from __future__ import annotations
import os
import sys
import re
import json
import logging
import time as _time
from collections import defaultdict
from pathlib import Path
from contextlib import asynccontextmanager

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

from fastapi import FastAPI, Request, Depends, HTTPException, Security
from fastapi.responses import StreamingResponse, JSONResponse
from fastapi.middleware.cors import CORSMiddleware
from fastapi.security import APIKeyHeader
from dotenv import find_dotenv, load_dotenv
from openai import OpenAI

# Setup path & env
REPO_ROOT = Path(__file__).resolve().parents[2]
if str(REPO_ROOT) not in sys.path:
    sys.path.insert(0, str(REPO_ROOT))

load_dotenv(find_dotenv(usecwd=True))

from core.rag.embedding_model import EmbeddingConfig, QwenEmbeddings
from core.rag.vector_store import ChromaConfig, ChromaVectorDB
from core.rag.retrieval import Retriever, RetrievalMode, get_retrieval_config
from core.rag.generator import RAGContextBuilder, SYSTEM_PROMPT

# Config
RETRIEVAL_MODE = RetrievalMode.HYBRID
RETRIEVAL_CFG = get_retrieval_config()
LLM_MODEL = os.getenv("LLM_MODEL", "qwen/qwen3-32b")
LLM_API_BASE = "https://api.groq.com/openai/v1"

# Shared state
_state = {}


def _filter_think_tags(text: str) -> str:
    return re.sub(r'<think>.*?</think>', '', text, flags=re.DOTALL).strip()


@asynccontextmanager
async def lifespan(app: FastAPI):
    """Initialize RAG resources on startup."""
    print("⏳ Initializing RAG pipeline...")
    emb = QwenEmbeddings(EmbeddingConfig())
    db = ChromaVectorDB(embedder=emb, config=ChromaConfig())
    retriever = Retriever(vector_db=db)

    api_key = (os.getenv("GROQ_API_KEY") or "").strip()
    if not api_key:
        raise RuntimeError("Missing GROQ_API_KEY")

    _state["rag"] = RAGContextBuilder(retriever=retriever)
    _state["llm"] = OpenAI(api_key=api_key, base_url=LLM_API_BASE)
    print("✅ Ready!")
    yield
    _state.clear()


app = FastAPI(title="HUST RAG API", lifespan=lifespan)

# ── Security: CORS ──────────────────────────────────────────────
# Chỉ cho phép frontend cùng origin hoặc origins cụ thể
ALLOWED_ORIGINS = os.getenv("ALLOWED_ORIGINS", "").split(",")
ALLOWED_ORIGINS = [o.strip() for o in ALLOWED_ORIGINS if o.strip()] or ["*"]

app.add_middleware(
    CORSMiddleware,
    allow_origins=ALLOWED_ORIGINS,
    allow_methods=["GET", "POST"],
    allow_headers=["Content-Type", "X-API-Key"],
)

# ── Security: API Key Authentication ────────────────────────────
_api_key_header = APIKeyHeader(name="X-API-Key", auto_error=False)
FRONTEND_API_KEY = os.getenv("FRONTEND_API_KEY", "").strip()


async def verify_api_key(api_key: str = Security(_api_key_header)):
    """Verify the API key from request header."""
    if not FRONTEND_API_KEY:
        # Nếu chưa đặt FRONTEND_API_KEY thì bỏ qua (dev mode)
        return None
    if api_key != FRONTEND_API_KEY:
        raise HTTPException(status_code=403, detail="Invalid or missing API key")
    return api_key


# ── Security: Rate Limiting (in-memory) ─────────────────────────
RATE_LIMIT_WINDOW = 60   # seconds
RATE_LIMIT_MAX = int(os.getenv("RATE_LIMIT_MAX", "30"))  # max requests per window
_rate_limit_store: dict[str, list[float]] = defaultdict(list)


async def rate_limit(request: Request):
    """Simple per-IP rate limiter."""
    client_ip = request.client.host if request.client else "unknown"
    now = _time.time()
    # Cleanup old entries
    _rate_limit_store[client_ip] = [
        t for t in _rate_limit_store[client_ip] if now - t < RATE_LIMIT_WINDOW
    ]
    if len(_rate_limit_store[client_ip]) >= RATE_LIMIT_MAX:
        raise HTTPException(
            status_code=429,
            detail=f"Rate limit exceeded. Max {RATE_LIMIT_MAX} requests per minute."
        )
    _rate_limit_store[client_ip].append(now)
    return client_ip

# Serve static files (CSS, JS, images, etc.)
STATIC_DIR = Path(__file__).parent / "static"
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse

app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")


@app.get("/")
async def index():
    """Serve the chat UI."""
    return FileResponse(str(STATIC_DIR / "index.html"))


@app.post("/api/chat")
async def chat(
    request: Request,
    _key: str = Depends(verify_api_key),
    _ip: str = Depends(rate_limit),
):
    """Chat endpoint with Server-Sent Events streaming."""
    body = await request.json()
    question = (body.get("message") or "").strip()

    if not question:
        return JSONResponse({"error": "Empty message"}, status_code=400)

    # Retrieve context
    import time
    start_time = time.time()
    logger.info(f"Start retrieval for question: {question}")
    prepared = _state["rag"].retrieve_and_prepare(
        question,
        k=RETRIEVAL_CFG.top_k,
        initial_k=RETRIEVAL_CFG.initial_k,
        mode=RETRIEVAL_MODE.value,
    )

    if not prepared["results"]:
        return JSONResponse({"answer": "Xin lỗi, tôi không tìm thấy thông tin phù hợp."})

    retrieval_time = time.time() - start_time
    logger.info(f"Retrieval took {retrieval_time:.2f}s")

    def stream():
        llm_start_time = time.time()
        first_token = True
        completion = _state["llm"].chat.completions.create(
            model=LLM_MODEL,
            messages=[{"role": "user", "content": prepared["prompt"]}],
            temperature=0.0,
            max_tokens=4096,
            stream=True,
        )
        for chunk in completion:
            delta = getattr(chunk.choices[0].delta, "content", "") or ""
            if delta:
                if first_token:
                    ttft = time.time() - llm_start_time
                    logger.info(f"LLM TTFT (Time To First Token): {ttft:.2f}s")
                    first_token = False
                # SSE format
                yield f"data: {json.dumps({'token': delta}, ensure_ascii=False)}\n\n"
        total_time = time.time() - start_time
        logger.info(f"Total request took: {total_time:.2f}s")
        yield "data: [DONE]\n\n"

    return StreamingResponse(stream(), media_type="text/event-stream")


@app.get("/api/config")
async def config():
    """Provide frontend config (API key for same-origin frontend)."""
    return {"api_key": FRONTEND_API_KEY}


@app.get("/api/health")
async def health():
    return {"status": "ok"}


if __name__ == "__main__":
    import uvicorn
    uvicorn.run(
        "core.api.server:app",
        host=os.getenv("API_HOST", "0.0.0.0"),
        port=int(os.getenv("API_PORT", "8000")),
        reload=False,
    )