app.py

import streamlit as st
import torch
import dill
import json
import re
from transformers import AutoTokenizer, AutoModelForSequenceClassification
import time
from models.spam_model import SpamNaiveBayes


# use cpu
device = torch.device("cpu")

# for tokenizing text
def tokenize(text):
    return re.findall(r"\w+|[!?.]", str(text).lower())

# for encoding text
def encode_text(text, vocab, max_len=40):
    toks = tokenize(text)
    ids = [vocab.get(t, 1) for t in toks[:max_len]]
    return ids + [0]*(max_len - len(ids))

# function for loading all 4 models
@st.cache_resource # cache so it doesn't reload everytime
def load_models():
    # load vocab for CNN and BiLSTM
    with open('./models/vocab.json', 'r') as f:
        vocab = json.load(f)

    # load Naive Bayes
    with open('./models/model_nb.pkl', 'rb') as f:
        nb_model = dill.load(f)

    # load CNN and BiLSTM
    cnn_model = torch.jit.load("./models/model_cnn.pt", map_location=device)
    lstm_model = torch.jit.load("./models/model_bilstm.pt", map_location=device)

    # load distilBert
    bert_tokenizer = AutoTokenizer.from_pretrained("./models/DistilBert")
    bert_model = AutoModelForSequenceClassification.from_pretrained("./models/DistilBert")

    return vocab, nb_model, cnn_model, lstm_model, bert_tokenizer, bert_model
    
# load everything
try:
    vocab, nb_model, cnn, lstm, bert_tok, bert = load_models()
    st.toast("System Ready!", icon="✅")
except Exception as e:
    st.error(f"Failed to load models. Error: {e}")
    st.stop()

## Streamlit Logic
st.title("Spam Message Classifier")
st.markdown("Compare 4 different AI architectures on the same message.")

# textbox
text = st.text_area("Enter Message:", "Congratulations! You've won a $1000 Walmart gift card. Click here to claim.")

# sidebar
with st.sidebar:
    st.header("About Project")
    st.write("The goal of this project is to compare Traditional Machine Learning vs. Deep Learning models for text classification.")
    st.divider()
    st.link_button("Dataset", "https://huggingface.co/datasets/mshenoda/spam-messages")

if st.button("Analyze Message", type="primary"):
    col1, col2 = st.columns(2)
    col3, col4 = st.columns(2)
    
    # Naive Bayes
    start = time.time()
    nb_res = nb_model.predict(text)
    end = time.time()
    lbl = "SPAM" if nb_res == 1 else "HAM"
    col1.metric("Naive Bayes", lbl, f"{(end-start)*1000:.1f} ms")
    
    # Prepare for CNN and LSTM
    input_ids = torch.tensor([encode_text(text, vocab)]).to(device)
    
    # CNN 
    start = time.time()
    with torch.no_grad():
        cnn_res = cnn(input_ids).argmax(1).item()
    end = time.time()
    lbl = "SPAM" if cnn_res == 1 else "HAM"
    col2.metric("CNN", lbl, f"{(end-start)*1000:.1f} ms")

    # BiLSTM
    start = time.time()
    with torch.no_grad():
        lstm_res = lstm(input_ids).argmax(1).item()
    end = time.time()
    lbl = "SPAM" if lstm_res == 1 else "HAM"
    col3.metric("BiLSTM", lbl, f"{(end-start)*1000:.1f} ms")

    # DistilBert
    start = time.time()
    inputs = bert_tok(text, return_tensors="pt", padding=True, truncation=True).to(device)
    with torch.no_grad():
        logits = bert(**inputs).logits
        bert_res = logits.argmax().item()
    end = time.time()
    lbl = "SPAM" if bert_res == 1 else "HAM"
    col4.metric("DistilBERT", lbl, f"{(end-start)*1000:.1f} ms")

with st.expander("View Model Details"):
    st.markdown("""
    * **Naive Bayes:** A traditional **Machine Learning** model that uses probability statistics (Bayes' Theorem) to predict spam based on simple word counts.
    * **CNN:** A **Deep Learning** model that uses sliding "filters" to detect specific patterns of words (like "free prize"), similar to how it detects edges in images.
    * **BiLSTM:** A **Recurrent Neural Network (RNN)** that reads the message forwards and backwards simultaneously to understand the context and sequence of words.
    * **DistilBERT:** A **Transformer** model that uses "Self-Attention" to understand the complex meaning and relationship between every word in the sentence.
    """)