"""user-to-user messages

Revision ID: 0026_messages
Revises: 0025_install_wizard
Create Date: 2026-06-25

Adds the `messages` table for direct user-to-user messaging (notification module phase 2).
A conversation is the set of rows between two users; both FKs cascade so a GDPR account
erasure removes that user's messages.
"""
from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

revision: str = "0026_messages"
down_revision: Union[str, None] = "0025_install_wizard"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.create_table(
        "messages",
        sa.Column("id", sa.Integer(), primary_key=True),
        sa.Column(
            "sender_id",
            sa.Integer(),
            sa.ForeignKey("users.id", ondelete="CASCADE"),
            nullable=False,
        ),
        sa.Column(
            "recipient_id",
            sa.Integer(),
            sa.ForeignKey("users.id", ondelete="CASCADE"),
            nullable=False,
        ),
        sa.Column("body", sa.Text(), nullable=False),
        sa.Column("read_at", sa.DateTime(timezone=True), nullable=True),
        sa.Column(
            "created_at",
            sa.DateTime(timezone=True),
            server_default=sa.func.now(),
            nullable=False,
        ),
    )
    op.create_index("ix_messages_sender_id", "messages", ["sender_id"])
    op.create_index("ix_messages_recipient_id", "messages", ["recipient_id"])
    op.create_index("ix_messages_created_at", "messages", ["created_at"])


def downgrade() -> None:
    op.drop_index("ix_messages_created_at", table_name="messages")
    op.drop_index("ix_messages_recipient_id", table_name="messages")
    op.drop_index("ix_messages_sender_id", table_name="messages")
    op.drop_table("messages")