,
    served from the in-process cache and reloading ONLY the characters whose
    updated_at changed. Empty dict when the store isn't populated yet (cold start
    → match_image falls back to the legacy on-the-fly reference build)."""
    import numpy as np

    versions = dict(
        (
            await session.execute(
                select(CcipPrototypeState.tag_id, CcipPrototypeState.updated_at)
            )
        ).all()
    )
    mats = _PROTO_CACHE["mats"]
    ver = _PROTO_CACHE["ver"]
    # Forget characters that no longer have prototypes.
    for tag_id in [t for t in mats if t not in versions]:
        mats.pop(tag_id, None)
        ver.pop(tag_id, None)
    # Reload only the characters whose prototypes changed since we cached them.
    stale = [t for t, u in versions.items() if ver.get(t) != u]
    if stale:
        rows = (
            await session.execute(
                select(
                    CharacterPrototype.tag_id, CharacterPrototype.ccip_embedding
                ).where(CharacterPrototype.tag_id.in_(stale))
            )
        ).all()
        by_tag: dict[int, list] = {}
        for tag_id, vec in rows:
            by_tag.setdefault(tag_id, []).append(
                np.asarray(vec, dtype=np.float32)
            )
        for tag_id in stale:
            vecs = by_tag.get(tag_id)
            if vecs:
                mats[tag_id] = _l2norm(np.vstack(vecs), np)
                ver[tag_id] = versions[tag_id]
            else:
                mats.pop(tag_id, None)
                ver.pop(tag_id, None)
    return mats


async def match_image(
    session: AsyncSession, image_id: int, threshold: float | None = None
) -> list[dict]:
    """Character suggestions for one image from its figure-region CCIP vectors:
    [{tag_id, name, category:'character', score, source:'ccip'}], ranked.
    Already-applied character tags are excluded. Empty if the image has no figure
    CCIP vectors or no character references exist yet. threshold defaults to the
    live ml_settings.ccip_match_threshold."""
    import numpy as np

    if threshold is None:
        threshold = await _settings_threshold(session)

    # Keep each figure region's bbox alongside its vector so a match can point at
    # the figure that matched (#1206 grounding), not just the score.
    fig_rows = (
        await session.execute(
            select(
                ImageRegion.ccip_embedding,
                ImageRegion.rx, ImageRegion.ry, ImageRegion.rw, ImageRegion.rh,
                ImageRegion.kind, ImageRegion.detector_version,
            ).where(
                ImageRegion.image_record_id == image_id,
                ImageRegion.kind.in_(_FIGURE_KINDS),
                ImageRegion.ccip_embedding.is_not(None),
            )
        )
    ).all()
    if not fig_rows:
        return []
    # Prefer the precomputed prototype store (fast, incremental). On a cold start
    # (store not yet populated post-deploy) fall back to the legacy on-the-fly
    # reference build so character suggestions work immediately — the background
    # refresh populates the store within ~15 min, after which this path is used
    # and the per-accept ~4s rebuild is gone (#1317).
    protos = await _load_prototypes(session)
    refs = protos if protos else await character_references(session)
    if not refs:
        return []
    applied = set(
        (
            await session.execute(
                select(image_tag.c.tag_id).where(
                    image_tag.c.image_record_id == image_id
                )
            )
        ).scalars()
    )
    names = await _tag_names(session, [t for t in refs if t not in applied])

    qvecs = [r[0] for r in fig_rows]
    fig_meta = [
        {"bbox": [rx, ry, rw, rh], "kind": kind, "detector": detector}
        for _v, rx, ry, rw, rh, kind, detector in fig_rows
    ]
    Q = _l2norm(np.vstack([np.asarray(v, dtype=np.float32) for v in qvecs]), np)
    out = []
    for tag_id, vecs in refs.items():
        if tag_id in applied:
            continue
        # Prototype matrices are already L2-normalized; legacy refs are raw
        # vector lists that still need stacking + normalizing.
        R = vecs if protos else _l2norm(
            np.vstack([np.asarray(v, dtype=np.float32) for v in vecs]), np
        )
        sims = Q @ R.T                       # (n_query_figures, n_references)
        per_figure = sims.max(axis=1)        # best reference cosine per figure
        best_figure = int(per_figure.argmax())
        best = float(per_figure[best_figure])
        if best >= threshold:
            out.append({
                "tag_id": tag_id,
                "name": names.get(tag_id, str(tag_id)),
                "category": "character",
                "score": round(best, 4),
                "source": "ccip",
                # the figure region that matched → grounds the character tag.
                "grounding": fig_meta[best_figure],
            })
    out.sort(key=lambda d: d["score"], reverse=True)
    return out