// Copyright 2014 Google Inc. 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.
// All Rights Reserved.

package com.google.devtools.build.lib.graph;

import java.io.PrintWriter;

/**
 *  <p> An implementation of GraphVisitor for displaying graphs in dot
 *  format. </p>
 */
public class DotOutputVisitor<T> implements GraphVisitor<T> {

  /**
   *  Constructs a dot output visitor.
   *
   *  The visitor writes to writer 'out', and rendering node labels as
   *  strings using the specified displayer, 'disp'.
   */
  public DotOutputVisitor(PrintWriter out, LabelSerializer<T> disp) {
    // assert disp != null;
    // assert out != null;
    this.out = out;
    this.disp = disp;
  }

  private final LabelSerializer<T> disp;
  protected final PrintWriter out;
  private boolean closeAtEnd = false;

  @Override
  public void beginVisit() {
    out.println("digraph mygraph {");
  }

  @Override
  public void endVisit() {
    out.println("}");
    out.flush();
    if (closeAtEnd) {
      out.close();
    }
  }

  @Override
  public void visitEdge(Node<T> lhs, Node<T> rhs) {
    String s_lhs = disp.serialize(lhs);
    String s_rhs = disp.serialize(rhs);
    out.println("\"" + s_lhs + "\" -> \"" + s_rhs + "\"");
  }

  @Override
  public void visitNode(Node<T> node) {
    out.println("\"" + disp.serialize(node) + "\"");
  }

  /******************************************************************
   *                                                                *
   *                           Factories                            *
   *                                                                *
   ******************************************************************/

  /**
   *  Create a DotOutputVisitor for output to a writer; uses default
   *  LabelSerializer.
   */
  public static <U> DotOutputVisitor<U> create(PrintWriter writer) {
    return new DotOutputVisitor<U>(writer, new DefaultLabelSerializer<U>());
  }

  /**
   *  The default implementation of LabelSerializer simply serializes
   *  each node using its toString method.
   */
  private static class DefaultLabelSerializer<T> implements LabelSerializer<T> {
    @Override
    public String serialize(Node<T> node) {
      return node.getLabel().toString();
    }
  }
}