from __future__ import annotations

import uuid
from datetime import datetime

from sqlalchemy import CheckConstraint, DateTime, ForeignKey, Text, func
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column

from . import Base


class Share(Base):
    """An additional access grant on one resource (identified by type + id).

    A resource's OWNER is tracked on the resource row itself (its owner_id column);
    this table records grants BEYOND the owner — to a single user or to a whole
    group. It is polymorphic (resource_type + resource_id) so every future
    shareable entity (notes first, in M1) reuses one table and one ACL predicate.
    Exactly one of shared_with_user_id / shared_with_group_id is set.
    """

    __tablename__ = "shares"
    __table_args__ = (
        CheckConstraint(
            "(shared_with_user_id IS NOT NULL) <> (shared_with_group_id IS NOT NULL)",
            name="ck_shares_one_target",
        ),
    )

    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    resource_type: Mapped[str] = mapped_column(Text(), nullable=False)
    resource_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), nullable=False)
    shared_with_user_id: Mapped[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=True
    )
    shared_with_group_id: Mapped[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True), ForeignKey("groups.id", ondelete="CASCADE"), nullable=True
    )
    permission: Mapped[str] = mapped_column(Text(), nullable=False, server_default="view")
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())