from datetime import datetime

from sqlalchemy import Column, Integer, String, Text, JSON, DateTime, ForeignKey, UniqueConstraint
from sqlalchemy.orm import relationship

from app.database import Base


class Article(Base):
    """Educator-authored topic reading with stable section IDs for linking."""

    __tablename__ = "articles"

    id = Column(Integer, primary_key=True, index=True)
    slug = Column(String(120), unique=True, nullable=False, index=True)
    title = Column(String(300), nullable=False)
    summary = Column(Text, nullable=True)
    content = Column(Text, nullable=True)  # Whole-article introduction (markdown).
    # Stable subsections: [{"id": uuid-hex, "slug": "...", "title": "...", "content": "markdown"}].
    sections = Column(JSON, nullable=False, default=list)
    category_id = Column(Integer, ForeignKey("question_categories.id", ondelete="SET NULL"), nullable=True)
    section_id = Column(Integer, ForeignKey("sections.id", ondelete="SET NULL"), nullable=True)  # Optional PDF source range.
    user_id = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    status = Column(String, default="draft")  # draft | published
    created_at = Column(DateTime, default=datetime.utcnow)
    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)

    category = relationship("QuestionCategory")
    links = relationship("QuestionArticleLink", back_populates="article", cascade="all, delete-orphan")


class QuestionArticleLink(Base):
    """Question -> whole article or one stable section."""

    __tablename__ = "question_article_links"
    __table_args__ = (UniqueConstraint("question_id", "article_id", "section_id", name="uq_question_article_section"),)

    id = Column(Integer, primary_key=True, index=True)
    question_id = Column(Integer, ForeignKey("questions.id", ondelete="CASCADE"), nullable=False)
    article_id = Column(Integer, ForeignKey("articles.id", ondelete="CASCADE"), nullable=False)
    section_id = Column(String(64), nullable=True)  # Article.sections[].id; None = whole article.
    user_id = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)

    article = relationship("Article", back_populates="links")