Use a FSM to determine application next state

- Separate cluster application UI state from server-side app status
- Use a state machine to determine cluster application next state
- Instead of using two variables to keep track of when an app
is installing or updating, just use the app status property and control
server-side and user events using the FSM service.

1 files changed, 141 insertions, 0 deletions

diff --git a/app/assets/javascripts/clusters/services/application_state_machine.js b/app/assets/javascripts/clusters/services/application_state_machine.js
new file mode 100644
index 00000000000..aafb2350ae4
--- /dev/null
+++ b/app/assets/javascripts/clusters/services/application_state_machine.js
@@ -0,0 +1,141 @@
+import { APPLICATION_STATUS, UPDATE_EVENT, INSTALL_EVENT } from '../constants';
+
+const {
+  NO_STATUS,
+  SCHEDULED,
+  NOT_INSTALLABLE,
+  INSTALLABLE,
+  INSTALLING,
+  INSTALLED,
+  ERROR,
+  UPDATING,
+  UPDATED,
+  UPDATE_ERRORED,
+} = APPLICATION_STATUS;
+
+const applicationStateMachine = {
+  /* When the application initially loads, it will have `NO_STATUS`
+   * It will transition from `NO_STATUS` once the async backend call is completed
+   */
+  [NO_STATUS]: {
+    on: {
+      [SCHEDULED]: {
+        target: INSTALLING,
+      },
+      [NOT_INSTALLABLE]: {
+        target: NOT_INSTALLABLE,
+      },
+      [INSTALLABLE]: {
+        target: INSTALLABLE,
+      },
+      [INSTALLING]: {
+        target: INSTALLING,
+      },
+      [INSTALLED]: {
+        target: INSTALLED,
+      },
+      [ERROR]: {
+        target: INSTALLABLE,
+        effects: {
+          installFailed: true,
+        },
+      },
+      [UPDATING]: {
+        target: UPDATING,
+      },
+      [UPDATED]: {
+        target: INSTALLED,
+      },
+      [UPDATE_ERRORED]: {
+        target: INSTALLED,
+        effects: {
+          updateFailed: true,
+        },
+      },
+    },
+  },
+  [NOT_INSTALLABLE]: {
+    on: {
+      [INSTALLABLE]: {
+        target: INSTALLABLE,
+      },
+    },
+  },
+  [INSTALLABLE]: {
+    on: {
+      [INSTALL_EVENT]: {
+        target: INSTALLING,
+        effects: {
+          installFailed: false,
+        },
+      },
+      // This is possible in artificial environments for E2E testing
+      [INSTALLED]: {
+        target: INSTALLED,
+      },
+    },
+  },
+  [INSTALLING]: {
+    on: {
+      [INSTALLED]: {
+        target: INSTALLED,
+      },
+      [ERROR]: {
+        target: INSTALLABLE,
+        effects: {
+          installFailed: true,
+        },
+      },
+    },
+  },
+  [INSTALLED]: {
+    on: {
+      [UPDATE_EVENT]: {
+        target: UPDATING,
+        effects: {
+          updateFailed: false,
+          updateSuccessful: false,
+        },
+      },
+    },
+  },
+  [UPDATING]: {
+    on: {
+      [UPDATED]: {
+        target: INSTALLED,
+        effects: {
+          updateSuccessful: true,
+          updateAcknowledged: false,
+        },
+      },
+      [UPDATE_ERRORED]: {
+        target: INSTALLED,
+        effects: {
+          updateFailed: true,
+        },
+      },
+    },
+  },
+};
+
+/**
+ * Determines an application new state based on the application current state
+ * and an event. If the application current state cannot handle a given event,
+ * the current state is returned.
+ *
+ * @param {*} application
+ * @param {*} event
+ */
+const transitionApplicationState = (application, event) => {
+  const newState = applicationStateMachine[application.status].on[event];
+
+  return newState
+    ? {
+        ...application,
+        status: newState.target,
+        ...newState.effects,
+      }
+    : application;
+};
+
+export default transitionApplicationState;