--
-- This module describes all supported ALGA commands. It also provides all
-- the functionality to load source files and patch XML files.
--
-- Copyright © 2015–2016 Mark Karpov
--
-- ALGA is free software: you can redistribute it and/or modify it under the
-- terms of the GNU General Public License as published by the Free Software
-- Foundation, either version 3 of the License, or (at your option) any
-- later version.
--
-- ALGA is distributed in the hope that it will be useful, but WITHOUT ANY
-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-- FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
-- details.
--
-- You should have received a copy of the GNU General Public License along
-- with this program. If not, see <http://www.gnu.org/licenses/>.

{-# LANGUAGE RecordWildCards #-}

module Alga.Interaction.Commands
  ( processCmd
  , completionFunc
  , cmdBackend
  , cmdLoad
  , cmdMake
  , cmdPrefix )
where

import Alga.Interaction.Base
import Alga.Language
import Alga.Representation
import Alga.Translation
import Control.Monad.Catch
import Control.Monad.IO.Class
import Control.Monad.Reader
import Control.Monad.State.Class
import Data.Char (isSpace)
import Data.Foldable (find)
import Data.List (elemIndex, isPrefixOf)
import Data.Maybe (fromMaybe, listToMaybe)
import Data.Ratio (approxRational)
import Data.Text.Lazy (Text)
import Formatting
import Numeric.Natural
import Path
import Path.IO
import System.Exit (exitSuccess, ExitCode)
import qualified Data.Text.Lazy as T
import qualified Data.Text.Lazy.IO as T
import qualified System.Console.Haskeline as L
import qualified System.FilePath as FP

-- | Description of REPL command.

data Cmd = Cmd
  { cmdName :: String  -- ^ Name of command
  , cmdFunc :: String -> Alga () -- ^ Action it performs
  , cmdDesc :: Text    -- ^ Description of command
  , cmdComp :: CompletionScheme -- ^ How to complete arguments of the command
  }

-- | Scale (linear or logarithmic) to use with some utilities.

data Scale = Lin | Log deriving (Eq, Show)

-- | How to complete arguments of command.

data CompletionScheme
  = None               -- ^ Don't complete at all
  | Files              -- ^ Complete as file names
  | Names              -- ^ Complete as definition names
    deriving (Eq, Show)

-- | All defined commands.

commands :: [Cmd]
commands =
  --    name      action     description                             completion
  [ Cmd "backend" cmdBackend "Set backend (name of DAW)"             None
  , Cmd "cd"      cmdCd      "Change working directory"              Files
  , Cmd "clear"   cmdClear   "Restore default state of environment"  None
  , Cmd "def"     cmdDef     "Print definition of given symbol"      Names
  , Cmd "help"    cmdHelp    "Show this help text"                   None
  , Cmd "lin"     cmdLin     "Linear scale conversion to ratio"      None
  , Cmd "load"    cmdLoad'   "Load definitions from given file"      Files
  , Cmd "log"     cmdLog     "Logarithmic scale conversion to ratio" None
  , Cmd "make"    cmdMake'   "Patch an XML file"                     Files
  , Cmd "prvlen"  cmdLength  "Set length of displayed results"       None
  , Cmd "purge"   cmdPurge   "Remove redundant definitions"          None
  , Cmd "pwd"     cmdPwd     "Print working directory"               None
  , Cmd "quit"    cmdQuit    "Quit the interactive environment"      None
  , Cmd "ratio"   cmdRatio   "Real number to ratio converter"        None
  , Cmd "save"    cmdSave    "Save current environment in file"      Files
  , Cmd "udef"    cmdUdef    "Remove definition of given symbol"     Names
  , Cmd "vol"     cmdVol     "Convert decibels to ratio"             None ]

-- | Process command (with its arguments).

processCmd :: Text -> Alga ()
processCmd txt =
  case find g commands of
    Just Cmd { cmdFunc = f } -> do
      result <- try . f . T.unpack . T.strip $ args
                :: Alga (Either SomeException ())
      case result of
        Left  e ->
          case fromException e :: Maybe ExitCode of
            Just  _ -> throwM e
            Nothing -> spitExc e
        Right _ -> return ()
    Nothing -> liftIO $
      fprint ("Unknown command, try " % string % "help\n") cmdPrefix
  where g Cmd { cmdName = c } = c == dropCmdPrefix (T.unpack cmd)
        (cmd, args)           = T.break isSpace (T.strip txt)

-- | Completion function to work with Haskeline.

completionFunc
  :: (HasEnv m, MonadIO m, MonadReader AlgaCfg m, MonadState AlgaSt m)
  => L.CompletionFunc m
completionFunc = L.completeWordWithPrev Nothing " " getCompletions

-- | Generate completions.

getCompletions
  :: (HasEnv m, MonadIO m, MonadReader AlgaCfg m, MonadState AlgaSt m)
  => String            -- ^ Contents of line before cursor, reversed
  -> String            -- ^ Contents of line after cursor
  -> m [L.Completion]  -- ^ List of completions
getCompletions prev word = do
  names <- getRefs
  files <- L.listFiles word
  let cmds    = (cmdPrefix ++) . cmdName <$> commands
      f       = fmap L.simpleCompletion . filter (word `isPrefixOf`)
      g None  = []
      g Files = files
      g Names = f names
  return $
    case words . reverse $ prev of
      []    -> f $ cmds ++ names
      (c:_) ->
        case c `elemIndex` cmds of
          Just i  -> g . cmdComp $ commands !! i
          Nothing -> f names

-- | Change set backend (name of DAW).

cmdBackend :: MonadState AlgaSt m => String -> m ()
cmdBackend arg = modify $ \st -> st { stBackend = toBackend arg }

-- | Change working directory.

cmdCd :: (MonadIO m, MonadCatch m) => String -> m ()
cmdCd next' = do
  mnext <- forgivingAbsence (resolveDir' next')
  case mnext of
    Nothing -> liftIO $ fprint ("Cannot cd to \"" % string % "\"\n") next'
    Just next -> do
      setCurrentDir next
      liftIO $ fprint ("Changed to \"" % string % "\".\n") (fromAbsDir next)

-- | Restore default state of environment.

cmdClear :: (HasEnv m, MonadIO m) => String -> m ()
cmdClear _ = do
  clearDefs
  liftIO (T.putStrLn "Environment cleared")

-- | Print definition of given symbol.

cmdDef :: (HasEnv m, MonadIO m) => String -> m ()
cmdDef arg = mapM_ f (words arg)
  where f name = getSrc name >>= liftIO . T.putStr

-- | Show help with list of all available commands.

cmdHelp :: MonadIO m => String -> m ()
cmdHelp _ = liftIO $ do
  T.putStrLn "Available commands:"
  mapM_ f commands
  where f Cmd {..} = fprint fmt cmdPrefix cmdName cmdDesc
        fmt = "  " % string % (right 24 ' ' %. string) % text % "\n"

-- | Linear scale conversion to ratio.

cmdLin :: (MonadIO m, MonadReader AlgaCfg m) => String -> m ()
cmdLin str = pRatio Lin (parseNum a 0) (parseNum b 1) (parseNum s 0)
  where (a:b:s:_) = parseArgs str

-- | Load definitions from given file. Note that this version of the command
-- is used in REPL, not 'cmdLoad'.

cmdLoad' :: (HasEnv m, MonadIO m, MonadState AlgaSt m, MonadThrow m)
  => String -> m ()
cmdLoad' = cmdLoad . words

-- | Alternative interface to loading functionality. This one is used in
-- main module.

cmdLoad :: (HasEnv m, MonadIO m, MonadState AlgaSt m, MonadThrow m)
  => [FilePath] -> m ()
cmdLoad = mapM_ loadOne

-- | Load single source file.

loadOne :: (HasEnv m, MonadIO m, MonadState AlgaSt m, MonadThrow m)
  => FilePath -> m ()
loadOne given = do
  file <- output given ""
  let fpath = fromAbsFile file
  b    <- doesFileExist file
  if b
    then do
      contents <- liftIO $ T.readFile fpath
      case parseAlga fpath contents of
        Right x -> do
          mapM_ f x
          setFileName file
          liftIO $ fprint
            ("\"" % string % "\" loaded successfully\n")
            fpath
        Left  x -> liftIO $ fprint (string % "\n") x
    else liftIO $ fprint ("Could not find \"" % string % "\"\n") fpath
      where f (Definition n t) = processDef n t
            f (Exposition   _) = return ()

-- | Logarithmic scale conversion to ratio.

cmdLog :: (MonadIO m, MonadReader AlgaCfg m) => String -> m ()
cmdLog str = pRatio Log (parseNum a 0) (parseNum b e) (parseNum s 0)
  where (a:b:s:_) = parseArgs str
        e         = exp 1

-- | Version of 'cmdMake' used by REPL.

cmdMake' :: (HasEnv m, MonadIO m, MonadState AlgaSt m, MonadThrow m)
  => String -> m ()
cmdMake' str =
  let (s:b:f:_) = parseArgs str
  in cmdMake (parseNum s defaultSeed)
             (parseNum b defaultBeats)
             f

-- | Patch an XML file.

cmdMake :: (HasEnv m, MonadIO m, MonadState AlgaSt m, MonadThrow m)
  => Natural           -- ^ Seed for random number generator
  -> Double            -- ^ Desired duration in number of whole notes
  -> FilePath          -- ^ Where to find file to patch
  -> m ()
cmdMake s b f = do
  file    <- output f "xml"
  backend <- gets stBackend
  status  <- patchAuto s b file backend
  let msg = if status == 0
       then "File patched successfully \"" % string % "\"\n"
       else "Failed to patch file \"" % string % "\"\n"
  liftIO $ fprint msg (fromAbsFile file)

-- | Set length of displayed results.

cmdLength :: MonadState AlgaSt m => String -> m ()
cmdLength arg = do
  len <- gets stPrevLen
  modify $ \st -> st { stPrevLen = parseNum (trim arg) len }

-- | Remove redundant definitions.

cmdPurge :: (HasEnv m, MonadIO m) => String -> m ()
cmdPurge _ = do
  topDefs >>= purgeEnv
  liftIO $ T.putStrLn "Environment purged"

-- | Print working directory.

cmdPwd :: MonadIO m => String -> m ()
cmdPwd _ = liftIO (getCurrentDir >>= putStrLn . fromAbsDir)

-- | Quit the interactive environment.

cmdQuit :: MonadIO m => String -> m ()
cmdQuit _ = liftIO exitSuccess

-- | Real number to ratio converter.

cmdRatio :: (MonadIO m, MonadReader AlgaCfg m) => String -> m ()
cmdRatio = pRatio Lin 0 1 . (`parseNum` 0)

-- | Save current environment in file.

cmdSave :: (HasEnv m, MonadIO m, MonadState AlgaSt m, MonadThrow m)
  => String -> m ()
cmdSave given = do
  file   <- output given ""
  let fpath = fromAbsFile file
  src    <- fullSrc
  liftIO $ T.writeFile fpath src
  setFileName file
  liftIO $ fprint ("Environment saved as \"" % string % "\"\n") fpath

-- | Undefine definitions.

cmdUdef :: (HasEnv m, MonadIO m) => String -> m ()
cmdUdef arg = mapM_ f (words arg)
  where f name = do
          remDef name
          liftIO $ fprint ("Definition for ‘" % string % "’ removed\n") name

-- | Convert decibels to ratio.

cmdVol :: (MonadIO m, MonadReader AlgaCfg m) => String -> m ()
cmdVol = pRatio Lin 0 1 . dBToRatio . (`parseNum` 0)
  where dBToRatio dB = 10 ** (dB / 10)

-- | Universal conversion to ratios.

pRatio :: (MonadIO m, MonadReader AlgaCfg m)
  => Scale             -- ^ Scale to use (linear or logarithmic)
  -> Double            -- ^ Minimum
  -> Double            -- ^ Maximum
  -> Double            -- ^ Value between minimum and maximum
  -> m ()
pRatio scale a b s = do
  ε <- asks cfgPrecision
  let σ = case scale of
            Lin -> (s - a) / (b - a)
            Log -> (log s - log a) / (log b - log a)
      x = approxRational σ ε
  liftIO $ fprint ("≈ " % string % "\n") (showRatio x)

parseArgs :: String -> [String]
parseArgs str = words str ++ repeat ""

-- | Parse a number defaulting to given value.

parseNum :: (Num a, Read a)
  => String            -- ^ String to parse
  -> a                 -- ^ Default value
  -> a                 -- ^ Result
parseNum s x = fromMaybe x $ fst <$> listToMaybe (reads s)

-- | Generate file name from given base name and extension.

output :: (MonadIO m, MonadThrow m, MonadState AlgaSt m)
  => FilePath          -- ^ Given file name
  -> String            -- ^ Extension
  -> m (Path Abs File) -- ^ Absolute path to output file
output given' ext =
  if null given'
    then do
      actual <- fromAbsFile <$> gets stSrcFile
      parseAbsFile (if null ext then actual else FP.replaceExtension actual ext)
    else resolveFile' given'

-- | Change current file name.

setFileName :: MonadState AlgaSt m => Path Abs File -> m ()
setFileName fpath = modify $ \st -> st { stSrcFile = fpath }

-- | Drop command prefix if it's present.

dropCmdPrefix :: String -> String
dropCmdPrefix arg
  | cmdPrefix `isPrefixOf` arg = drop (length cmdPrefix) arg
  | otherwise = arg

-- | All REPL commands are prefixed with this.

cmdPrefix :: String
cmdPrefix = ":"

-- | Print out an exception.

spitExc :: MonadIO m => SomeException -> m ()
spitExc = liftIO . fprint ("× " % string % "\n") . show

-- | Stupid trimming for strings.

trim :: String -> String
trim = let f = reverse . dropWhile isSpace in f . f