from datetime import datetime

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

from app.database import Base


class DraftBatch(Base):
    """One run of extraction, held apart from the question bank.

    Questions pulled out of a PDF used to be written straight into `questions`,
    which meant a machine's first attempt took a permanent id the moment it was
    produced. Ids come from a sequence and are never reissued, so every
    rejected draft burned one, and every draft that needed fixing was already
    in the bank while it was being fixed.

    A batch is where a run lands instead: readable, editable, and rejectable,
    with nothing in the bank until somebody says so.
    """

    __tablename__ = "draft_batches"

    id = Column(Integer, primary_key=True, index=True)
    title = Column(String(200), nullable=False)
    #: Where it came from, so a draft can be checked against its source.
    document_id = Column(Integer, ForeignKey("pdf_documents.id", ondelete="SET NULL"), nullable=True)
    section_id = Column(Integer, ForeignKey("sections.id", ondelete="SET NULL"), nullable=True)
    job_id = Column(String(64), nullable=True, index=True)
    #: Which model produced it, and how it was asked. Two batches from the same
    #: pages can differ entirely on these, and an educator comparing them
    #: should not have to guess which was which.
    model_id = Column(String(160), nullable=True)
    extraction_mode = Column(String(40), nullable=True)
    #: Where the questions go when they are accepted. Chosen up front so a
    #: batch has a home before anyone reads it.
    category_id = Column(Integer, ForeignKey("question_categories.id", ondelete="SET NULL"), nullable=True)
    created_by = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)
    #: open — being worked through. closed — nothing left to decide.
    status = Column(String(20), default="open", index=True)

    drafts = relationship("DraftQuestion", back_populates="batch",
                          cascade="all, delete-orphan", order_by="DraftQuestion.position")


class DraftQuestion(Base):
    """A proposed question. It has an id here, and no id in the bank.

    The fields mirror `Question` because promoting one is a copy, not a
    translation — anything that cannot be expressed here would be lost at the
    moment of acceptance, which is the worst possible time to discover it.
    """

    __tablename__ = "draft_questions"

    id = Column(Integer, primary_key=True, index=True)
    batch_id = Column(Integer, ForeignKey("draft_batches.id", ondelete="CASCADE"), nullable=False, index=True)
    position = Column(Integer, default=0)

    question_text = Column(Text, nullable=False)
    question_type = Column(String, nullable=False, default="mcq")
    options = Column(JSON, nullable=True)
    correct_answer = Column(String, nullable=True)
    explanation = Column(Text, nullable=True)
    option_explanations = Column(JSON, nullable=True)
    key_points = Column(JSON, nullable=True)
    attending_tip = Column(Text, nullable=True)
    difficulty = Column(String(10), nullable=True)
    page_reference = Column(Integer, nullable=True)
    image_path = Column(String, nullable=True)
    explanation_image_path = Column(String, nullable=True)
    #: Overrides the batch's category for this one draft.
    category_id = Column(Integer, ForeignKey("question_categories.id", ondelete="SET NULL"), nullable=True)

    #: pending | accepted | rejected. An accepted draft keeps its row and
    #: records which question it became, so the batch still reads as a history
    #: of what was decided rather than emptying as it is worked through.
    status = Column(String(20), default="pending", index=True)
    question_id = Column(Integer, ForeignKey("questions.id", ondelete="SET NULL"), nullable=True)
    #: Why it was turned down, for whoever tunes the extraction next.
    note = Column(Text, nullable=True)
    decided_by = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    decided_at = Column(DateTime, nullable=True)
    #: Whether a human changed it before deciding — the number worth knowing
    #: about a model's output.
    edited = Column(Integer, default=0)
    created_at = Column(DateTime, default=datetime.utcnow)

    batch = relationship("DraftBatch", back_populates="drafts")