import streamlit as st
import math

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

st.title("🧮 Advanced Calculator")
st.write("A simple and powerful calculator built with Streamlit")

# Sidebar for mode selection
mode = st.sidebar.selectbox(
    "Select Calculator Mode",
    ["Basic", "Scientific", "Expression"]
)

# ---------------- BASIC CALCULATOR ----------------
if mode == "Basic":
    st.subheader("Basic Calculator")

    num1 = st.number_input("Enter first number", value=0.0)
    num2 = st.number_input("Enter second number", value=0.0)

    operation = st.selectbox(
        "Choose operation",
        ["+", "-", "*", "/", "**", "%"]
    )

    if st.button("Calculate"):
        try:
            if operation == "+":
                result = num1 + num2
            elif operation == "-":
                result = num1 - num2
            elif operation == "*":
                result = num1 * num2
            elif operation == "/":
                if num2 == 0:
                    st.error("Division by zero is not allowed")
                    result = None
                else:
                    result = num1 / num2
            elif operation == "**":
                result = num1 ** num2
            elif operation == "%":
                result = num1 % num2

            if result is not None:
                st.success(f"Result: {result}")

        except Exception as e:
            st.error("Something went wrong")

# ---------------- SCIENTIFIC CALCULATOR ----------------
elif mode == "Scientific":
    st.subheader("Scientific Calculator")

    number = st.number_input("Enter a number", value=0.0)

    operation = st.selectbox(
        "Choose function",
        ["sin", "cos", "tan", "sqrt", "log", "exp"]
    )

    if st.button("Calculate"):
        try:
            if operation == "sin":
                result = math.sin(math.radians(number))
            elif operation == "cos":
                result = math.cos(math.radians(number))
            elif operation == "tan":
                result = math.tan(math.radians(number))
            elif operation == "sqrt":
                if number < 0:
                    st.error("Cannot calculate square root of negative number")
                    result = None
                else:
                    result = math.sqrt(number)
            elif operation == "log":
                if number <= 0:
                    st.error("Logarithm input must be positive")
                    result = None
                else:
                    result = math.log(number)
            elif operation == "exp":
                result = math.exp(number)

            if result is not None:
                st.success(f"Result: {result}")

        except Exception:
            st.error("Invalid calculation")

# ---------------- EXPRESSION CALCULATOR ----------------
elif mode == "Expression":
    st.subheader("Expression Calculator")
    st.write("Example: `3 + 5 * (2 - 1) ** 2`")

    expression = st.text_input("Enter expression")

    if st.button("Evaluate"):
        try:
            allowed_chars = "0123456789+-*/().% "
            if all(char in allowed_chars for char in expression):
                result = eval(expression)
                st.success(f"Result: {result}")
            else:
                st.error("Invalid characters in expression")

        except Exception:
            st.error("Invalid expression")

st.markdown("---")
st.caption("Built with Streamlit • Deployable on Hugging Face Spaces")