require 'active_model/naming'

module Scrivito

# @api public
# This class represents a CMS workspace, called "working copy" in the UI. A working copy lets
# editors create and modify content independently of the published content or other working copies.
# On creation, a working copy is based on the currently published content.
# @see https://scrivito.com/about-working-copies About working copies

class Workspace
  extend ActiveModel::Naming

  include ModelIdentity

  PublishPreventedDueToContentChange = Class.new(ScrivitoError)

  # Set the workspace to use for subsequent workspace operations.
  # @api public
  # @param [Scrivito::Workspace] workspace
  def self.current=(workspace)
    Thread.current[:scrivito_current_workspace] = workspace
  end

  def self.current_using_proc=(workspace_proc)
    Thread.current[:scrivito_current_workspace] = workspace_proc
  end

  # Returns the currently used workspace.
  # @api public
  # @return [Scrivito::Workspace]
  def self.current
    workspace = Thread.current[:scrivito_current_workspace]
    if workspace.respond_to?(:call)
      Thread.current[:scrivito_current_workspace] = workspace.call
    else
      Thread.current[:scrivito_current_workspace] ||= published
    end
  end

  # Returns all workspaces.
  # @api public
  # @return [Array<Scrivito::Workspace>]
  def self.all
    result_json = CmsRestApi.get('/workspaces')

    result_json['results'].map do |raw_data|
      Workspace.new(WorkspaceData.new(raw_data))
    end
  end

  # @api public
  # Returns the published workspace.
  #
  # @return [Scrivito::Workspace]
  def self.published
    find("published")
  end

  def self.published_with_fallback
    cached_workspace_data = CmsBackend.find_workspace_data_from_cache('published')

    if cached_workspace_data
      workspace_data = begin
        CmsBackend.find_workspace_data_by_id('published', 0.5)
      rescue => e
        warn_backend_not_available(e.message)
        cached_workspace_data
      end

      from_workspace_data('published', workspace_data)
    else
      published
    end
  end

  # Find a workspace by its id.
  # @api public
  # @param [String] id
  # @return [Scrivito::Workspace]
  # @raise [Scrivito::ResourceNotFound]
  def self.find(id)
    cache.fetch(id) do
      workspace_data = CmsBackend.find_workspace_data_by_id(id)

      from_workspace_data(id, workspace_data)
    end
  end

  # Find a workspace by its title.
  # If multiple workspaces share the same title, one of them is returned.
  # If no workspace with the given title can be found, +nil+ is returned.
  # @api public
  # @param [String] title
  # @return [Scrivito::Workspace]
  def self.find_by_title(title)
    all.detect { |workspace| workspace.title == title }
  end

  #
  # Find a workspace by its title or ID and set it as the currently used workspace.
  #
  # @api public
  #
  # @param [String] title_or_id title or id of the workspace
  # @raise [Scrivito::ResourceNotFound]
  # @note This method is intended to be used in the Rails console. Please avoid using it in
  #   application code.
  #
  # @example
  #   Scrivito::Workspace.use("my working copy")
  #   Scrivito::Workspace.current.title
  #   # => "my working copy"
  #
  #   Scrivito::Workspace.use("6a75fe694eeeb093")
  #   Scrivito::Workspace.current.id
  #   # => "6a75fe694eeeb093"
  #
  #   # Raises Scrivito::ResourceNotFound:
  #   Scrivito::Workspace.use("missing")
  #
  def self.use(title_or_id)
    self.current = find_by_title(title_or_id) || find(title_or_id)
  rescue ResourceNotFound
    raise ResourceNotFound, %{Could not find #{self} with title or ID "#{title_or_id}"}
  end

  delegate :content_state_id, :base_content_state_id, :content_state,
    :base_revision_id, :auto_update?, :base_content_state, to: :data

  # Create a new workspace.
  # @api public
  # @param [Hash] attributes
  # @option attributes [String] :title title of the workspace.
  # @option attributes [Boolean] :auto_update Specifies whether changes published intermediately
  #   are applied automatically and instantly to the working copy. The default is +true+. Setting
  #   this option to +false+ requires {#rebase rebasing} the working copy (manually) to keep it up
  #   to date.
  # @example Create a workspace, providing its title:
  #   Scrivito::Workspace.create(title: "Jane")
  # @example Create a workspace, providing auto_update:
  #   # Workspace will not be updated until it is published.
  #   Scrivito::Workspace.create(auto_update: false)
  #
  # @return [Scrivito::Workspace]
  def self.create(attributes)
    find(create_async(attributes).result['id'])
  end

  def self.create_async(attributes)
    Task.new do
      attributes = attributes.reverse_merge(auto_update: true)
      CmsRestApi.task_unaware_request(:post, 'workspaces', workspace: attributes)
    end
  end

  # Reloads the current workspace to reflect the changes that were made to it concurrently
  # since it was loaded.
  # @api public
  def self.reload
    current.reload
  end

  # @api public
  #
  # This method provides a string that can be used as part of a cache key. It changes
  # whenever any content ({Scrivito::BasicObj Obj} or {Scrivito::BasicWidget Widget})
  # changes. Due to this, caches using the +cache_key+ are invalidated whenever
  # a CMS object in the working copy has been changed.
  #
  # Scrivito provides the {ScrivitoHelper#scrivito_cache scrivito_cache} method which
  # integrates the +cache_key+ with Rails' fragment caching. You might want to check whether
  # +scrivito_cache+ satisfies your needs before implementing your own solution.
  #
  # @return [String] A string that changes whenever the content of the working copy
  #   changes.
  def cache_key
    @cache_key ||= Digest::SHA1.hexdigest("#{id}|#{content_state_id}")
  end

  def self.cache
    @cache ||= {}
  end

  def initialize(workspace_data)
    update_data(workspace_data)
    @id = data.id
  end

  # Reloads this workspace to reflect the changes that were made to it concurrently since
  # it was loaded.
  # @api public
  def reload
    update_data(method(:fetch_workspace_data))
  end

  def eager_reload
    update_data(fetch_workspace_data)
  end

  def api_request(verb, path, payload = nil)
    response = CmsRestApi.public_send(verb, "#{backend_url}#{path}", payload)
    reload if [:post, :put, :delete].include?(verb)
    response
  end

  def create_obj(attributes)
    update_obj(attributes[:obj]['_id'], attributes)
  end

  def update_obj(obj_id, attributes)
    CmsBackend.write_obj(id, obj_id, attributes).tap { reload }
  end

  def task_unaware_api_request(verb, path, payload = nil)
    CmsRestApi.task_unaware_request(verb, "#{backend_url}#{path}", payload)
  end

  # Updates the attributes of this workspace.
  # @api public
  # @param [Hash] attributes
  # @return [Scrivito::Workspace]
  def update(attributes)
    raise ScrivitoError, 'published workspace is not modifiable' if published?
    CmsRestApi.put(backend_url, workspace: attributes)
    reload
  end

  # Destroy this workspace.
  # @api public
  def destroy
    reset_workspace_if_current
    CmsRestApi.delete(backend_url)
  end

  # Publish the changes that were made to this workspace.
  # @api public
  def publish
    publish_async.result
    Workspace.published.reload
    reset_workspace_if_current
  end

  def publish_async
    Task.new do
      task_unaware_api_request(:put, '/publish')
    end
  end

  # Rebases the current workspace from the published content in order to integrate the changes
  # that were published in the meantime.
  # @note This action is not required for auto-updated workspaces.
  # @api public
  def rebase
    rebase_async.result
    reload
  end

  def rebase_async
    Task.new do
      task_unaware_api_request(:put, '/rebase')
    end
  end

  # Returns the id of the workspace.
  # @api public
  # @return [String]
  def id
    @id
  end

  def revision_id
    data.revision_id
  end

  # Returns the title of the workspace if present. Otherwise, and for the published content,
  # an empty +String+ is returned.
  # @api public
  # @return [String]
  def title
    return '' if published?
    data.title || ''
  end

  # @api public
  # Returns the memberships (users and their roles) of this workspace.
  # @return [Scrivito::MembershipCollection]
  def memberships
    @memberships ||= MembershipCollection.new(self)
  end

  def data
    if @workspace_data.respond_to?(:call)
      @workspace_data = @workspace_data.call
    else
      @workspace_data
    end
  end

  # @api public
  # This method indicates whether the workspace is the published one.
  #
  # @return +true+ if the workspace is the published one
  def published?
    self.id == 'published'
  end

  def outdated?
    !published? && Workspace.published.revision.id != base_revision_id
  end

  def revision
    unless data.content_state_id?
      # reload data from changes feed in order to obtain content_state_id
      reload

      raise InternalError unless data.content_state_id?
    end

    @revision ||= Revision.new(id: revision_id, workspace: self)
  end

  def base_revision
    if base_revision_id
      @base_revision ||= Revision.new(
        id: base_revision_id,
        workspace: self,
        base: true
      )
    end
  end

  def as_current(&block)
    old_workspace = Workspace.current

    begin
      Workspace.current = self

      yield
    ensure
      Workspace.current = old_workspace
    end
  end

  def assert_revertable
    raise ScrivitoError, 'published workspace is not modifiable' if published?
  end

  # Returns an {Scrivito::ObjCollection} of this working copy for accessing its CMS objects.
  # @api public
  # @return {Scrivito::ObjCollection}
  def objs
    @objs ||= ObjCollection.new(self)
  end

  def inspect
    "<#{self.class} id=\"#{id}\" title=\"#{title}\">"
  end

  private

  def update_data(new_data)
    @workspace_data = new_data

    # Clear all cached instance variables.
    @base_revision = nil
    @memberships   = nil
    @revision      = nil
    @cache_key     = nil
  end

  def fetch_workspace_data
    CmsBackend.find_workspace_data_by_id(id)
  end

  def backend_url
    "/workspaces/#{id}"
  end

  def reset_workspace_if_current
    Workspace.cache.delete(id)

    if Workspace.current == self
      Workspace.current = Workspace.published
    end
  end

  private_class_method def self.from_workspace_data(id, data)
    unless data
      raise ResourceNotFound, "Could not find #{self} with id #{id}"
    end

    cache[id] = Workspace.new(data)
  end

  private_class_method def self.warn_backend_not_available(error_message)
    Warning.warn <<-EOS

      Couldn't connect to backend to fetch published workspace.
      #{error_message}
      Serving from cache.

    EOS
  end
end

end