main.py

'''
        Created By Lewis Kamau Kimaru 
        Sema translator fastapi implementation
        January 2024
        Docker deployment
'''

from fastapi import FastAPI, HTTPException, Request, Depends
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import HTMLResponse
import uvicorn

from pydantic import BaseModel
from pymongo import MongoClient
import jwt
from jwt import encode as jwt_encode
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from bson import ObjectId

import ctranslate2
import sentencepiece as spm
import fasttext

import pytz
from datetime import datetime
import os

app = FastAPI()

origins = ["*"]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=False,
    allow_methods=["*"],
    allow_headers=["*"],
)

fasttext.FastText.eprint = lambda x: None

# set this key as an environment variable
os.environ["HUGGINGFACEHUB_API_TOKEN"] = st.secrets['huggingface_token']

# User interface
templates_folder = os.path.join(os.path.dirname(__file__), "templates")

# Authentication
class User(BaseModel):
 username: str = None # Make the username field optional
 email: str
 password: str

# Connect to the MongoDB database
client = MongoClient("mongodb://localhost:27017")
db = client["mydatabase"]
users_collection = db["users"]

# Secret key for signing the token
SECRET_KEY = "helloworld"
security = HTTPBearer()

#Implement the login route:

@app.post("/login")
def login(user: User):
 # Check if user exists in the database
 user_data = users_collection.find_one(
 {"email": user.email, "password": user.password}
 )
 if user_data:
     # Generate a token
     token = generate_token(user.email)
     # Convert ObjectId to string
     user_data["_id"] = str(user_data["_id"])
     # Store user details and token in local storage
     user_data["token"] = token
     return user_data
 return {"message": "Invalid email or password"}

#Implement the registration route:
@app.post("/register")
def register(user: User):
 # Check if user already exists in the database
 existing_user = users_collection.find_one({"email": user.email})
 if existing_user:
     return {"message": "User already exists"}
 #Insert the new user into the database
 user_dict = user.dict()
 users_collection.insert_one(user_dict)
 # Generate a token
 token = generate_token(user.email)
 # Convert ObjectId to string
 user_dict["_id"] = str(user_dict["_id"])
 # Store user details and token in local storage
 user_dict["token"] = token
 return user_dict


#Implement the `/api/user` route to fetch user data based on the JWT token
@app.get("/api/user")
def get_user(credentials: HTTPAuthorizationCredentials = Depends(security)):
 # Extract the token from the Authorization header
 token = credentials.credentials
 # Authenticate and retrieve the user data from the database based on the token
 # Here, you would implement the authentication logic and fetch user details
 # based on the token from the database or any other authentication mechanism
 # For demonstration purposes, assuming the user data is stored in local storage
 # Note: Local storage is not accessible from server-side code
 # This is just a placeholder to demonstrate the concept
 user_data = {
 "username": "John Doe",
 "email": "johndoe@example.com"
 }
if user_data["username"] and user_data["email"]:
 return user_data
raise HTTPException(status_code=401, detail="Invalid token")

#Define a helper function to generate a JWT token
def generate_token(email: str) -> str:
 payload = {"email": email}
 token = jwt_encode(payload, SECRET_KEY, algorithm="HS256")
 return token

    
# Get time of request

def get_time():
    nairobi_timezone = pytz.timezone('Africa/Nairobi')
    current_time_nairobi = datetime.now(nairobi_timezone)
    
    curr_day = current_time_nairobi.strftime('%A')
    curr_date = current_time_nairobi.strftime('%Y-%m-%d')
    curr_time = current_time_nairobi.strftime('%H:%M:%S')
    
    full_date = f"{curr_day} | {curr_date} | {curr_time}"
    return full_date, curr_time
    
# Load the model and tokenizer ..... only once!
beam_size = 1  # change to a smaller value for faster inference
device = "cpu"  # or "cuda"

# Language Prediction model
print("\nimporting Language Prediction model")
lang_model_file = "lid218e.bin"
lang_model_full_path = os.path.join(os.path.dirname(__file__), lang_model_file)
lang_model = fasttext.load_model(lang_model_full_path)


# Load the source SentencePiece model
print("\nimporting SentencePiece model")
sp_model_file = "spm.model"
sp_model_full_path = os.path.join(os.path.dirname(__file__), sp_model_file)
sp = spm.SentencePieceProcessor()
sp.load(sp_model_full_path)

# Import The Translator model
print("\nimporting Translator model")
ct_model_file = "sematrans-3.3B"
ct_model_full_path = os.path.join(os.path.dirname(__file__), ct_model_file)
translator = ctranslate2.Translator(ct_model_full_path, device)

print('\nDone importing models\n')

    
def translate_detect(userinput: str, target_lang: str):
    source_sents = [userinput]
    source_sents = [sent.strip() for sent in source_sents]
    target_prefix = [[target_lang]] * len(source_sents)

    # Predict the source language
    predictions = lang_model.predict(source_sents[0], k=1)
    source_lang = predictions[0][0].replace('__label__', '')

    # Subword the source sentences
    source_sents_subworded = sp.encode(source_sents, out_type=str)
    source_sents_subworded = [[source_lang] + sent + ["</s>"] for sent in source_sents_subworded]

    # Translate the source sentences
    translations = translator.translate_batch(
        source_sents_subworded,
        batch_type="tokens",
        max_batch_size=2024,
        beam_size=beam_size,
        target_prefix=target_prefix,
    )
    translations = [translation[0]['tokens'] for translation in translations]

    # Desubword the target sentences
    translations_desubword = sp.decode(translations)
    translations_desubword = [sent[len(target_lang):] for sent in translations_desubword]

    # Return the source language and the translated text
    return source_lang, translations_desubword

def translate_enter(userinput: str, source_lang: str, target_lang: str):  
  source_sents = [userinput]
  source_sents = [sent.strip() for sent in source_sents]
  target_prefix = [[target_lang]] * len(source_sents)

  # Subword the source sentences
  source_sents_subworded = sp.encode(source_sents, out_type=str)
  source_sents_subworded = [[source_lang] + sent + ["</s>"] for sent in source_sents_subworded]

  # Translate the source sentences
  translations = translator.translate_batch(source_sents_subworded, batch_type="tokens", max_batch_size=2024, beam_size=beam_size, target_prefix=target_prefix)
  translations = [translation[0]['tokens'] for translation in translations]

  # Desubword the target sentences
  translations_desubword = sp.decode(translations)
  translations_desubword = [sent[len(target_lang):] for sent in translations_desubword]

  # Return the source language and the translated text
  return translations_desubword[0]

    
@app.get("/", response_class=HTMLResponse)
async def read_root(request: Request):
    return HTMLResponse(content=open(os.path.join(templates_folder, "translator.html"), "r").read(), status_code=200)

    
@app.post("/translate_detect/")
async def translate_detect_endpoint(request: Request):
    datad = await request.json()
    userinputd = datad.get("userinput")
    target_langd = datad.get("target_lang")
    dfull_date = get_time()[0]
    print(f"\nrequest: {dfull_date}\nTarget Language; {target_langd}, User Input: {userinputd}\n")

    if not userinputd or not target_langd:
        raise HTTPException(status_code=422, detail="Both 'userinput' and 'target_lang' are required.")

    source_langd, translated_text_d = translate_detect(userinputd, target_langd)
    dcurrent_time = get_time()[1]
    print(f"\nresponse: {dcurrent_time}; ... Source_language: {source_langd}, Translated Text: {translated_text_d}\n\n")
    return {
        "source_language": source_langd,
        "translated_text": translated_text_d[0],
    }


@app.post("/translate_enter/")
async def translate_enter_endpoint(request: Request):
    datae = await request.json()
    userinpute = datae.get("userinput")
    source_lange = datae.get("source_lang")
    target_lange = datae.get("target_lang")
    efull_date = get_time()[0]
    print(f"\nrequest: {efull_date}\nSource_language; {source_lange}, Target Language; {target_lange}, User Input: {userinpute}\n")

    if not userinpute or not target_lange:
        raise HTTPException(status_code=422, detail="'userinput' 'sourc_lang'and 'target_lang' are required.")

    translated_text_e = translate_enter(userinpute, source_lange, target_lange)
    ecurrent_time = get_time()[1]
    print(f"\nresponse: {ecurrent_time}; ... Translated Text: {translated_text_e}\n\n")
    return {
        "translated_text": translated_text_e,
    }


print("\nAPI starting .......\n")