Update template for example plugin

Author: saep

stack-template.hsfiles

@@ -22,9 +22,10 @@ executable my-nvim-hs
                      , Neovim.Example.Plugin.Fibonacci
                      , Neovim.Example.Plugin.Random
   build-depends:       base >= 4.7 && < 5
-                     , nvim-hs >= 0.2.5 && < 1.0.0
-                     -- The dependency below is only needed for the example plugin
+                     , nvim-hs >= 1 && < 2
+                     -- The dependencies below are only needed for the example plugin
                      , random
+                     , unliftio
   default-language:    Haskell2010
 
 {-# START_FILE lib/Neovim/Example/Plugin.hs #-}
@@ -40,29 +41,24 @@ import Neovim
 import Neovim.Example.Plugin.Random (nextRandom, setNextRandom, randomNumbers)
 import Neovim.Example.Plugin.Fibonacci (fibonacci)
 
-plugin :: Neovim (StartupConfig NeovimConfig) () NeovimPlugin
+plugin :: Neovim (StartupConfig NeovimConfig) NeovimPlugin
 plugin = do
     randomPluginState <- randomNumbers
     wrapPlugin Plugin
-        { exports =
+        { environment = randomPluginState
+        , exports =
             [ $(function' 'fibonacci) Sync
             -- Notice the quotation mark before the functin name, this is
             -- important!
-            ]
-        , statefulExports =
-            [ StatefulFunctionality
-                { readOnly = ()
-                , writable = randomPluginState
-                , functionalities =
-                    [ $(function' 'nextRandom) Sync
-                    , $(function "SetNextRandom" 'setNextRandom) Async
-                    ]
-                }
+
+            , $(function' 'nextRandom) Sync
+            , $(function "SetNextRandom" 'setNextRandom) Async
             ]
         }
 
 {-# START_FILE lib/Neovim/Example/Plugin/Random.hs #-}
 {-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TemplateHaskell #-}
 module Neovim.Example.Plugin.Random
     ( nextRandom
     , setNextRandom
@@ -71,45 +67,50 @@ module Neovim.Example.Plugin.Random
 
 import Neovim
 import System.Random (newStdGen, randoms)
+import UnliftIO.STM  (TVar, atomically, readTVar, modifyTVar, newTVarIO)
 
--- | This is the start up code. It initializes the random number generator and
--- returns a convenient list of random numbers.
---
--- Except for the last @[Int16]@ return values, this type signature is mandatory
--- for your startup code. The internals of the plugin recompilation leak here a
--- bit, it might be changed in the future. If you don't mind warnings, you can
--- leave the signature undefined, but then you would have to add a type
--- signature to the value of @randoms g@.
+-- | This type alias encodes the type of your plugin's environment, namely
+-- '(TVar [Int16)' in this case.
 --
--- See <https://github.com/neovimhaskell/nvim-hs/issues/13> for details.
+-- Since this plugin needs to store some state, we have to put it in a mutable
+-- variable. I chose TVar here because I like the Software Transactional Memory
+-- library.
+type MyNeovim a = Neovim (TVar [Int16]) a
+
+-- | This is the start up code. It initializes the random number generator and
+-- returns a convenient list of random numbers. It returns the environment and
+-- is executed in the startup code, so this is the only place where you can't
+-- use the type alias defined above.
 --
 -- Neovim isn't so good with big numbers, so limit to 16 bits.
-randomNumbers :: Neovim (StartupConfig NeovimConfig) () [Int16]
+randomNumbers :: Neovim startupEnv (TVar [Int16])
 randomNumbers = do
     g <- liftIO newStdGen -- Create a new seed for a pseudo random number generator
-    return (randoms g)    -- Return an infinite list of random numbers
-
--- You could write this shorter in more idiomatic Haskell:
--- randomNumbers = randoms <$> liftIO newStdGen
+    newTVarIO (randoms g) -- Put an infinite list of random numbers into a TVar
 
 -- | Get the next random number and update the state of the list.
-nextRandom :: Neovim r [Int16] Int16
+nextRandom :: MyNeovim Int16
 nextRandom = do
-    r <- gets head -- get the head of the infinite random number list
-    modify tail    -- set the list to its tail
-    return r
+    tVarWithRandomNumbers <- ask
+    atomically $ do
+        -- pick the head of our list of random numbers
+        r <- head <$> readTVar tVarWithRandomNumbers
+
+        -- Since we do not want to return the same number all over the place
+        -- remove the head of our list of random numbers
+        modifyTVar tVarWithRandomNumbers tail
+
+        return r
 
--- An alternative equivalent implementation with pattern matching on the list
--- nextRandom :: Neovim r [Int16] Int16
--- nextRandom = do
---     (r:rs) <- get
---     put rs
---     return r
 
 -- | You probably don't want this in a random number generator, but this shows
 -- hoy you can edit the state of a stateful plugin.
-setNextRandom :: Int16 -> Neovim r [Int16] ()
-setNextRandom n = modify (n:) -- cons n to the front of the infinite list
+setNextRandom :: Int16 -> MyNeovim ()
+setNextRandom n = do
+    tVarWithRandomNumbers <- ask
+
+    -- cons n to the front of the infinite list
+    atomically $ modifyTVar tVarWithRandomNumbers (n:)
 
 {-# START_FILE lib/Neovim/Example/Plugin/Fibonacci.hs #-}
 module Neovim.Example.Plugin.Fibonacci
@@ -124,7 +125,7 @@ fibonacciNumbers = 0:fibs -- Since were using !! to index an element in a list,
     where fibs = 1:scanl1 (+) fibs
 
 -- | Neovim is not really good with big numbers, so we return a 'String' here.
-fibonacci :: Int -> Neovim' String
+fibonacci :: Int -> Neovim env String
 fibonacci n = return . show $ fibonacciNumbers !! n
 
 {-# START_FILE nvim.hs #-}