require 'net/ssh'
require 'net/sftp'

module Dor

  class DigitalStacksService

    # Delete files from stacks that have change type 'deleted', 'copydeleted', or 'modified'
    # @param [Pathname] stacks_object_pathname the stacks location of the digital object
    # @param [Moab::FileGroupDifference] content_diff the content file version differences report
    def self.remove_from_stacks(stacks_object_pathname, content_diff)
      [:deleted, :copydeleted, :modified].each do |change_type|
        subset = content_diff.subset(change_type) # {Moab::FileGroupDifferenceSubset}
        subset.files.each do |moab_file| # {Moab::FileInstanceDifference}
          moab_signature = moab_file.signatures.first # {Moab::FileSignature}
          file_pathname = stacks_object_pathname.join(moab_file.basis_path)
          self.delete_file(file_pathname, moab_signature)
        end
      end
    end

    # Delete a file, but only if it exists and matches the expected signature
    # @param [Pathname] file_pathname The location of the file to be deleted
    # @param [Moab::FileSignature] moab_signature The fixity values of the file
    # @return [Boolean] true if file deleted, false otherwise
    def self.delete_file(file_pathname, moab_signature)
      if file_pathname.exist? and (file_pathname.size == moab_signature.size)
        file_signature = Moab::FileSignature.new.signature_from_file(file_pathname)
        if (file_signature == moab_signature)
          file_pathname.delete
          return true
        end
      end
      return false
    end

    # Rename files from stacks that have change type 'renamed' using an intermediate temp filename.
    # The 2-step renaming allows chained or cyclic renames to occur without file collisions.
    # @param [Pathname] stacks_object_pathname the stacks location of the digital object
    # @param [Moab::FileGroupDifference] content_diff the content file version differences report
    def self.rename_in_stacks(stacks_object_pathname, content_diff)
      subset = content_diff.subset(:renamed) # {Moab::FileGroupDifferenceSubset

      # 1st Pass - rename files from original name to checksum-based name
      subset.files.each do |moab_file| # {Moab::FileInstanceDifference}
        moab_signature = moab_file.signatures.first # {Moab::FileSignature}
        original_pathname = stacks_object_pathname.join(moab_file.basis_path)
        temp_pathname = stacks_object_pathname.join(moab_signature.checksums.values.last)
        self.rename_file(original_pathname, temp_pathname, moab_signature)
      end

      # 2nd Pass - rename files from checksum-based name to new name
      subset.files.each do |moab_file| # {Moab::FileInstanceDifference}
        moab_signature = moab_file.signatures.first # {Moab::FileSignature}
        temp_pathname = stacks_object_pathname.join(moab_signature.checksums.values.last)
        new_pathname = stacks_object_pathname.join(moab_file.other_path)
        self.rename_file(temp_pathname, new_pathname, moab_signature)
      end

    end

    # Rename a file, but only if it exists and has the expected signature
    # @param [Pathname] old_pathname The original location/name of the file being renamed
    # @param [Pathname] new_pathname The new location/name of the file
    # @param [Moab::FileSignature] moab_signature The fixity values of the file
    # @return [Boolean] true if file renamed, false otherwise
    def self.rename_file(old_pathname, new_pathname, moab_signature)
      if old_pathname.exist? and (old_pathname.size == moab_signature.size)
        file_signature = Moab::FileSignature.new.signature_from_file(old_pathname)
        if (file_signature == moab_signature)
          new_pathname.parent.mkpath
          old_pathname.rename(new_pathname)
          return true
        end
      end
      return false
    end

    # Add files to stacks that have change type 'added', 'copyadded' or 'modified'.
    # @param [Pathname] workspace_content_pathname The dor workspace location of the digital object's content fies
    # @param [Pathname] stacks_object_pathname the stacks location of the digital object's shelved files
    # @param [Moab::FileGroupDifference] content_diff the content file version differences report
    def self.shelve_to_stacks(workspace_content_pathname, stacks_object_pathname, content_diff)
      return false if workspace_content_pathname.nil?
      [:added, :copyadded, :modified,].each do |change_type|
        subset = content_diff.subset(change_type) # {Moab::FileGroupDifferenceSubset
        subset.files.each do |moab_file| # {Moab::FileInstanceDifference}
          moab_signature = moab_file.signatures.last # {Moab::FileSignature}
          filename = (change_type == :modified) ? moab_file.basis_path : moab_file.other_path
          workspace_pathname = workspace_content_pathname.join(filename)
          stacks_pathname = stacks_object_pathname.join(filename)
          self.copy_file(workspace_pathname, stacks_pathname, moab_signature)
        end
      end
      true
    end

    # Copy a file to stacks, but only if it does not yet exist with the expected signature
    # @param [Pathname] workspace_pathname The location of the file in the DOR workspace
    # @param [Pathname] stacks_pathname The location of the file in the stacks
    # @param [Moab::FileSignature] moab_signature The fixity values of the file
    # @return [Boolean] true if file copied, false otherwise
    def self.copy_file(workspace_pathname, stacks_pathname, moab_signature)
      if stacks_pathname.exist?
        file_signature = Moab::FileSignature.new.signature_from_file(stacks_pathname)
        stacks_pathname.delete if (file_signature != moab_signature)
      end
      unless stacks_pathname.exist?
        FileUtils.cp workspace_pathname.to_s, stacks_pathname.to_s
        return true
      end
      return false
    end

    ### depricated ???

    # Create a file inside the content directory under the stacks.local_document_cache_root
    # @param [String] id The druid identifier for the object
    # @param [String] content The contents of the file to be created
    # @param [String] filename The name of the file to be created
    # @return [void]
    def self.transfer_to_document_store(id, content, filename)
      druid = DruidTools::PurlDruid.new id, Config.stacks.local_document_cache_root
      druid.content_dir # create the druid tree if it doesn't exist yet
      File.open(File.join(druid.content_dir, filename), 'w') { |f| f.write content }
    end

    # Assumes the digital stacks storage root is mounted to the local file system
    # TODO since this is delegating to the Druid, this method may not be necessary
    def self.prune_stacks_dir(id)
      stacks_druid_tree = DruidTools::StacksDruid.new(id, Config.stacks.local_stacks_root)
      stacks_druid_tree.prune!
    end

    def self.prune_purl_dir(id)
      druid = DruidTools::PurlDruid.new(id, Dor::Config.stacks.local_document_cache_root)
      druid.prune!
    end
  end

end