"""Replace dashboard_widgets.position with a Grafana-style grid (x/y/w/h)

Revision ID: 0021_dashboard_widget_grid
Revises: 0020_ansible_run_results
Create Date: 2026-06-17
"""
from typing import Sequence, Union
from alembic import op
import sqlalchemy as sa

revision: str = "0021_dashboard_widget_grid"
down_revision: Union[str, None] = "0020_ansible_run_results"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    # New grid columns (server_default so existing rows are populated; the ORM
    # supplies these on insert thereafter). 12-col grid, default widget 4x4.
    op.add_column("dashboard_widgets",
                  sa.Column("grid_x", sa.Integer, nullable=False, server_default="0"))
    op.add_column("dashboard_widgets",
                  sa.Column("grid_y", sa.Integer, nullable=False, server_default="0"))
    op.add_column("dashboard_widgets",
                  sa.Column("grid_w", sa.Integer, nullable=False, server_default="4"))
    op.add_column("dashboard_widgets",
                  sa.Column("grid_h", sa.Integer, nullable=False, server_default="4"))
    # Backfill from the old `position` order into a 3-up grid, reproducing the
    # previous masonry layout: 3 widgets per row, each 4 cols wide x 4 cells tall.
    op.execute(
        "UPDATE dashboard_widgets "
        "SET grid_x = (position % 3) * 4, grid_y = (position / 3) * 4"
    )
    op.drop_column("dashboard_widgets", "position")


def downgrade() -> None:
    op.add_column("dashboard_widgets",
                  sa.Column("position", sa.Integer, nullable=False, server_default="0"))
    # Reconstruct a linear order from the grid (reading order: top-to-bottom,
    # then left-to-right within a row).
    op.execute(
        "UPDATE dashboard_widgets SET position = grid_y * 3 + (grid_x / 4)"
    )
    op.drop_column("dashboard_widgets", "grid_h")
    op.drop_column("dashboard_widgets", "grid_w")
    op.drop_column("dashboard_widgets", "grid_y")
    op.drop_column("dashboard_widgets", "grid_x")