"""procurement serial counters for concurrency-safe human numbers.

Revision ID: 446
Revises: 445
Create Date: 2026-08-02

One transactional counter row per (prefix, calendar year). The allocator
self-bootstraps from existing resource rows, so this migration never rewrites
or deletes issued numbers and needs no speculative data cleanup.
"""
from __future__ import annotations

import sqlalchemy as sa

from alembic import op

revision = "446"
down_revision = "445"
branch_labels = None
depends_on = None

TABLE = "procurement_serial_counters"


def _table_exists(bind, name: str) -> bool:
    return bind.execute(
        sa.text(
            "SELECT 1 FROM information_schema.TABLES "
            "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :name"
        ),
        {"name": name},
    ).scalar() is not None


def upgrade() -> None:
    bind = op.get_bind()
    if _table_exists(bind, TABLE):
        return
    op.create_table(
        TABLE,
        sa.Column("prefix", sa.String(length=16), nullable=False),
        sa.Column("serial_year", sa.Integer(), nullable=False),
        sa.Column("last_value", sa.BigInteger(), nullable=False),
        sa.Column(
            "updated_at",
            sa.DateTime(timezone=True),
            server_default=sa.text("CURRENT_TIMESTAMP"),
            nullable=False,
        ),
        sa.PrimaryKeyConstraint("prefix", "serial_year"),
        mysql_engine="InnoDB",
        mysql_charset="utf8mb4",
        mysql_collate="utf8mb4_unicode_ci",
    )


def downgrade() -> None:
    bind = op.get_bind()
    if _table_exists(bind, TABLE):
        op.drop_table(TABLE)