app.py

import streamlit as st
import joblib
import numpy as np
from huggingface_hub import hf_hub_download

# Page configuration
st.set_page_config(
    page_title="Loan Approval System",
    page_icon="🏦",
    layout="centered",
    initial_sidebar_state="collapsed"
)

# Custom CSS for styling with the specified color theme
st.markdown("""
<style>
    /* Color Theme */
    :root {
        --primary-purple: #7950F2;
        --primary-purple-light: #9775F3;
        --primary-purple-dark: #5F3DC4;
        --complementary-orange: #FF5E3A;
        --complementary-orange-light: #FF8A6C;
        --light-gray: #F8F9FA;
        --dark-gray: #343A40;
    }
    
    /* Main containers */
    .main .block-container {
        padding: 2rem;
        border-radius: 10px;
        background-color: white;
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
    }
    
    /* Font family */
    body, .stMarkdown, p, h1, h2, h3, h4, h5, h6, .stButton, .stSelectbox, .stNumberInput {
        font-family: 'Helvetica', 'Arial', sans-serif !important;
    }
    
    /* Headers */
    h1, h2, h3 {
        color: var(--primary-purple-dark);
    }
    
    /* Custom cards for sections */
    .section-card {
        background-color: var(--light-gray);
        border-radius: 8px;
        padding: 1.5rem;
        margin-bottom: 1.5rem;
        border-left: 4px solid var(--primary-purple);
    }
    
    /* Button styling */
    .stButton > button {
        background-color: var(--primary-purple);
        color: white;
        border: none;
        border-radius: 5px;
        padding: 0.5rem 1rem;
        font-weight: bold;
        width: 100%;
        transition: all 0.3s;
    }
    .stButton > button:hover {
        background-color: var(--primary-purple-dark);
        transform: translateY(-2px);
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    }
    
    /* Result styling */
    .result-approved {
        background-color: #E8F5E9;
        border-left: 4px solid #4CAF50;
        padding: 1rem;
        border-radius: 5px;
        margin-top: 1rem;
    }
    .result-rejected {
        background-color: #FFEBEE;
        border-left: 4px solid #F44336;
        padding: 1rem;
        border-radius: 5px;
        margin-top: 1rem;
    }
    
    /* Input widgets */
    .stNumberInput, .stSelectbox {
        margin-bottom: 1rem;
    }
    
    /* Footer */
    .footer {
        text-align: center;
        margin-top: 2rem;
        padding-top: 1rem;
        border-top: 1px solid #EEEEEE;
        font-size: 0.8rem;
        color: #666666;
    }
    
    /* Divider */
    .divider {
        border-top: 1px solid #EEEEEE;
        margin: 1.5rem 0;
    }
    
    /* Badge */
    .badge {
        display: inline-block;
        background-color: var(--complementary-orange);
        color: white;
        padding: 0.25rem 0.5rem;
        border-radius: 4px;
        font-size: 0.8rem;
        margin-left: 0.5rem;
    }
</style>
""", unsafe_allow_html=True)

# App header with logo
col1, col2 = st.columns([1, 5])
with col1:
    st.markdown('<div style="text-align: center; padding: 10px;"><span style="font-size: 40px;">🏦</span></div>', unsafe_allow_html=True)
with col2:
    st.title("AI-Powered Loan Approval System")
    st.markdown('<p style="color: #666;">Fast and reliable loan approval decisions</p>', unsafe_allow_html=True)

# Load the trained model from Hugging Face
@st.cache_resource
def load_model():
    model_path = hf_hub_download(repo_id="ifiecas/LoanApproval-DT-v1.0", filename="best_pruned_dt.pkl")
    return joblib.load(model_path)

model = load_model()

# Initialize session state for restart functionality
if 'restart_clicked' not in st.session_state:
    st.session_state.restart_clicked = False

# Create tabs for better organization
tab1, tab2 = st.tabs(["Loan Application", "About the System"])

with tab1:
    # Reset all form values if restart was clicked
    if st.session_state.restart_clicked:
        st.session_state.restart_clicked = False  # Reset flag
        
        # Add any other reset logic here if needed
        # Note: Streamlit will reset most inputs automatically on rerun
    
    # Personal Information Section
    st.markdown('<div class="section-card"><h3>Personal Information</h3>', unsafe_allow_html=True)
    
    col1, col2 = st.columns(2)
    with col1:
        gender = st.selectbox("Gender", ["Male", "Female"])
        education = st.selectbox("Education Level", ["Graduate", "Under Graduate"])
    
    with col2:
        marital_status = st.selectbox("Marital Status", ["Married", "Not Married"])
        number_of_dependents = st.number_input("Number of Dependents", min_value=0, max_value=10, value=0)
    
    self_employed = st.selectbox("Self-Employed", ["No", "Yes"])
    st.markdown('</div>', unsafe_allow_html=True)
    
    # Financial Details Section
    st.markdown('<div class="section-card"><h3>Financial Details</h3>', unsafe_allow_html=True)
    
    col1, col2 = st.columns(2)
    with col1:
        applicant_income = st.number_input("Monthly Income ($)", min_value=0, value=5000)
        loan_amount = st.number_input("Loan Amount ($)", min_value=0, value=100000)
        credit_history = st.selectbox("Credit History Status", [1, 0], 
                                     format_func=lambda x: "No existing unsettled loans (1)" if x == 1 else "Have unsettled loans (0)")
    
    with col2:
        coapplicant_income = st.number_input("Co-Applicant's Income ($)", min_value=0)
        loan_term = st.slider("Loan Term (months)", min_value=12, max_value=360, value=180, step=12)
        location = st.selectbox("Property Location", ["Urban", "Semiurban", "Rural"])
    
    st.markdown('</div>', unsafe_allow_html=True)
    
    # Summary section
    st.markdown('<div class="section-card"><h3>Application Summary</h3>', unsafe_allow_html=True)
    
    total_income = applicant_income + coapplicant_income
    
    # Calculate monthly payment (simplified calculation)
    interest_rate = 0.05  # Assuming 5% annual interest rate
    monthly_interest = interest_rate / 12
    num_payments = loan_term
    
    # Monthly payment using the loan amortization formula
    if monthly_interest == 0 or num_payments == 0:
        monthly_payment = 0
    else:
        monthly_payment = loan_amount * (monthly_interest * (1 + monthly_interest) ** num_payments) / \
                        ((1 + monthly_interest) ** num_payments - 1)
    
    # Calculate proper Debt-to-Income ratio (monthly payment / monthly income)
    dti = (monthly_payment / total_income) if total_income > 0 else 0
    dti_percent = dti * 100
    
    col1, col2, col3 = st.columns(3)
    col1.metric("Total Monthly Income", f"${total_income:,}")
    col2.metric("Estimated Monthly Payment", f"${monthly_payment:.2f}")
    col3.metric("Loan Term", f"{loan_term//12} years")
    
    # Create DTI visualization section
    st.markdown("<h4>Debt-to-Income Assessment</h4>", unsafe_allow_html=True)
    
    # Cap the displayed percentage at 100% for the visual
    display_percent = min(dti_percent, 100)
    
    # Determine the status and color
    if dti_percent <= 36:
        dti_status = "Good"
        dti_color = "#4CAF50"  # Green
        emoji = "✅"
    elif dti_percent <= 43:
        dti_status = "Moderate"
        dti_color = "#FF9800"  # Orange
        emoji = "⚠️"
    else:
        dti_status = "High"
        dti_color = "#F44336"  # Red
        emoji = "❗"
    
    # Create a visual progress bar
    st.markdown(f"""
    <div style="margin-bottom: 10px;">
        <div style="background-color: #e0e0e0; border-radius: 10px; height: 20px; width: 100%;">
            <div style="background-color: {dti_color}; width: {display_percent}%; height: 20px; border-radius: 10px;"></div>
        </div>
        <div style="display: flex; justify-content: space-between; font-size: 0.8rem;">
            <span>0%</span>
            <span>50%</span>
            <span>100%+</span>
        </div>
    </div>
    """, unsafe_allow_html=True)
    
    # Show a simple explanation of DTI with actual values
    if dti_percent > 100:
        st.markdown(f"""
        <div style="padding: 10px; background-color: #FFEBEE; border-radius: 5px; margin-bottom: 15px;">
            {emoji} <strong>Your monthly payment (${monthly_payment:.2f}) would be {dti_percent/100:.1f}× your monthly income (${total_income:,})</strong>
            <p style="margin: 5px 0 0 0; font-size: 0.9rem;">Most lenders require this to be below 43% for approval</p>
        </div>
        """, unsafe_allow_html=True)
    else:
        st.markdown(f"""
        <div style="padding: 10px; background-color: #F5F5F5; border-radius: 5px; margin-bottom: 15px;">
            {emoji} <strong>Your monthly payment (${monthly_payment:.2f}) would be {dti_percent:.1f}% of your monthly income (${total_income:,})</strong>
            <p style="margin: 5px 0 0 0; font-size: 0.9rem;">Most lenders require this to be below 43% for approval</p>
        </div>
        """, unsafe_allow_html=True)
    
    # Add eligibility check section
    st.markdown('<h4>Loan Eligibility Check</h4>', unsafe_allow_html=True)
    
    eligibility_issues = []
    
    # Check minimum income threshold (example: $1500/month)
    if total_income < 1500:
        eligibility_issues.append("⚠️ Total monthly income below minimum requirement ($1,500)")
    
    # Check if DTI is too high (above 43% is typically problematic)
    if dti_percent > 43:
        eligibility_issues.append("⚠️ Debt-to-income ratio exceeds maximum threshold (43%)")
    
    # Credit history is critical
    if credit_history == 0:
        eligibility_issues.append("⚠️ Existing unsettled loans may affect approval odds")
    
    # Display eligibility issues if any
    if eligibility_issues:
        st.markdown('<div style="background-color:#FFF3E0;padding:10px;border-radius:5px;margin-bottom:15px;">', unsafe_allow_html=True)
        st.markdown("<p><strong>Potential eligibility concerns:</strong></p>", unsafe_allow_html=True)
        for issue in eligibility_issues:
            st.markdown(f"<p>{issue}</p>", unsafe_allow_html=True)
        st.markdown("</div>", unsafe_allow_html=True)
    else:
        st.markdown('<div style="background-color:#E8F5E9;padding:10px;border-radius:5px;margin-bottom:15px;">', unsafe_allow_html=True)
        st.markdown("<p>✅ <strong>No obvious eligibility concerns</strong></p>", unsafe_allow_html=True)
        st.markdown("</div>", unsafe_allow_html=True)
    
    st.markdown('</div>', unsafe_allow_html=True)
    
    # Prediction and restart buttons
    col1, col2 = st.columns([3, 1])
    
    with col1:
        predict_button = st.button("Check Loan Approval Status", use_container_width=True)
    
    with col2:
        restart_button = st.button("🔄 Restart", use_container_width=True, 
                                 help="Reset all form fields and start over")
    
    def preprocess_input():
        # Convert categorical inputs to numerical format based on encoding reference
        gender_num = 0 if gender == "Male" else 1
        marital_status_num = 0 if marital_status == "Not Married" else 1
        education_num = 0 if education == "Under Graduate" else 1
        self_employed_num = 0 if self_employed == "No" else 1
        credit_history_num = credit_history  # Already numerical (0,1)
        
        # One-Hot Encoding for Location
        location_semiurban = 1 if location == "Semiurban" else 0
        location_urban = 1 if location == "Urban" else 0
        
        # Convert Term from months to years
        term_years = loan_term / 12
        
        # Compute Derived Features - use the same monthly payment calculated above
        debt_to_income = monthly_payment / total_income if total_income > 0 else 0  
        credit_amount_interaction = loan_amount * credit_history_num  # Interaction effect
        income_term_ratio = total_income / term_years if term_years > 0 else 0  # Avoid divide by zero
        
        # Return array with all 16 features
        return np.array([[
            gender_num, marital_status_num, number_of_dependents, education_num, self_employed_num,
            applicant_income, coapplicant_income, loan_amount, credit_history_num,
            total_income, debt_to_income, location_semiurban, location_urban, term_years,
            credit_amount_interaction, income_term_ratio
        ]])
    
    # Handle restart button click
    if restart_button:
        st.session_state.restart_clicked = True
        st.rerun()  # Using st.rerun() instead of st.experimental_rerun()
    
    # Display prediction
    if predict_button:
        with st.spinner("Processing your application..."):
            input_data = preprocess_input()
            prediction = model.predict(input_data)
            
            # Apply additional rules to override the model in certain cases
            manual_rejection = False
            rejection_reason = ""
            
            # Rule-based rejections that override the model
            if total_income < 1500:
                manual_rejection = True
                rejection_reason = "Insufficient income (below $1,500 monthly minimum)"
            elif dti_percent > 50:  # Very high DTI is an automatic rejection
                manual_rejection = True
                rejection_reason = "Debt-to-income ratio too high (exceeds 50%)"
            elif credit_history == 0 and dti_percent > 35:
                manual_rejection = True  
                rejection_reason = "Combination of unsettled loans and high debt-to-income ratio"
            
            # Final decision combines model prediction and manual eligibility checks
            final_approval = (prediction[0] == 1) and not manual_rejection
            
            # Show result with enhanced styling
            if final_approval:
                st.markdown("""
                <div class="result-approved">
                    <h3 style="color: #2E7D32;">✅ Loan Approved</h3>
                    <p>Congratulations! Based on your information, you're eligible for this loan.</p>
                </div>
                """, unsafe_allow_html=True)
            else:
                st.markdown(f"""
                <div class="result-rejected">
                    <h3 style="color: #C62828;">❌ Loan Not Approved</h3>
                    <p>Unfortunately, based on your current information, we cannot approve your loan application.</p>
                    <p><strong>Primary reason:</strong> {rejection_reason if manual_rejection else "Multiple factors considered by our approval algorithm"}</p>
                    <p>Consider improving your credit score, reducing existing debt, or applying with a co-applicant with higher income.</p>
                </div>
                """, unsafe_allow_html=True)

with tab2:
    st.markdown("""
    <div class="section-card">
        <h3>About the Loan Approval System</h3>
        <p>This AI-powered system uses advanced machine learning algorithms to determine loan approval eligibility based on multiple factors.</p>
    </div>
    """, unsafe_allow_html=True)
    
    st.markdown("<h4>How it works</h4>", unsafe_allow_html=True)
    st.write("The system analyzes various factors including:")
    st.markdown("""
    - Personal and financial information
    - Credit history status
    - Loan amount and term
    - Income and employment status
    - Debt-to-income ratio
    """)
    
    st.write("""
    Our decision engine combines a trained machine learning model with industry-standard lending criteria. 
    The system evaluates your application against patterns from thousands of previous loan applications 
    while also applying standard financial rules used by major lenders.
    """)
    
    st.markdown('<div class="section-card">', unsafe_allow_html=True)
    st.markdown("<h3>Important Factors for Approval</h3>", unsafe_allow_html=True)
    st.write("To maximize your chances of approval:")
    st.markdown("""
    - Maintain a debt-to-income ratio below 43%
    - Have sufficient monthly income (minimum $1,500)
    - Clear existing unsettled loans when possible
    - Consider adding a co-applicant to strengthen your application
    """)
    st.markdown('</div>', unsafe_allow_html=True)
    
    st.markdown('<div class="section-card">', unsafe_allow_html=True)
    st.markdown("<h3>Key Features</h3>", unsafe_allow_html=True)
    st.write("Our system provides:")
    st.markdown("""
    - Instant loan approval decisions
    - Transparent evaluation process
    - Detailed eligibility assessment
    - Secure data handling
    """)
    st.markdown('</div>', unsafe_allow_html=True)

# Footer
st.markdown("""
<div class="footer">
    <p>© 2025 AI-Powered Loan Approval System | <a href="#" style="color: #7950F2;">Terms of Service</a> | <a href="#" style="color: #7950F2;">Privacy Policy</a></p>
</div>
""", unsafe_allow_html=True)