// Copyright 2014 The Bazel 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 com.google.devtools.build.docgen;

import static java.nio.charset.StandardCharsets.UTF_8;

import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;

/**
 * Class that represents a page to be generated using the {@link TemplateEngine}.
 */
class Page {
  private final VelocityEngine engine;
  private final VelocityContext context;
  private final String template;

  /**
   * Creates a new Page instance using the reference to the VelocityEngine and the .vm
   * template file path.
   */
  public Page(VelocityEngine engine, String template) {
    this.engine = engine;
    this.template = template;
    this.context = new VelocityContext();
  }

  /**
   * Sets a Velocity variable in the template with the given value.
   */
  public void add(String var, Object value) {
    context.put(var, value);
  }

  /**
   * Renders the template and writes the output to the given file.
   */
  public void write(File outputFile) throws IOException {
    OutputStream out = new FileOutputStream(outputFile);
    try (Writer writer = new OutputStreamWriter(out, UTF_8)) {
      engine.mergeTemplate(template, "UTF-8", context, writer);
    } catch (ResourceNotFoundException|ParseErrorException|MethodInvocationException e) {
      throw new IOException(e);
    }
  }
}

@@ -1026,28 +1026,51 @@
 .io.File
-OutputStream
+Writer;%0Aimport java.io.StringWriter
 ;%0Aimport
@@ -1920,185 +1920,192 @@
    *
-/%0A  public void write(File outputFile) throws IOException %7B%0A    OutputStream out = new FileOutputStream(outputFile);%0A    try (Writer writer = new OutputStreamWriter(out, UTF_8))
+%0A   * Strips all trailing whitespace before writing to file.%0A   */%0A  public void write(File outputFile) throws IOException %7B%0A    StringWriter stringWriter = new StringWriter();%0A    try
  %7B%0A 
@@ -2158,17 +2158,23 @@
 ontext, 
-w
+stringW
 riter);%0A
@@ -2301,14 +2301,391 @@
 ;%0A    %7D%0A
+    stringWriter.close();%0A%0A    String%5B%5D lines = stringWriter.toString().split(System.getProperty(%22line.separator%22));%0A    FileWriter fileWriter = new FileWriter(outputFile);%0A    for (String line : lines) %7B%0A      // Strip trailing whitespace then append newline before writing to file.%0A      fileWriter.write(line.replaceFirst(%22%5C%5Cs+$%22, %22%22) + %22%5Cn%22);%0A    %7D%0A    fileWriter.close();%0A
   %7D%0A%7D%0A

Remove trailing whitespace in generated Skylark Library and BE files.