import streamlit as st
from transformers import MarianMTModel, MarianTokenizer

# Supported models for different language pairs
MODELS = {
    'French': "Helsinki-NLP/opus-mt-en-fr",
    'Spanish': "Helsinki-NLP/opus-mt-en-es",
    'German': "Helsinki-NLP/opus-mt-en-de",
    'Chinese': "Helsinki-NLP/opus-mt-en-zh",
    'Russian': "Helsinki-NLP/opus-mt-en-ru",
    'Japanese': "Helsinki-NLP/opus-mt-en-ja",
    'Arabic': "Helsinki-NLP/opus-mt-en-ar",
    'Urdu': "Helsinki-NLP/opus-mt-en-ur",
    'Hindi': "Helsinki-NLP/opus-mt-en-hi",
    'Bengali': "Helsinki-NLP/opus-mt-en-bn",
}

# Language codes for different models
LANG_CODE_MAP = {
    'French': 'fr',
    'Spanish': 'es',
    'German': 'de',
    'Chinese': 'zh',
    'Russian': 'ru',
    'Japanese': 'ja',
    'Arabic': 'ar',
    'Urdu': 'ur',
    'Hindi': 'hi',
    'Bengali': 'bn',
}

def translate_text(text, target_lang):
    # Load the appropriate model and tokenizer for the target language
    model_name = MODELS.get(target_lang)
    if not model_name:
        return "Error: Language not supported."

    model = MarianMTModel.from_pretrained(model_name)
    tokenizer = MarianTokenizer.from_pretrained(model_name)
    
    # Encode the text
    encoded_text = tokenizer(text, return_tensors="pt")
    
    # Language code for forced_bos_token_id
    lang_code = LANG_CODE_MAP.get(target_lang)
    if not lang_code:
        return "Error: Language code not found."
    
    # Translate text
    translated = model.generate(**encoded_text, forced_bos_token_id=tokenizer.convert_tokens_to_ids(lang_code))
    
    # Decode the translated text
    translated_text = tokenizer.decode(translated[0], skip_special_tokens=True)
    return translated_text

# Streamlit app
st.title('Language Translator')

# Input text and language selection
text_to_translate = st.text_area("Enter text to translate")
target_language = st.selectbox("Select target language", list(MODELS.keys()))

# Translate button
if st.button('Translate'):
    if text_to_translate:
        translated_text = translate_text(text_to_translate, target_language)
        st.write(f"Translated text ({target_language}): {translated_text}")
    else:
        st.error("Please enter text to translate.")