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::Configuration.editing_auth})
  #   +:workspace_changed+: A boolean, determining if the workspace has been changed with this request.
  # @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 }
    @workspace_changed = !!options[:workspace_changed]
  end

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

      if @editor && !@editor.is_a?(Scrivito::User)
        raise ScrivitoError.new(
          "The editing auth callback has to return a Scrivito::User or falsy."+
          " To upgrade please return Scrivito::User.define(id) and set the permissions" +
          " of the user. See the documentation for further details."
        )
      end
    end

    @editor
  end

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

  def workspace_changed?
    @workspace_changed
  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 [Scrivito::Workspace]
  def selected_workspace
    @selected_workspace ||= find_selected_workspace
  end

  # when authenticated_editor? return selected_workspace, otherwise published workspace.
  # @return [Scrivito::Workspace]
  def visible_workspace
    @visible_workspace ||= find_visible_workspace
  end

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

  def editable_display_mode?
    display_mode == 'editing'
  end

  def to_params
    {
      _scrivito_display_mode: display_mode,
      _scrivito_workspace_id: selected_workspace.id,
    }
  end

  private

  def find_selected_workspace
    if @selected_workspace_id
      workspace =
        begin
          Workspace.find(@selected_workspace_id)
        rescue
          Rails.logger.info "Workspace with ID #{@selected_workspace_id} is " +
            "not available, using 'published' instead."

          published_workspace
        end

      if editor && editor.can?(:read, workspace)
        workspace
      else
        published_workspace
      end
    else
      published_workspace
    end
  end

  def find_visible_workspace
    if authenticated_editor?
      display_mode == 'deleted' ? published_workspace : selected_workspace
    else
      published_workspace
    end
  end

  def published_workspace
    Workspace.published
  end

  # @return [Scrivito::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