app.py

import streamlit as st
from transformers import T5Tokenizer, T5ForConditionalGeneration, AutoTokenizer, AutoModelForSeq2SeqLM, pipeline, logging
import torch
import os
import httpx

logging.set_verbosity_error()
device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')

def download_argos_model(from_code, to_code):
    import argostranslate.package
    print('Downloading model', from_code, to_code) 
    # Download and install Argos Translate package
    argostranslate.package.update_package_index()
    available_packages = argostranslate.package.get_available_packages()
    package_to_install = next(
        filter(
            lambda x: x.from_code == from_code and x.to_code == to_code, available_packages
        )
    )
    argostranslate.package.install_from_path(package_to_install.download())

# App layout
st.header("Text Machine Translation")
input_text = st.text_input("Enter text to translate:")

# Language options and mappings
options = ["German", "Romanian", "English", "French", "Spanish", "Italian"]
langs = {"English": "en", "Romanian": "ro", "German": "de", "French": "fr", "Spanish": "es", "Italian": "it"}
models = ["Helsinki-NLP", "Argos", "t5-base", "t5-small", "t5-large", "Unbabel/Tower-Plus-2B", 
          "Unbabel/TowerInstruct-Mistral-7B-v0.2", "Google"]

# Initialize session state if not already set
if "sselected_language" not in st.session_state:
    st.session_state["sselected_language"] = options[0]
if "tselected_language" not in st.session_state:
    st.session_state["tselected_language"] = options[1]
if "model_name" not in st.session_state:
    st.session_state["model_name"] = models[1]

# Model selection FIRST
model_name = st.selectbox("Select a model:", models, 
                          index=models.index(st.session_state["model_name"]))

# Create columns for language selection
scol, swapcol, tcol = st.columns([3, 1, 3])

with scol:
    sselected_language = st.selectbox("Source language:", options, 
                                      index=options.index(st.session_state["sselected_language"]))
with swapcol:
    if st.button("🔄 Swap"):
        st.session_state["model_name"] = model_name  # Preserve model
        st.session_state["sselected_language"], st.session_state["tselected_language"] = \
            st.session_state["tselected_language"], st.session_state["sselected_language"]
        st.rerun()
with tcol:
    tselected_language = st.selectbox("Target language:", options, 
                                      index=options.index(st.session_state["tselected_language"]))

# Language codes
sl = langs[st.session_state["sselected_language"]]
tl = langs[st.session_state["tselected_language"]]

# Store selections
st.session_state["sselected_language"] = sselected_language
st.session_state["tselected_language"] = tselected_language
st.session_state["model_name"] = model_name

if model_name == 'Helsinki-NLP':
    try:
        model_name = f"Helsinki-NLP/opus-mt-{sl}-{tl}"
        tokenizer = AutoTokenizer.from_pretrained(model_name)
        model = AutoModelForSeq2SeqLM.from_pretrained(model_name)
    except EnvironmentError:
        model_name = f"Helsinki-NLP/opus-tatoeba-{sl}-{tl}"
        tokenizer = AutoTokenizer.from_pretrained(model_name)
        model = AutoModelForSeq2SeqLM.from_pretrained(model_name)
if model_name.startswith('t5'):
    tokenizer = T5Tokenizer.from_pretrained(model_name)
    model = T5ForConditionalGeneration.from_pretrained(model_name).to(device)

st.write("Selected language combination:", sselected_language, " - ", tselected_language, "Selected model:", model_name)
submit_button = st.button("Translate")
translated_textarea = st.text("")

# Handle the submit button click
if submit_button:
    if model_name.startswith('Helsinki-NLP'):
        prompt = input_text
        print(prompt)
        input_ids = tokenizer.encode(prompt, return_tensors='pt')
        # Perform translation
        output_ids = model.generate(input_ids)
        # Decode the translated text
        translated_text = tokenizer.decode(output_ids[0], skip_special_tokens=True)
    elif model_name.startswith('Google'): 
        url = os.environ['GCLIENT'] + f'sl={sl}&tl={tl}&q={input_text}'
        response = httpx.get(url)
        translated_text = response.json()[0][0][0]
        print(response.json()[0][0])
    elif model_name.startswith('t5'):
        prompt = f'translate {sselected_language} to {tselected_language}: {input_text}'
        print(prompt)
        input_ids = tokenizer.encode(prompt, return_tensors='pt').to(device)
        # Perform translation
        output_ids = model.generate(input_ids)
        # Decode the translated text
        translated_text = tokenizer.decode(output_ids[0], skip_special_tokens=True)
    if 'Unbabel' in model_name:   
        pipe = pipeline("text-generation", model=model_name, torch_dtype=torch.bfloat16, device_map="auto")
        # We use the tokenizer’s chat template to format each message - see https://huggingface.co/docs/transformers/main/en/chat_templating
        messages = [{"role": "user",
                     "content": f"Translate the following text from {sselected_language} into {tselected_language}.\n{sselected_language}: {input_text}.\n{tselected_language}:"}]
        prompt = pipe.tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=False)
        outputs = pipe(prompt, max_new_tokens=256, do_sample=False)
        translated_text = outputs[0]["generated_text"]
        start_marker = "<end_of_turn>"
        if start_marker in translated_text:
            translated_text = translated_text.split(start_marker)[1].strip()
        translated_text = translated_text.replace('Answer:', '').strip() if translated_text.startswith('Answer:') else translated_text
    if 'Argos' in model_name:   
        import argostranslate.translate       
        # Translate
        try:
            download_argos_model(sl, tl)
            translated_text = argostranslate.translate.translate(input_text, sl, tl)
        except StopIteration:
            translated_text = f"No Argos model for {sselected_language} to {tselected_language}. Try other model or languages combination!"
        except Exception as error:
            translated_text = error
    # Display the translated text
    print(translated_text)
    st.write(f"Translated text from {sselected_language} to {tselected_language} using {model_name}:")
    translated_textarea = st.text(translated_text)