#+title: cogs ⚙ configuration object generation system

This package provides the core services and facilities to define,
produce and deliver configuration information to applications in a
flexible and coordinated manner.  The core of cogs consists of the
following elements:

- object schema :: using [[https://brettviren.github.io/moo/][moo]], cogs provides an abstract object schema
  definition language which may compile to validating or generating
  schema.

- codegen :: again using moo, cogs provides code generation to produce
  C++/Python classes matching object schema.

- services :: cogs provides services for an application to receive a
  sequence of configuration object in a manner that allows easy
  dispatch to application internals.  The services follow an abstract
  interface to allow different implementations to be swapped without
  application changes.  File based services are included and services
  using ZeroMQ or gRPC may be found in corresponding ~cogs-*~ packages.

- components :: applications may simplify dispatch of configuration to
  components by using cogs mixin classes which handle the
  deserialization of configuration objects to appropriate native
  (generated) types.

- exceptions :: cogs follows an exception based error handling policy
  and uses [[https://github.com/DUNE-DAQ/ers][ERS]] to report issues and logging.

In C++ a configuration object is an instance of a ~cogs::object~ which
is a [[https://github.com/nlohmann/json][nlohmann::json]] object.

* Demo

See the [[file:demo/README.org][demo]] for an example package that uses cogs.

* Roadmap

Near term

- [X] initial package and build and install
- [X] hook in ERS and ~nlohmann::json~
- [X] abstract configuration stream class
- [X] simple JSON file stream implementations
- [X] configurable base hierarchy
- [X] port demo application and schema from moo/moc
- [X] +port demo ~Makefile~ to ~wscript~+ use generate.sh for codegen but o.w. build 
- [X] user documentation: https://brettviren.github.io/cogs/demo.html 

Longer term
 
- [ ] understand what CCM message passing will be (gRPC? Cap'N Proto? ZeroMQ?)
- [ ] develop a ~cogs::Stream~ to support it
- [ ] integrate use of cogs into appfmk