1 files changed, 54 insertions, 0 deletions
diff --git a/src/main/java/de/thedevstack/conversationsplus/enums/MessageStatus.java b/src/main/java/de/thedevstack/conversationsplus/enums/MessageStatus.java
new file mode 100644
index 00000000..8a31a325
--- /dev/null
+++ b/src/main/java/de/thedevstack/conversationsplus/enums/MessageStatus.java
@@ -0,0 +1,54 @@
+package de.thedevstack.conversationsplus.enums;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+
+/**
+ */
+public enum MessageStatus {
+    WAITING,
+    TRANSMITTING,
+    TRANSMITTED,
+    FAILED,
+    CANCELED,
+    DISPLAYED,
+    RECEIVED;
+
+    static {
+        /*
+         * Initialization of valid next states in this block,
+         * because the enum values need to be known at initialization.
+         * If trying to initialize in Constructor, then only forward transitions are possible.,
+         * no way to handle jumping back.
+        */
+        WAITING.initValidNextStates(TRANSMITTING);
+        TRANSMITTING.initValidNextStates(FAILED, TRANSMITTED, CANCELED);
+        CANCELED.initValidNextStates(WAITING);
+        FAILED.initValidNextStates(WAITING);
+
+        // Restrict some transitions to be only valid for outgoing messages
+        TRANSMITTED.initValidNextStatesForDirection(MessageDirection.OUT, RECEIVED, DISPLAYED);
+        RECEIVED.initValidNextStatesForDirection(MessageDirection.OUT, DISPLAYED);
+    }
+
+    private List<MessageStatus> validNextStates;
+    private HashMap<MessageDirection, List<MessageStatus>> directionRestricted = new HashMap<>();
+
+    private void initValidNextStates(MessageStatus... validNextStates) {
+        this.validNextStates = Arrays.asList(validNextStates);
+    }
+
+    private void initValidNextStatesForDirection(MessageDirection direction, MessageStatus... newStatus) {
+        this.directionRestricted.put(direction, Arrays.asList(newStatus));
+    }
+
+    public boolean isTransitionToStateAllowed(MessageStatus newStatus, MessageDirection direction) {
+        boolean hasNoValidNextStates = this.validNextStates.isEmpty() && (!this.directionRestricted.containsKey(direction) || this.directionRestricted.get(direction).isEmpty());
+        boolean isValidNextState = this.validNextStates.contains(newStatus);
+        boolean isValidNextStateForDirection = (this.directionRestricted.containsKey(direction) && this.directionRestricted.get(direction).contains(newStatus));
+        return hasNoValidNextStates // no valid next states -> every new state is allowed
+                || isValidNextState // if newStatus is conditionless
+                || isValidNextStateForDirection; // if the newStatus is valid for the direction
+    }
+}