module Scrivito
  class CmsBackend
    VALID_INDEX_NAMES = %w[id path ppath permalink].freeze

    class << self
      def instance
        @instance ||= new
      end
    end

    def initialize
      @query_counter = 0
      @caching = true
    end

    def begin_caching
      @caching = true
    end

    def end_caching
      CmsDataCache.clear_request_cache
      @caching = false
    end

    def clear_cache
      CmsDataCache.clear_request_cache
    end

    def caching?
      !!@caching
    end

    def query_counter
      @query_counter
    end

    # For test purpose only.
    def reset_query_counter!
      @query_counter = 0
    end

    def find_workspace_data_from_cache(id)
      cached_workspace_state = CmsDataCache.read_workspace_state(id)
      cached_data_tag = cached_workspace_state.try(:second)
      cached_content_state_id = cached_workspace_state.try(:first)

      if cached_data_tag && cached_content_state_id
        if raw_workspace_data = fetch_cached_data_by_tag(cached_data_tag)
          build_workspace_data(raw_workspace_data, cached_content_state_id)
        end
      end
    end

    def find_workspace_data_by_id(id, timeout=nil)
      options = timeout ? {timeout: timeout} : {}

      cached_workspace_state = CmsDataCache.read_workspace_state(id)

      cached_csid = cached_workspace_state.try(:first)
      cached_workspace_data_tag = cached_workspace_state.try(:second)

      changes = CmsRestApi.get("/workspaces/#{id}/changes", {from: cached_csid}, options)

      update_obj_cache(id, cached_csid, changes)

      raw_workspace_data, workspace_data_tag = update_workspace_cache(
          id, cached_workspace_data_tag, changes["workspace"], options)

      current_csid = changes["current"]
      current_workspace_state = [current_csid, workspace_data_tag]

      if current_workspace_state != cached_workspace_state
        CmsDataCache.write_workspace_state(id, current_workspace_state)
      end

      build_workspace_data(raw_workspace_data, current_csid)
    rescue Scrivito::ClientError => client_error
      if client_error.http_code == 404
        nil
      else
        raise
      end
    end

    def find_obj_data_by(revision, index, keys)
      index = index.to_s

      if index == "id"
        obj_datas = Backend::ObjLoad.load(revision, keys)
        obj_datas.map { |obj_data| obj_data ? [obj_data] : [] }
      else
        index_implementation = Backend::Index.by_name(index)
        Backend::ObjQuery.query(revision, index_implementation, keys)
      end
    end

    def find_blob_data(id, access, verb, options = {})
      if blob_data = find_blob_data_from_cache(id, access, verb, options)
        blob_data
      else
        id = normalize_blob_id(id)
        blob_datas = request_blob_datas_from_backend(id, options)
        store_blob_datas_in_cache(id, options, blob_datas)
        blob_datas[access][verb]
      end
    end

    def find_blob_data_from_cache(id, access, verb, options)
      cache_key = blob_data_cache_key(normalize_blob_id(id), access, verb, options)
      CmsDataCache.cache.read(cache_key)
    end

    def find_binary_meta_data(blob_id)
      blob_id = normalize_blob_id(blob_id)
      cache_key = "binary_meta_data/#{blob_id}"
      if meta_data = CmsDataCache.cache.read(cache_key)
        meta_data
      else
        meta_data = CmsRestApi.get("blobs/#{blob_id}/meta_data")['meta_data']
        CmsDataCache.cache.write(cache_key, meta_data)
        meta_data
      end
    end

    def search_objs(workspace, params)
      cache_index = 'search'
      cache_key = params.to_param
      cache = Backend::ObjDataCache.view_for_revision(workspace.revision)

      if hit = cache.read_index(cache_index, cache_key)
        return hit
      end

      result = request_search_result_from_backend(workspace, params)
      persistent = !result.delete('tentative')
      cache.write_index_not_updatable(cache_index, cache_key, result, persistent: persistent)
      result
    end

    def create_obj(workspace_id, attributes)
      write_obj(:post, "/workspaces/#{workspace_id}/objs", attributes)
    end

    def update_obj(workspace_id, obj_id, attributes)
      write_obj(:put, "/workspaces/#{workspace_id}/objs/#{obj_id}", attributes)
    end

    private

    def write_obj(verb, path, attributes)
      Backend::ObjDataFromRest.new(CmsRestApi.task_unaware_request(verb, path, attributes))
    end

    def update_workspace_cache(id, cached_data_tag, changed_workspace, options)
      if changed_workspace
        workspace_data = changed_workspace
      else
        if cached_workspace_data = fetch_cached_data_by_tag(cached_data_tag)
          workspace_data = cached_workspace_data
          workspace_data_tag = cached_data_tag
        else
          workspace_data = CmsRestApi.get("/workspaces/#{id}", nil, options)
        end
      end

      workspace_data_tag ||= CmsDataCache.write_data_to_tag(workspace_data)

      [workspace_data, workspace_data_tag]
    end

    def fetch_cached_data_by_tag(data_tag)
      data_tag && CmsDataCache.read_data_from_tag(data_tag)
    end

    def build_workspace_data(raw_data, content_state_id)
      WorkspaceData.new(raw_data.merge('content_state_id' => content_state_id))
    end

    def update_obj_cache(workspace_id, cached_csid, changes)
      objs = changes["objs"]
      if objs.present? && objs != "*"
        last_state = Backend::ContentStateNode.find(cached_csid)
        changes_index = Backend::ObjDataCache.changes_index_from(objs)
        successor = last_state.create_successor(changes["to"], changes_index)

        cache = Backend::ObjDataCache.view_for_workspace(workspace_id, successor)
        changes_index.each do |id, tag|
          cache.write_obj_tag(id, tag)
        end
      end
    end

    def request_search_result_from_backend(workspace, params)
      params = params.merge(consistent_with: workspace.content_state_id)
      CmsRestApi.get("workspaces/#{workspace.id}/objs/search", params)
    end

    def request_blob_datas_from_backend(id, options)
      @query_counter += 1
      case
      when transformation_definition = options[:transformation_definition]
        CmsRestApi.get("blobs/#{id}/transform", transformation: transformation_definition)
      when options[:no_cache]
        CmsRestApi.get("blobs/#{id}/no_cache")
      else
        CmsRestApi.get("blobs/#{id}")
      end
    end

    def store_blob_datas_in_cache(id, options, blob_datas)
      %w[public_access private_access].each do |access|
        %w[get head].each do |verb|
          if access_blob_data = blob_datas[access]
            if blob_data = access_blob_data[verb]
              cache_key = blob_data_cache_key(id, access, verb, options)
              CmsDataCache.cache.write(cache_key, blob_data, expires_in: blob_data['maxage'])
            end
          end
        end
      end
    end

    def blob_data_cache_key(id, access, verb, options)
      cache_key = "blob_data/#{id}/#{access}/#{verb}"

      if transformation_definition = options[:transformation_definition]
        cache_key << "/#{transformation_definition.to_query}"
      end

      if options[:no_cache]
        cache_key << '/no_cache'
      end

      cache_key
    end

    def normalize_blob_id(id)
      CmsRestApi.normalize_path_component(id)
    end
  end
end