import streamlit as st
import math

st.set_page_config(page_title="Simple Calculator", layout="centered")

st.title("🧮 Simple Calculator")

# Operation selection
operation = st.selectbox(
    "Choose Operation",
    [
        "Addition",
        "Subtraction",
        "Multiplication",
        "Division",
        "Square Root",
        "Power",
        "Log (ln)"
    ]
)

# Inputs
if operation in ["Addition", "Subtraction", "Multiplication", "Division", "Power"]:
    num1 = st.number_input("Enter first number", value=0.0)
    num2 = st.number_input("Enter second number", value=0.0)

elif operation in ["Square Root", "Log (ln)"]:
    num1 = st.number_input("Enter number", value=0.0)

# Calculate button
if st.button("Calculate"):
    result = None

    try:
        if operation == "Addition":
            result = num1 + num2

        elif operation == "Subtraction":
            result = num1 - num2

        elif operation == "Multiplication":
            result = num1 * num2

        elif operation == "Division":
            if num2 == 0:
                result = "Error: Division by zero!"
            else:
                result = num1 / num2

        elif operation == "Square Root":
            if num1 < 0:
                result = "Error: Negative number!"
            else:
                result = math.sqrt(num1)

        elif operation == "Power":
            result = math.pow(num1, num2)

        elif operation == "Log (ln)":
            if num1 <= 0:
                result = "Error: Log undefined!"
            else:
                result = math.log(num1)

    except Exception as e:
        result = f"Error: {e}"

    st.subheader("Result:")
    st.write(result)