{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE StrictData        #-}

{-|
Module      : Headroom.Configuration.Enrich
Description : Simple enrichment of YAML configuration stubs
Copyright   : (c) 2019-2021 Vaclav Svejcar
License     : BSD-3-Clause
Maintainer  : vaclav.svejcar@gmail.com
Stability   : experimental
Portability : POSIX

This module contains mini-DSL for enrichment of generated /YAML/ configurations,
i.e. replacing default values with real ones, etc. This is intentionally done
without the "Data.Yaml" and parsing, because that way all comments inside YAML
file would be lost.
-}

module Headroom.Configuration.Enrich
  ( -- * Data Types
    Enrich(..)
  , ValueType(..)
    -- * Field Generators
  , withArray
  , withText
    -- * Field Manipulation
  , replaceEmptyValue
  )
where

import           Data.Aeson                          ( ToJSON(..) )
import           Headroom.Serialization              ( prettyPrintYAML )
import           RIO
import qualified RIO.Map                            as M
import qualified RIO.Text                           as T
import qualified RIO.Text.Partial                   as TP


---------------------------------  DATA TYPES  ---------------------------------

-- | Simple wrapper representing single step of enrichment.
newtype Enrich = Enrich
  { enrich :: Text -> Text
  -- ^ takes input text and does enrichment
  }


instance Semigroup Enrich where
  Enrich fnA <> Enrich fnB = Enrich $ fnA . fnB


instance Monoid Enrich where
  mempty = Enrich id


-- | Represents type of the field value.
data ValueType
  = Array
  -- ^ type of /YAML/ array
  | String
  -- ^ type of /YAML/ string
  deriving (Eq, Show)


------------------------------  PUBLIC FUNCTIONS  ------------------------------

-- | Generates /YAML/ array field from given list and field name.
withArray :: ToJSON a
          => [a]
          -- ^ input list used as value
          -> Text
          -- ^ field name
          -> (ValueType, Text)
          -- ^ generated fields as @(valueType, generatedField)@
withArray list field = (Array, asYAML field list)


-- | Generates /YAML/ string from given text value and field name.
withText :: Text
         -- ^ input text value
         -> Text
         -- ^ field name
         -> (ValueType, Text)
         -- ^ generated fields as @(valueType, generatedField)@
withText text field = (String, asYAML field text)


-- | Replaces empty value of given field with actual generated value.
replaceEmptyValue :: Text
                  -- ^ field name
                  -> (Text -> (ValueType, Text))
                  -- ^ field value generator function
                  -> Enrich
                  -- ^ resulting enrichment step
replaceEmptyValue field replaceFn = Enrich $ \doc -> do
  TP.replace old new doc
 where
  (tpe, new) = replaceFn field
  old        = field <> ": " <> emptyValue tpe


------------------------------  PRIVATE FUNCTIONS  -----------------------------

asYAML :: ToJSON a => Text -> a -> Text
asYAML field value = T.stripEnd . prettyPrintYAML $ M.fromList [(field, value)]


emptyValue :: ValueType -> Text
emptyValue Array  = "[]"
emptyValue String = "\"\""