"""feed_posts.client_token — server-side idempotency for post creation

``POST /feed/posts`` had no idempotency at all. The year-in-review's "share my
recap" guarded itself with a ``localStorage`` flag, which is per-browser-tab
and invisible to curl and to the ``feed_create_post`` MCP tool; two tabs (or
one double-click that outran the disabled state) published two identical
recaps and fanned out two rounds of mention pushes.

The token is unique **per author**, not globally: two people may legitimately
send the same deterministic token (``wrapped:2026``). NULL is exempt — MySQL
allows unlimited NULLs in a unique index — so every existing row, every
celebration post, and every announcement keeps working untouched.

Revision ID: 457
Revises: 456
"""
from __future__ import annotations

import sqlalchemy as sa
from alembic import op

revision = "457"
down_revision = "456"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.add_column(
        "feed_posts",
        sa.Column("client_token", sa.String(length=128), nullable=True),
    )
    op.create_index(
        "uq_feed_posts_author_client_token",
        "feed_posts",
        ["author_person_id", "client_token"],
        unique=True,
    )


def downgrade() -> None:
    op.drop_index("uq_feed_posts_author_client_token", table_name="feed_posts")
    op.drop_column("feed_posts", "client_token")