import streamlit as st
import torch
import os
import time
from threading import Thread
from transformers import AutoTokenizer, AutoModelForCausalLM, TextIteratorStreamer
from langchain_community.document_loaders import PyPDFLoader, TextLoader
from langchain_text_splitters import RecursiveCharacterTextSplitter
from langchain_community.embeddings import HuggingFaceEmbeddings
from langchain.vectorstores import FAISS
from langchain.schema import Document

# --- HF Token ---
HF_TOKEN = st.secrets["HF_TOKEN"]

# --- Page Config ---
st.set_page_config(page_title="DigiTwin RAG", page_icon="📂", layout="centered")
st.title("📂 DigiTs the Twin")

# --- Upload Files Sidebar ---
with st.sidebar:
    st.header("📄 Upload Knowledge Files")
    uploaded_files = st.file_uploader("Upload PDFs or .txt files", accept_multiple_files=True, type=["pdf", "txt"])
    if uploaded_files:
        st.success(f"{len(uploaded_files)} file(s) uploaded")

# --- Model Loading ---
@st.cache_resource
def load_model():
    tokenizer = AutoTokenizer.from_pretrained("amiguel/GM_Qwen1.8B_Finetune", trust_remote_code=True, token=HF_TOKEN)
    model = AutoModelForCausalLM.from_pretrained(
        "amiguel/GM_Qwen1.8B_Finetune",
        device_map="auto",
        torch_dtype=torch.bfloat16 if torch.cuda.is_bf16_supported() else torch.float32,
        trust_remote_code=True,
        token=HF_TOKEN
    )
    return model, tokenizer

model, tokenizer = load_model()

# --- Prompt Helper ---
SYSTEM_PROMPT = (
    "You are DigiTwin, an expert advisor in asset integrity and reliability engineering. "
    "Use the provided context from uploaded documents to answer precisely and professionally."
)

def build_prompt(messages, context=""):
    prompt = f"<|im_start|>system\n{SYSTEM_PROMPT}\n\nContext:\n{context}<|im_end|>\n"
    for msg in messages:
        role = msg["role"]
        prompt += f"<|im_start|>{role}\n{msg['content']}<|im_end|>\n"
    prompt += "<|im_start|>assistant\n"
    return prompt


# --- RAG Embedding and Search ---
@st.cache_resource
def embed_uploaded_files(files):
    raw_docs = []
    for f in files:
        file_path = f"/tmp/{f.name}"
        with open(file_path, "wb") as out_file:
            out_file.write(f.read())

        loader = PyPDFLoader(file_path) if f.name.endswith(".pdf") else TextLoader(file_path)
        raw_docs.extend(loader.load())

    splitter = RecursiveCharacterTextSplitter(chunk_size=512, chunk_overlap=64)
    chunks = splitter.split_documents(raw_docs)
    embeddings = HuggingFaceEmbeddings(model_name="sentence-transformers/all-MiniLM-L6-v2")
    db = FAISS.from_documents(chunks, embedding=embeddings)
    return db

retriever = embed_uploaded_files(uploaded_files) if uploaded_files else None

# --- Streaming Response ---
def generate_response(prompt_text):
    streamer = TextIteratorStreamer(tokenizer, skip_prompt=True, skip_special_tokens=True)
    inputs = tokenizer(prompt_text, return_tensors="pt").to(model.device)
    thread = Thread(target=model.generate, kwargs={
        "input_ids": inputs["input_ids"],
        "attention_mask": inputs["attention_mask"],
        "max_new_tokens": 1024,
        "temperature": 0.7,
        "top_p": 0.9,
        "repetition_penalty": 1.1,
        "do_sample": True,
        "streamer": streamer
    })
    thread.start()
    return streamer

# --- Avatars & Messages ---
USER_AVATAR = "https://raw.githubusercontent.com/achilela/vila_fofoka_analysis/9904d9a0d445ab0488cf7395cb863cce7621d897/USER_AVATAR.png"
BOT_AVATAR = "https://raw.githubusercontent.com/achilela/vila_fofoka_analysis/991f4c6e4e1dc7a8e24876ca5aae5228bcdb4dba/Ataliba_Avatar.jpg"

if "messages" not in st.session_state:
    st.session_state.messages = []

for msg in st.session_state.messages:
    avatar = USER_AVATAR if msg["role"] == "user" else BOT_AVATAR
    with st.chat_message(msg["role"], avatar=avatar):
        st.markdown(msg["content"])

# --- Chat UI ---
if prompt := st.chat_input("Ask something based on uploaded documents..."):
    st.chat_message("user", avatar=USER_AVATAR).markdown(prompt)
    st.session_state.messages.append({"role": "user", "content": prompt})

    context = ""
    if retriever:
        docs = retriever.similarity_search(prompt, k=3)
        context = "\n\n".join([d.page_content for d in docs])

    full_prompt = build_prompt(st.session_state.messages, context=context)

    with st.chat_message("assistant", avatar=BOT_AVATAR):
        start_time = time.time()
        streamer = generate_response(full_prompt)
        container = st.empty()
        answer = ""
        for chunk in streamer:
            answer += chunk
            container.markdown(answer + "▌", unsafe_allow_html=True)
        container.markdown(answer)
        st.session_state.messages.append({"role": "assistant", "content": answer})