import math
import streamlit as st

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

# ---- Helpers ----
def safe_div(a, b):
    if b == 0:
        raise ZeroDivisionError("Cannot divide by zero")
    return a / b

def fmt(x):
    try:
        # Show ints without .0
        return int(x) if float(x).is_integer() else x
    except Exception:
        return x

def add_history(expr, result):
    st.session_state.setdefault("history", [])
    st.session_state.history.insert(0, f"{expr} = {result}")
    # keep last 20
    st.session_state.history = st.session_state.history[:20]

# ---- Sidebar ----
with st.sidebar:
    st.header("⚙️ Options")
    theme = st.radio("Mode", ["Basic", "Scientific"], horizontal=True)
    show_history = st.checkbox("Show history", True)
    st.markdown("---")
    st.caption("Tip: Use the Basic tab for two number math. Use Scientific for single number functions and powers.")

st.title("🧮 Streamlit Calculator")
st.write("A simple calculator ready for Hugging Face Spaces.")

# ---- Basic Calculator ----
if theme == "Basic":
    col1, col2 = st.columns(2)
    with col1:
        a = st.number_input("First number (a)", value=0.0, step=1.0, format="%.10f")
    with col2:
        b = st.number_input("Second number (b)", value=0.0, step=1.0, format="%.10f")

    op = st.selectbox(
        "Operation",
        ["+", "-", "×", "÷", "a^b (power)", "a % b (mod)"],
        index=0
    )

    if st.button("Calculate", use_container_width=True):
        try:
            if op == "+":
                result = a + b
                expr = f"{a} + {b}"
            elif op == "-":
                result = a - b
                expr = f"{a} - {b}"
            elif op == "×":
                result = a * b
                expr = f"{a} × {b}"
            elif op == "÷":
                result = safe_div(a, b)
                expr = f"{a} ÷ {b}"
            elif op == "a^b (power)":
                result = math.pow(a, b)
                expr = f"{a}^{b}"
            elif op == "a % b (mod)":
                if b == 0:
                    raise ZeroDivisionError("Cannot mod by zero")
                result = a % b
                expr = f"{a} % {b}"
            else:
                raise ValueError("Unknown operation")

            result_fmt = fmt(result)
            st.success(f"Result: {result_fmt}")
            add_history(expr, result_fmt)
        except Exception as e:
            st.error(f"Error: {e}")

# ---- Scientific Calculator ----
else:
    col_a, col_b = st.columns([2, 1])
    with col_a:
        x = st.number_input("Value (x)", value=0.0, step=1.0, format="%.10f")
    with col_b:
        use_degrees = st.checkbox("Trig in degrees", True)

    func = st.selectbox(
        "Function",
        [
            "sin(x)", "cos(x)", "tan(x)",
            "asin(x)", "acos(x)", "atan(x)",
            "ln(x)", "log10(x)", "sqrt(x)",
            "exp(x)", "abs(x)", "factorial(x) (non negative integer)",
            "x^n (power)"
        ],
        index=0
    )

    n = None
    if func == "x^n (power)":
        n = st.number_input("Exponent (n)", value=2.0, step=1.0, format="%.10f")

    if st.button("Calculate", use_container_width=True):
        try:
            val = x
            angle = math.radians(x) if use_degrees else x

            if func == "sin(x)":
                res = math.sin(angle)
                expr = f"sin({x}{'°' if use_degrees else ''})"
            elif func == "cos(x)":
                res = math.cos(angle)
                expr = f"cos({x}{'°' if use_degrees else ''})"
            elif func == "tan(x)":
                res = math.tan(angle)
                expr = f"tan({x}{'°' if use_degrees else ''})"
            elif func == "asin(x)":
                if val < -1 or val > 1:
                    raise ValueError("asin domain is [-1, 1]")
                ang = math.asin(val)
                res = math.degrees(ang) if use_degrees else ang
                expr = f"asin({x})"
            elif func == "acos(x)":
                if val < -1 or val > 1:
                    raise ValueError("acos domain is [-1, 1]")
                ang = math.acos(val)
                res = math.degrees(ang) if use_degrees else ang
                expr = f"acos({x})"
            elif func == "atan(x)":
                ang = math.atan(val)
                res = math.degrees(ang) if use_degrees else ang
                expr = f"atan({x})"
            elif func == "ln(x)":
                if val <= 0:
                    raise ValueError("ln domain is x > 0")
                res = math.log(val)
                expr = f"ln({x})"
            elif func == "log10(x)":
                if val <= 0:
                    raise ValueError("log10 domain is x > 0")
                res = math.log10(val)
                expr = f"log10({x})"
            elif func == "sqrt(x)":
                if val < 0:
                    raise ValueError("sqrt domain is x >= 0")
                res = math.sqrt(val)
                expr = f"√({x})"
            elif func == "exp(x)":
                res = math.exp(val)
                expr = f"exp({x})"
            elif func == "abs(x)":
                res = abs(val)
                expr = f"|{x}|"
            elif func == "factorial(x) (non negative integer)":
                if val < 0 or not float(val).is_integer():
                    raise ValueError("factorial requires a non negative integer")
                res = math.factorial(int(val))
                expr = f"{int(val)}!"
            elif func == "x^n (power)":
                res = math.pow(val, n)
                expr = f"{val}^{n}"
            else:
                raise ValueError("Unknown function")

            res_fmt = fmt(res)
            st.success(f"Result: {res_fmt}")
            add_history(expr, res_fmt)
        except OverflowError:
            st.error("Result overflowed for given input")
        except Exception as e:
            st.error(f"Error: {e}")

# ---- History ----
if show_history:
    st.markdown("### 📝 History")
    if st.session_state.get("history"):
        for i, line in enumerate(st.session_state.history, 1):
            st.code(f"{i}. {line}")
        if st.button("Clear history"):
            st.session_state.history = []
            st.toast("History cleared")
    else:
        st.caption("No calculations yet")

# ---- Footer ----
st.markdown("---")
st.caption("Built with Streamlit. Ready for Hugging Face Spaces.")