"""add messages.delivery_id

The real header Message-ID as delivered, kept even when message_id_hdr is
synthesized for a cross-account duplicate (SPEC §7.1). It identifies a single
delivery, so the same email delivered to several of the user's accounts can be
collapsed to one row in the thread view. Backfilled from message_id_hdr for
non-synthetic ids; synthetic rows are recovered from the raw blob by a script.

Revision ID: 0011
Revises: 0010
Create Date: 2026-07-22
"""

from __future__ import annotations

from collections.abc import Sequence

from alembic import op

revision: str = "0011"
down_revision: str | None = "0010"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None


def upgrade() -> None:
    op.execute("ALTER TABLE messages ADD COLUMN delivery_id text")
    # Non-synthetic ids are the real Message-ID already; use them directly.
    op.execute(
        "UPDATE messages SET delivery_id = message_id_hdr "
        "WHERE message_id_hdr IS NOT NULL AND message_id_hdr NOT LIKE '%@synthetic.local'"
    )
    op.execute("CREATE INDEX ix_messages_delivery ON messages (user_id, delivery_id)")


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS ix_messages_delivery")
    op.execute("ALTER TABLE messages DROP COLUMN IF EXISTS delivery_id")