Jul 30 - Internal handler files

migrations/versions/phase44_internal_handler.py

@@ -0,0 +1,110 @@
+"""phase44 — issue internal_handler_name / internal_handler_contact,
+and convergence of handler_type to NOT NULL DEFAULT 'internal'
+
+Ports single-tenant phase41 + phase42 into the multi-tenant chain, and closes the
+last divergence in the handler model.
+
+1. Adds `internal_handler_name` and `internal_handler_contact` to `issues`,
+   capturing the janitorial staff member who will handle an issue when
+   handler_type == 'internal'. Distinct from `assigned_to` (the JQC User who owns
+   follow-up) — the actual crew member may not be a system user. Parallels the
+   existing facility_handler_* and vendor_* contact pairs.
+
+2. Converges `handler_type` from MT's `NULL`-able column onto the single-tenant
+   definition, `NOT NULL DEFAULT 'internal'`. MT's application code already
+   treats NULL and 'internal' as the same thing (`handler_type or 'internal'`
+   appears in the model property, the API payload and the templates), so this
+   only removes a redundant second representation of "internal". Existing NULL
+   rows are backfilled to 'internal' BEFORE the MODIFY, otherwise the ALTER
+   fails on a table containing NULLs.
+
+RE-RUNNABLE. Step 1 uses an INFORMATION_SCHEMA column-existence check. Step 2
+cannot use one — the column already exists; what changes is its nullability — so
+it checks IS_NULLABLE instead and skips when the column is already NOT NULL.
+Checking only for existence there would silently make this migration a no-op on
+re-run against a half-applied schema.
+
+No batch_alter_table (MySQL).
+"""
+
+revision      = 'phase44_internal_handler'
+down_revision = 'phase43_schedule_plan_fields'
+branch_labels = None
+depends_on    = None
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def _column_exists(conn, table, column):
+    result = 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})
+    return result.scalar() > 0
+
+
+def _column_is_nullable(conn, table, column):
+    """True when the column exists AND is declared NULL-able.
+
+    Returns False for a missing column so callers never attempt to MODIFY
+    something that isn't there.
+    """
+    result = conn.execute(sa.text(
+        "SELECT IS_NULLABLE FROM INFORMATION_SCHEMA.COLUMNS "
+        "WHERE TABLE_SCHEMA = DATABASE() "
+        "AND TABLE_NAME = :t AND COLUMN_NAME = :c"
+    ), {"t": table, "c": column})
+    row = result.first()
+    return bool(row) and row[0] == 'YES'
+
+
+def upgrade():
+    bind = op.get_bind()
+
+    # ── 1. internal_handler_name ──────────────────────────────────────────
+    if not _column_exists(bind, 'issues', 'internal_handler_name'):
+        op.execute(sa.text(
+            "ALTER TABLE issues ADD COLUMN internal_handler_name VARCHAR(100) NULL"
+        ))
+
+    # ── 2. internal_handler_contact ───────────────────────────────────────
+    if not _column_exists(bind, 'issues', 'internal_handler_contact'):
+        op.execute(sa.text(
+            "ALTER TABLE issues ADD COLUMN internal_handler_contact VARCHAR(200) NULL"
+        ))
+
+    # ── 3. handler_type -> NOT NULL DEFAULT 'internal' ────────────────────
+    # Backfill first: MODIFY ... NOT NULL fails outright if any row holds NULL.
+    # This runs unconditionally (it is itself idempotent — a second run matches
+    # zero rows) so the data is correct even if a previous attempt aborted
+    # between the UPDATE and the ALTER.
+    if _column_is_nullable(bind, 'issues', 'handler_type'):
+        op.execute(sa.text(
+            "UPDATE issues SET handler_type = 'internal' WHERE handler_type IS NULL"
+        ))
+        op.execute(sa.text(
+            "ALTER TABLE issues MODIFY COLUMN handler_type "
+            "ENUM('internal','facility','vendor') NOT NULL DEFAULT 'internal'"
+        ))
+
+
+def downgrade():
+    bind = op.get_bind()
+
+    # Revert handler_type to nullable with no default. Stored values are left
+    # as-is: rows that were NULL before the upgrade are now 'internal', which is
+    # semantically identical under the application's `handler_type or 'internal'`
+    # reads, so there is nothing to undo in the data.
+    if not _column_is_nullable(bind, 'issues', 'handler_type'):
+        op.execute(sa.text(
+            "ALTER TABLE issues MODIFY COLUMN handler_type "
+            "ENUM('internal','facility','vendor') NULL"
+        ))
+
+    if _column_exists(bind, 'issues', 'internal_handler_contact'):
+        op.execute(sa.text("ALTER TABLE issues DROP COLUMN internal_handler_contact"))
+
+    if _column_exists(bind, 'issues', 'internal_handler_name'):
+        op.execute(sa.text("ALTER TABLE issues DROP COLUMN internal_handler_name"))