"""Universal entity permission model — ACLs for ANY entity in the system.

This single table stores permissions for contacts, files, mailboxes,
calendar events, tasks, workflows, and any future entity type.

Architecture:
- entity_type + entity_id identify the datensatz
- principal_type + principal_id identify who gets access
- permission_level defines what they can do
- expires_at enables time-limited sharing

Resolution (highest wins):
1. Owner → 'owner' (from owner_id on the entity)
2. Direct user permission
3. Group permission (via user_groups)
4. Role permission (via user_tenants.role_id)
5. No access → 'none'
"""

from __future__ import annotations

import uuid
from datetime import datetime

from sqlalchemy import (
    CheckConstraint,
    DateTime,
    ForeignKey,
    Index,
    String,
    UniqueConstraint,
    func,
)
from sqlalchemy.dialects.postgresql import UUID as PGUUID
from sqlalchemy.orm import Mapped, mapped_column

from app.core.db import Base, TenantMixin


class EntityPermission(Base, TenantMixin):
    """Universal ACL entry for any entity in the system.

    entity_type examples: 'contact', 'dms_file', 'mailbox', 'calendar_event',
    'task', 'workflow', 'contact_folder', etc.

    principal_type: 'user', 'group', 'role', 'guest'

    permission_level: 'none' | 'read' | 'write' | 'admin' | 'delete'
    - none:   explicit deny (overrides allow)
    - read:   view the entity
    - write:  read + edit entity fields
    - admin:  write + delete + manage permissions
    - delete: admin + transfer ownership
    """

    __tablename__ = "entity_permissions"
    __table_args__ = (
        UniqueConstraint(
            "entity_type",
            "entity_id",
            "principal_type",
            "principal_id",
            "tenant_id",
            name="uq_ep_entity_principal_tenant",
        ),
        CheckConstraint(
            "principal_type IN ('user', 'group', 'role', 'guest')",
            name="ck_ep_principal_type",
        ),
        CheckConstraint(
            "permission_level IN ('none', 'read', 'write', 'admin', 'delete')",
            name="ck_ep_permission_level",
        ),
        Index("ix_ep_entity", "entity_type", "entity_id"),
        Index("ix_ep_principal", "principal_type", "principal_id"),
        Index("ix_ep_tenant", "tenant_id"),
        Index("ix_ep_expires", "expires_at"),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        PGUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
    )
    entity_type: Mapped[str] = mapped_column(String(50), nullable=False)
    entity_id: Mapped[uuid.UUID] = mapped_column(
        PGUUID(as_uuid=True), nullable=False
    )
    principal_type: Mapped[str] = mapped_column(String(10), nullable=False)
    principal_id: Mapped[uuid.UUID] = mapped_column(
        PGUUID(as_uuid=True), nullable=False
    )
    permission_level: Mapped[str] = mapped_column(
        String(20), nullable=False, default="read"
    )
    expires_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True, default=None
    )
    created_by: Mapped[uuid.UUID | None] = mapped_column(
        PGUUID(as_uuid=True),
        ForeignKey("users.id", ondelete="SET NULL"),
        nullable=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(),
    )