from fastapi import APIRouter, HTTPException
from pydantic import BaseModel
import math

router = APIRouter()

class DistanceRequest(BaseModel):
    lat1: float
    lon1: float
    lat2: float
    lon2: float

class DistanceResponse(BaseModel):
    distance: float  # Distance in kilometers

@router.post("/api/distance", response_model=DistanceResponse)
async def calculate_distance(request: DistanceRequest):
    """Calculate the distance between two coordinates using the Haversine formula."""
    try:
        # Haversine formula
        R = 6371.0  # Earth radius in kilometers
        lat1_rad = math.radians(request.lat1)
        lon1_rad = math.radians(request.lon1)
        lat2_rad = math.radians(request.lat2)
        lon2_rad = math.radians(request.lon2)

        dlat = lat2_rad - lat1_rad
        dlon = lon2_rad - lon1_rad

        a = math.sin(dlat / 2)**2 + math.cos(lat1_rad) * math.cos(lat2_rad) * math.sin(dlon / 2)**2
        c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))

        distance = R * c  # Distance in kilometers
        return DistanceResponse(distance=distance)
    except Exception as e:
        raise HTTPException(status_code=500, detail=str(e))