from datetime import datetime

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

from app.database import Base


class StudyPlan(Base):
    """An ordered set of question blocks a learner works through."""

    __tablename__ = "study_plans"

    id = Column(Integer, primary_key=True, index=True)
    slug = Column(String(120), unique=True, nullable=False, index=True)
    name = Column(String(200), nullable=False)
    description = Column(Text, nullable=True)
    exam_id = Column(Integer, ForeignKey("exams.id", ondelete="SET NULL"), nullable=True)
    kind = Column(String(20), default="set")  # set | mixed
    sort_order = Column(Integer, default=100)
    is_published = Column(Integer, default=1)
    created_at = Column(DateTime, default=datetime.utcnow)

    blocks = relationship("StudyPlanBlock", back_populates="plan",
                          cascade="all, delete-orphan", order_by="StudyPlanBlock.position")


class StudyPlanBlock(Base):
    """One numbered block. Its question ids are fixed, not a live filter.

    A plan you are part-way through must not reshuffle between visits, so the
    membership is snapshotted when the plan is built.
    """

    __tablename__ = "study_plan_blocks"
    __table_args__ = (UniqueConstraint("plan_id", "position", name="uq_plan_block"),)

    id = Column(Integer, primary_key=True, index=True)
    plan_id = Column(Integer, ForeignKey("study_plans.id", ondelete="CASCADE"), nullable=False, index=True)
    position = Column(Integer, nullable=False)
    title = Column(String(200), nullable=False)
    question_ids = Column(JSON, nullable=False, default=list)

    plan = relationship("StudyPlan", back_populates="blocks")


class StudyPlanBlockArticle(Base):
    """Reading attached to a block, in the order it should be read.

    A block was questions only, which put the reading that prepares you for them
    somewhere else entirely. This is the "read this, then sit this" pairing.
    """

    __tablename__ = "study_plan_block_articles"
    __table_args__ = (UniqueConstraint("block_id", "article_id", name="uq_block_article"),)

    id = Column(Integer, primary_key=True, index=True)
    block_id = Column(Integer, ForeignKey("study_plan_blocks.id", ondelete="CASCADE"), nullable=False, index=True)
    article_id = Column(Integer, ForeignKey("articles.id", ondelete="CASCADE"), nullable=False, index=True)
    position = Column(Integer, default=0)


class StudyPlanArticleRead(Base):
    """One learner marking one of a block's articles as read.

    Deliberately separate from `article_views`: opening an article is not the
    same claim as having finished with it, and the plan's progress is the second.
    """

    __tablename__ = "study_plan_article_reads"
    __table_args__ = (UniqueConstraint("block_article_id", "user_id", name="uq_block_article_read"),)

    id = Column(Integer, primary_key=True, index=True)
    block_article_id = Column(Integer, ForeignKey("study_plan_block_articles.id", ondelete="CASCADE"), nullable=False, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    read_at = Column(DateTime, default=datetime.utcnow)


class StudyPlanBlockProgress(Base):
    """Which block a learner has started, and the quiz it produced."""

    __tablename__ = "study_plan_block_progress"
    __table_args__ = (UniqueConstraint("block_id", "user_id", name="uq_block_progress"),)

    id = Column(Integer, primary_key=True, index=True)
    block_id = Column(Integer, ForeignKey("study_plan_blocks.id", ondelete="CASCADE"), nullable=False, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    quiz_id = Column(Integer, ForeignKey("quizzes.id", ondelete="SET NULL"), nullable=True)
    completed_at = Column(DateTime, nullable=True)