import streamlit as st
import math

# -----------------------------
# Page Configuration
# -----------------------------
st.set_page_config(
    page_title="Advanced Calculator",
    page_icon="🧮",
    layout="centered"
)

st.title("🧮 Advanced Calculator")
st.write("Supports basic, power, modulus & scientific operations")

# -----------------------------
# Safe math functions
# -----------------------------
safe_dict = {
    "sqrt": math.sqrt,
    "log": math.log,
    "log10": math.log10,
    "sin": math.sin,
    "cos": math.cos,
    "tan": math.tan,
    "pi": math.pi,
    "e": math.e,
    "pow": pow,
    "abs": abs,
    "round": round
}

# -----------------------------
# Session state for history
# -----------------------------
if "history" not in st.session_state:
    st.session_state.history = []

# -----------------------------
# Calculator UI
# -----------------------------
expression = st.text_input(
    "Enter mathematical expression:",
    placeholder="Example: sqrt(25) + 2**3 or sin(pi/2)"
)

st.markdown("""
**Allowed operations:**
- `+  -  *  /  %  **`
- `sqrt(x), log(x), log10(x)`
- `sin(x), cos(x), tan(x)`
- `pi, e`
""")

# -----------------------------
# Calculate Button
# -----------------------------
if st.button("Calculate"):
    try:
        result = eval(expression, {"__builtins__": None}, safe_dict)
        st.success(f"Result: {result}")
        st.session_state.history.append(f"{expression} = {result}")
    except ZeroDivisionError:
        st.error("Error: Division by zero!")
    except Exception:
        st.error("Invalid expression!")

# -----------------------------
# History Section
# -----------------------------
if st.session_state.history:
    st.subheader("📜 Calculation History")
    for item in reversed(st.session_state.history):
        st.write(item)

# -----------------------------
# Clear History
# -----------------------------
if st.button("Clear History"):
    st.session_state.history = []
    st.info("History cleared!")