backend/server.py

import asyncio
import json
import subprocess
from pathlib import Path
from datetime import datetime, timezone, timedelta
from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import FileResponse
from fastapi.staticfiles import StaticFiles

# --------------------------------------------------------
# FASTAPI INIT
# --------------------------------------------------------

app = FastAPI()

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],      # allow all for HF Spaces
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# --------------------------------------------------------
# JSON DATABASE (file-based persistence)
# --------------------------------------------------------

ROOT_DIR = Path(__file__).parent.parent
DATA_DIR = ROOT_DIR / "data"
DATA_DIR.mkdir(exist_ok=True)

DB_FILE = DATA_DIR / "history.json"


def load_messages():
    if not DB_FILE.exists():
        return []
    try:
        with open(DB_FILE, "r") as f:
            return json.load(f)
    except:
        return []


def save_messages(msgs):
    with open(DB_FILE, "w") as f:
        json.dump(msgs, f, indent=2)


def add_message(role, text, src=None):
    msgs = load_messages()
    entry = {
        "role": role,
        "text": text,
        "src": src,
        "timestamp": datetime.now(timezone(timedelta(hours=5, minutes=30))).replace(tzinfo=None)
    }
    msgs.append(entry)
    save_messages(msgs)
    return entry


# --------------------------------------------------------
# PYTHON ENGINE
# --------------------------------------------------------

python_engine_path = ROOT_DIR / "python_engine" / "engine_server.py"

python = subprocess.Popen(
    ["python3", str(python_engine_path)],   # Docker/HF safe
    stdin=subprocess.PIPE,
    stdout=subprocess.PIPE,
    stderr=subprocess.PIPE,
    text=True,
    bufsize=1
)

ready = False
callbacks = []


async def read_stdout():
    """Reads JSON responses from python engine."""
    global callbacks
    loop = asyncio.get_event_loop()

    while True:
        line = await loop.run_in_executor(None, python.stdout.readline)
        if not line:
            continue

        line = line.strip()
        if callbacks:
            cb = callbacks.pop(0)
            try:
                cb(json.loads(line))
            except Exception as err:
                print("JSON decode error:", err)
                print("Line:", line)


async def read_stderr():
    """Reads stderr for READY signal + logs."""
    global ready
    loop = asyncio.get_event_loop()

    while True:
        line = await loop.run_in_executor(None, python.stderr.readline)
        if not line:
            continue

        msg = line.strip()
        print("[PY]", msg)

        if "READY" in msg:
            ready = True


@app.on_event("startup")
async def startup_event():
    asyncio.create_task(read_stdout())
    asyncio.create_task(read_stderr())


async def ask_python(query: str):
    if not ready:
        raise HTTPException(503, "Python engine not ready")

    loop = asyncio.get_event_loop()
    future = loop.create_future()

    callbacks.append(future.set_result)

    python.stdin.write(json.dumps({"query": query}) + "\n")
    python.stdin.flush()

    return await future


# --------------------------------------------------------
# API ROUTES
# --------------------------------------------------------

@app.post("/ask")
async def ask(payload: dict):
    user_query = payload.get("query")
    if not user_query:
        raise HTTPException(400, "Missing 'query' field")

    # Save user message
    add_message("user", user_query)

    # Engine response
    result = await ask_python(user_query)

    # Save bot messages
    if isinstance(result.get("response"), list):
        for msg in result["response"]:
            add_message("bot", msg)

    return result


@app.get("/history")
async def history():
    return load_messages()


@app.post("/clear")
async def clear_route():
    msgs = []
    greeting = {
        "role": "bot",
        "text": "Hi. I am Dwarakesh. Ask me anything.",
        "timestamp": datetime.now(timezone(timedelta(hours=5, minutes=30))).replace(tzinfo=None)
    }
    msgs.append(greeting)
    save_messages(msgs)
    return {"success": True, "message": greeting}


# --------------------------------------------------------
# STATIC FRONTEND (Vite build)
# --------------------------------------------------------

FRONTEND_DIR = ROOT_DIR / "frontend"
DIST_DIR = FRONTEND_DIR / "dist"
PUBLIC_DIR = FRONTEND_DIR / "public"

# Files in /public → /static/*
app.mount("/static", StaticFiles(directory=PUBLIC_DIR), name="static")

# /assets/* → dist/assets
app.mount("/assets", StaticFiles(directory=DIST_DIR / "assets"), name="assets")

# favicon
@app.get("/favicon.png")
async def favicon():
    return FileResponse(DIST_DIR / "favicon.png")

# Everything else → index.html
@app.get("/{full_path:path}")
async def serve_spa(full_path: str):
    return FileResponse(DIST_DIR / "index.html")