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A general-purpose Scala utility library
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/*
  ---------------------------------------------------------------------------
  This software is released under a BSD license, adapted from
  http://opensource.org/licenses/bsd-license.php

  Copyright (c) 2009, Brian M. Clapper
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:

   * Redistributions of source code must retain the above copyright notice,
    this list of conditions and the following disclaimer.

   * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

   * Neither the names "clapper.org", "Grizzled Scala Library", nor the
    names of its contributors may be used to endorse or promote products
    derived from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  ---------------------------------------------------------------------------
*/

package grizzled.net

import grizzled.file.{util => FileUtil}

import java.net.URL
import java.io.{File, IOException, FileInputStream}

/** URL-related utility methods.
  */
object url {
  private lazy val ExtRegexp = """^(.*)(\.[^.]+)$""".r

  private[net] def getOutputFile(url: URL): File = {
    val urlPath = url.getPath
    val extension = urlPath match {
      case ExtRegexp(pathNoExt, ext) => ext
      case _                         => ".dat"
    }

    urlPath(urlPath.length - 1) match {
      case '/' =>
        File.createTempFile("urldownload", extension)

      case _   => 
        new File(FileUtil.joinPath(System.getProperty("java.io.tmpdir"),
                                   FileUtil.basename(urlPath)))
    }
  }

  /** Download the specified URL to a file. The name of the file is
    * taken from the URL, if possible, or generated otherwise.
    *
    * @param url  The string containing the URI/URL
    *
    * @return the file to which the output was written.
    */
  def download(url: String): File = {
    val output = getOutputFile(new URL(url))

    download(new URL(url), output)
    output
  }

  /** Download the specified URL to a file.
    *
    * @param url      The string containing the URI/URL
    * @param pathOut  Path of file to receive the output. If the file
    *                 exists, it is overwritten. If the file does not
    *                 exist, it is created. If any of the directories in
    *                 the path do not exist, they are created.
    */
  def download(url: String, pathOut: String): Unit =
    download(new URL(url), new File(pathOut))

  /** Download the specified URL to a file.
    *
    * @param url      The URL
    * @param pathOut  Path of file to receive the output. If the file
    *                 exists, it is overwritten. If the file does not
    *                 exist, it is created. If any of the directories in
    *                 the path do not exist, they are created.
    */
  def download(url: URL, pathOut: String): Unit =
    download(url, new File(pathOut))

  /** Download the specified URL to a file.
    *
    * @param url      The string containing the URI/URL
    * @param pathOut  File to receive the output. If the file exists, it
    *                 is overwritten. If the file does not exist, it is
    *                 created. If any of the directories in the path do not
    *                 exist, they are created.
    */
  def download(url: String, pathOut: File): Unit =
    download(new URL(url), pathOut)

  /** Download the specified URL to a file.
    *
    * @param url      The URL
    * @param pathOut  File to receive the output. If the file exists, it
    *                 is overwritten. If the file does not exist, it is
    *                 created. If any of the directories in the path do not
    *                 exist, they are created.
    *
    * @return the `pathOut` parameter, for convenience
    */
  def download(url: URL, pathOut: File): File = {
    import java.io.{BufferedInputStream, BufferedOutputStream}
    import java.io.{FileOutputStream}
    import grizzled.io.RichInputStream._

    if (pathOut.isDirectory)
      throw new IOException("Output file \"" + pathOut + "\" exists " +
                            "and is a directory.")

    val dir = new File(FileUtil.dirname(pathOut.getCanonicalPath))
    if ((! dir.exists) && (! dir.mkdirs()))
      throw new IOException("Can't create either target directory \"" +
                            dir.toString + "\" or one of its parents.")

    // Open the URL and the output file. (Do the URL first. That way, if it
    // fails, we don't get a zero-length output file.
    val in = new BufferedInputStream(url.openStream())
    val out = new BufferedOutputStream(new FileOutputStream(pathOut))

    // Copy and close.
    try {
      in.copyTo(out)
    }

    finally {
      out.close()
      in.close()
    }

    pathOut
  }

  /** Execute a block of code with a downloaded, temporary file.
    * The specified URL is downloaded to a file, the file is passed
    * to the block, and when the block exits, the file is removed.
    *
    * @param url    the URL
    * @param block  the block to execute
    *
    * @return whatever the block returns
    */
  def withDownloadedFile[T](url: String)(block: File => T): T =
    withDownloadedFile(new URL(url))(block)

  /** Execute a block of code with a downloaded, temporary file.
    * The specified URL is downloaded to a file, the file is passed
    * to the block, and when the block exits, the file is removed.
    *
    * @param url    the URL
    * @param block  the block to execute
    *
    * @return whatever the block returns
    */
  def withDownloadedFile[T](url: URL)(block: File => T): T = {
    val file = File.createTempFile("grizzled", ".dat")
    try {
      block(download(url, file))
    }

    finally {
      file.delete()
    }
  }
}