Aug 4 - Update code to follow up - MT11

migrations/versions/phase46_schedule_recurrence.py

@@ -0,0 +1,84 @@
+"""phase46 — inspection schedule day-of-week / day-of-month recurrence
+
+Ports single-tenant phase43 onto MT's `inspection_schedules` table (MT's name
+for the same thing — no rename, rule 7). Adds the recurrence-detail columns so a
+weekly schedule can name the weekdays it runs on (Mon/Wed/Fri) and a monthly (or
+quarterly / bi-annual / annual) schedule can name either a day of the month
+("the 15th") or an nth weekday ("the 2nd Tuesday"):
+
+    weekdays     VARCHAR(20)  -- CSV of Python weekday ints, Mon=0, e.g. '0,2,4'
+    month_mode   VARCHAR(20)  -- 'day_of_month' | 'nth_weekday'
+    day_of_month SMALLINT     -- 1–31, clamped to the month's last day
+    nth_week     SMALLINT     -- 1–5, or -1 for "last"
+    nth_weekday  SMALLINT     -- 0–6, Mon=0
+
+All nullable with no backfill: existing phase34/phase43 rows keep NULLs and fall
+back to the plain-interval behaviour in InspectionSchedule._add_interval(), so
+no schedule changes cadence on deploy.
+
+`next_run_at` is NOT touched — it keeps its name, its DATETIME type and its
+index. It remains the due datetime (ST's `next_due_date` by another name); the
+recurrence maths runs on its DATE part and preserves its TIME part.
+
+`month_mode` is VARCHAR rather than ENUM so adding a recurrence style later
+needs no 3-step MySQL ENUM migration.
+
+Uses INFORMATION_SCHEMA column-existence checks — safe to re-run on every
+tenant DB. Additive only: nothing is renamed, retyped or dropped.
+"""
+
+revision      = 'phase46_schedule_recurrence'
+down_revision = 'phase45_schedule_frequency_enum'
+branch_labels = None
+depends_on    = None
+
+from alembic import op
+import sqlalchemy as sa
+
+
+_TABLE = 'inspection_schedules'
+
+_COLUMNS = (
+    ('weekdays',     'VARCHAR(20) NULL'),
+    ('month_mode',   'VARCHAR(20) NULL'),
+    ('day_of_month', 'SMALLINT NULL'),
+    ('nth_week',     'SMALLINT NULL'),
+    ('nth_weekday',  'SMALLINT NULL'),
+)
+
+
+def _table_exists(conn, table):
+    return conn.execute(sa.text(
+        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES "
+        "WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = :t"
+    ), {"t": table}).scalar() > 0
+
+
+def _column_exists(conn, table, column):
+    return conn.execute(sa.text(
+        "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS "
+        "WHERE TABLE_SCHEMA = DATABASE() "
+        "AND TABLE_NAME = :t AND COLUMN_NAME = :c"
+    ), {"t": table, "c": column}).scalar() > 0
+
+
+def upgrade():
+    bind = op.get_bind()
+    if not _table_exists(bind, _TABLE):
+        return
+    for name, ddl in _COLUMNS:
+        if not _column_exists(bind, _TABLE, name):
+            op.execute(sa.text(
+                f"ALTER TABLE {_TABLE} ADD COLUMN {name} {ddl}"
+            ))
+
+
+def downgrade():
+    bind = op.get_bind()
+    if not _table_exists(bind, _TABLE):
+        return
+    for name, _ddl in reversed(_COLUMNS):
+        if _column_exists(bind, _TABLE, name):
+            op.execute(sa.text(
+                f"ALTER TABLE {_TABLE} DROP COLUMN {name}"
+            ))