main.py

from fastapi import FastAPI, Form, Depends, Request, File, UploadFile
from fastapi.encoders import jsonable_encoder
from fastapi.responses import JSONResponse
from fastapi.middleware.cors import CORSMiddleware
import os
import pypdf

from langchain.text_splitter import RecursiveCharacterTextSplitter
from pymilvus import MilvusClient, db, utility, Collection, CollectionSchema, FieldSchema, DataType
from sentence_transformers import SentenceTransformer
import torch
from milvus_singleton import MilvusClientSingleton


os.environ['HF_HOME'] = '/app/cache'
os.environ['HF_MODULES_CACHE'] = '/app/cache/hf_modules'
embedding_model = SentenceTransformer('Alibaba-NLP/gte-large-en-v1.5', 
                                      trust_remote_code=True, 
                                      device='cuda' if torch.cuda.is_available() else 'cpu',
                                      cache_folder='/app/cache'
)
collection_name="rag"


global milvus_client
milvus_client = MilvusClientSingleton.get_instance(uri="/app/milvus_data/milvus_demo.db")

def document_to_embeddings(content:str) -> list:
    return embedding_model.encode(content, show_progress_bar=True)

app = FastAPI()

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # Replace with the list of allowed origins for production
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

def split_documents(document_data):
    splitter = RecursiveCharacterTextSplitter(chunk_size=512, chunk_overlap=10)
    return splitter.split_documents(document_data)

def create_a_collection(milvus_client, collection_name):
    content = FieldSchema(name="content", dtype=DataType.VARCHAR, max_length=4096)
    vector = FieldSchema(name="vector", dtype=DataType.FLOAT_VECTOR, dim=1024)

    schema = CollectionSchema([
        content, vector
    ])

    vector_index = {
        "index_type": "IVF_FLAT",
        "metric_type": "COSINE",
        "params": {
            "nlist": 128
        }
    }
    
    milvus_client.create_collection(
        collection_name=collection_name,
        schema=schema,
        index_params=vector_index,
    )

@app.get("/")
async def root():
    return {"message": "Hello World"}

@app.post("/insert")
async def insert(file: UploadFile = File(...)):
    contents = await file.read()

    if not milvus_client.has_collection(collection_name):
        create_a_collection(milvus_client, collection_name)

    contents = pypdf.PdfReader(contents)
    
    splitted_document_data = split_documents(contents)

    print(splitted_document_data)

    data_objects = []
    for doc in splitted_document_data:
        data = {
            "vector": document_to_embeddings(doc.page_content),
            "content": doc.page_content,
        }
        data_objects.append(data)

    print(data_objects)

    try:
        milvus_client.insert(collection_name=collection_name, data=data_objects)

    except Exception as e:
        raise JSONResponse(status_code=500, content={"error": str(e)})
    else:
        return JSONResponse(status_code=200, content={"result": 'good'})
    
@app.post("/rag")
async def insert(question):
    if not question:
        return JSONResponse(status_code=400, content={"message": "Please a question!"})
    
    try:
        search_res = milvus_client.search(
            collection_name=collection_name,
            data=[
                document_to_embeddings(question)
            ], 
            limit=5,  # Return top 3 results
            search_params={"metric_type": "COSINE"},  # Inner product distance
            output_fields=["content"],  # Return the text field
        )

        retrieved_lines_with_distances = [
            (res["entity"]["content"]) for res in search_res[0]
        ]
        return JSONResponse(status_code=200, content={"result": retrieved_lines_with_distances[0]})
    except Exception as e:
        return JSONResponse(status_code=400, content={"error": str(e)})