Check for authinstances in use when deleting institutions (bug #917873)

When you delete an institution, and one of the institution's
authinstances is still in use by some users, you get an sql error and
a nonrecoverable error screen. (This can only happen when the users
still using the authinstance are not institution members, because
there is already a check to stop deletion of institutions with
members).

This patch allows the institution to be deleted anyway, reassigning
the offending users to a 'default' authinstance.  If we can't find a
sensible default authinstance, it will at least display a more helpful
error message.

Also, when attempting to delete an institution with members, set an
error on the form rather than throwing a ConfigException.

Change-Id: I9c85a3c8c80411e3cf526767b9142efb12907e5c
Signed-off-by: Richard Mansfield <richard.mansfield@catalyst.net.nz>

htdocs/admin/users/institutions.php

@@ -82,8 +82,28 @@ if ($institution || $add) {
 
     if ($delete) {
         function delete_validate(Pieform $form, $values) {
-            if (get_field('usr_institution', 'COUNT(*)', 'institution', $values['i'])) {
-                throw new ConfigException('Attempt to delete an institution that has members');
+            // Ensure the institution has no members left
+            if ($members = get_field('usr_institution', 'COUNT(*)', 'institution', $values['i'])) {
+                $form->set_error('submit', get_string('institutionstillhas', 'admin', get_string('nmembers', 'group', $members)));
+            }
+
+            // If some users are still using one of this institution's authinstances, it's okay if
+            // we can find a default authinstance for those users, otherwise it's an error.
+            if ($authinstanceids = get_column('auth_instance', 'id', 'institution', $values['i'])) {
+                $badusers = count_records_select(
+                    'usr',
+                    'authinstance IN (' . join(',', array_fill(0, count($authinstanceids), '?')) . ')',
+                    $authinstanceids
+                );
+                if ($badusers) {
+                    $defaultauth = record_exists('auth_instance', 'institution', 'mahara', 'authname', 'internal');
+                    if ($values['i'] == 'mahara' || !$defaultauth) {
+                        $form->set_error(
+                            'submit',
+                            get_string('institutionauthinuseby', 'admin', get_string('nusers', 'mahara', $badusers))
+                        );
+                    }
+                }
             }
         }
 
@@ -117,6 +137,19 @@ if ($institution || $add) {
                     }
                 }
             }
+
+            // If any users are still using this institution's authinstances, change them now.
+            if ($authinstanceids) {
+                execute_sql("
+                    UPDATE {usr}
+                    SET authinstance = (
+                        SELECT MIN(id) FROM {auth_instance} WHERE institution = 'mahara' AND authname = 'internal'
+                    )
+                    WHERE authinstance IN (" . join(',', array_fill(0, count($authinstanceids), '?')) . ')',
+                    $authinstanceids
+                );
+            }
+
             foreach ($authinstanceids as $id) {
                 delete_records('auth_instance_config', 'instance', $id);
             }

htdocs/lang/en.utf8/admin.php

@@ -683,6 +683,8 @@ $string['addinstitution'] = 'Add Institution';
 $string['authplugin'] = 'Authentication plugin';
 $string['deleteinstitution'] = 'Delete Institution';
 $string['deleteinstitutionconfirm'] = 'Are you really sure you wish to delete this institution?';
+$string['institutionstillhas'] = 'This institution still has %s';
+$string['institutionauthinuseby'] = "This institution's authentication is still in use by %s";
 $string['institutiononly'] = 'Institution only';
 $string['institutionaddedsuccessfully2'] = 'Institution added successfully';
 $string['institutiondeletedsuccessfully'] = 'Institution deleted successfully';

htdocs/lang/en.utf8/group.php

@@ -130,6 +130,10 @@ $string['invites'] = "Invites";
 $string['member'] = 'member';
 $string['members'] = 'members';
 $string['Members'] = 'Members';
+$string['nmembers'] = array(
+    '1 member',
+    '%s members',
+);
 
 $string['memberrequests'] = 'Membership requests';
 $string['declinerequest'] = 'Decline request';

htdocs/lang/en.utf8/mahara.php

@@ -951,6 +951,10 @@ $string['Visits'] = 'Visits';
 $string['after'] = 'after';
 $string['before'] = 'before';
 $string['Visibility'] = 'Visibility';
+$string['nusers'] = array(
+    '1 user',
+    '%s users',
+);
 
 // import related strings (maybe separated later)
 $string['importedfrom'] = 'Imported from %s';