cabal-version:      3.0
name:               moo-nad
version:            0.1.0.2

synopsis:           Invocation helpers for the ReaderT-record-of-functions style.
description:
  Using a record-of-functions as the environment of some 
  reader-like monad is a common way of structuring Haskell 
  applications, somewhat resembling dependency injection in OOP.
   
  We often want our program logic to be polymorphic over both the
  concrete monad and the environment. One common solution is to
  abstract the monad using @MonadReader@, and abstract the environment
  using @HasX@-style typeclasses.
   
  One minor annoyance though is that invoking the function in the 
  environment is often a bit cumbersome: you have to ask
  the environment for the function, and then lift the result of
  the function back into the reader-like monad.
    
  This library supports a special twist on @ReaderT@-record-of-functions                     
  style: instead of depending only on typeclasses for abstraction, 
  we also use a module signature. This comes with different tradeoffs.
   
  One benefit is that we support a simpler way of invoking functions from the
  environment, using a helper that takes care of both asking the environment
  and lifting function results, and which works uniformly for functions of any
  arity.

license:            BSD-3-Clause
license-file:       LICENSE
author:             Daniel Diaz Carrete
maintainer:         diaz_carrete@yahoo.com
category:           Control
extra-source-files: CHANGELOG.md, README.md

source-repository    head
    type:     git
    location: https://github.com/danidiaz/moo-nad.git

common common
    build-depends:    base >= 4.11.0.0 && < 5,
                      mtl  ^>= 2.2,
                      dep-t ^>= 0.4.4
    default-language: Haskell2010

-- Indefinite library which provides an invocation helper over some abstract
-- readerlike monad which carries a record-of-functions.
library
    import:           common
    signatures:       Moo
    exposed-modules:  Moo.Prelude
    build-depends:    
    hs-source-dirs:   lib

-- Example indefinite program logic.
library example-logic-that-logs
    import:           common
    -- The Moo signature is enriched locally through signature merging.
    signatures:       Moo
    exposed-modules:  LogicThatLogs
    build-depends:   
                      moo-nad
    hs-source-dirs:   lib-example-logic-that-logs

-- Example library that implements the Moo signature.
library example-impl
    import:           common
    exposed-modules:  Moo
    -- Notice that we don't depend explicitly on the Moo signature.
    build-depends:    
                      transformers ^>= 0.5
    hs-source-dirs:   lib-example-impl

-- The tests put together the moo-nad library, the example indefinite package
-- with the program logic, and the sublibrary carrying the implementation.
test-suite tests
    import:           common
    type:             exitcode-stdio-1.0
    hs-source-dirs:   test
    main-is:          tests.hs
    build-depends:    
      tasty           ^>= 1.3.1,
      tasty-hunit     ^>= 0.10.0.2,
      example-logic-that-logs,
      example-impl