"""Add notificationtypes.boardorder (row order on the shopfloor board).

Rows were ordered by display style and then type name, so what led the screen
was an accident of styling and the alphabet. A site decides its own running
order now: low first, and rows sharing a category sort by the lowest order
among their types.

Existing rows default to 100. Recognition and Recertification are seeded ahead
of that (10 and 20) so the out-of-the-box board keeps the order sites already
expect, without pinning anything a site has since renamed.

Idempotent; downgrade drops the column.

Revision ID: notifications0005boardorder
Revises: notifications0004category
"""
from alembic import op
import sqlalchemy as sa


revision = 'notifications0005boardorder'
down_revision = 'notifications0004category'
branch_labels = None
depends_on = None

_TABLE = 'notificationtypes'
_COLUMN = 'boardorder'

# Only the two types every site starts with; anything else keeps the default.
_SEEDED_ORDER = (('Recognition', 10), ('Recertification', 20))


def _column_names(insp, table):
    return {c['name'] for c in insp.get_columns(table)}


def upgrade():
    bind = op.get_bind()
    insp = sa.inspect(bind)
    if _TABLE not in insp.get_table_names():
        return
    if _COLUMN in _column_names(insp, _TABLE):
        return
    op.add_column(_TABLE, sa.Column(_COLUMN, sa.Integer(), nullable=False,
                                    server_default='100'))
    # Seed the shipped types' order. Guarded on the default so a site that has
    # already set an order (re-running after a manual add) is left alone.
    for typename, order in _SEEDED_ORDER:
        bind.execute(
            sa.text('UPDATE notificationtypes SET boardorder = :order '
                    'WHERE typename = :typename AND boardorder = 100'),
            {'order': order, 'typename': typename})


def downgrade():
    bind = op.get_bind()
    insp = sa.inspect(bind)
    if _TABLE not in insp.get_table_names():
        return
    if _COLUMN in _column_names(insp, _TABLE):
        op.drop_column(_TABLE, _COLUMN)