sequenceDiagram
    participant Client
    participant Controller as PartyController
    participant Service as PartyService
    participant DB as Repository
    participant Calculator as DistanceCalculator

    Client->>Controller: GET /parties?category=...&sortType=DISTANCE<br/>&userLat=37.5&userLon=126.9
    
    rect rgb(220, 240, 255)
    Note over Controller: 파라미터 검증
    Controller->>Controller: sortType이 DISTANCE인 경우<br/>위도/경도 범위 검증
    end
    
    Controller->>Controller: PartyListRequest 생성<br/>(category, sortType, userLat, userLon)
    Controller->>Service: getPartyList(userId, request)
    
    rect rgb(220, 255, 220)
    Note over Service: 파티 조회
    Service->>DB: findByCategory() 또는<br/>fetchPartiesByLocation()
    DB-->>Service: Party 리스트
    end
    
    alt sortType == DISTANCE
        rect rgb(255, 240, 220)
        Note over Service: 거리 기반 정렬
        loop 각 Party마다
            Service->>Calculator: calculateDistance(party.lat, party.lon,<br/>userLat, userLon)
            Calculator-->>Service: distance (Double)
            Service->>Service: convertToCardResponseWithDistance<br/>(party, distance)
            Service->>Calculator: formatDistance(distance)
            Calculator-->>Service: 포맷된 거리 (String)
        end
        Service->>Service: DISTANCE 기준으로 정렬
        end
    else sortType == LATEST
        Service->>Service: LATEST 기준으로 정렬
    end
    
    Service-->>Controller: PartyListResponse
    Controller-->>Client: 200 OK with parties