app.py

from fastapi import FastAPI, HTTPException
from transformers import pipeline
import langdetect
import logging
import os
from typing import Optional

# Set environment variables for Hugging Face cache
os.environ["HF_HOME"] = "/app/cache"
os.environ["TRANSFORMERS_CACHE"] = "/app/cache"

app = FastAPI()

# Configure logging
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# Map of supported language models
MODEL_MAP = {
    "id": "Helsinki-NLP/opus-mt-id-en",
    "th": "Helsinki-NLP/opus-mt-th-en",
    "fr": "Helsinki-NLP/opus-mt-fr-en",
    "es": "Helsinki-NLP/opus-mt-es-en",
    "ja": "Helsinki-NLP/opus-mt-ja-en",
    "zh": "Helsinki-NLP/opus-mt-zh-en",
    "vi": "Helsinki-NLP/opus-mt-vi-en",
}

# List of terms to protect from translation
PROTECTED_TERMS = ["2030 Aspirations"]

translators = {}
try:
    for lang, model_name in MODEL_MAP.items():
        logger.info(f"Loading model for {lang} from {model_name}...")
        translators[lang] = pipeline("translation", model=model_name)
        logger.info(f"Model for {lang} loaded successfully.")
except Exception as e:
    logger.error(f"Model initialization failed: {str(e)}")
    raise Exception(f"Model initialization failed: {str(e)}")

def detect_language(text: str) -> str:
    try:
        detected_lang = langdetect.detect(text)
        logger.info(f"langdetect raw result: '{detected_lang}' for text: '{text[:50]}...'")
        if detected_lang.startswith('zh'):
            logger.info(f"Normalizing '{detected_lang}' to 'zh' for Mandarin.")
            return 'zh'
        final_lang = detected_lang if detected_lang in MODEL_MAP else "en"
        logger.info(f"Final determined language: '{final_lang}'. (Based on raw detected: '{detected_lang}')")
        return final_lang
    except Exception as e:
        logger.warning(f"Language detection FAILED for text: '{text[:50]}...'. Error: {str(e)}. Defaulting to English.")
        return "en"

def protect_terms(text: str, protected_terms: list) -> tuple[str, dict]:
    """
    Replace protected terms with placeholders to prevent translation.
    Returns the modified text and a dictionary mapping placeholders to original terms.
    """
    modified_text = text
    replacements = {}
    for i, term in enumerate(protected_terms):
        placeholder = f"__PROTECTED_{i}__"
        replacements[placeholder] = term
        modified_text = modified_text.replace(term, placeholder)
    return modified_text, replacements

def restore_terms(text: str, replacements: dict) -> str:
    """
    Restore protected terms in the translated text using the replacements dictionary.
    """
    restored_text = text
    for placeholder, term in replacements.items():
        restored_text = restored_text.replace(placeholder, term)
    return restored_text

@app.post("/translate")
async def translate(text: str, source_lang_override: Optional[str] = None):
    """
    Translate text to English, preserving protected terms like '2030 Aspirations'.
    Automatically detects source language or uses override.
    """
    if not text:
        raise HTTPException(status_code=400, detail="Text input is required.")

    try:
        # Determine source language
        if source_lang_override and source_lang_override in MODEL_MAP:
            source_lang = source_lang_override
            logger.info(f"Source language overridden by user to: '{source_lang_override}'.")
        else:
            source_lang = detect_language(text)
            logger.info(f"Determined source language for translation: '{source_lang}'.")

        # If source language is English, return original text
        if source_lang == "en":
            logger.info("Source language is English or unrecognized, returning original text.")
            return {"translated_text": text}

        # Get translator
        translator = translators.get(source_lang)
        if not translator:
            logger.error(f"No translator found for language: '{source_lang}'.")
            raise HTTPException(
                status_code=400,
                detail=f"Translation not supported for language: {source_lang}."
            )

        # Protect terms before translation
        modified_text, replacements = protect_terms(text, PROTECTED_TERMS)
        logger.info(f"Text after protecting terms: '{modified_text[:50]}...'")

        # Perform translation
        logger.info(f"Translating text from '{source_lang}' to English...")
        result = translator(modified_text)
        translated_text = result[0]["translation_text"]
        logger.info(f"Translation successful. Original: '{modified_text[:50]}...', Translated: '{translated_text[:50]}...'")

        # Restore protected terms
        final_text = restore_terms(translated_text, replacements)
        logger.info(f"Final translated text with restored terms: '{final_text[:50]}...'")

        return {"translated_text": final_text}
    except HTTPException as e:
        raise e
    except Exception as e:
        logger.error(f"An unexpected error occurred during processing: {str(e)}", exc_info=True)
        raise HTTPException(status_code=500, detail=f"Processing failed: {str(e)}")