Enable flow documentation in external build

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=241934689

java/google/registry/documentation/DocumentationGenerator.java

@@ -0,0 +1,70 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.documentation;
+
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static java.util.Comparator.comparing;
+
+import com.google.common.collect.ImmutableList;
+import com.sun.javadoc.ClassDoc;
+import com.sun.javadoc.RootDoc;
+import google.registry.documentation.FlowDocumentation.ErrorCase;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.stream.Stream;
+
+/**
+ * Main entry point class for documentation generation.  An instance of this class reads data
+ * via the javadoc system upon creation and stores it for answering future queries for
+ * documentation information.
+ */
+public final class DocumentationGenerator {
+
+  private final RootDoc sourceRoot;
+
+  /** Returns a new DocumentationGenerator object with parsed information from javadoc. */
+  public DocumentationGenerator() throws IOException {
+    sourceRoot = JavadocWrapper.getRootDoc();
+  }
+
+  /** Returns generated Markdown output for the flows.  Convenience method for clients. */
+  public String generateMarkdown() {
+    return MarkdownDocumentationFormatter.generateMarkdownOutput(getFlowDocs());
+  }
+
+  /** Returns a list of flow documentation objects derived from this generator's data. */
+  public ImmutableList<FlowDocumentation> getFlowDocs() {
+    // Relevant flows are leaf flows: precisely the concrete subclasses of Flow.
+    return getConcreteSubclassesStream(FlowDocumentation.BASE_FLOW_CLASS_NAME)
+        .sorted(comparing(ClassDoc::typeName))
+        .map(FlowDocumentation::new)
+        .collect(toImmutableList());
+  }
+
+  /** Returns a list of all possible error cases that might occur. */
+  public ImmutableList<ErrorCase> getAllErrors() {
+    // Relevant error cases are precisely the concrete subclasses of EppException.
+    return getConcreteSubclassesStream(FlowDocumentation.EXCEPTION_CLASS_NAME)
+        .map(ErrorCase::new)
+        .collect(toImmutableList());
+  }
+
+  /** Helper to return all concrete subclasses of a given named class. */
+  private Stream<ClassDoc> getConcreteSubclassesStream(String baseClassName) {
+    final ClassDoc baseFlowClassDoc = sourceRoot.classNamed(baseClassName);
+    return Arrays.stream(sourceRoot.classes())
+        .filter(classDoc -> classDoc.subclassOf(baseFlowClassDoc) && !classDoc.isAbstract());
+  }
+}