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.

4 files changed, 24 insertions, 1 deletions

diff --git a/src/Conftrack/Source.hs b/src/Conftrack/Source.hs
index ecfa20d..ab13172 100644
--- a/src/Conftrack/Source.hs
+++ b/src/Conftrack/Source.hs
@@ -12,11 +12,27 @@ import Control.Monad.State (StateT (..))
 import Data.Text (Text)
 
 
+-- | An abstraction over "config sources". This might mean file formats,
+-- environment variables, or any other kind of format that can be seen as a
+-- key-value store.
 class ConfigSource s where
+  -- | Some sources require state, e.g. to keep track of which values were
+  -- already read.
   type SourceState s
+
+  -- | read a single value from the source.
   fetchValue :: Key -> s -> StateT (SourceState s) IO (Either ConfigError (Value, Text))
+
+  -- | given @s@, determine if any keys are "left over" and were not used.
+  -- This is used to produce warnings for unknown configuration options;
+  -- since not all sources can support this, this function's return type
+  -- includes @Maybe@ and sources are free to return @Nothing@ if they
+  -- cannot determine if any unknown keys are present.
   leftovers :: s -> StateT (SourceState s) IO (Maybe [Key])
 
+-- | An opaque type for any kind of config sources. Values of this type can be
+-- acquired from they @Conftrack.Source.*@ modules, or by implementing the
+-- 'ConfigSource' type class.
 data SomeSource = forall source. ConfigSource source
    => SomeSource (source, SourceState source)
 
diff --git a/src/Conftrack/Source/Aeson.hs b/src/Conftrack/Source/Aeson.hs
index 97353d0..17ea4ee 100644
--- a/src/Conftrack/Source/Aeson.hs
+++ b/src/Conftrack/Source/Aeson.hs
@@ -7,7 +7,8 @@
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE LambdaCase #-}
 
-module Conftrack.Source.Aeson (JsonSource(..), mkJsonSource, mkJsonSourceWith, mkJsonFileSource) where
+-- | Functions for producing sources reading from json strings or files, using the aeson library.
+module Conftrack.Source.Aeson (mkJsonSource, mkJsonSourceWith, mkJsonFileSource, JsonSource(..)) where
 
 import Conftrack.Value (Key (..), ConfigError(..), Value (..), KeyPart)
 import Conftrack.Source (SomeSource(..), ConfigSource (..))
@@ -37,13 +38,17 @@ data JsonSource = JsonSource
   , jsonSourceDescription :: Text
   } deriving (Show)
 
+-- | Make a source from an aeson value
 mkJsonSource :: A.Value -> SomeSource
 mkJsonSource value = mkJsonSourceWith ("JSON string " <> LT.toStrict (A.encodeToLazyText value)) value
 
+-- | same as 'mkJsonSource', but with an additional description to be shown
+-- in output of 'Conftrack.Pretty.printConfigOrigins'.
 mkJsonSourceWith :: Text -> A.Value -> SomeSource
 mkJsonSourceWith description value = SomeSource (source, [])
   where source = JsonSource value description
 
+-- | Make a source from a json file.
 mkJsonFileSource :: OsPath -> IO (Maybe SomeSource)
 mkJsonFileSource path = do
   bytes <- readFile path
diff --git a/src/Conftrack/Source/Trivial.hs b/src/Conftrack/Source/Trivial.hs
index d4151c2..842ca46 100644
--- a/src/Conftrack/Source/Trivial.hs
+++ b/src/Conftrack/Source/Trivial.hs
@@ -5,6 +5,7 @@
 {-# LANGUAGE AllowAmbiguousTypes #-}
 {-# LANGUAGE OverloadedStrings #-}
 
+-- | A trivial source reading from a @Map Key Value@, only useful as a demonstration or for tests.
 module Conftrack.Source.Trivial where
 
 import Conftrack.Value (Key, Value(..), ConfigError(..))
diff --git a/src/Conftrack/Source/Yaml.hs b/src/Conftrack/Source/Yaml.hs
index 6adc798..4642922 100644
--- a/src/Conftrack/Source/Yaml.hs
+++ b/src/Conftrack/Source/Yaml.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE UndecidableInstances #-}
 
+-- | Functions for producing sources reading from yaml strings or files, using the aeson library.
 module Conftrack.Source.Yaml (YamlSource(..), mkYamlSource, mkYamlSourceWith, mkYamlFileSource) where
 
 import Conftrack.Source (SomeSource(..), ConfigSource (..))