from fastapi import FastAPI, HTTPException
from pydantic import BaseModel
from enum import Enum

# Initialize the FastAPI app
app = FastAPI()

# Define allowed operations using Enum for better validation
class Operation(str, Enum):
    add = "+"
    subtract = "-"
    multiply = "*"
    divide = "/"

# Define the request model for the calculator
class CalculationRequest(BaseModel):
    operation: Operation  # Operation can be '+', '-', '*', '/'
    num1: float
    num2: float

# Calculator logic function
def calculate(operation: str, num1: float, num2: float):
    if operation == '+':
        return num1 + num2
    elif operation == '-':
        return num1 - num2
    elif operation == '*':
        return num1 * num2
    elif operation == '/':
        if num2 == 0:
            raise HTTPException(status_code=400, detail="Division by zero is not allowed")
        return num1 / num2
    else:
        raise HTTPException(status_code=400, detail="Invalid operation")

# Define the POST endpoint for calculations
@app.post("/calculate")
def perform_calculation(request: CalculationRequest):
    result = calculate(request.operation, request.num1, request.num2)
    return {"result": result}