"""여행 일정(1박2일·2박3일) 생성 — 순수 함수 모듈."""
from typing import Optional

from common.utils.geo import haversine_km

# 하루 구성 정원.
_SPOTS_PER_DAY = 2
_MEALS_PER_DAY = 2
# 후보 반경(km).
_MAX_RADIUS_KM = 30.0

_STOP_ATTRACTION = "attraction"
_STOP_RESTAURANT = "restaurant"
_STOP_FESTIVAL = "festival"


def _as_float(value) -> Optional[float]:
    try:
        return float(value)
    except (TypeError, ValueError):
        return None


def _candidates(rows: list[dict], stop_type: str,
                base_lat: float, base_lng: float) -> list[dict]:
    """payload 지역정보 행 → 거리 오름차순 후보."""
    out = []
    for row in rows:
        body = row.get("body") or {}
        name = str(body.get("name") or row.get("title") or "").strip()
        lat, lng = _as_float(row.get("latitude")), _as_float(row.get("longitude"))
        if not name or lat is None or lng is None:
            continue
        dist = haversine_km(base_lat, base_lng, lat, lng)
        if dist > _MAX_RADIUS_KM:
            continue
        out.append({"type": stop_type, "name": name, "lat": lat, "lng": lng,
                    "distanceKm": round(dist, 1)})
    out.sort(key=lambda c: c["distanceKm"])
    return out


def _order_by_route(stops: list[dict], base_lat: float, base_lng: float) -> list[dict]:
    """일자 안 동선: 업체에서 출발해 최근접 이웃 순으로 잇는다."""
    remaining = list(stops)
    ordered: list[dict] = []
    lat, lng = base_lat, base_lng
    while remaining:
        nxt = min(remaining, key=lambda s: haversine_km(lat, lng, s["lat"], s["lng"]))
        remaining.remove(nxt)
        ordered.append(nxt)
        lat, lng = nxt["lat"], nxt["lng"]
    return ordered


def _take(pool: list[dict], count: int) -> list[dict]:
    taken, pool[:] = pool[:count], pool[count:]
    return taken


# 일자 이름.
_DAY_LABEL = {1: "첫째 날", 2: "둘째 날", 3: "셋째 날"}
# 며칠짜리인가 → 사람이 읽는 말.
_DURATION = {2: "1박 2일", 3: "2박 3일"}


def _to_stop(cand: dict) -> dict:
    """후보 → 렌더러의 PlannerStop."""
    return {
        "name": cand["name"],
        "searchQuery": cand["name"],
        "latitude": cand["lat"],
        "longitude": cand["lng"],
    }


def _plan_days(days: int, attractions: list[dict], restaurants: list[dict],
               festivals: list[dict], base_lat: float, base_lng: float) -> Optional[dict]:
    """일자별 계획."""
    spots = list(attractions)
    meals = list(restaurants)
    fests = list(festivals)
    plan = []
    for day in range(1, days + 1):
        day_stops = []
        # 축제는 하루 하나까지, 관광지 한 자리를 대신한다.
        fest = _take(fests, 1)
        day_stops += fest
        day_stops += _take(spots, _SPOTS_PER_DAY - len(fest))
        day_stops += _take(meals, _MEALS_PER_DAY)
        if not day_stops:
            break
        plan.append({
            "label": _DAY_LABEL.get(day, f"{day}일차"),
            "stops": [_to_stop(s) for s in _order_by_route(day_stops, base_lat, base_lng)],
        })
    if not plan:
        return None
    # 렌더러 계약(`shared` ItineraryItem)의 모양으로 낸다.
    return {"name": _DURATION[days], "duration": _DURATION[days], "days": plan}


def build_itineraries(base_lat: Optional[float], base_lng: Optional[float],
                      attractions: list[dict], restaurants: list[dict],
                      festivals: list[dict]) -> list[dict]:
    """업체 좌표 기준 1박2일(2일)·2박3일(3일) 일정."""
    if base_lat is None or base_lng is None:
        return []
    spot_pool = _candidates(attractions, _STOP_ATTRACTION, base_lat, base_lng)
    meal_pool = _candidates(restaurants, _STOP_RESTAURANT, base_lat, base_lng)
    fest_pool = _candidates(festivals, _STOP_FESTIVAL, base_lat, base_lng)

    out = []
    for days in (2, 3):
        # 세트마다 독립된 풀 복사 — 1박2일이 소비한 후보가 2박3일에서 빠지면 안 된다.
        built = _plan_days(days, list(spot_pool), list(meal_pool), list(fest_pool),
                           base_lat, base_lng)
        if built:
            out.append(built)
    return out