from sqlalchemy import create_engine, UnicodeText, DateTime, ForeignKey
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, Session, joinedload, relationship
from sqlalchemy.sql import func
from contextlib import contextmanager
import os
import datetime
import logging
from cachetools import cached, TTLCache


CACHE_TTL_SECONDS = 600


class Base(DeclarativeBase):
    pass


class Article(Base):
    __tablename__ = 'article'

    id: Mapped[int] = mapped_column(primary_key=True)
    title: Mapped[str] = mapped_column(UnicodeText)
    content: Mapped[str] = mapped_column(UnicodeText)
    date: Mapped[datetime.datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
    category: Mapped[str] = mapped_column(UnicodeText, server_default='news')
    image_url: Mapped[str] = mapped_column(UnicodeText, nullable=True, server_default=None)

    sources = relationship('Source', backref='article')

    def __repr__(self) -> str:
        return f'Article(id={self.id}, title={self.title}, content={self.content})'
    

class Source(Base):
    '''
    Represents a source URL for an article.
    '''
    __tablename__ = 'source'

    id: Mapped[int] = mapped_column(primary_key=True)
    url: Mapped[str] = mapped_column(UnicodeText)
    article_id: Mapped[int] = mapped_column(ForeignKey('article.id'))


# get environment variables for database
USE_TURSO = os.environ.get('USE_TURSO', 'false')
TURSO_DATABASE_URL = os.getenv('TURSO_DATABASE_URL')
TURSO_AUTH_TOKEN = os.getenv('TURSO_AUTH_TOKEN')

# create an engine
connected_to_turso = False
if (USE_TURSO == 'true' and TURSO_DATABASE_URL and TURSO_AUTH_TOKEN):
    try:
        engine = create_engine(
            f'sqlite+{TURSO_DATABASE_URL}?secure=true',
            connect_args={
                'auth_token': TURSO_AUTH_TOKEN
            },
            echo=False,
            pool_recycle=7000,
            pool_pre_ping=True,
        )
        Base.metadata.create_all(engine)
        connected_to_turso = True
    except:
        logging.error('Failed to connect to remote Turso database')

if not connected_to_turso:
    logging.warning('Using local SQLite database')
    engine = create_engine('sqlite:///news.db', echo=False)
    Base.metadata.create_all(engine)


# cache to hold articles
article_cache = TTLCache(1, ttl=CACHE_TTL_SECONDS)


@contextmanager
def get_session():
    '''
    Context manager for creating and closing a database session
    '''
    # create a session
    session = Session(engine)
    try:
        yield session
    finally:
        session.close()


def add_article(session: Session, article: Article):
    '''
    Adds a new article to the database
    '''
    session.add(article)


def _retrieve_articles_from_db(session: Session):
    '''
    Returns a list containing all articles from the database
    '''
    return session.query(Article).options(joinedload(Article.sources)).all()


@cached(article_cache)
def get_cached_articles():
    '''
    Returns a list containing all articles from the in-memory cache
    '''
    with get_session() as session:
        return _retrieve_articles_from_db(session=session)


def clear_articles(session: Session):
    '''
    Deletes all articles and sources in the database
    '''
    session.query(Source).delete()
    session.query(Article).delete()


def add_sources(session: Session, sources: list[Source]):
    '''
    Adds the given sources to the database
    '''
    for source in sources:
        session.add(source)