"""P0-02: 积分榜改为追加快照(append-only) + available_at

去掉 uq_standings_league_season_team(league,season,team 唯一),
改为 (league, season, team, available_at) 唯一;
每次采集 INSERT 新行(available_at=now),支持回测还原历史榜单。

Revision ID: 0023_standings_append_only
Revises: 0022_match_score_status
Create Date: 2026-09-22
"""

from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa

revision: str = '0023_standings_append_only'
down_revision: Union[str, None] = '0022_match_score_status'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    from datetime import datetime, timezone

    # 1) 加 available_at 列(非空,默认 now;存量回填 retrieved_at 或 now)
    op.add_column(
        'standings',
        sa.Column('available_at', sa.DateTime(timezone=True), nullable=False,
                  server_default=sa.func.now()),
    )
    # 存量行: available_at 取 retrieved_at(若存在)否则 now
    op.execute("UPDATE standings SET available_at = COALESCE(retrieved_at, NOW())")

    # 2) 去旧唯一约束,加新唯一约束(league, season, team, available_at)
    op.drop_constraint('uq_standings_league_season_team', 'standings', type_='unique')
    op.drop_index('ix_standings_leason_season_pos', table_name='standings')
    op.create_index('ix_standings_league_season_pos', 'standings', ['league_id', 'season', 'position'])
    op.create_unique_constraint(
        'uq_standings_league_season_team_available', 'standings',
        ['league_id', 'season', 'team_id', 'available_at'],
    )
    op.create_index(
        'ix_standings_league_season_team_available', 'standings',
        ['league_id', 'season', 'team_id', 'available_at'],
    )


def downgrade() -> None:
    op.drop_index('ix_standings_league_season_team_available', table_name='standings')
    op.drop_constraint('uq_standings_league_season_team_available', 'standings', type_='unique')
    op.drop_index('ix_standings_league_season_pos', table_name='standings')
    op.create_index('ix_standings_leason_season_pos', 'standings', ['league_id', 'season', 'position'])
    op.create_unique_constraint(
        'uq_standings_league_season_team', 'standings',
        ['league_id', 'season', 'team_id'],
    )
    op.drop_column('standings', 'available_at')