app.py

import gradio as gr
import re
import torch
from transformers import AutoTokenizer, AutoModelForSeq2SeqLM
from nltk.corpus import stopwords
import nltk

# Download NLTK stopwords
nltk.download('stopwords')
stop_words = set(stopwords.words('english'))

# Best lightweight summarization models
model_choices = {
    "DistilBART CNN (sshleifer/distilbart-cnn-12-6)": "sshleifer/distilbart-cnn-12-6",
    "T5 Small (t5-small)": "t5-small",
    "T5 Base (t5-base)": "t5-base",
    "Flan-T5 Base (google/flan-t5-base)": "google/flan-t5-base",
    "DistilBART XSum (sshleifer/distilbart-xsum-12-6)": "sshleifer/distilbart-xsum-12-6"
}

model_cache = {}

# Clean input text (remove stopwords and SKUs/product codes)
def clean_text(input_text):
    # Remove simple SKU codes (e.g., ST1642, AB1234, etc.)
    cleaned_text = re.sub(r'\b[A-Za-z]{2,}[0-9]{3,}\b', '', input_text)  # Alphanumeric SKU
    
    # Replace special characters with a space
    cleaned_text = re.sub(r'[^A-Za-z0-9\s]', ' ', cleaned_text)
    
    # Tokenize the input text and remove stop words
    words = cleaned_text.split()
    words = [word for word in words if word.lower() not in stop_words]
    
    # Rebuild the cleaned text
    cleaned_text = " ".join(words)
    
    # Strip leading and trailing spaces
    cleaned_text = cleaned_text.strip()
    
    return cleaned_text

# Load model and tokenizer
def load_model(model_name):
    if model_name not in model_cache:
        tokenizer = AutoTokenizer.from_pretrained(model_name)
        model = AutoModelForSeq2SeqLM.from_pretrained(
            model_name,
            torch_dtype=torch.float16 if torch.cuda.is_available() else torch.float32
        )
        device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
        model.to(device)

        # Warm-up
        dummy_input = tokenizer("summarize: warm up", return_tensors="pt").input_ids.to(device)
        model.generate(dummy_input, max_length=10)

        model_cache[model_name] = (tokenizer, model)
    return model_cache[model_name]

# Summarize the text using a selected model
def summarize_text(input_text, model_label, char_limit):
    if not input_text.strip():
        return "Please enter some text."

    input_text = clean_text(input_text)
    model_name = model_choices[model_label]
    tokenizer, model = load_model(model_name)

    if "t5" in model_name.lower() or "flan" in model_name.lower():
        input_text = "summarize: " + input_text

    device = model.device
    inputs = tokenizer(input_text, return_tensors="pt", truncation=True)
    input_ids = inputs["input_ids"].to(device)

    # Adjust the length constraints to make sure min_length < max_length
    max_len = 30  # Set your desired max length
    min_len = 5   # Ensure min_length is smaller than max_length

    # Generate summary
    summary_ids = model.generate(
        input_ids,
        max_length=max_len,
        min_length=min_len,
        do_sample=False
    )

    # Decode the summary
    summary = tokenizer.decode(summary_ids[0], skip_special_tokens=True)
    return summary[:char_limit].strip()

# Gradio UI
iface = gr.Interface(
    fn=summarize_text,
    inputs=[
        gr.Textbox(lines=6, label="Enter text to summarize"),
        gr.Dropdown(choices=list(model_choices.keys()), label="Choose summarization model", value="DistilBART CNN (sshleifer/distilbart-cnn-12-6)"),
        gr.Slider(minimum=30, maximum=200, value=80, step=1, label="Max Character Limit")
    ],
    outputs=gr.Textbox(lines=3, label="Summary (truncated to character limit)"),
    title="🚀 Fast Lightweight Summarizer (GPU Optimized)",
    description="Summarize text quickly using compact models ideal for low-latency and ZeroGPU Spaces."
)

iface.launch()