package jalview.util;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.PathMatcher;
import java.util.ArrayList;
import java.util.List;

/**
 * Miscellaneous file-related functions
 */
public final class FileUtils
{

  /**
   * Answers the executable file for the given command, or null if not found or
   * not executable. The path to the executable is the command name prefixed by
   * the given folder path, optionally with .exe appended.
   * 
   * @param cmd
   *          command short name, for example hmmbuild
   * @param binaryPath
   *          parent folder for the executable
   * @return
   */
  public static File getExecutable(String cmd, String binaryPath)
  {
    File file = new File(binaryPath, cmd);
    if (!file.canExecute())
    {
      file = new File(binaryPath, cmd + ".exe");
      {
        if (!file.canExecute())
        {
          file = null;
        }
      }
    }
    return file;
  }

  /**
   * Answers the path to the folder containing the given executable file, by
   * searching the PATH environment variable. Answers null if no such executable
   * can be found.
   * 
   * @param cmd
   * @return
   */
  public static String getPathTo(String cmd)
  {
    String paths = System.getenv("PATH");
    // backslash is to escape regular expression argument
    for (String path : paths.split("\\" + File.pathSeparator))
    {
      if (getExecutable(cmd, path) != null)
      {
        return path;
      }
    }
    return null;
  }

  /**
   * A convenience method to create a temporary file that is deleted on exit of
   * the JVM
   * 
   * @param prefix
   * @param suffix
   * @return
   * @throws IOException
   */
  public static File createTempFile(String prefix, String suffix)
          throws IOException
  {
    File f = File.createTempFile(prefix, suffix);
    f.deleteOnExit();
    return f;
  }

  /**
   * Answers a (possibly empty) list of file paths found by searching below
   * <code>from</code> that match the supplied regular expression
   * <code>pattern</code>. Results may include <code>from</code> itself if it
   * matches. If an exception occurs it is written to syserr and any results up
   * to that point are returned. Note that the regular expression match applies
   * to the whole path of any matched file.
   * <p>
   * Because the whole directory tree below <code>from</code> is searched, this
   * method may be slow if used for a high level directory.
   * 
   * <pre>
   * Example: 
   *   findMatchingPaths(".*&#47chimera.exe$", Paths.get("C:/Program Files"))
   * </pre>
   * 
   * @param pattern
   * @param from
   * @return
   * @see https://stackoverflow.com/questions/794381/how-to-find-files-that-match-a-wildcard-string-in-java/31685610#comment62441832_31685610
   */
  public static List<String> findMatchingPaths(String pattern, Path from)
  {
    List<String> matches = new ArrayList<>();
    PathMatcher pathMatcher = FileSystems.getDefault()
            .getPathMatcher("regex:" + pattern);
    try
    {
      Files.walk(from).filter(pathMatcher::matches)
              .forEach(m -> matches.add(m.toString()));
    } catch (IOException e)
    {
      System.err.println(
              "Error searching for " + pattern + " : " + e.toString());
    }

    return matches;
  }
}