mxqkill: Add function cancel_group and refactor group cancellation …

…logic

Refactor the group cancellation process by moving the code from main()
into new functions, similar to the existing jobs cancellation functions.

Added `cancel_group` function along with its helper functions.

Notable change:

- Removed constraints from the old code, making it no longer mandatory
  for the group to have `groups_status OK`, or pending/running jobs.

This allows cancellations of both inactive and previously cancelled
groups.

These changes enable more flexible group management and simplify the
cancellation logic.

Note: The old code will be removed in the next commit for cleaner diffs
and improved clarity.

mxqkill.c

@@ -207,6 +207,86 @@ static void cancel_job(struct mx_mysql *mysql, uint64_t job_id, uint64_t user_ui
     set_job_cancelled(mysql, job_id);
 }
 
+static void verify_group_owner(struct mx_mysql *mysql, uint64_t group_id, uint64_t user_uid) {
+    struct mx_mysql_stmt *stmt = mx_mysql_statement_prepare(mysql,
+        "SELECT user_uid FROM mxq_group"
+        "  WHERE group_id = ?"
+    );
+    if (!stmt)
+        mx_die("mx_mysql_statement_prepare(): %s\n", mx_mysql_error());
+
+    mx_mysql_statement_param_bind(stmt, 0, uint64, &group_id);
+
+    unsigned long long num_rows;
+    int res = mx_mysql_statement_execute(stmt, &num_rows);
+    if (res < 0)
+        mx_die("mx_mysql_statement_execute(): %s\n", mx_mysql_error());
+
+    if (num_rows == 0)
+        mx_die("no such group_id %lu\n", group_id);
+
+    uint64_t uid;
+    mx_mysql_statement_result_bind(stmt, 0, uint64, &uid);
+
+    res = mx_mysql_statement_fetch(stmt);
+    if (res < 0)
+        mx_die("mx_mysql_statement_fetch: %s\n", mx_mysql_error());
+
+    if (uid != user_uid)
+        mx_die("group %lu: permission denied\n", group_id);
+
+    mx_mysql_statement_close(&stmt);
+}
+
+static void set_group_cancelled(struct mx_mysql *mysql, uint64_t group_id) {
+    struct mx_mysql_stmt *stmt = mx_mysql_statement_prepare(mysql,
+            "UPDATE mxq_group SET group_status = " status_str(MXQ_GROUP_STATUS_CANCELLED)
+            " WHERE group_id = ?"
+    );
+    if (!stmt)
+        mx_die("mx_mysql_statement_prepare(): %s\n", mx_mysql_error());
+
+    mx_mysql_statement_param_bind(stmt, 0, uint64, &group_id);
+
+    unsigned long long num_rows;
+    int res = mx_mysql_statement_execute(stmt, &num_rows);
+    if (res < 0)
+        mx_die("mx_mysql_statement_execute(): %s\n", mx_mysql_error());
+    if (num_rows == 0)
+        mx_die("no such group_id %lu\n", group_id);
+
+    mx_mysql_statement_close(&stmt);
+}
+
+static void cancel_pending_jobs(struct mx_mysql *mysql, uint64_t group_id) {
+    struct mx_mysql_stmt *stmt = mx_mysql_statement_prepare(mysql,
+            "UPDATE mxq_job SET job_cancelled = TRUE"
+            "  WHERE group_id = ?"
+            "  AND job_status = " status_str(MXQ_JOB_STATUS_INQ)
+    );
+    if (!stmt)
+        mx_die("mx_mysql_statement_prepare(): %s\n", mx_mysql_error());
+
+    mx_mysql_statement_param_bind(stmt, 0, uint64, &group_id);
+
+    unsigned long long num_rows;
+    int res = mx_mysql_statement_execute(stmt, &num_rows);
+    if (res < 0)
+        mx_die("mx_mysql_statement_execute(): %s\n", mx_mysql_error());
+    if (num_rows)
+        mx_log_notice("cancelled %llu jobs in group with group_id=%lu", num_rows, group_id);
+    mx_mysql_statement_close(&stmt);
+}
+
+void cancel_group(struct mx_mysql *mysql, uint64_t group_id, uint64_t user_uid) {
+
+    verify_group_owner(mysql, group_id, user_uid);
+    set_group_cancelled(mysql, group_id);
+    cancel_pending_jobs(mysql, group_id);
+    mx_log_notice("marked all running jobs in group with group_id=%lu to be killed by executing servers.", group_id);
+    mx_log_notice("deactivated group with group_id=%lu", group_id);
+}
+
 int main(int argc, char *argv[])
 {
     struct mx_mysql *mysql = NULL;