"""saved_chats.share_token: the anonymous share link (phase 51)

Revision ID: 0009
Revises: 0008
Create Date: 2026-08-29

Phase 51 (share-a-chat-by-link, owner-locked 2026-08-29): a saved chat
can be turned into a public link — ``/shared/<token>`` — that anyone
with the URL can read anonymously (no admin session); unsharing sets
the token back to NULL and revokes the link.

* ``saved_chats.share_token`` — ``UUID`` (a 128-bit ``uuid4``), NULL =
  not shared. One column, no new table (A10 extension unchanged —
  sharing reuses the already-stored row).
* ``ix_saved_chats_share_token`` — UNIQUE index on the column. A unique
  index on a NULLable column: Postgres treats NULLs as distinct, so any
  number of unshared chats coexist while two identical non-NULL tokens
  can never exist (the ``git_sources.path`` house precedent, phase 38).
"""
from __future__ import annotations

import sqlalchemy as sa
from sqlalchemy.dialects import postgresql

from alembic import op

revision = "0009"
down_revision = "0008"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.add_column(
        "saved_chats",
        sa.Column("share_token", postgresql.UUID(as_uuid=True), nullable=True),
    )
    op.create_index(
        "ix_saved_chats_share_token", "saved_chats", ["share_token"], unique=True
    )


def downgrade() -> None:
    op.drop_index("ix_saved_chats_share_token", table_name="saved_chats")
    op.drop_column("saved_chats", "share_token")