Issue #1228 add ditto header for new 'liveChannelCondition' header

Similar to the 'condition' header, the only useful validation could be a RQL-Syntax check.
Such a check is not supported by the current RQL-Parser and there is also no type for it yet.
For now, only use 'String' as type.

Signed-off-by: Joel Bartelheimer <joel.bartelheimer@bosch.io>

base/model/src/main/java/org/eclipse/ditto/base/model/headers/AbstractDittoHeaders.java

@@ -273,6 +273,11 @@ public Optional<String> getCondition() {
         return getStringForDefinition(DittoHeaderDefinition.CONDITION);
     }
 
+    @Override
+    public Optional<String> getLiveChannelCondition() {
+        return getStringForDefinition(DittoHeaderDefinition.LIVE_CHANNEL_CONDITION);
+    }
+
     @Override
     public Optional<String> getOrigin() {
         return getStringForDefinition(DittoHeaderDefinition.ORIGIN);

base/model/src/main/java/org/eclipse/ditto/base/model/headers/AbstractDittoHeadersBuilder.java

@@ -465,6 +465,12 @@ public S condition(final String condition) {
         return myself;
     }
 
+    @Override
+    public S liveChannelCondition(final String liveChannelCondition) {
+        putCharSequence(DittoHeaderDefinition.LIVE_CHANNEL_CONDITION, liveChannelCondition);
+        return myself;
+    }
+
     @Override
     public S putHeader(final CharSequence key, final CharSequence value) {
         validateKey(key);

base/model/src/main/java/org/eclipse/ditto/base/model/headers/DittoHeaderDefinition.java

@@ -378,6 +378,20 @@ public enum DittoHeaderDefinition implements HeaderDefinition {
      * @since 2.1.0
      */
     CONDITION("condition", String.class, true, false,
+            HeaderValueValidators.getNoOpValidator()),
+
+    /**
+     * Header definition to identify a request with a conditional channel.
+     * The condition is defined via a RQL expressions, which is evaluated in the things service. If the condition is
+     * evaluated to 'true', then the live-channel is used instead of the regular twin-channel.
+     *
+     * <p>
+     * Key {@code "live-channel-condition"}, Java type: {@link String}.
+     * </p>
+     *
+     * @since 2.2.0
+     */
+    LIVE_CHANNEL_CONDITION("live-channel-condition", String.class, true, false,
             HeaderValueValidators.getNoOpValidator());
 
     /**

base/model/src/main/java/org/eclipse/ditto/base/model/headers/DittoHeaders.java

@@ -212,6 +212,14 @@ static DittoHeadersBuilder newBuilder(final JsonObject jsonObject) {
      */
     Optional<String> getCondition();
 
+    /**
+     * Returns the channel condition, if the live-channel shall be used for the request.
+     *
+     * @return the condition contained in the Condition header.
+     * @since 2.2.0
+     */
+    Optional<String> getLiveChannelCondition();
+
     /**
      * Returns the id of the originating session (e.g. WebSocket, AMQP, ...)
      *

base/model/src/main/java/org/eclipse/ditto/base/model/headers/DittoHeadersBuilder.java

@@ -312,6 +312,15 @@ B acknowledgementRequest(AcknowledgementRequest acknowledgementRequest,
      */
     B condition(String condition);
 
+    /**
+     * Sets the channel condition which decides, if the live channel shall be used for the request.
+     *
+     * @param liveChannelCondition the channel condition to check before applying the request.
+     * @return this builder for method chaining.
+     * @since 2.2.0
+     */
+    B liveChannelCondition(String liveChannelCondition);
+
     /**
      * Puts an arbitrary header with the specified {@code name} and String {@code value} to this builder.
      *

base/model/src/test/java/org/eclipse/ditto/base/model/headers/ImmutableDittoHeadersTest.java

@@ -109,6 +109,7 @@ public final class ImmutableDittoHeadersTest {
     private static final List<String> KNOWN_JOURNAL_TAGS = Lists.list("tag-a", "tag-b");
     private static final boolean KNOWN_IS_SUDO = true;
     private static final String KNOWN_CONDITION = "eq(attributes/value)";
+    private static final String KNOWN_LIVE_CHANNEL_CONDITION = "eq(attributes/value,\"livePolling\")";
     private static final String KNOWN_TRACEPARENT = "00-dfca0d990402884d22e909a87ac677ec-94fc4da95e842f96-01";
     private static final String KNOWN_TRACESTATE = "eclipse=ditto";
     private static final boolean KNOWN_DITTO_RETRIEVE_DELETED = true;
@@ -175,6 +176,7 @@ public void settingAllKnownHeadersWorksAsExpected() {
                 .putHeader(DittoHeaderDefinition.W3C_TRACEPARENT.getKey(), KNOWN_TRACEPARENT)
                 .putHeader(DittoHeaderDefinition.W3C_TRACESTATE.getKey(), KNOWN_TRACESTATE)
                 .condition(KNOWN_CONDITION)
+                .liveChannelCondition(KNOWN_LIVE_CHANNEL_CONDITION)
                 .build();
 
         assertThat(underTest).isEqualTo(expectedHeaderMap);
@@ -331,6 +333,16 @@ public void isSudoIsTrueWhenTrue() {
         assertThat(underTest.isSudo()).isTrue();
     }
 
+    @Test
+    public void liveChannelConditionNotEmptyWhenSet() {
+        final String testValue = "some-condition";
+        final DittoHeaders underTest = DittoHeaders.newBuilder()
+                .putHeader(DittoHeaderDefinition.LIVE_CHANNEL_CONDITION.getKey(), testValue)
+                .build();
+
+        assertThat(underTest.getLiveChannelCondition()).hasValue(testValue);
+    }
+
     @Test
     public void getRequestedAckLabelsReturnsExpected() {
         final DittoHeaders underTest = DittoHeaders.newBuilder()
@@ -423,6 +435,7 @@ public void toJsonReturnsExpected() {
                 .set(DittoHeaderDefinition.W3C_TRACEPARENT.getKey(), KNOWN_TRACEPARENT)
                 .set(DittoHeaderDefinition.W3C_TRACESTATE.getKey(), KNOWN_TRACESTATE)
                 .set(DittoHeaderDefinition.CONDITION.getKey(), KNOWN_CONDITION)
+                .set(DittoHeaderDefinition.LIVE_CHANNEL_CONDITION.getKey(), KNOWN_LIVE_CHANNEL_CONDITION)
                 .build();
 
         final Map<String, String> allKnownHeaders = createMapContainingAllKnownHeaders();
@@ -652,6 +665,7 @@ private static Map<String, String> createMapContainingAllKnownHeaders() {
         result.put(DittoHeaderDefinition.W3C_TRACEPARENT.getKey(), KNOWN_TRACEPARENT);
         result.put(DittoHeaderDefinition.W3C_TRACESTATE.getKey(), KNOWN_TRACESTATE);
         result.put(DittoHeaderDefinition.CONDITION.getKey(), KNOWN_CONDITION);
+        result.put(DittoHeaderDefinition.LIVE_CHANNEL_CONDITION.getKey(), KNOWN_LIVE_CHANNEL_CONDITION);
 
         return result;
     }