import streamlit as st
import math

st.set_page_config(
    page_title="Advanced Calculator",
    layout="centered",
    page_icon="🧮"
)

st.title("🧮 Advanced Calculator")

# Initialize history if not already present
if 'history' not in st.session_state:
    st.session_state.history = []

# Layout inputs side by side
col1, col2 = st.columns(2)
with col1:
    num1 = st.number_input("First Number", format="%.4f", key="num1")
with col2:
    num2 = st.number_input("Second Number", format="%.4f", key="num2")

# Operation selection
operation = st.selectbox("Select Operation", [
    "➕ Addition",
    "➖ Subtraction",
    "✖️ Multiplication",
    "➗ Division",
    "🟰 Power (num1^num2)",
    "√ Square Root of First Number",
    "% Percentage (num1% of num2)",
    "1/x Reciprocal of First Number"
])

# Result calculation
result = None
symbol = ""
error = None

if st.button("🔢 Calculate"):
    try:
        if operation == "➕ Addition":
            result = num1 + num2
            symbol = "+"
        elif operation == "➖ Subtraction":
            result = num1 - num2
            symbol = "-"
        elif operation == "✖️ Multiplication":
            result = num1 * num2
            symbol = "*"
        elif operation == "➗ Division":
            if num2 != 0:
                result = num1 / num2
                symbol = "/"
            else:
                error = "Division by zero is not allowed."
        elif operation == "🟰 Power (num1^num2)":
            result = math.pow(num1, num2)
            symbol = "^"
        elif operation == "√ Square Root of First Number":
            if num1 >= 0:
                result = math.sqrt(num1)
                symbol = "√"
            else:
                error = "Cannot take square root of a negative number."
        elif operation == "% Percentage (num1% of num2)":
            result = (num1 / 100) * num2
            symbol = "%"
        elif operation == "1/x Reciprocal of First Number":
            if num1 != 0:
                result = 1 / num1
                symbol = "1/x"
            else:
                error = "Reciprocal of 0 is undefined."

        # Display result
        if error:
            st.warning(f"⚠️ {error}")
        else:
            if operation == "√ Square Root of First Number":
                st.success(f"Result: √{num1} = {result}")
                st.session_state.history.append(f"√{num1} = {result}")
            elif operation == "1/x Reciprocal of First Number":
                st.success(f"Result: 1/{num1} = {result}")
                st.session_state.history.append(f"1/{num1} = {result}")
            else:
                st.success(f"Result: {num1} {symbol} {num2} = {result}")
                st.session_state.history.append(f"{num1} {symbol} {num2} = {result}")

    except Exception as e:
        st.error(f"An error occurred: {str(e)}")

# Show history
if st.session_state.history:
    st.write("### 📜 Calculation History")
    for record in reversed(st.session_state.history[-5:]):  # show last 5 only
        st.write(record)

# Reset button
if st.button("🔄 Reset Calculator"):
    st.session_state.history.clear()
    st.experimental_rerun()