import uuid

from fastapi import APIRouter, Query
from sqlalchemy import Integer, case, cast, func, select
from sqlalchemy.orm import selectinload

from app.db import SessionDep
from app.models import Prediction, Variant
from app.schemas import VariantOut, VariantPage

router = APIRouter()

# Karyotype order (1..22, X, Y, MT) instead of text order, where "10" sorts before "2".
_chrom = func.regexp_replace(Variant.chrom, "^chr", "", "i")
CHROM_ORDER = case(
    (_chrom.regexp_match("^[0-9]+$"), cast(_chrom, Integer)),
    (_chrom == "X", 23),
    (_chrom == "Y", 24),
    (_chrom.in_(["M", "MT"]), 25),
    else_=26,
)


@router.get("", response_model=VariantPage)
async def list_variants(
    job_id: uuid.UUID,
    session: SessionDep,
    gene: str | None = None,
    impact: str | None = Query(None, pattern="^(HIGH|MODERATE|LOW|MODIFIER)$"),
    max_af: float | None = Query(None, ge=0, le=1),
    min_score: float | None = Query(None, ge=0, le=1),
    limit: int = Query(50, ge=1, le=500),
    offset: int = Query(0, ge=0),
) -> VariantPage:
    stmt = select(Variant).where(Variant.job_id == job_id)
    if gene:
        stmt = stmt.where(Variant.gene == gene.upper())
    if impact:
        stmt = stmt.where(Variant.impact == impact)
    if max_af is not None:
        stmt = stmt.where((Variant.gnomad_af.is_(None)) | (Variant.gnomad_af <= max_af))
    if min_score is not None:
        stmt = stmt.join(Prediction, Prediction.variant_id == Variant.id).where(
            Prediction.score >= min_score
        )

    total = await session.scalar(select(func.count()).select_from(stmt.subquery()))
    rows = await session.scalars(
        stmt.options(selectinload(Variant.prediction))
        # id breaks ties between split multiallelics at one position, keeping pages stable.
        .order_by(CHROM_ORDER, Variant.chrom, Variant.pos, Variant.id)
        .limit(limit)
        .offset(offset)
    )
    return VariantPage(
        items=[VariantOut.model_validate(v) for v in rows],
        total=total or 0,
        limit=limit,
        offset=offset,
    )