import json
import logging
import httpx
import bcrypt
from contextlib import asynccontextmanager
from fastapi import FastAPI, HTTPException, Depends, Header
from database import create_tables, create_user, get_user_by_username, create_session, get_user_from_token, delete_session
from fastapi.responses import HTMLResponse, StreamingResponse
from fastapi.staticfiles import StaticFiles
from pydantic import BaseModel
from typing import List, Generator, Optional

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

@asynccontextmanager
async def lifespan(app: FastAPI):
    create_tables()
    yield

app = FastAPI(title="LocalFoodAI Chat", lifespan=lifespan)

# Use direct bcrypt for better environment compatibility
def get_password_hash(password: str):
    # Hash requires bytes
    pwd_bytes = password.encode('utf-8')
    salt = bcrypt.gensalt()
    hashed = bcrypt.hashpw(pwd_bytes, salt)
    return hashed.decode('utf-8')

def verify_password(plain_password: str, hashed_password: str):
    # bcrypt.checkpw handles verification
    return bcrypt.checkpw(plain_password.encode('utf-8'), hashed_password.encode('utf-8'))

class UserCreate(BaseModel):
    username: str
    password: str

class UserLogin(BaseModel):
    username: str
    password: str

async def get_current_user(authorization: Optional[str] = Header(None)):
    if not authorization or not authorization.startswith("Bearer "):
        raise HTTPException(status_code=401, detail="Authentication required")
    
    token = authorization.split(" ")[1]
    user = get_user_from_token(token)
    if not user:
        raise HTTPException(status_code=401, detail="Invalid or expired session")
    return user

OLLAMA_URL = "http://localhost:11434/api/chat"
MODEL_NAME = "llama3.1:8b"

# Mount static files to serve the frontend
app.mount("/static", StaticFiles(directory="static"), name="static")

class ChatMessage(BaseModel):
    role: str
    content: str

class ChatRequest(BaseModel):
    messages: List[ChatMessage]

@app.get("/", response_class=HTMLResponse)
async def read_root():
    """Serve the chat interface HTML"""
    try:
        with open("static/index.html", "r", encoding="utf-8") as f:
            return HTMLResponse(content=f.read())
    except FileNotFoundError:
        return HTMLResponse(content="<h1>Welcome to LocalFoodAI</h1><p>static/index.html not found. Please create the frontend.</p>")

@app.post("/api/register")
async def register_user(user: UserCreate):
    if len(user.username.strip()) < 3:
        raise HTTPException(status_code=400, detail="Username must be at least 3 characters")
    if len(user.password.strip()) < 6:
        raise HTTPException(status_code=400, detail="Password must be at least 6 characters")
    
    hashed_password = get_password_hash(user.password)
    user_id = create_user(user.username.strip(), hashed_password)
    if not user_id:
        raise HTTPException(status_code=400, detail="Username already exists")
    
    # Auto-login after registration
    token = create_session(user_id)
    return {"message": "User registered successfully", "token": token, "username": user.username.strip()}

@app.post("/api/login")
async def login_user(user: UserLogin):
    db_user = get_user_by_username(user.username.strip())
    if not db_user:
        raise HTTPException(status_code=401, detail="Invalid username or password")
    
    if not verify_password(user.password, db_user["password_hash"]):
        raise HTTPException(status_code=401, detail="Invalid username or password")
    
    token = create_session(db_user["id"])
    return {"status": "success", "username": db_user["username"], "token": token}

@app.post("/api/logout")
async def logout(authorization: Optional[str] = Header(None)):
    if authorization and authorization.startswith("Bearer "):
        token = authorization.split(" ")[1]
        delete_session(token)
    return {"message": "Logged out successfully"}

@app.post("/chat")
async def chat_endpoint(request: ChatRequest, current_user: dict = Depends(get_current_user)):
    """Proxy chat requests to the local Ollama instance with streaming support"""
    payload = {
        "model": MODEL_NAME,
        "messages": [msg.model_dump() for msg in request.messages],
        "stream": True  # Enable streaming for a better UI experience
    }
    
    async def generate_response():
        try:
            async with httpx.AsyncClient() as client:
                async with client.stream("POST", OLLAMA_URL, json=payload, timeout=120.0) as response:
                    if response.status_code != 200:
                        error_detail = await response.aread()
                        logger.error(f"Error communicating with Ollama: {error_detail}")
                        yield f"data: {json.dumps({'error': 'Error communicating with local LLM.'})}\n\n"
                        return

                    async for line in response.aiter_lines():
                        if line:
                            data = json.loads(line)
                            if "message" in data and "content" in data["message"]:
                                content = data["message"]["content"]
                                yield f"data: {json.dumps({'content': content})}\n\n"
                            if data.get("done"):
                                break
        except Exception as e:
            logger.error(f"Unexpected error during stream: {e}")
            yield f"data: {json.dumps({'error': str(e)})}\n\n"

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

if __name__ == "__main__":
    import uvicorn
    uvicorn.run("main:app", host="127.0.0.1", port=8000, reload=True)