1 files changed, 118 insertions, 0 deletions
diff --git a/framework/src/onos/utils/jdvue/src/main/java/org/onlab/jdvue/DependencyCycle.java b/framework/src/onos/utils/jdvue/src/main/java/org/onlab/jdvue/DependencyCycle.java
new file mode 100644
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--- /dev/null
+++ b/framework/src/onos/utils/jdvue/src/main/java/org/onlab/jdvue/DependencyCycle.java
@@ -0,0 +1,118 @@
+package org.onlab.jdvue;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * Simple representation of a Java package dependency cycle.
+ */
+public class DependencyCycle {
+
+    private final List<JavaPackage> cycle;
+
+    /**
+     * Creates a normalized dependency cycle represented by the specified list
+     * of Java packages, which are expected to be given in order of dependency.
+     * List is assumed to be non-empty.
+     *
+     * @param cycle list of Java packages in the dependency cycle
+     * @param cause Java package that caused the cycle
+     */
+    DependencyCycle(List<JavaPackage> cycle, JavaPackage cause) {
+        this.cycle = normalize(cycle, cause);
+    }
+
+    /**
+     * Produces a normalized dependency cycle list. Normalization is performed
+     * by rotating the list so that the package with the least lexicographic
+     * name is at the start of the list.
+     *
+     * @param cycle list of Java packages in the dependency cycle
+     * @param cause Java package that caused the cycle
+     * @return normalized cycle
+     */
+    private List<JavaPackage> normalize(List<JavaPackage> cycle, JavaPackage cause) {
+        int start = cycle.indexOf(cause);
+        List<JavaPackage> clone = new ArrayList<>(cycle.subList(start, cycle.size()));
+        int leastIndex = findIndexOfLeastName(clone);
+        Collections.rotate(clone, -leastIndex);
+        return Collections.unmodifiableList(clone);
+    }
+
+    /**
+     * Returns the index of the Java package with the least name.
+     *
+     * @param cycle list of Java packages in the dependency cycle
+     * @return index of the least Java package name
+     */
+    private int findIndexOfLeastName(List<JavaPackage> cycle) {
+        int leastIndex = 0;
+        String leastName = cycle.get(leastIndex).name();
+        for (int i = 1, n = cycle.size(); i < n; i++) {
+            JavaPackage javaPackage = cycle.get(i);
+            if (leastName.compareTo(javaPackage.name()) > 0) {
+                leastIndex = i;
+                leastName = javaPackage.name();
+            }
+        }
+        return leastIndex;
+    }
+
+    /**
+     * Returns the normalized Java package dependency cycle
+     *
+     * @return list of packages in the dependency cycle
+     */
+    public List<JavaPackage> getCycle() {
+        return cycle;
+    }
+
+    /**
+     * Returns the dependency cycle in form of individual dependencies.
+     *
+     * @return list of dependencies forming the cycle
+     */
+    public List<Dependency> getCycleSegments() {
+        List<Dependency> dependencies = new ArrayList<>();
+        for (int i = 0, n = cycle.size(); i < n; i++) {
+            dependencies.add(new Dependency(cycle.get(i), cycle.get(i < n - 1 ? i + 1 : 0)));
+        }
+        return dependencies;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o instanceof DependencyCycle) {
+            DependencyCycle that = (DependencyCycle) o;
+            return Objects.equals(cycle, that.cycle);
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(cycle);
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this).add("cycle", cycle).toString();
+    }
+
+    public String toShortString() {
+        StringBuilder sb = new StringBuilder("[");
+        for (JavaPackage javaPackage : cycle) {
+            sb.append(javaPackage.name()).append(", ");
+        }
+        if (sb.length() > 1) {
+            sb.delete(sb.length() - 2, sb.length());
+        }
+        sb.append("]");
+        return sb.toString();
+    }
+
+}