import streamlit as st
import math

# Custom CSS for green button (should be at top)
st.markdown("""
<style>
    div.stButton > button:first-child {
        background-color: #4CAF50;
        color: white;
        border: none;
        padding: 0.5rem 1rem;
    }
            
    div.stButton > button:hover {
        background-color: #45a049;
        color: white;
    }
</style>
""", unsafe_allow_html=True)

# Unit conversion dictionaries
flow_units = {
    'm³/hr': 1/3600,
    'L/s': 0.001,
    'US gal/min (GPM)': 0.00006309,
    'ft³/s': 0.0283168
}

velocity_units = {
    'm/s': 1,
    'ft/s': 0.3048,
    'cm/s': 0.01,
    'km/h': 0.277778
}

st.title("Pipe Size Helper 🔧")
st.write("This app calculates required pipe diameter based on flow rate and velocity")

# Formula expander
with st.expander("Formula", expanded=False):
    st.subheader("Calculation Formula")
    st.latex(r"D = \sqrt{\frac{4Q}{\pi v}}")
    st.write("Where:")
    st.write("- D = Pipe diameter (meters)")
    st.write("- Q = Flow rate in m³/s (converted from input units)")
    st.write("- v = Velocity in m/s (converted from input units)")

# Guidelines expander
with st.expander("General Design Guidelines by Fluid Type", expanded=False):
    st.markdown("""
    **Fluid Velocity Recommendations**

    **Water:**
    - Cold Water: 0.6–1.8 m/s (2–6 ft/s)
    - Hot Water: 1.2–2.4 m/s (4–8 ft/s)
    - High-pressure systems: Up to 3 m/s (10 ft/s)

    **Steam:**
    - Saturated Steam: 25–40 m/s (80–130 ft/s)
    - Superheated Steam: 30–60 m/s (100–200 ft/s)

    **Compressed Air/Gases:**
    - Low-pressure: 10–20 m/s (30–65 ft/s)
    - High-pressure: 15–30 m/s (50–100 ft/s)

    **Oil/High-Viscosity Fluids:**
    - Light oils: 1–2 m/s (3–6 ft/s)
    - Heavy oils: 0.5–1.5 m/s (1.5–5 ft/s)

    **Slurries/Sewage:**
    - 0.5–1.5 m/s (1.5–5 ft/s)

    **HVAC Systems:**
    - Chilled/Hot Water: 1–2 m/s (3–6 ft/s)

    **Key Design Considerations**
    - Erosion: <1.5 m/s for abrasive fluids
    - Noise: <2 m/s for residential areas
    - Material: PVC has lower max velocities than steel
    - Flow Regime: Higher velocities for turbulent flow

    *Always consult relevant engineering standards (ASME, ISO) for specific applications*
    """)

# Input section
st.subheader("Input Parameters")
col1, col2 = st.columns(2)

with col1:
    # Flow rate input
    flow_col1, flow_col2 = st.columns([2, 1])
    with flow_col1:
        flow_value = st.number_input(
            "Flow Rate",
            min_value=0.1,
            max_value=1e6,
            value=3600.0,
            step=1.0,
            format="%.2f"
        )
    with flow_col2:
        flow_unit = st.selectbox(
            "Flow Unit",
            options=list(flow_units.keys()),
            index=0
        )

with col2:
    # Velocity input
    vel_col1, vel_col2 = st.columns([2, 1])
    with vel_col1:
        velocity_value = st.number_input(
            "Velocity",
            min_value=0.1,
            max_value=100.0,
            value=1.0,
            step=0.1,
            format="%.2f"
        )
    with vel_col2:
        velocity_unit = st.selectbox(
            "Velocity Unit",
            options=list(velocity_units.keys()),
            index=0
        )

# Calculate button
if st.button("Calculate Pipe Diameter", type="primary"):
    try:
        # Convert inputs to SI units
        Q = flow_value * flow_units[flow_unit]
        v = velocity_value * velocity_units[velocity_unit]
        
        # Validate inputs
        if v <= 0:
            raise ValueError("Velocity must be greater than zero")
            
        # Calculate diameter
        diameter_m = math.sqrt((4 * Q) / (math.pi * v))
        diameter_in = diameter_m * 39.3701  # Convert to inches
        
        # Display results
        st.subheader("Results")
        st.metric("Pipe Diameter", 
                 f"{diameter_in:.2f} inches",
                 f"{diameter_m:.3f} meters")
        
        st.success("Calculation completed successfully! ✅")
    

        # Conversion details
        with st.expander("Show unit conversions"):
            st.write(f"Converted flow rate: {Q:.6f} m³/s")
            st.write(f"Converted velocity: {v:.3f} m/s")
            
    except ZeroDivisionError:
        st.error("Error: Velocity cannot be zero. Please enter a positive value.")
    except ValueError as ve:
        st.error(f"Input Error: {str(ve)}")
    except Exception as e:
        st.error(f"Calculation Error: {str(e)}")