Restructure part of the Conf.hs to provide more to do and with added guidance

level02/README.md

@@ -11,9 +11,8 @@ inputs sufficiently.
 To build this application we're going to need some requirements:
 
 ### Requirements
-We have a WebThing(TM) somewhere and we would like, for some
-unknown reason, to be able to add comments to various topics on this
-WebThing(TM).
+We have a WebThing(TM) somewhere and we would like, for some unknown reason, to
+be able to add comments to various topics on this WebThing(TM).
 
 ### "Spec"
 Let's pretend we've completed a dozen specification meetings with our Project

level03/src/FirstApp/Conf.hs

@@ -110,12 +110,38 @@ parseOptions =
 -- need. The package we're using is the ``aeson`` package to parse some JSON and
 -- we'll pick the bits off the Object.
 
--- The documentation for this package will guide you in the right direction
+-- Complete the helper function that will be used to retrieve values off the
+-- JSON object.
+
+-- | fromJsonObjWithKey
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"foo\":\"Susan\"}")
+-- Last (Just "Susan")
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"bar\":33}")
+-- Last Nothing
+fromJsonObjWithKey
+  :: FromJSON a
+  => Text
+  -> (a -> b)
+  -> Aeson.Object
+  -> Last b
+fromJsonObjWithKey =
+  error "fromJsonObjWithKey not implemented"
+
+-- Construct the function that will take a FilePath, read it in and attempt to
+-- decode it as a valid JSON object, using the ``aeson`` package. Then pull
+-- specific keys off this object and construct our ``PartialConf``. Using the
+-- function we wrote above to assist in pulling items off the object.
 parseJSONConfigFile
   :: FilePath
   -> IO PartialConf
 parseJSONConfigFile =
   error "parseJSONConfigFile not implemented"
+  where
+    -- Use the ``bracketOnError`` function to guard against exceptions.
+    readObject
+      :: IO (Maybe Aeson.Object)
+    readObject =
+      error "readObject not implemented"
 
 -- | Command Line Parsing
 

level04/src/FirstApp/Conf.hs

@@ -108,6 +108,20 @@ parseOptions fp = do
 
 -- | File Parsing
 
+-- | fromJsonObjWithKey
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"foo\":\"Susan\"}")
+-- Last (Just "Susan")
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"bar\":33}")
+-- Last Nothing
+fromJsonObjWithKey
+  :: FromJSON a
+  => Text
+  -> (a -> b)
+  -> Aeson.Object
+  -> Last b
+fromJsonObjWithKey k c obj =
+  Last $ c <$> Aeson.parseMaybe (Aeson..: k) obj
+
 -- Additional Exercise: Rewrite this without using Do notation
 -- 'fmap' should be sufficient.
 parseJSONConfigFile
@@ -118,25 +132,10 @@ parseJSONConfigFile fp = do
   pure . fromMaybe mempty $ toPartialConf <$> fc
   where
     toPartialConf cObj = PartialConf
-      ( offObj "port" Port cObj )
-      ( offObj "helloMsg" helloFromStr cObj )
+      ( fromJsonObjWithKey "port" Port cObj )
+      ( fromJsonObjWithKey "helloMsg" helloFromStr cObj )
 
-    -- Parse out the keys from the object, maybe...
-    offObj
-      :: FromJSON a
-      => Text
-      -> (a -> b)
-      -> Aeson.Object
-      -> Last b
-    offObj k c obj =
-      -- Too weird ?
-      Last $ c <$> Aeson.parseMaybe (Aeson..: k) obj
-
-    -- Use bracket to save ourselves from horrible exceptions, which are
-    -- horrible.
-    --
-    -- Better ways to do this ?
-    readObject
+     readObject
       :: IO (Maybe Aeson.Object)
     readObject = bracketOnError
       (LBS.readFile fp)

level05/src/FirstApp/Conf.hs

@@ -116,6 +116,16 @@ parseOptions fp = do
 
 -- | File Parsing
 
+-- Parse out the keys from the object, maybe...
+fromJsonObjWithKey
+  :: FromJSON a
+  => Text
+  -> (a -> b)
+  -> Aeson.Object
+  -> Last b
+fromJsonObjWithKey k c obj =
+  Last (c <$> Aeson.parseMaybe (Aeson..: k) obj)
+
 parseJSONConfigFile
   :: FilePath
   -> IO PartialConf
@@ -124,23 +134,9 @@ parseJSONConfigFile fp = do
   pure . fromMaybe mempty $ toPartialConf <$> fc
   where
     toPartialConf cObj = PartialConf
-      ( fromObj "port" Port cObj )
-      ( fromObj "helloMsg" helloFromStr cObj )
-
-    -- Parse out the keys from the object, maybe...
-    fromObj
-      :: FromJSON a
-      => Text
-      -> (a -> b)
-      -> Aeson.Object
-      -> Last b
-    fromObj k c obj =
-      Last (c <$> Aeson.parseMaybe (Aeson..: k) obj)
-
-    -- Use bracket to save ourselves from horrible exceptions, which are
-    -- horrible.
-    --
-    -- Better ways to do this ?
+      ( fromJsonObjWithKey "port" Port cObj )
+      ( fromJsonObjWithKey "helloMsg" helloFromStr cObj )
+    -- Use bracket to save ourselves from horrible exceptions.
     readObject
       :: IO (Maybe Aeson.Object)
     readObject = bracketOnError

level06/src/FirstApp/Conf.hs

@@ -129,6 +129,20 @@ parseOptions fp = do
 
 -- | File Parsing
 
+-- | fromJsonObjWithKey
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"foo\":\"Susan\"}")
+-- Last (Just "Susan")
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"bar\":33}")
+-- Last Nothing
+fromJsonObjWithKey
+  :: FromJSON a
+  => Text
+  -> (a -> b)
+  -> Aeson.Object
+  -> Last b
+fromJsonObjWithKey k c obj =
+  Last $ c <$> Aeson.parseMaybe (Aeson..: k) obj
+
 parseJSONConfigFile
   :: FilePath
   -> IO PartialConf
@@ -137,27 +151,12 @@ parseJSONConfigFile fp = do
   pure . fromMaybe mempty $ toPartialConf <$> fc
   where
     toPartialConf cObj = PartialConf
-      ( fromObj "port" Port cObj )
-      ( fromObj "helloMsg" helloFromStr cObj )
+      ( fromJsonObjWithKey "port" Port cObj )
+      ( fromJsonObjWithKey "helloMsg" helloFromStr cObj )
       -- Pull the extra keys off the configuration file.
-      ( fromObj "tableName" Table cObj )
-      ( fromObj "dbFilePath" id cObj )
+      ( fromJsonObjWithKey "tableName" Table cObj )
+      ( fromJsonObjWithKey "dbFilePath" id cObj )
 
-    -- Parse out the keys from the object, maybe...
-    fromObj
-      :: FromJSON a
-      => Text
-      -> (a -> b)
-      -> Aeson.Object
-      -> Last b
-    fromObj k c obj =
-      -- Too weird ?
-      Last $ c <$> Aeson.parseMaybe (Aeson..: k) obj
-
-    -- Use bracket to save ourselves from horrible exceptions, which are
-    -- horrible.
-    --
-    -- Better ways to do this ?
     readObject
       :: IO (Maybe Aeson.Object)
     readObject = bracketOnError

level07/src/FirstApp/Conf.hs

@@ -129,9 +129,20 @@ parseOptions fp = do
 
 -- | File Parsing
 
--- Avoiding too many complications with selecting a configuration file package
--- from hackage. We'll use an encoding that you are probably familiar with, for
--- better or worse, and write a small parser to pull out the bits we need.
+-- | fromJsonObjWithKey
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"foo\":\"Susan\"}")
+-- Last (Just "Susan")
+-- >>> fromJsonObjWithKey "foo" id (encode "{\"bar\":33}")
+-- Last Nothing
+fromJsonObjWithKey
+  :: FromJSON a
+  => Text
+  -> (a -> b)
+  -> Aeson.Object
+  -> Last b
+fromJsonObjWithKey k c obj =
+  Last (c <$> Aeson.parseMaybe (Aeson..: k) obj)
+
 parseJSONConfigFile
   :: FilePath
   -> IO PartialConf
@@ -140,32 +151,12 @@ parseJSONConfigFile fp = do
   pure . fromMaybe mempty $ toPartialConf <$> fc
   where
     toPartialConf cObj = PartialConf
-      ( fromObj "port" Port cObj )
-      ( fromObj "helloMsg" helloFromStr cObj )
+      ( fromJsonObjWithKey "port" Port cObj )
+      ( fromJsonObjWithKey "helloMsg" helloFromStr cObj )
       -- Pull the extra keys off the configuration file.
-      ( fromObj "tableName" Table cObj )
-      ( fromObj "dbFilePath" id cObj )
+      ( fromJsonObjWithKey "tableName" Table cObj )
+      ( fromJsonObjWithKey "dbFilePath" id cObj )
 
-    -- Parse out the keys from the object, maybe...
-    -- >>> fromObj "foo" id (encode "{\"foo\":\"Susan\"}")
-    -- Last (Just "Susan")
-    -- >>> fromObj "foo" id (encode "{\"bar\":33}")
-    -- Last Nothing
-    --
-    fromObj
-      :: FromJSON a
-      => Text
-      -> (a -> b)
-      -> Aeson.Object
-      -> Last b
-    fromObj k c obj =
-      -- Too weird ?
-      Last (c <$> Aeson.parseMaybe (Aeson..: k) obj)
-
-    -- Use bracket to save ourselves from horrible exceptions, which are
-    -- horrible.
-    --
-    -- Better ways to do this ?
     readObject
       :: IO (Maybe Aeson.Object)
     readObject = bracketOnError