app.py

import gradio as gr
import numpy as np
import plotly.graph_objects as go

def calculate_chemeng_tvm(capex, revenue, opex_fixed, opex_var, plant_life, marr_pct, salvage_pct, inflation_pct):
    capex = float(capex)
    revenue = float(revenue)
    opex_fixed = float(opex_fixed)
    opex_var = float(opex_var)
    plant_life = int(plant_life)
    marr = float(marr_pct) / 100
    salvage = float(salvage_pct) / 100
    inflation = float(inflation_pct) / 100
    
    # Generate cash flows
    cashflows = [-capex]
    for year in range(1, plant_life + 1):
        opex_total = (opex_fixed + opex_var) * (1 + inflation) ** year
        rev = revenue * (1 + inflation) ** year
        net_cf = rev - opex_total
        cashflows.append(net_cf)
    cashflows[-1] += capex * salvage
    
    # NPV Calculation
    npv_val = sum(cf / (1 + marr)**i for i, cf in enumerate(cashflows))
    
    # IRR Approximation (Newton-Raphson)
    irr_guess = 0.1
    for _ in range(50):
        npv_est = sum(cf / (1 + irr_guess)**i for i, cf in enumerate(cashflows))
        deriv = sum(-i * cf / (1 + irr_guess)**(i+1) for i, cf in enumerate(cashflows))
        if abs(deriv) < 1e-10: break
        irr_guess -= npv_est / deriv
    irr_val = max(0, irr_guess * 100)
    
    # Payback Period
    cum_cf = [0]
    for cf in cashflows[1:]:
        cum_cf.append(cum_cf[-1] + cf)
    payback = next((i for i, total in enumerate(cum_cf) if total >= 0), plant_life)
    
    # Results HTML
    results_html = f"""
    <div style='font-family: Arial; padding: 20px;'>
        <h2 style='color: #1f77b4;'>🧪 Chemical Engineering Economics</h2>
        <table style='width: 100%; border-collapse: collapse; margin: 20px 0;'>
            <tr style='background: #f0f8ff;'>
                <th style='border: 1px solid #ddd; padding: 12px;'>Metric</th>
                <th style='border: 1px solid #ddd; padding: 12px; text-align: right;'>Value</th>
            </tr>
            <tr>
                <td style='border: 1px solid #ddd; padding: 12px;'><b>💎 NPV</b></td>
                <td style='border: 1px solid #ddd; padding: 12px; text-align: right; font-size: 18px; color: {'green' if npv_val > 0 else 'red'};'>${npv_val:,.0f}</td>
            </tr>
            <tr style='background: #f9f9f9;'>
                <td style='border: 1px solid #ddd; padding: 12px;'><b>⚡ IRR</b></td>
                <td style='border: 1px solid #ddd; padding: 12px; text-align: right; font-size: 18px;'>{irr_val:.1f}%</td>
            </tr>
            <tr>
                <td style='border: 1px solid #ddd; padding: 12px;'><b>⏱️ Payback</b></td>
                <td style='border: 1px solid #ddd; padding: 12px; text-align: right;'>{payback:.1f} years</td>
            </tr>
            <tr style='background: #f9f9f9;'>
                <td style='border: 1px solid #ddd; padding: 12px;'><b>📊 Profitability Index</b></td>
                <td style='border: 1px solid #ddd; padding: 12px; text-align: right;'>{abs(npv_val/capex)*100:.1f}%</td>
            </tr>
        </table>
        <div style='background: {'#d4edda' if npv_val > 0 else '#f8d7da'}; padding: 15px; border-radius: 8px; border-left: 5px solid {'#28a745' if npv_val > 0 else '#dc3545'};'>
            <b>Status: {'✅ PROJECT VIABLE (NPV > 0)' if npv_val > 0 else '⚠️ REVIEW REQUIRED'}</b>
        </div>
    </div>
    """
    
    # Cash Flow Chart
    years = list(range(len(cashflows)))
    fig = go.Figure()
    fig.add_trace(go.Bar(x=years[1:], y=cashflows[1:], 
                        name="Annual Cash Flow", marker_color='#1f77b4'))
    fig.add_trace(go.Scatter(x=years, y=cum_cf, 
                            mode='lines+markers', name="Cumulative CF",
                            line=dict(color='#ff4444', width=4)))
    fig.add_hline(y=0, line_dash="dash", line_color="gray", annotation_text="Breakeven")
    fig.update_layout(
        title="💸 Chemical Plant Cash Flow Analysis",
        xaxis_title="Year", yaxis_title="Cash Flow ($)",
        height=400, showlegend=True,
        font=dict(size=12)
    )
    
    return results_html, fig.to_html(full_html=False, div_id="cashflow-chart")

# Gradio Interface
with gr.Blocks(title="ChemEng TVM Calculator") as demo:
    gr.Markdown("# 🧪 Chemical Engineering TVM Calculator")
    gr.Markdown("**CAPEX • OPEX • NPV • IRR • Plant Investment Analysis**")
    
    with gr.Row():
        with gr.Column(scale=1):
            gr.Markdown("### 📊 Chemical Plant Inputs")
            
            gr.Markdown("**💰 Investment & Revenue**")
            with gr.Row():
                capex_input = gr.Number(value=10000000, label="CAPEX ($)", precision=0)
                revenue_input = gr.Number(value=5000000, label="Revenue/Year ($)", precision=0)
            
            gr.Markdown("**🏭 Operating Costs**")
            with gr.Row():
                opex_fixed_input = gr.Number(value=1500000, label="Fixed OPEX ($)", precision=0)
                opex_var_input = gr.Number(value=2000000, label="Variable OPEX ($)", precision=0)
            
            gr.Markdown("**📅 Economic Parameters**")
            with gr.Row():
                plant_life_input = gr.Slider(5, 30, value=15, step=1, label="Plant Life (years)")
                marr_input = gr.Slider(8, 20, value=12, step=1, label="MARR (%)")
            
            with gr.Row():
                salvage_input = gr.Slider(0, 20, value=10, step=1, label="Salvage Value (%)")
                inflation_input = gr.Slider(1, 8, value=3, step=0.5, label="Inflation (%)")
            
            calculate_btn = gr.Button("🔬 RUN ECONOMIC ANALYSIS", variant="primary", size="lg")
        
        with gr.Column(scale=2):
            results_output = gr.HTML()
            chart_output = gr.HTML()
    
    # Connect button to function
    calculate_btn.click(
        calculate_chemeng_tvm,
        inputs=[capex_input, revenue_input, opex_fixed_input, opex_var_input, 
                plant_life_input, marr_input, salvage_input, inflation_input],
        outputs=[results_output, chart_output]
    )
    
    gr.Markdown("---")
    gr.Markdown("*Professional tool for Chemical Engineers | Powered by Gradio*")

# Launch (Hugging Face auto-runs this)
demo.launch()