"""테마/카테고리 API.

토스 '주식 골라보기' 의 테마 그리드와 비슷한 결.
정적 매핑(seed/themes.py)을 베이스로, DB 에서 최신 종가/등락만 채워 응답.

GET /api/themes
  - 모든 테마 인덱스 (slug/name/description/code_count)

GET /api/themes/{slug}
  ?limit=20
  - 해당 테마의 종목 카드 (종목명/시장/종가/등락률). 거래량 기준 정렬.
  - ohlcv_daily 가 아직 안 채워져 있으면 close/pct_change 가 NULL.
"""
from __future__ import annotations

from fastapi import APIRouter, HTTPException, Query
from sqlalchemy import text

from app.db.connection import get_engine
from app.seed.themes import THEMES, theme_by_slug, themes_index

router = APIRouter(prefix="/api/themes", tags=["themes"])


@router.get("")
def list_themes() -> dict:
    return {"items": themes_index(), "total": len(THEMES)}


@router.get("/{slug}")
def get_theme(slug: str, limit: int = Query(default=30, ge=1, le=100)) -> dict:
    th = theme_by_slug(slug)
    if th is None:
        raise HTTPException(status_code=404, detail=f"unknown theme: {slug}")

    codes = list(th.codes)[:limit]
    if not codes:
        return {
            "slug": th.slug,
            "name": th.name,
            "description": th.description,
            "items": [],
        }

    sql = text(
        """
        WITH last2 AS (
          SELECT DISTINCT date FROM ohlcv_daily ORDER BY date DESC LIMIT 2
        ),
        bounds AS (SELECT MAX(date) AS d0, MIN(date) AS d1 FROM last2),
        latest AS (
          SELECT o.code, o.close AS close0, o.volume AS vol0
            FROM ohlcv_daily o, bounds WHERE o.date = bounds.d0
        ),
        prev AS (
          SELECT o.code, o.close AS close1
            FROM ohlcv_daily o, bounds WHERE o.date = bounds.d1
        )
        SELECT s.code, s.name, s.market,
               l.close0  AS close,
               p.close1  AS prev_close,
               l.vol0    AS volume,
               CASE WHEN p.close1 > 0 THEN (l.close0 - p.close1) / p.close1 * 100 ELSE NULL END AS pct_change
          FROM symbols s
          LEFT JOIN latest l ON l.code = s.code
          LEFT JOIN prev   p ON p.code = s.code
         WHERE s.code = ANY(:codes)
         ORDER BY vol0 DESC NULLS LAST, s.name ASC
        """
    )

    eng = get_engine()
    with eng.connect() as conn:
        rows = conn.execute(sql, {"codes": codes}).all()

    # symbols 테이블에 시드만 있고 codes 일부가 누락된 경우, 그래도 코드/이름 자리는 비워서 카드 표시.
    by_code = {r[0]: r for r in rows}
    items: list[dict] = []
    for c in codes:
        r = by_code.get(c)
        if r is None:
            items.append(
                {
                    "code": c,
                    "name": c,  # symbols 미등재 — 코드로 노출
                    "market": None,
                    "close": None,
                    "prev_close": None,
                    "volume": None,
                    "pct_change": None,
                }
            )
        else:
            items.append(
                {
                    "code": r[0],
                    "name": r[1],
                    "market": r[2],
                    "close": float(r[3]) if r[3] is not None else None,
                    "prev_close": float(r[4]) if r[4] is not None else None,
                    "volume": int(r[5]) if r[5] is not None else None,
                    "pct_change": float(r[6]) if r[6] is not None else None,
                }
            )

    return {
        "slug": th.slug,
        "name": th.name,
        "description": th.description,
        "items": items,
    }