"""Permission delegation model — temporary permission handover between users.

Allows a user to delegate their permissions to another user for a specified
time period and scope.
"""

from __future__ import annotations

import uuid
from datetime import datetime

from sqlalchemy import (
    Boolean,
    CheckConstraint,
    DateTime,
    ForeignKey,
    func,
)
from sqlalchemy.dialects.postgresql import JSONB
from sqlalchemy.dialects.postgresql import UUID as PGUUID
from sqlalchemy.orm import Mapped, mapped_column

from app.core.db import Base, TenantMixin
from app.models.owned_mixin import OwnedMixin


class PermissionDelegation(Base, TenantMixin, OwnedMixin):
    """Permission delegation — temporary handover of permissions.

    from_user_id delegates their permissions to to_user_id
    for the duration [start_at, end_at].

    scope: JSONB defining which permissions are delegated.
    Examples:
    - {"all": true} — all permissions
    - {"entity_types": ["contact", "document"]} — specific entity types
    - {"permissions": ["contacts:read", "contacts:write"]} — specific permissions
    """

    __tablename__ = "permission_delegations"
    __table_args__ = (
        CheckConstraint(
            "end_at > start_at",
            name="ck_pd_end_after_start",
        ),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        PGUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
    )
    from_user_id: Mapped[uuid.UUID] = mapped_column(
        PGUUID(as_uuid=True),
        ForeignKey("users.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    to_user_id: Mapped[uuid.UUID] = mapped_column(
        PGUUID(as_uuid=True),
        ForeignKey("users.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    start_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False
    )
    end_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False
    )
    scope: Mapped[dict | None] = mapped_column(JSONB, nullable=True, default=None)
    active: Mapped[bool] = mapped_column(
        Boolean, nullable=False, default=True
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, server_default=func.now()
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, server_default=func.now(),
        onupdate=func.now(),
    )