require 'addressable/uri'

module Scrivito

  class ContentServiceObjQueries
    def initialize(queries)
      @queries = queries
      @open_queries = queries.dup
      @results = {}
    end

    def open_queries
      @open_queries[0..99]
    end

    def handle_response(response)
      objs = {}
      response["objs"].each do |obj|
        objs[obj["_id"].first] = obj
      end

      queries_to_delete = []
      response["results"].each_with_index do |response, i|
        query = @open_queries[i]
        if response["continuation_handle"]
          query[:continuation_handle] = response["continuation_handle"]
        else
          queries_to_delete << i
        end
        result = (@results[query.__id__] ||= [])
        response["refs"].each do |obj_ref|
          id = obj_ref["id"]
          # TODO fetch missing ObjData from Service
          result << (objs[id] or raise "Data for Obj with id #{id} missing!")
        end
      end
      queries_to_delete.reverse_each {|i| @open_queries.delete_at(i) }
    end

    def results
      @queries.map {|query| @results[query.__id__] || [] }
    end

    def finished?
      open_queries.empty?
    end
  end

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

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

    def initialize
      @query_counter = 0
    end

    def begin_caching
      @caching = true
    end

    def end_caching
      CmsDataCache.cache.clear
      @caching = false
    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_by_id(id)
      workspace_data_from_cache = WorkspaceDataFromService.find_from_cache(id)
      from_content_state_id = workspace_data_from_cache.try(:content_state_id)

      request_params = {:workspace_id => id}
      request_params[:content_state_id] = from_content_state_id if from_content_state_id

      raw_data = if id == 'published' && workspace_data_from_cache
        begin
          ContentService.query('workspaces/query', request_params, timeout: 1)
        rescue CommunicationError => e
          warn_backend_not_available(id, from_content_state_id, e.message)
          return workspace_data_from_cache
        end
      else
        ContentService.query('workspaces/query', request_params)
      end

      if raw_workspace_data = raw_data['workspace']
        workspace_data = WorkspaceDataFromService.new(raw_workspace_data)
        workspace_data.store_in_cache if from_content_state_id != workspace_data.content_state_id
        workspace_data
      end
    end

    def find_obj_data_by(revision, index, keys)
      find_obj_data_filtering_deleted_by(revision, index, keys, false)
    end

    def find_obj_data_including_deleted_by(revision, index, keys)
      find_obj_data_filtering_deleted_by(revision, index, keys, true)
    end

    def find_blob_data(id, access, verb)
      id = Addressable::URI.normalize_component(id, Addressable::URI::CharacterClasses::UNRESERVED)
      if blob_data = fetch_blob_data_from_cache(id, access, verb)
        blob_data
      else
        blob_datas = request_blob_datas_from_backend(id)
        store_blob_datas_in_cache(id, blob_datas)
        blob_datas[access][verb]
      end
    end

    def find_blob_metadata(id, url)
      if blob_metadata = fetch_blob_metadata_from_cache(id)
        blob_metadata
      else
        blob_metadata = request_blob_metadata_from_s3(url)
        store_blob_metadata_in_cache(id, blob_metadata)
        blob_metadata
      end
    end

    def search_objs(workspace, params)
      content_state = workspace.revision.content_state
      cache_index = 'search'
      cache_key = params.to_param

      if result = fetch_search_result_from_cache(content_state, cache_index, cache_key)
        result
      else
        request_search_result_from_backend(workspace, params).tap do |result|
          store_search_result_in_cache(content_state, cache_index, cache_key, result)
        end
      end
    end

    def find_obj_class_data_by_name(revision, name)
      find_all_obj_class_data(revision).find { |obj_class_data| obj_class_data.name == name }
    end

    def find_all_obj_class_data(revision)
      content_state = revision.content_state
      if obj_classes_data = fetch_obj_classes_data_from_cache(content_state)
        obj_classes_data
      else
        request_obj_classes_data_from_backend(revision).tap do |obj_classes_data|
          store_obj_classes_data_in_cache(content_state, obj_classes_data)
        end
      end
    end

    private

    def fetch_obj_classes_data_from_cache(content_state)
      ContentStateCaching.find_obj_classes_data(content_state) if caching?
    end

    def request_obj_classes_data_from_backend(revision)
      response = CmsRestApi.get("revisions/#{revision.id}/obj_classes", include_inactive: true)
      response['results'].map { |raw_data| ObjClassData.new(raw_data) }
    end

    def store_obj_classes_data_in_cache(content_state, obj_classes_data)
      ContentStateCaching.store_obj_classes_data(content_state, obj_classes_data) if caching?
    end

    def fetch_search_result_from_cache(content_state, cache_index, cache_key)
      content_state.find_obj_data(cache_index, cache_key) if caching?
    end

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

    def store_search_result_in_cache(content_state, cache_index, cache_key, result)
      content_state.save_obj_data(cache_index, cache_key, result) if caching?
    end

    def fetch_blob_data_from_cache(id, access, verb)
      CmsDataCache.cache.read(blob_data_cache_key(id, access, verb))
    end

    def request_blob_datas_from_backend(id)
      @query_counter += 1
      CmsRestApi.get("blobs/#{id}")
    end

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

    def blob_data_cache_key(id, access, verb)
      "blob_data/#{id}/#{access}/#{verb}"
    end

    def fetch_blob_metadata_from_cache(id)
      CmsDataCache.cache.read(blob_metadata_cache_key(id))
    end

    def request_blob_metadata_from_s3(url)
      uri = URI.parse(url)
      retried = false
      begin
        response = ConnectionManager.request(uri, Net::HTTP::Head.new(uri))
        @query_counter += 1
      rescue NetworkError
        raise if retried
        retried = true
        retry
      end

      raise ScrivitoError, "S3 responded with #{response.code}" unless response.code == '200'

      {
        content_length: response['content-length'],
        content_type:   response['content-type'],
        cache_control:  response['cache-control'],
      }
    end

    def store_blob_metadata_in_cache(id, blob_metadata)
      max_age = blob_metadata.delete(:cache_control) =~ /max-age=(.*),/ && $1
      max_age = max_age.to_i if max_age
      CmsDataCache.cache.write(blob_metadata_cache_key(id), blob_metadata, expires_in: max_age)
    end

    def blob_metadata_cache_key(id)
      "blob_metadata/#{id}"
    end

    def find_obj_data_filtering_deleted_by(revision, index, keys, include_deleted)
      index = index.to_s
      assert_valid_index_name(index)
      raw_data = find_raw_data_from_cache_or_database_by(revision, index, keys)

      raw_data.map do |raw_result|
        raw_result.each_with_object([]) do |raw_data, result|
          next if raw_data['_modification'] == ['deleted'] && !include_deleted
          result << ObjDataFromService.new(raw_data)
        end
      end
    end

    def find_raw_data_from_cache_or_database_by(revision, index, keys)
      keys_from_database = []
      # load results from cache
      results_from_cache = keys.map do |key|
        find_raw_data_from_cache_by(revision, index, key).tap do |objs|
          keys_from_database << key unless objs
        end
      end

      # load cache misses from database and store them in cache
      results_from_database =
          find_raw_data_from_database_by(revision, index, keys_from_database)
      keys_from_database.each_with_index do |key, key_number|
        store_raw_data_list_in_cache(revision, index, key, results_from_database[key_number])
      end

      # combine the results
      results_from_cache.map do |objs_from_cache|
        objs_from_cache || results_from_database.shift
      end
    end

    def find_raw_data_from_cache_by(revision, index, key)
      ContentStateCaching.find_obj_data(revision.content_state, index, key) if caching?
    end

    def find_raw_data_from_database_by(revision, index, keys)
      return [] if keys.blank?
      instrumenter = ActiveSupport::Notifications.instrumenter
      instrumenter.instrument(
        "cms_load.scrivito", :name => "Obj Load", :index => index, :keys => keys
      ) do
        @query_counter += 1
        queries = ContentServiceObjQueries.new(keys.map {|key| {:type => index, :param => key} })
        queries.handle_response(request_content_service(queries, revision)) until queries.finished?
        queries.results
      end
    end

    def request_content_service(queries, revision)
      ContentService.query('objs/query', content_service_request_params(queries, revision))
    end

    def content_service_request_params(queries, revision)
      params = {
        queries: queries.open_queries,
        revision_id: revision.id,
        include_deleted: true
      }

      # A base revision doesn't have a directly corresponding workspace. Instead it uses its
      # derivative workspace as fallback to access the contents. Thus fallback workspace of a base
      # revision may not be used for backend requests.
      params[:workspace_id] = revision.workspace.id unless revision.base?

      params
    end

    UNIQUE_INDICES = [:id, :path, :permalink].freeze

    def store_raw_data_list_in_cache(revision, index, key, raw_data_list)
      raw_data_list.each do |values|
        UNIQUE_INDICES.each do |unique_index|
          unique_index_values = values["_#{unique_index}"]
          if unique_index_values.present?
            store_item_in_cache(revision, unique_index, unique_index_values.first, [values])
          end
        end
      end
      unless UNIQUE_INDICES.include?(index)
        store_item_in_cache(revision, index, key, raw_data_list)
      end
    end

    def store_item_in_cache(revision, index, key, item)
      ContentStateCaching.store_obj_data(revision.content_state, index, key, item)
    end

    def assert_valid_index_name(index)
      raise ArgumentError, "invalid index name '#{index}'" unless VALID_INDEX_NAMES.include?(index)
    end

    def warn_backend_not_available(workspace_id, content_state_id, error_message)
      message = <<-EOS
        Couldn't connect to content service for workspace with id=#{workspace_id} and content_state_id=#{content_state_id}.
        #{error_message}
        Serving from cache.
      EOS
      Rails.logger.warn(message)
    end

  end

end