refactor db_subscr_ps() to db_subscr_nam()

Allow to set nam_ps and nam_cs from this same function, by adding the is_ps
arg.

Combine both NAM_PS stmts to DB_STMT_UPD_NAM_PS_BY_IMSI, add another such stmt
for CS. Use named parameters instead of parameter indexes.

Improve error return values as well as error logging to clearly indicate
whether the operation could not find the requested IMSI, or other errors
occured.

Adjust the single caller.

This prepares for upcoming VTY and possibly CTRL commands, and the error
handling introduced here has been or will be adopted by other functions in
previous or subsequent patches.

Change-Id: I6e70e15228f5bb10bee6758ae5dc9687d65839bd
diff --git a/src/db_hlr.c b/src/db_hlr.c
index 8df4bcb..9bdb372 100644
--- a/src/db_hlr.c
+++ b/src/db_hlr.c
@@ -259,31 +259,58 @@
 	return rc;
 }
 
-int db_subscr_ps(struct db_context *dbc, const char *imsi, bool enable)
+/* Enable or disable PS or CS for a subscriber.
+ * For the subscriber with the given imsi, set nam_ps (when is_ps == true) or
+ * nam_cs (when is_ps == false) to nam_val in the database.
+ * Returns 0 on success, -ENOENT when the given IMSI does not exist, -EINVAL if
+ * the SQL statement could not be composed, -ENOEXEC if running the SQL
+ * statement failed, -EIO if the amount of rows modified is unexpected.
+ */
+int db_subscr_nam(struct db_context *dbc, const char *imsi, bool nam_val, bool is_ps)
 {
-	sqlite3_stmt *stmt =
-		dbc->stmt[enable ? DB_STMT_SET_NAM_PS_BY_IMSI : DB_STMT_UNSET_NAM_PS_BY_IMSI];
+	sqlite3_stmt *stmt;
 	int rc;
+	int ret = 0;
 
-	if (!db_bind_text(stmt, NULL, imsi))
-		return -EINVAL;
+	stmt = dbc->stmt[is_ps ? DB_STMT_UPD_NAM_PS_BY_IMSI
+			       : DB_STMT_UPD_NAM_CS_BY_IMSI];
 
-	rc = sqlite3_step(stmt); /* execute the statement */
+	if (!db_bind_text(stmt, "$imsi", imsi))
+		return -EIO;
+	if (!db_bind_int(stmt, "$val", nam_val ? 1 : 0))
+		return -EIO;
+
+	/* execute the statement */
+	rc = sqlite3_step(stmt);
 	if (rc != SQLITE_DONE) {
-		LOGHLR(imsi, LOGL_ERROR, "Error executing SQL: %d\n", rc);
-		db_remove_reset(stmt);
-		return -ENOEXEC;
+		LOGHLR(imsi, LOGL_ERROR, "%s %s: SQL error: %s\n",
+		       nam_val ? "enable" : "disable",
+		       is_ps ? "PS" : "CS",
+		       sqlite3_errmsg(dbc->db));
+		ret = -EIO;
+		goto out;
 	}
 
-	rc = sqlite3_changes(dbc->db); /* verify execution result */
-	if (rc != 1) {
-		LOGHLR(imsi, LOGL_ERROR, "SQL modified %d rows (expected 1)\n",
+	/* verify execution result */
+	rc = sqlite3_changes(dbc->db);
+	if (!rc) {
+		LOGP(DAUC, LOGL_ERROR, "Cannot %s %s: no such subscriber: IMSI='%s'\n",
+		     nam_val ? "enable" : "disable",
+		     is_ps ? "PS" : "CS",
+		     imsi);
+		ret = -ENOENT;
+		goto out;
+	} else if (rc != 1) {
+		LOGHLR(imsi, LOGL_ERROR, "%s %s: SQL modified %d rows (expected 1)\n",
+		       nam_val ? "enable" : "disable",
+		       is_ps ? "PS" : "CS",
 		       rc);
-		rc = -EINVAL;
+		ret = -EIO;
 	}
 
+out:
 	db_remove_reset(stmt);
-	return rc;
+	return ret;
 }
 
 int db_subscr_lu(struct db_context *dbc,