// 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 google.registry.documentation.FlowDocumentation.ErrorCase;
import java.util.stream.Stream;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.TypeElement;
import javax.lang.model.util.ElementFilter;
import jdk.javadoc.doclet.DocletEnvironment;

/**
 * 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 DocletEnvironment sourceRoot;

  /** Returns a new DocumentationGenerator object with parsed information from javadoc. */
  public DocumentationGenerator() throws Exception {
    sourceRoot = JavadocWrapper.getDocletEnv();
  }

  /** 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(element -> element.getSimpleName().toString()))
        .map(typeElement -> new FlowDocumentation(typeElement, sourceRoot))
        .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(
            typeElement ->
                new ErrorCase(
                    typeElement,
                    sourceRoot.getDocTrees().getDocCommentTree(typeElement),
                    sourceRoot.getTypeUtils()))
        .collect(toImmutableList());
  }

  /** Helper to return all concrete subclasses of a given named class. */
  private Stream<TypeElement> getConcreteSubclassesStream(String baseClassName) {
    final TypeElement baseFlowTypeElement =
        sourceRoot.getElementUtils().getTypeElement(baseClassName);
    return ElementFilter.typesIn(sourceRoot.getIncludedElements()).stream()
        .filter(
            typeElement ->
                sourceRoot
                        .getTypeUtils()
                        .isSubtype(typeElement.asType(), baseFlowTypeElement.asType())
                    && !typeElement.getModifiers().contains(Modifier.ABSTRACT));
  }
}