require 'fileutils'
require 'systemu'

# File Utilities for use in transferring filesystem objects,
# decrypting a file, unpacking a targz archive, and validating checksums
# @author rnanders@stanford.edu
module LyberUtils

  class FileUtilities


    # Executes a system command in a subprocess.
    # The method will return stdout from the command if execution was successful.
    # The method will raise an exception if if execution fails.
    # The exception's message will contain the explaination of the failure.
    # @param [String] command the command to be executed
    # @return [String] stdout from the command if execution was successful
    def FileUtilities.execute(command)
      status, stdout, stderr = systemu(command)
      if (status.exitstatus != 0)
        raise stderr
      end
      return stdout
    rescue
      msg = "Command failed to execute: [#{command}] caused by <STDERR = #{stderr.split($/).join('; ')}>"
      msg << " STDOUT = #{stdout.split($/).join('; ')}" if (stdout && (stdout.length > 0))
      raise msg

    end

      # Generates a dirname for storing or retrieving a file in
      # "pair tree" hierachical structure, where the path is derived
      # from segments of a barcode string
      #
      # = Input:
      # * barcode = barcode string
      #
      # = Return value:
      # * A string containing a slash-delimited dirname derived from the barcode
    def FileUtilities.pair_tree_from_barcode(barcode)
      if (barcode.class != String)
        raise "Barcode must be a String"
      end
        # figure out if this is a SUL barcode or from coordinate library
      library_prefix=barcode[0..4]
      if (library_prefix == '36105')
        pair_tree=barcode[5..10].gsub(/(..)/, '\1/')
      else
        library_prefix=barcode[0..2]
        pair_tree=barcode[3..8].gsub(/(..)/, '\1/')
      end
      return "#{library_prefix}/#{pair_tree}"
    end

      # Transfers a filesystem object (file or directory)
      # from a source to a target location. Uses rsync in "archive" mode
      # over an ssh connection.
      #
      # = Inputs:
      # * filename = basename of the filesystem object to be transferred
      # * source_dir = dirname of the source location from which the object is read
      # * dest_dir = dirname of the target location to which the object is written
      # If one of the locations is on a remote server, then the dirname should be
      # prefixed with  user@hosthame:
      #
      # = Return value:
      # * The method will return true if the transfer is successful.
      # * The method will raise an exception if either the rsync command fails,
      # or a test for the existence of the transferred object fails.
      # The exception's message will contain the explaination of the failure
      #
      # Network transfers will only succeed if the appropriate public key
      # authentication has been previously set up.
    def FileUtilities.transfer_object(filename, source_dir, dest_dir)
      source_path=File.join(source_dir, filename)
      rsync='rsync -a -e ssh '
      rsync_cmd = rsync + "'" + source_path + "' " + dest_dir
#      LyberCore::Log.debug("rsync command is: #{rsync_cmd}")
      self.execute(rsync_cmd)
      if not File.exists?(File.join(dest_dir, filename))
        raise "#{filename} is not found in  #{dest_dir}"
      end
      return true
    end

      # Decrypts a GPG encrypted file using the "gpg" command
      #
      # = Inputs:
      # * workspace_dir = dirname containing the file
      # * targzgpg = the filename of the GPG encrypted file
      # * targz = the filename of the unencrypted file
      # * passphrase = the string used to decrypt the file
      #
      # = Return value:
      # * The method will return true if the decryption is successful.
      # * The method will raise an exception if either the decryption command fails,
      # or a test for the existence of the decrypted file fails.
      # The exception's message will contain the explaination of the failure
    def FileUtilities.gpgdecrypt(workspace_dir, targzgpg, targz, passphrase)
#      LyberCore::Log.debug("decrypting #{targzgpg}")
      gpg_cmd="/usr/bin/gpg --passphrase '#{passphrase}'  " +
          "--batch --no-mdc-warning --no-secmem-warning " +
          " --output " + File.join(workspace_dir, targz) +
          " --decrypt " + File.join(workspace_dir, targzgpg)
      self.execute(gpg_cmd)
      if not File.exists?(File.join(workspace_dir, targz))
        raise "#{targz} was not created in  #{workspace_dir}"
      end
      return true
    end

      # Unpacks a TAR-ed, GZipped archive using a "tar -xzf" command
      #
      # = Inputs:
      # * original_dir = dirname containing the archive file
      # * targz = the filename of the archive file
      # * destination_dir = the target directory into which the contents are written
      #
      # = Return value:
      # * The method will return true if the unpacking is successful.
      # * The method will raise an exception if either the unpack command fails,
      # or a test for the existence of files in the target directory fails.
      # The exception's message will contain the explaination of the failure.
    def FileUtilities.unpack(original_dir, targz, destination_dir)
 #     LyberCore::Log.debug("unpacking #{targz}")
      FileUtils.mkdir_p(destination_dir)
      dir_save = Dir.pwd
      Dir.chdir(destination_dir)
      unpack_cmd="tar -xzf " + File.join(original_dir, targz)
      self.execute(unpack_cmd)
      if not (Dir.entries(destination_dir).length > 0)
        raise "#{destination_dir} is empty"
      end
      return true
    ensure
      Dir.chdir(dir_save)
    end

      # Tars a directory hierarchy
      #
      # = Inputs:
      # * source_path = the filesystem object to be tarred
      # * dest_path = name of the tar file to be written
      #     (if nil create sourcname.tar in the same dir as the source object)
      #
      # = Return value:
      # * The method will return true if the transfer is successful.
      # * The method will raise an exception if either the rsync command fails,
      # or a test for the existence of the transferred object fails.
      # The exception's message will contain the explaination of the failure
      #
      def FileUtilities.tar_object(source_path, dest_path=nil)
        if (dest_path.nil?)
            dest_path = source_path + ".tar"
        end
        parent_path = File.dirname(source_path)
        object_name = File.basename(source_path)
        tar="cd #{parent_path}; tar --force-local -chf "
        tar_cmd = "#{tar} '#{dest_path}' '#{object_name}'"
        self.execute(tar_cmd)
        if not File.exists?(dest_path)
          raise "#{dest_path} was not created"
        end
        return true
      end

  end

end