app.py

import os
import uuid
import threading
import logging
from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
from pydantic import BaseModel
from llama_cpp import Llama
from fastapi.middleware.cors import CORSMiddleware
from huggingface_hub import hf_hub_download
from contextlib import asynccontextmanager

# --- Setup ---
logging.basicConfig(level=logging.INFO)

# --- MODEL MAP (Using the smarter Phi-3) ---
MODEL_MAP = {
    "light": {
        "repo_id": "microsoft/Phi-3-mini-4k-instruct-gguf",
        "filename": "Phi-3-mini-4k-instruct-q4.gguf" # 2.13 GB
    },
    "medium": {
        "repo_id": "TheBloke/DeepSeek-LLM-7B-Chat-GGUF",
        "filename": "deepseek-llm-7b-chat.Q4_K_M.gguf" # 4.08 GB
    },
    "heavy": {
        "repo_id": "TheBloke/DeepSeek-LLM-7B-Chat-GGUF",
        "filename": "deepseek-llm-7b-chat.Q5_K_M.gguf" # 4.78 GB
    }
}

# --- GLOBAL CACHE & LOCKS ---
llm_cache = {} 
model_lock = threading.Lock() # Ensures only one model loads at a time
llm_lock = threading.Lock() # Ensures only one generation job runs at a time
JOBS = {} # Our in-memory "database" for background jobs

# --- Helper: Load Model ---
def get_llm_instance(choice: str) -> Llama:
    with model_lock:
        if choice not in MODEL_MAP:
            logging.error(f"Invalid model choice: {choice}")
            return None
        if choice in llm_cache:
            logging.info(f"Using cached model: {choice}")
            return llm_cache[choice]

        model_info = MODEL_MAP[choice]
        repo_id = model_info["repo_id"]
        filename = model_info["filename"]
        
        try:
            logging.info(f"Downloading model: {filename} from {repo_id}")
            model_path = hf_hub_download(repo_id=repo_id, filename=filename)
            logging.info(f"Model downloaded to: {model_path}")
            
            logging.info("Loading model into memory...")
            llm = Llama(
                model_path=model_path,
                n_ctx=4096,       
                n_threads=2,      
                n_gpu_layers=0,   
                verbose=True
            )
            
            llm_cache.clear() 
            llm_cache[choice] = llm
            logging.info(f"Model {choice} loaded successfully.")
            return llm
            
        except Exception as e:
            logging.critical(f"CRITICAL ERROR: Failed to download/load model {filename}. Error: {e}", exc_info=True)
            return None

# --- Helper: The Background AI Task ---
def run_generation_in_background(job_id: str, model_choice: str, prompt: str):
    """
    This function runs in a separate thread.
    It performs the long-running AI generation.
    """
    global JOBS
    try:
        logging.info(f"Job {job_id}: Waiting to acquire LLM lock...")
        with llm_lock:
            logging.info(f"Job {job_id}: Lock acquired. Loading model.")
            llm = get_llm_instance(model_choice)
            if llm is None:
                raise Exception("Model could not be loaded.")
            
            JOBS[job_id]["status"] = "processing"
            logging.info(f"Job {job_id}: Processing prompt...")
            
            output = llm(
                prompt,
                max_tokens=512,
                stop=["<|user|>", "<|endoftext|>", "user:"],
                echo=False
            )
            
            generated_text = output["choices"][0]["text"].strip()
            
            JOBS[job_id]["status"] = "complete"
            JOBS[job_id]["result"] = generated_text
            logging.info(f"Job {job_id}: Complete.")
            
    except Exception as e:
        logging.error(f"Job {job_id}: Failed. Error: {e}")
        JOBS[job_id]["status"] = "error"
        JOBS[job_id]["result"] = str(e)
    finally:
        logging.info(f"Job {job_id}: LLM lock released.")


# --- FastAPI App & Lifespan ---
@asynccontextmanager
async def lifespan(app: FastAPI):
    logging.info("Server starting up... Pre-loading 'light' model.")
    get_llm_instance("light")
    logging.info("Server is ready and 'light' model is loaded.")
    yield
    logging.info("Server shutting down...")
    llm_cache.clear()

app = FastAPI(lifespan=lifespan)

# --- !!! THIS IS THE CORS FIX !!! ---
# We are explicitly adding your GitHub Pages URL
origins = [
    "https://fugthchat.github.io", # <-- YOUR LIVE SITE
    "http://localhost",           # For local testing
    "http://127.0.0.1:5500"       # For local testing
]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins, 
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)
# --- END OF CORS FIX ---

# --- API Data Models ---
class SubmitPrompt(BaseModel):
    prompt: str
    model_choice: str

# --- API Endpoints ---
@app.get("/")
def get_status():
    """This is the 'wake up' and status check endpoint."""
    loaded_model = list(llm_cache.keys())[0] if llm_cache else "None"
    return {
        "status": "AI server is online",
        "model_loaded": loaded_model,
        "models": list(MODEL_MAP.keys()) 
    }

@app.post("/submit_job")
async def submit_job(prompt: SubmitPrompt):
    """
    Instantly accepts a job and starts it in the background.
    """
    job_id = str(uuid.uuid4())
    JOBS[job_id] = {"status": "pending", "result": None}
    
    thread = threading.Thread(
        target=run_generation_in_background,
        args=(job_id, prompt.model_choice, prompt.prompt)
    )
    thread.start()
    
    logging.info(f"Job {job_id} submitted.")
    return {"job_id": job_id}

@app.get("/get_job_status/{job_id}")
async def get_job_status(job_id: str):
    """
    Allows the frontend to check on a job.
    """
    job = JOBS.get(job_id)
    
    if job is None:
        return JSONResponse(status_code=404, content={"error": "Job not found."})
    
    if job["status"] in ["complete", "error"]:
        result = job
        del JOBS[job_id] # Clean up
        return result
        
    return {"status": job["status"]}