Introduce PluginDependencyTracker

scm-webapp/src/main/java/sonia/scm/plugin/PluginDependencyTracker.java

@@ -0,0 +1,42 @@
+package sonia.scm.plugin;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+
+import static sonia.scm.ScmConstraintViolationException.Builder.doThrow;
+
+class PluginDependencyTracker {
+
+  private final Map<String, Collection<String>> plugins = new HashMap<>();
+
+  void addInstalled(PluginDescriptor plugin) {
+    plugin.getDependencies().forEach(dependency -> addDependency(plugin.getInformation().getName(), dependency));
+  }
+
+  void removeInstalled(PluginDescriptor plugin) {
+    doThrow()
+      .violation("Plugin is needed as a dependency for other plugins", "plugin")
+      .when(!mayUninstall(plugin.getInformation().getName()));
+    plugin.getDependencies().forEach(dependency -> removeDependency(plugin.getInformation().getName(), dependency));
+  }
+
+  boolean mayUninstall(String name) {
+    return plugins.computeIfAbsent(name, x -> new HashSet<>()).isEmpty();
+  }
+
+  private void addDependency(String from, String to) {
+    plugins.computeIfAbsent(to, name -> createInitialDependencyCollection(from));
+  }
+
+  private void removeDependency(String from, String to) {
+    plugins.get(to).remove(from);
+  }
+
+  private Collection<String> createInitialDependencyCollection(String from) {
+    Collection<String> dependencies = new HashSet<>();
+    dependencies.add(from);
+    return dependencies;
+  }
+}

scm-webapp/src/test/java/sonia/scm/plugin/PluginDependencyTrackerTest.java

@@ -0,0 +1,81 @@
+package sonia.scm.plugin;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import sonia.scm.ScmConstraintViolationException;
+
+import static java.util.Collections.emptySet;
+import static java.util.Collections.singleton;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+import static sonia.scm.plugin.PluginTestHelper.createInstalled;
+
+class PluginDependencyTrackerTest {
+
+  @Test
+  void simpleInstalledPluginWithoutDependingPluginsCanBeUninstalled() {
+    PluginDescriptor mail = createInstalled("scm-mail-plugin").getDescriptor();
+    when(mail.getDependencies()).thenReturn(emptySet());
+
+    PluginDependencyTracker pluginDependencyTracker = new PluginDependencyTracker();
+    pluginDependencyTracker.addInstalled(mail);
+
+    boolean mayUninstall = pluginDependencyTracker.mayUninstall("scm-mail-plugin");
+    assertThat(mayUninstall).isTrue();
+  }
+
+  @Test
+  void installedPluginWithDependingPluginCannotBeUninstalled() {
+    PluginDescriptor review = createInstalled("scm-review-plugin").getDescriptor();
+    when(review.getDependencies()).thenReturn(singleton("scm-mail-plugin"));
+
+    PluginDependencyTracker pluginDependencyTracker = new PluginDependencyTracker();
+    pluginDependencyTracker.addInstalled(review);
+
+    boolean mayUninstall = pluginDependencyTracker.mayUninstall("scm-mail-plugin");
+    assertThat(mayUninstall).isFalse();
+  }
+
+  @Test
+  void uninstallOfRequiredPluginShouldThrowException() {
+    PluginDescriptor review = createInstalled("scm-review-plugin").getDescriptor();
+    when(review.getDependencies()).thenReturn(singleton("scm-mail-plugin"));
+
+    PluginDependencyTracker pluginDependencyTracker = new PluginDependencyTracker();
+    pluginDependencyTracker.addInstalled(review);
+
+    Assertions.assertThrows(
+      ScmConstraintViolationException.class,
+      () -> pluginDependencyTracker.removeInstalled(createInstalled("scm-mail-plugin").getDescriptor())
+    );
+  }
+
+  @Test
+  void installedPluginWithDependingPluginCanBeUninstalledAfterDependingPluginIsUninstalled() {
+    PluginDescriptor review = createInstalled("scm-review-plugin").getDescriptor();
+    when(review.getDependencies()).thenReturn(singleton("scm-mail-plugin"));
+
+    PluginDependencyTracker pluginDependencyTracker = new PluginDependencyTracker();
+    pluginDependencyTracker.addInstalled(review);
+    pluginDependencyTracker.removeInstalled(review);
+
+    boolean mayUninstall = pluginDependencyTracker.mayUninstall("scm-mail-plugin");
+    assertThat(mayUninstall).isTrue();
+  }
+
+  @Test
+  void installedPluginWithMultipleDependingPluginCannotBeUninstalledAfterOnlyOneDependingPluginIsUninstalled() {
+    PluginDescriptor review = createInstalled("scm-review-plugin").getDescriptor();
+    when(review.getDependencies()).thenReturn(singleton("scm-mail-plugin"));
+    PluginDescriptor jira = createInstalled("scm-jira-plugin").getDescriptor();
+    when(jira.getDependencies()).thenReturn(singleton("scm-mail-plugin"));
+
+    PluginDependencyTracker pluginDependencyTracker = new PluginDependencyTracker();
+    pluginDependencyTracker.addInstalled(review);
+    pluginDependencyTracker.addInstalled(jira);
+    pluginDependencyTracker.removeInstalled(jira);
+
+    boolean mayUninstall = pluginDependencyTracker.mayUninstall("scm-mail-plugin");
+    assertThat(mayUninstall).isFalse();
+  }
+}