from datetime import datetime
from typing import List, Optional
from fastapi import HTTPException
from app.db.database import db
from bson import ObjectId
from app.models.news import NewsCreate, NewsUpdate, NewsInDB

news_collection = db["news"]

class NewsService:
    @staticmethod
    def _to_news_in_db(doc) -> NewsInDB:
        return NewsInDB(
            id=str(doc["_id"]),
            title=doc["title"],
            markdown=doc["markdown"],
            preview=doc.get("preview"),
            tags=doc.get("tags", []),
            is_published=doc.get("is_published", True),
            created_at=doc["created_at"],
            updated_at=doc["updated_at"],
        )

    async def list_news(self, limit: int = 20, skip: int = 0, include_unpublished: bool = False) -> List[NewsInDB]:
        query = {}
        if not include_unpublished:
            query["is_published"] = True

        cursor = (
            news_collection
            .find(query)
            .sort("created_at", -1)
            .skip(skip)
            .limit(limit)
        )
        docs = await cursor.to_list(length=limit)
        return [self._to_news_in_db(d) for d in docs]

    async def get_news(self, news_id: str) -> NewsInDB:
        try:
            oid = ObjectId(news_id)
        except:
            raise HTTPException(status_code=400, detail="Invalid news id")

        doc = await news_collection.find_one({"_id": oid})
        if not doc:
            raise HTTPException(status_code=404, detail="News not found")
        return self._to_news_in_db(doc)

    async def create_news(self, payload: NewsCreate) -> NewsInDB:
        now = datetime.utcnow()
        doc = {
            "title": payload.title,
            "markdown": payload.markdown,
            "preview": payload.preview,
            "tags": payload.tags,
            "is_published": payload.is_published,
            "created_at": now,
            "updated_at": now,
        }
        result = await news_collection.insert_one(doc)
        doc["_id"] = result.inserted_id
        return self._to_news_in_db(doc)

    async def update_news(self, news_id: str, payload: NewsUpdate) -> NewsInDB:
        try:
            oid = ObjectId(news_id)
        except:
            raise HTTPException(status_code=400, detail="Invalid news id")

        update_data = {k: v for k, v in payload.dict(exclude_unset=True).items()}
        if not update_data:
            return await self.get_news(news_id)

        update_data["updated_at"] = datetime.utcnow()

        result = await news_collection.find_one_and_update(
            {"_id": oid},
            {"$set": update_data},
            return_document=True,
        )

        if not result:
            raise HTTPException(status_code=404, detail="News not found")

        return self._to_news_in_db(result)

    async def delete_news(self, news_id: str):
        try:
            oid = ObjectId(news_id)
        except:
            raise HTTPException(status_code=400, detail="Invalid news id")

        result = await news_collection.delete_one({"_id": oid})
        if result.deleted_count == 0:
            raise HTTPException(status_code=404, detail="News not found")
        return {"status": "success"}