document publicly exposed interface

this documents most functions that might be used by downstream consumers
of this library, except for those in Conftrack.Pretty, which aren't done
yet.

1 files changed, 17 insertions, 1 deletions

diff --git a/src/Conftrack/Value.hs b/src/Conftrack/Value.hs
index 3eda24a..1d6e6a7 100644
--- a/src/Conftrack/Value.hs
+++ b/src/Conftrack/Value.hs
@@ -8,7 +8,7 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE DefaultSignatures #-}
 
-module Conftrack.Value (key, Value(..), ConfigError(..), Key(..), ConfigValue(..), Origin(..), KeyPart, prefixedWith) where
+module Conftrack.Value (key, Value(..), ConfigError(..), Key(..), ConfigValue(..), Origin(..), KeyPart, prefixedWith, withString) where
 
 import Data.Text(Text)
 import qualified Data.Text as T
@@ -21,9 +21,13 @@ import qualified Data.Text.Encoding as BS
 import Language.Haskell.TH.Quote (QuasiQuoter(..))
 import Language.Haskell.TH.Syntax (Lift(lift))
 
+-- | A generic value read from a config source, to be parsed into a more useful type
+-- (see the 'ConfigValue' class).
 data Value =
   ConfigString BS.ByteString
   | ConfigInteger Integer
+  -- | A value which may be an integer, but the source cannot say for sure, e.g. because
+  -- its values are entirely untyped. Use 'withString' to handle such cases.
   | ConfigMaybeInteger BS.ByteString Integer
   | ConfigOther Text Text
   | ConfigBool Bool
@@ -32,6 +36,14 @@ data Value =
 
 type KeyPart = Text
 
+-- | A configuration key is a non-empty list of parts. By convention, these parts
+-- are separated by dots when written, although dots withing parts are not disallowed.
+--
+-- For writing values easily, consider enabling the @QuasiQuotes@ language extension
+-- to use 'key':
+--
+-- >>> [key|foo.bar|]
+-- foo.bar
 newtype Key = Key (NonEmpty KeyPart)
   deriving newtype (Eq, Ord)
   deriving (Lift)
@@ -39,6 +51,7 @@ newtype Key = Key (NonEmpty KeyPart)
 instance Show Key where
   show (Key parts) = T.unpack (T.intercalate "." (NonEmpty.toList parts))
 
+-- | to write values of 'Key' easily
 key :: QuasiQuoter
 key = QuasiQuoter
   { quoteExp = lift . Key . NonEmpty.fromList . T.splitOn "." . T.pack
@@ -57,8 +70,11 @@ data ConfigError =
   | Shadowed
   deriving Show
 
+-- | Values which can be read from a config source must implement this class
 class ConfigValue a where
   fromConfig :: Value -> Either ConfigError a
+  -- | optionally, a function to pretty-print values of this type, used by the
+  -- functions of "Conftrack.Pretty". If not given, defaults to @a@'s 'Show' instance.
   prettyValue :: a -> Text
 
   default prettyValue :: Show a => a -> Text