module Scrivito

class EditingContext
  # +options+:
  #   +:selected_workspace_id+: The id of the selected workspace. If empty +published+ workspace is used.
  #   +:display_mode+: Can be +view+, +editing+, +added+ or +deleted+. If empty +view+ is used.
  #   +:editor+: A block, which is lazy evaluated on first access, to determine the editor (details see {Scrivito::Configuation.editing_auth})
  # @param [Hash] options
  def initialize(options = {})
    @selected_workspace_id = options[:selected_workspace_id]
    @display_mode = options[:display_mode] || "view"
    @editor_callback = options[:editor] || proc { false }
  end

  def editor
    unless @editor_already_evaluated
      @editor_already_evaluated = true
      @editor = @editor_callback.call
    end

    @editor
  end

  # true iff {editor} truish
  def authenticated_editor?
    editor.present?
  end

  # @return [String]
  def display_mode
    if authenticated_editor? && !selected_workspace.published?
      @display_mode
    else
      'view'
    end
  end

  # defaults to "published" if no workspace with `selected_workspace_id` can be found.
  # @return [Workspace]
  def selected_workspace
    unless @selected_workspace
      if @selected_workspace_id
        begin
          @selected_workspace = Workspace.find(@selected_workspace_id)
        rescue Scrivito::ResourceNotFound
          @selected_workspace = Workspace.default
        end
      else
        @selected_workspace = Workspace.default
      end
    end

    @selected_workspace
  end

  # when authenticated_editor? return selected_workspace, otherwise published workspace.
  # @return [Workspace]
  def visible_workspace
    unless @visible_workspace
      if authenticated_editor?
        if display_mode == 'deleted'
          @visible_workspace = Workspace.default
        else
          @visible_workspace = selected_workspace
        end
      else
        @visible_workspace = Workspace.default
      end
    end

    @visible_workspace
  end

  def comparison
    @comparison ||=
      begin
        revision = compare_revision
        Comparison.new(
          revision, display_mode == 'deleted', revision ? display_mode : nil
        )
      end
  end

  def to_params
    {
      '_scrivito_display_mode' => display_mode,
      '_scrivito_workspace_id' => selected_workspace.id,
    }
  end

  private

  # @return [Revision] or +nil+
  def compare_revision
    case display_mode
    when 'added'
      selected_workspace.base_revision
    when 'deleted'
      selected_workspace.revision
    when 'diff'
      selected_workspace.base_revision
    end
  end
end

end # module Scrivito