Backend
=======

.. _summary:

Summary
-------

The backend is split into 3 layers, with a total of 4 conceptual components.
The layers are organized to fulfill the different levels of abstractive needs a developer requires to achieve user requirments.
The layers are as follows:


    * **Interface Layer**
        This layer is the top most layer, acting as the interface for a given frontend implementation.
        It is responsible for handling the frontend's requests and passing them to the appropriate backend component.
        It is also responsible for handling the backend's responses and passing them back to the frontend (including errors).
        The interface layer is the only layer that should be exposed to the frontend.
    * **Orchestration Layer**
        * **Service Component**
            This :term:`Component` is the data and calculation orchestration Component.
            It is responsible for stitching together calls between the :term:`Data Component` and the :term:`Recipe Component` in order to fulfill complex requirements.
            This includes things like handling a :term:`User Request`, :term:`Data State Management`, and :term:`Software Metadata`.
    * **Processing Layer**
        * **Data Component**
            This Component is the persistence Component.
            It is responsible for handling the storage and retrieval of data from the disk or wherever the data is stored.
            It provides an interface agnostic of the storage medium, allowing the :term:`Service Component` to be agnostic of the storage medium.
            It does no calculations, it just stores, retrieves, and packages data.
        * **Recipe Component**
            This Component is the calculation Component.
            It is responsible for handling the calculations required to fulfill a given :term:`User Request`.
            It provides an interface agnostic of the calculation medium, allowing the :term:`Service Component` to be agnostic of the calculation medium.
            It does no persistence, it just calculates and packages data.


Layer interaction
-----------------

The layers operate off a principle of limited visibility.

 .. mermaid::

    flowchart TD
        interface["Interface Layer"] --> orchestration["Orchestration Layer"]
        orchestration --> processing["Processing Layer"]

        subgraph processing["Processing Layer"]
        Data["Data Component"] --> Data
        Recipe["Recipe Component"] --> Recipe
        end

A lower layer is ignorant of the existence of the higher layers.
This means that the :term:`Data Component` and :term:`Recipe Component` are ignorant of the existence of the :term:`Interface Layer` and :term:`Orchestration Layer`.
The further down the stack you go, the more concrete the objectives become.

For a simplified breakdown of where you may want to implement parts of your code, refer to the :doc:`Implementation Decision Tree <../../implFlowchart>`.

.. toctree::
   :maxdepth: 1
   :caption: Index

   api/normalization/normalization_request
   api/normalization/normalization_export_request
   api/normalization/normalization_index_entry
   api/normalization/normalization_record
   api/normalization/normalization_response
   api/normalization/normalization_service
   api/normalization/normalization
   api/object_sha
   data/index
   recipe
   grocery_service
   mantid_snapper
   api/normalization/smooth_data_excluding_peaks_request
   api/calibration/calibration_assessment_request
   api/calibration/calibration_assessment_response
   api/calibration/calibration_export_request
   api/calibration/calibration_index_entry
   api/calibration/calibration_index_request
   api/calibration/calibration_load_assessment_request
   api/calibration/calibration_metric
   api/calibration/calibration_metrics_workspace_ingredient
   api/calibration/calibration_record
   api/calibration/calibration_service
   api/calibration/calibration
   api/calibration/diffraction_calibration_ingredients
   api/calibration/diffraction_calibration_recipe
   api/calibration/diffraction_calibration_request
   api/calibration/focus_group_metric
   api/calibration/generate_calibration_metrics_workspace_recipe
   algorithms/calculate_diffcal_table
   algorithms/calibration_metric_extraction_algorithm
   algorithms/conjoin_table_workspaces
   algorithms/crystallographic_info_algorithm
   algorithms/custom_group_workspace
   algorithms/detector_peak_predictor
   algorithms/diffraction_spectrum_weight_calculator
   algorithms/fetch_groceries_algorithm
   algorithms/fit_mutliple_peaks_algorithm
   algorithms/focus_spectra_algorithm
   algorithms/generate_table_workspace_from_list_of_dict
   algorithms/lite_data_creation_algo
   algorithms/load_calibration_workspaces
   algorithms/load_grouping_definition
   algorithms/make_dirty_dish
   algorithms/mask_detector_flags
   algorithms/normalize_by_current_but_the_correct_way
   algorithms/pixel_grouping_parameters_calculation
   algorithms/purge_overlapping_peaks_algorithm
   algorithms/raw_vanadium_correction_algorithm
   algorithms/save_grouping_definition
   algorithms/smooth_data_excluding_peaks_algo
   algorithms/utensils
   algorithms/wash_dishes