app.py

import sys

try:
    import streamlit as st
    import torch
    import os
    from SeqXGPT.model import TransformerOnlyClassifier
    from SeqXGPT.generate_features import FeatureExtractor
    from SeqXGPT.transform import predict_with_model
except ImportError as e:
    print(f"Error importing required modules: {e}")
    print("Please make sure all dependencies are installed by running: pip install -r requirements.txt")
    sys.exit(1)

# Set page configuration
st.set_page_config(
    page_title="SeqXGPT - AI Text Detector",
    page_icon="🔍",
    layout="centered",
    initial_sidebar_state="collapsed"
)

id2label = {0: 'gpt2', 1: 'llama', 2: 'human', 3: 'gpt3re'}

@st.cache_resource
def load_extractor():
    return FeatureExtractor()

@st.cache_resource
def load_model(ckpt_name):
    """Unified model loading method"""
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    model = TransformerOnlyClassifier(id2labels=id2label, seq_len=1024)
    
    if not os.path.exists(ckpt_name):
        print(f"Warning: Checkpoint {ckpt_name} not found")
        return None
    
    try:
        state_dict = torch.load(
            ckpt_name,
            map_location=device,
            weights_only=True
        )
        model.load_state_dict(state_dict)
        model.to(device)
        model.eval()
        print(f"Model loaded from {ckpt_name}")
        return model
    except Exception as e:
        print(f"Error loading model: {e}")
        return None

# Initialize feature extractor
with st.spinner("Loading feature extractor and model..."):
    extractor = load_extractor()
    model = load_model('SeqXGPT/transformer_cls.pt')
    if model is None:
        st.error("Failed to load model checkpoint")

# Custom CSS for better appearance
st.markdown("""
<style>
    .main-header {
        font-size: 2.5rem;
        color: #2563eb;
        text-align: center;
        text-shadow: 1px 1px 2px rgba(0,0,0,0.1);
    }
    .sub-header {
        font-size: 1.2rem;
        color: #64748b;
        text-align: center;
        margin-bottom: 2rem;
    }
    .result-box {
        padding: 1.5rem;
        border-radius: 0.75rem;
        margin: 1rem 0;
        box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1);
        color: #333333;
    }
    .human-text {
        background-color: #c6f6d5;
        border-left: 5px solid #059669;
        border-bottom: 1px solid rgba(5,150,105,0.1);
    }
    .ai-text {
        background-color: #fed7d7;
        border-left: 5px solid #dc2626;
        border-bottom: 1px solid rgba(220,38,38,0.1);
    }
</style>
""", unsafe_allow_html=True)

# App header
st.markdown("<h1 class='main-header'>SeqXGPT</h1>", unsafe_allow_html=True)
st.markdown("<p class='sub-header'>AI Text Detection Made Simple</p>", unsafe_allow_html=True)

# Text input area
text_input = st.text_area("Enter text to analyze:", height=200, 
                          placeholder="Paste or type text here to check if it's AI-generated...")

# Analysis button
if st.button("Analyze Text", type="primary", use_container_width=True):
    if not text_input or len(text_input.strip()) < 50:
        st.error("Please enter at least 50 characters.")
    else:
        with st.spinner("Analyzing text..."):
            try:
                # Extract features
                features = extractor.extract_features(text_input)
                
                # Make prediction
                result = predict_with_model(model, features, id2label)
                
                # Get prediction and confidence
                prediction = result['text_prediction']
                logits = result['token_logits']
                
                # Calculate confidence score
                confidence = (result['token_predictions'].count(prediction) / len(result['token_predictions'])) * 100
                
                # Display results
                st.markdown("### Analysis Results")
                
                # Progress bar for confidence
                st.progress(min(max(confidence/100, 0.0), 1.0))
                
                # Verdict based on prediction
                if prediction in ['gpt2', 'llama', 'gpt3re']:
                    st.markdown(f"""
                    <div class='result-box ai-text'>
                        <h3>🤖 Likely AI-Generated ({confidence:.1f}%)</h3>
                        <p>This text shows strong indicators of being generated by {prediction.upper()}.</p>
                    </div>
                    """, unsafe_allow_html=True)
                elif prediction == 'human':
                    st.markdown(f"""
                    <div class='result-box human-text'>
                        <h3>👤 Likely Human-Written ({confidence:.1f}%)</h3>
                        <p>This text appears to be written by a human.</p>
                    </div>
                    """, unsafe_allow_html=True)
                else:
                    st.markdown(f"""
                    <div class='result-box'>
                        <h3>⚠️ Uncertain ({confidence:.1f}%)</h3>
                        <p>Unable to confidently determine if this text is AI-generated or human-written.</p>
                    </div>
                    """, unsafe_allow_html=True)
                
            except Exception as e:
                st.error(f"An error occurred during analysis: {str(e)}")
                st.info("Try with a different text or check if the model is properly loaded.")

# Footer
st.markdown("---")
st.markdown("SeqXGPT is an AI text detection tool that analyzes text patterns to identify AI-generated content.")