{- |
Module      :  Neovim
Description :  API for the neovim plugin provider /nvim-hs/
Copyright   :  (c) Sebastian Witte
License     :  Apache-2.0

Maintainer  :  woozletoff@gmail.com
Stability   :  experimental
Portability :  GHC (due to Template Haskell)

This module should contain all the things you need to write neovim plugins in
your favorite language! @:-)@

The documentation in this module should provide every information you need to start
writing plugins.
-}
module Neovim (
    -- * Installation
    -- $installation

    -- * Tutorial
    -- ** tl;dr
    -- $tldrgettingstarted
    Neovim,
    Neovim',
    neovim,
    NeovimConfig(..),
    defaultConfig,
    StartupConfig(..),
    def,

    -- ** Using existing plugins
    -- $existingplugins

    -- ** Creating a plugin
    -- $creatingplugins
    NeovimPlugin(..),
    StatefulFunctionality(..),
    Plugin(..),
    NvimObject(..),
    (+:),
    Dictionary,
    Object(..),
    wrapPlugin,
    function,
    function',
    command,
    command',
    autocmd,
    Synchronous(..),
    CommandOption(..),
    RangeSpecification(..),
    CommandArguments(..),
    AutocmdOptions(..),
    addAutocmd,
    addAutocmd',

    ask,
    asks,
    put,
    get,
    gets,
    modify,

    -- ** Creating a stateful plugin
    -- $statefulplugin

    -- ** Calling remote functions
    -- $remote
    wait,
    wait',
    waitErr,
    waitErr',
    err,
    Doc,
    Pretty(..),
    errOnInvalidResult,
    text,
    NeovimException(..),
    -- ** Generated functions for neovim interaction
    module Neovim.API.String,

    -- * Unsorted exports
    -- This section contains just a bunch of more or less useful functions which
    -- were not introduced in any of the previous sections.
    liftIO,
    withCustomEnvironment,
    whenM,
    unlessM,
    docToObject,
    docFromObject,
    Priority(..),
    module Control.Monad,
    module Control.Applicative,
    module Data.Monoid,
    module Data.Int,
    module Data.Word,

    ) where

import           Control.Applicative
import           Control.Monad                (void)
import           Control.Monad.IO.Class       (liftIO)
import           Data.Default                 (def)
import           Data.Int                     (Int16, Int32, Int64, Int8)
import           Data.MessagePack             (Object (..))
import           Data.Monoid
import           Data.Word                    (Word, Word16, Word32, Word8)
import           Neovim.API.String
import           Neovim.API.TH                (autocmd, command, command',
                                               function, function')
import           Neovim.Classes               (Dictionary, NvimObject (..),
                                               docFromObject, docToObject, (+:))
import           Neovim.Config                (NeovimConfig (..))
import           Neovim.Context               (Neovim, Neovim',
                                               NeovimException (ErrorMessage),
                                               ask, asks, err,
                                               errOnInvalidResult, get, gets,
                                               modify, put)
import           Neovim.Main                  (neovim)
import           Neovim.Plugin                (addAutocmd, addAutocmd')
import           Neovim.Plugin.Classes        (AutocmdOptions (..),
                                               CommandArguments (..),
                                               CommandOption (CmdBang, CmdCount, CmdRange, CmdRegister, CmdSync),
                                               RangeSpecification (..),
                                               Synchronous (..))
import qualified Neovim.Plugin.ConfigHelper   as ConfigHelper
import           Neovim.Plugin.Internal       (NeovimPlugin (..), Plugin (..),
                                               StatefulFunctionality(..), wrapPlugin)
import           Neovim.Plugin.Startup        (StartupConfig (..))
import           Neovim.RPC.FunctionCall      (wait, wait', waitErr, waitErr')
import           Neovim.Util                  (unlessM, whenM,
                                               withCustomEnvironment)
import           System.Log.Logger            (Priority (..))
import           Text.PrettyPrint.ANSI.Leijen (Doc, Pretty (..), text)

-- Installation {{{1
{- $installation

Installation instructions are in the README.md file that comes with the source
of this package. It is also on the repositories front page.

-}
-- 1}}}

-- Tutorial {{{1
-- tl;dr {{{2
{- $tldrgettingstarted
If you are proficient with Haskell, it may be sufficient to point you at some of the
important data structures and functions. So, I will do it here. If you need more
assistance, please skip to the next section and follow the links for functions or data
types you do no understand how to use. If you think that the documentation is lacking,
please create an issue on github (or even better, a pull request with a fix @;-)@).
The code sections that describe new functionality are followed by the source code
documentation of the used functions (and possibly a few more).

The config directory location adheres to the
<http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html XDG-basedir specification>.
Unless you have changed some \$XDG_\* environment variables, the configuration
directory on unixoid systems (e.g. MacOS X, most GNU/Linux distribution, most
BSD distributions) is @\$HOME\/.config\/nvim@.

Create a file called @nvim.hs@ in @\$XDG_CONFIG_HOME\/nvim@ (usually
@~\/.config\/nvim@) with the following content:

@
import Neovim

main = 'neovim' 'defaultConfig'
@

Adjust the fields in 'defaultConfig' according to the parameters in 'NeovimConfig'.
Depending on how you define the parameters, you may have to add some language extensions
which GHC should point you to.

-}


-- | Default configuration options for /nvim-hs/. If you want to keep the
-- default plugins enabled, you can define your config like this:
--
-- @
-- main = 'neovim' 'defaultConfig'
--          { plugins = myPlugins ++ plugins defaultConfig
--          }
-- @
--
defaultConfig :: NeovimConfig
defaultConfig = Config
    { plugins      = [ ConfigHelper.plugin ]
    , logOptions   = Nothing
    , errorMessage = Nothing
    }


-- 2}}}

-- Existing Plugins {{{2
{- $existingplugins
/nvim-hs/ is all about importing and creating plugins. This is done following a
concise API. Let's start by making a given plugin available inside
our plugin provider. Assuming that we have installed a cabal package that exports
an @examplePlugin@ from the module @TestPlugin.ExamplePlugin@. A minimal
configuration would then look like this:

@
import TestPlugin.ExamplePlugin (examplePlugin)

main = 'neovim' 'def'
        { 'plugins' = [ examplePlugin ] ++ 'plugins' 'defaultConfig'
        }
@

That's all you have to do! Multiple plugins are simply imported and put in a
list.

If the plugin is not packaged, you can also put the source files of the plugin
inside @\$XDG_CONFIG_HOME\/nvim\/lib@ (usually @~\/.config\/nvim\/lib@).
Assuming the same module name and plugin name, you can use the same configuration
file. The source for the plugin must be located at
@\$XDG_CONFIG_HOME\/nvim\/lib\/TestPlugin\/ExamplePlugin.hs@ and all source
files it depends on must follow the same structure. This is the standard way
how Haskell modules are defined in cabal projects. Having all plugins as source
files can increase the compilation times, so plugins should be put in a cabal
project once they are mature enough. This also makes them easy to share!

-}
-- 2}}}
-- Creating a plugin {{{2
{- $creatingplugins
Creating plugins isn't difficult either. You just have to follow and survive the
compile time errors of seemingly valid code. This may sound scary, but it is not
so bad. We will cover most pitfalls in the following paragraphs and if there
isn't a solution for your error, you can always ask any friendly Haskeller in
\#haskell on @irc.freenode.net@!

Enough scary stuff said for now, let's write a plugin!
Due to a stage restriction in GHC when using Template Haskell, we must define
our functions in a different module than @\$XDG_CONFIG_HOME\/nvim\/nvim.hs@.
This is a bit unfortunate, but it will save you a lot of boring boilerplate and
it will present you with helpful error messages if your plugin's functions do
not work together with neovim.

So, let\'s write a plugin that calculates the @n@th Fibonacci number. Don\'t we all
love those!

File @\~\/.config\/nvim\/lib\/Fibonacci\/Plugin.hs@:

@
module Fibonacci.Plugin (fibonacci) where

import "Neovim"

\-\- \| Neovim is not really good with big numbers, so we return a 'String' here.
fibonacci :: 'Int' -> 'Neovim'' 'String'
fibonacci n = 'return' . 'show' \$ fibs !! n
  where
    fibs :: [Integer]
    fibs = 0:1:'scanl1' (+) fibs
@

File @\~\/.config\/nvim\/lib\/Fibonacci.hs@:

@
\{\-\# LANGUAGE TemplateHaskell \#\-\}
module Fibonacci (plugin) where

import "Neovim"
import Fibonacci.Plugin (fibonacci)

plugin :: 'Neovim' ('StartupConfig' 'NeovimConfig') () 'NeovimPlugin'
plugin = 'wrapPlugin' Plugin
    { 'exports'         = [ $('function'' 'fibonacci) 'Sync' ]
    , 'statefulExports' = []
    }
@

File @~\/.config\/nvim\/nvim.hs@:

@
import "Neovim"

import qualified Fibonacci as Fibonacci

main :: 'IO' ()
main = 'neovim' 'defaultConfig'
    { 'plugins' = 'plugins' 'defaultConfig' ++ [ Fibonacci.plugin ]
    }
@

Let's analyze how it works. The module @Fibonacci.Plugin@ simply defines a function
that takes the @n@th element of the infinite list of Fibonacci numbers. Even though
the definition is very concise and asthetically pleasing, the important part is the
type signature for @fibonacci@. Similarly how @main :: IO ()@ works in normal Haskell
programs, 'Neovim'' is the environment we need for plugins. Internally, it stores a
few things that are needed to communicate with neovim, but that shouldn't bother you
too much. Simply remember that every plugin function must have a function signature
whose last element is of type @'Neovim' r st something@. The result of @fibonacci@
is 'String' because neovim cannot handle big numbers so well. :-)
You can use any argument or result type as long as it is an instance of 'NvimObject'.

The second part of of the puzzle, which is the definition of @plugin@
in @~\/.config\/nvim\/lib\/Fibonacci.hs@, shows what a plugin is. It is essentially two
lists of stateless and stateful functionality. A functionality can currently be one
of three things: a function, a command and an autocmd in the context of vim
terminology. In the end, all of those functionalities map to a function at the side
of /nvim-hs/. If you really want to know what the distinction between those is, you
have to consult the @:help@ pages of neovim (e.g. @:help :function@, @:help :command@
and @:help :autocmd@). What's relevant from the side of /nvim-hs/ is the distinction
between __stateful__ and __stateless__. A stateless function can be called at any
time and it does not share any of its internals with other functions. A stateful
function on the other hand can share a well-defined amount of state with other
functions and in the next section I will show you a simple example for that.
Anyhow, if you take a look at the type alias for 'Neovim', you notice the two
type variables @r@ and @st@. These can be accessed with different semantics
each. A value of type @r@ can only be read. It is more or less a static value
you can query with 'ask' or 'asks' if you
are inside a 'Neovim' environment. The value @st@ can be changed and those
changes will be available to other functions which run in the same environment.
You can get the current value with 'get', you can replace an existing value with
'put' and you can also apply a function to the current state with 'modify'.
Notice how 'Neovim'' is just a specialization of 'Neovim' with its @r@ and
@st@ set to @()@.

Now to the magical part: @\$('function'' 'fibonacci)@. This is a so called
Template Haskell splice and this is why you need
@\{\-\# LANGUAGE TemplateHaskell \#\-\}@ at the top of your Haskell file. This
splice simply generates Haskell code that, in this case, still needs a value
of type 'Synchronous' which indicates whether calling the function will make
neovim wait for its result or not. Internally, the expression
@\$('function'' 'fibonacci) 'Sync'@ creates a value that contains all the
necessary information to properly register the function with neovim. Note the
prime symbol before the function name! This would have probably caused you
some trouble if I haven't mentioned it here! Template Haskell simply requires
you to put that in front of function names that are passed in a splice.

If you compile this (which should happen automatically if you have put those
files at the appropriate places), you can restart /nvim-hs/ with the command
@:RestartNvimhs@ which is available as long as you do not remove the default
plugins from you rconfig. Afterwards, you can calculate the 2000th Fibonacci
number like as if it were a normal vim-script function:

@
:echo Fibonacci(2000)
@

You can also directly insert the result inside any text file opened with neovim
by using the evaluation register by pressing the following key sequence in insert
mode:

@
\<C-r\>=Fibonacci(2000)
@

-}
-- 2}}}
-- Creating a stateful plugin {{{2
{- $statefulplugin
Now that we are a little bit comfortable with the interface provided by /nvim-hs/,
we can start to write a more complicated plugin. Let's create a random number
generator!

File @~\/.config\/nvim\/lib\/Random\/Plugin.hs@:

@
module Random.Plugin (nextRandom, setNextRandom) where

import "Neovim"

\-\- | Neovim isn't so good with big numbers here either.
nextRandom :: 'Neovim' r ['Int16'] '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

setNextRandom :: 'Int16' -> 'Neovim' r ['Int16'] ()
setNextRandom n = 'modify' (n:) -- cons to the front of the infinite list
@

File @~\/.config\/nvim\/lib\/Random.hs@:

@
\{\-\# LANGUAGE TemplateHaskell \#\-\}
module Random (plugin) where

import "Neovim"
import Random.Plugin (nextRandom, setNextRandom)
import "System.Random" ('newStdGen', 'randoms')

plugin :: 'Neovim' ('StartupConfig' 'NeovimConfig') () 'NeovimPlugin'
plugin = do
    g <- 'liftIO' 'newStdGen'         -- initialize with a random seed
    let randomNumbers = 'randoms' g -- an infinite list of random numbers
    'wrapPlugin' 'Plugin'
        { 'exports'         = []
        , 'statefulExports' =  [ 'StatefulFunctionality'
            { readOnly = ()
            , writable = randomNumbers
            , functionalities =
                [ $('function'' 'nextRandom) 'Sync'
                , $('function' \"SetNextRandom\" 'setNextRandom) 'Async'
                ]
            }]
        }
@

File @~\/.config\/nvim\/nvim.hs@:

@
import "Neovim"

import qualified Fibonacci as Fibonacci
import qualified Random    as Random

main :: 'IO' ()
main = 'neovim' 'defaultConfig'
    { 'plugins' = 'plugins' 'defaultConfig' ++ [ Fibonacci.plugin, Random.plugin ]
    }
@


That wasn't too hard, was it? The definition is very similar to the previous
example, we just were able to mutate our state and share that with other
functions. The only slightly tedious thing was to define the 'statefulExports'
field because it is a list of triples which has a list of exported
functionalities as its third argument. Another noteworthy detail, in case you
are not familiar with it, is the use of 'liftIO' in front of 'newStdGen'. You
have to do this, because 'newStdGen' has type @'IO' 'StdGen'@ but the actions
inside the startup code are of type
@'Neovim' ('StartupConfig' 'NeovimConfig') () something@. 'liftIO' lifts an
'IO' function so that it can be run inside the 'Neovim' context (or more
generally, any monad that implements the 'MonadIO' type class).

After you have saved these files (and removed any typos @:-)@), you can restart
/nvim-hs/ with @:RestartNvimhs@ and insert random numbers in your text files!

@
\<C-r\>=NextRandom()
@

You can also cheat and pretend you know the next number:

@
:call SetNextRandom(42)
@

-}
-- 2}}}
-- Calling remote functions {{{2
{- $remote
Calling remote functions is only possible inside a 'Neovim' context. There are
a few patterns of return values for the available functions. Let's start with
getting some abstract 'Buffer' object, test whether it is valid and then try
to rename it.

@
inspectBuffer :: 'Neovim' r st ()
inspectBuffer = do
    cb <- 'vim_get_current_buffer'
    isValid <- 'buffer_is_valid' cb
    when isValid $ do
        let newName = "magic"
        retval <- 'wait'' $ 'buffer_set_name' cb newName
        case retval of
            Right cbName | cbName == newName -> 'return' ()
            Right _ -> 'err' $ "Renaming the current buffer failed!"
            Left e -> 'err' $ 'show' e
@

You may have noticed the 'wait'' function in there. Some functions have a return
type with 'STM' in it. This means that the function call is asynchronous. We can
'wait' (or 'wait'') for the result at the point at which we actually need it. In
this short example, we put the 'wait'' directly in front of the remote function
call because we want to inspect the result immediately, though. The other
functions either returned a result directly or they returned
@'Either' 'Object' something@ whose result we inspected ourselves. The 'err'
function directly terminates the current thread and sends the given error
message to neovim which the user immediately notices. Since it is not unusual to
not know what to do if the remote function call failed, the functions 'waitErr'
and 'waitErr'' can save you from some typing and deeply nested case expressions.

That's pretty much all there is to it.
-}
-- 2}}}
-- 1}}}

-- vim: foldmethod=marker