import streamlit as st
import numpy as np
import matplotlib.pyplot as plt

# Title and description
st.title("Beam Deflection Calculator")
st.markdown("""
### Problem:
This app calculates the deflection of a beam under a load. It is designed for mechanical engineers who need accurate and quick calculations during design.

### Instructions:
1. Enter the beam parameters below.
2. Select the type of support and load.
3. The app will calculate the maximum deflection and plot the deflection curve.
""")

# User Inputs
st.sidebar.header("Beam Parameters")
length = st.sidebar.number_input("Beam Length (m)", min_value=0.1, step=0.1, value=5.0)
load = st.sidebar.number_input("Load Magnitude (N)", min_value=0.0, step=1.0, value=1000.0)
youngs_modulus = st.sidebar.number_input("Young's Modulus (Pa)", min_value=1e6, step=1e6, value=2.0e11)
moment_of_inertia = st.sidebar.number_input("Moment of Inertia (m⁴)", min_value=1e-6, step=1e-6, value=1.0e-4)

support_type = st.sidebar.selectbox("Support Type", ["Simply Supported", "Fixed Supported"])
load_type = st.sidebar.selectbox("Load Type", ["Point Load at Center", "Uniformly Distributed Load"])

# Calculation
x = np.linspace(0, length, 500)

if support_type == "Simply Supported" and load_type == "Point Load at Center":
    max_deflection = (load * length**3) / (48 * youngs_modulus * moment_of_inertia)
    deflection = (load * x * (length**3 - 2 * length * x**2 + x**3)) / (48 * youngs_modulus * moment_of_inertia)

elif support_type == "Simply Supported" and load_type == "Uniformly Distributed Load":
    max_deflection = (5 * load * length**4) / (384 * youngs_modulus * moment_of_inertia)
    deflection = ((load * x**2) / (24 * youngs_modulus * moment_of_inertia)) * (length**3 - 2 * length * x**2 + x**3)

elif support_type == "Fixed Supported" and load_type == "Point Load at Center":
    max_deflection = (load * length**3) / (192 * youngs_modulus * moment_of_inertia)
    deflection = (load * x**2 * (3 * length - x)) / (48 * youngs_modulus * moment_of_inertia)

elif support_type == "Fixed Supported" and load_type == "Uniformly Distributed Load":
    max_deflection = (load * length**4) / (384 * youngs_modulus * moment_of_inertia)
    deflection = (load * x**2 * (length - x)**2) / (24 * youngs_modulus * moment_of_inertia)

else:
    st.error("Invalid combination of support and load type.")
    deflection = None

# Display Results
if deflection is not None:
    st.subheader("Results")
    st.write(f"**Maximum Deflection**: {max_deflection:.5e} m")
    
    # Plot Deflection Curve
    st.subheader("Deflection Curve")
    fig, ax = plt.subplots()
    ax.plot(x, deflection, label="Deflection Curve")
    ax.axhline(0, color="black", linewidth=0.5, linestyle="--")
    ax.set_title("Beam Deflection Curve")
    ax.set_xlabel("Position along the beam (m)")
    ax.set_ylabel("Deflection (m)")
    ax.legend()
    ax.grid(True)
    st.pyplot(fig)