totoro: fix up valve index alerting

ops/nixos/totoro/default.nix

@@ -206,7 +206,7 @@ in {
         - name: valve_index
           rules:
           - alert: ValveIndexInStock
-            expr: valve_index_in_stock == 0
+            expr: valve_index_in_stock > 0
             for: 1s
             labels:
               severity: page
@@ -225,10 +225,8 @@ in {
         };
         receivers = [{
           name = "default-receiver";
-          slack_configs = [{
-            send_resolved = true;
-            api_url = secrets.monitoring.alertmanager.discord.api_url;
-            channel = "#alerts";
+          webhook_configs = [{
+            url = "http://localhost:9997";
           }];
         }];
       };
@@ -296,5 +294,22 @@ in {
   };
   my.prometheus.additionalExporterPorts.valveindexinstock = 9998;
 
+  systemd.services.alertmanager-discord = {
+    enable = true;
+    serviceConfig = {
+      ExecStart = "${depot.pkgs.alertmanager-discord}/bin/alertmanager-discord -listen.address 127.0.0.1:9997";
+      EnvironmentFile = pkgs.writeText "discord-secret" ''
+        DISCORD_WEBHOOK=${secrets.monitoring.alertmanager.discord.api_url}
+      '';
+      DynamicUser = true;
+      MountAPIVFS = true;
+      PrivateTmp = true;
+      PrivateUsers = true;
+      ProtectControlGroups = true;
+      ProtectKernelModules = true;
+      ProtectKernelTunables = true;
+    };
+  };
+
   system.stateVersion = "20.03";
 }