from datetime import datetime

from sqlalchemy import (Column, DateTime, ForeignKey, Integer, JSON, String, Text,
                        UniqueConstraint)

from app.database import Base
from app.models.embeddable import Embeddable


class MediaAsset(Base, Embeddable):
    """An image in the bank, searchable by what it shows rather than its filename.

    The embedding column is filled from the caption today. A vision-capable model
    can fill it from the image itself later; `embedding_model` records which one
    produced each vector, so the two are never mixed silently.
    """

    __tablename__ = "media_assets"

    id = Column(Integer, primary_key=True, index=True)
    path = Column(String(500), unique=True, nullable=False)
    title = Column(String(300), nullable=True)
    caption = Column(Text, nullable=True)
    alt_text = Column(Text, nullable=True)
    # Where the image came from, and where to check that. Kept on the asset
    # rather than typed into a caption because a citation belongs to the file:
    # the same figure used in three articles is cited the same way in all
    # three, and a licence that turns out to be wrong is one row to fix.
    source = Column(Text, nullable=True)
    source_url = Column(String(600), nullable=True)
    # Regions an educator has marked on the image, as vector shapes in
    # normalised coordinates — see `docs/image-overlays.md`. Vectors rather
    # than a second burnt-in picture: a raster overlay cannot be turned off,
    # cannot be corrected without redrawing it, doubles the storage, and looks
    # wrong at any size but the one it was drawn at.
    #
    #     {"shapes": [{"kind": "path", "points": [[0.31, 0.52], …],
    #                  "color": "#5eead4", "width": 0.006, "label": "lead lines"}]}
    overlay = Column(JSON, nullable=True)
    kind = Column(String(20), default="image")
    library_id = Column(Integer, ForeignKey("media_libraries.id", ondelete="SET NULL"), nullable=True, index=True)
    # Which backend holds the bytes; reads fall back to the volume either way.
    storage = Column(String(10), default="local")
    byte_size = Column(Integer, nullable=True)
    category_id = Column(Integer, ForeignKey("question_categories.id", ondelete="SET NULL"), nullable=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)


class MediaTagLink(Base):
    __tablename__ = "media_tag_links"
    __table_args__ = (UniqueConstraint("media_id", "tag_id", name="uq_media_tag"),)

    id = Column(Integer, primary_key=True, index=True)
    media_id = Column(Integer, ForeignKey("media_assets.id", ondelete="CASCADE"), nullable=False, index=True)
    # `question_tags` is created by raw DDL rather than an ORM model, so the
    # constraint is declared in the migration; the mapper only stores the id.
    tag_id = Column(Integer, nullable=False, index=True)


class MediaLibrary(Base):
    """A named group of images, so access can be given to some without all."""

    __tablename__ = "media_libraries"

    id = Column(Integer, primary_key=True, index=True)
    name = Column(String(200), unique=True, nullable=False)
    description = Column(Text, nullable=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)


class MediaLibraryGrant(Base):
    """Lets one person work with one library, mirroring the category grants."""

    __tablename__ = "media_library_grants"
    __table_args__ = (UniqueConstraint("library_id", "user_id", name="uq_media_library_grant"),)

    id = Column(Integer, primary_key=True, index=True)
    library_id = Column(Integer, ForeignKey("media_libraries.id", ondelete="CASCADE"), nullable=False, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True)
    granted_by = Column(Integer, ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=datetime.utcnow)