-- |
--   Copyright   :  (c) Sam Truzjan 2013
--   License     :  BSD3
--   Maintainer  :  pxqr.sta@gmail.com
--   Stability   :  experimental
--   Portability :  portable
--
--   Layout of files in torrent.
--
{-# LANGUAGE BangPatterns               #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE StandaloneDeriving         #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE DeriveDataTypeable         #-}
{-# LANGUAGE DeriveFunctor              #-}
{-# LANGUAGE DeriveFoldable             #-}
{-# LANGUAGE DeriveTraversable          #-}
{-# LANGUAGE TemplateHaskell            #-}
{-# OPTIONS  -fno-warn-orphans          #-}
module Data.Torrent.Layout
       ( -- * File attributes
         FileOffset
       , FileSize

         -- * Single file info
       , FileInfo (..)

         -- ** Lens
       , fileLength
       , filePath
       , fileMD5Sum

         -- * File layout
       , LayoutInfo (..)
       , joinFilePath

         -- ** Lens
       , singleFile
       , multiFile
       , rootDirName

         -- ** Predicates
       , isSingleFile
       , isMultiFile

         -- ** Query
       , suggestedName
       , contentLength
       , fileCount
       , blockCount

         -- * Flat file layout
       , FileLayout
       , flatLayout
       , accumPositions
       , fileOffset

         -- * Internal
       , getLayoutInfo
       , putLayoutInfo
       ) where

import Control.Applicative
import Control.DeepSeq
import Control.Lens
import Data.Aeson.TH
import Data.Aeson.Types (FromJSON, ToJSON)
import Data.BEncode
import Data.BEncode.Types
import Data.ByteString as BS
import Data.ByteString.Base16 as Base16
import Data.ByteString.Char8 as BC
import Data.Foldable as F
import Data.List as L
import Data.Text as T
import Data.Text.Encoding as T
import Data.Typeable
import Text.PrettyPrint as PP
import Text.PrettyPrint.Class
import System.FilePath
import System.Posix.Types

import Data.Torrent.JSON

{-----------------------------------------------------------------------
--  File attribytes
-----------------------------------------------------------------------}

-- | Size of a file in bytes.
type FileSize = FileOffset

deriving instance FromJSON FileOffset
deriving instance ToJSON   FileOffset
deriving instance BEncode  FileOffset

{-----------------------------------------------------------------------
--  File info both either from info dict or file list
-----------------------------------------------------------------------}

-- | Contain metainfo about one single file.
data FileInfo a = FileInfo {
      fiLength      :: {-# UNPACK #-} !FileSize
      -- ^ Length of the file in bytes.

      -- TODO unpacked MD5 sum
    , fiMD5Sum      :: !(Maybe ByteString)
      -- ^ 32 character long MD5 sum of the file.  Used by third-party
      -- tools, not by bittorrent protocol itself.

    , fiName        :: !a
      -- ^ One or more string elements that together represent the
      -- path and filename. Each element in the list corresponds to
      -- either a directory name or (in the case of the last element)
      -- the filename.  For example, the file:
      --
      --   > "dir1/dir2/file.ext"
      --
      --   would consist of three string elements:
      --
      --   > ["dir1", "dir2", "file.ext"]
      --
    } deriving (Show, Read, Eq, Typeable
               , Functor, Foldable
               )

$(deriveJSON omitRecordPrefix ''FileInfo)

makeLensesFor
  [ ("fiLength", "fileLength")
  , ("fiMD5Sum", "fileMD5Sum")
  , ("fiName"  , "filePath"  )
  ]
  ''FileInfo

instance NFData a => NFData (FileInfo a) where
  rnf FileInfo {..} = rnf fiName
  {-# INLINE rnf #-}

instance BEncode (FileInfo [ByteString]) where
  toBEncode FileInfo {..} = toDict $
       "length" .=! fiLength
    .: "md5sum" .=? fiMD5Sum
    .: "path"   .=! fiName
    .: endDict
  {-# INLINE toBEncode #-}

  fromBEncode = fromDict $ do
    FileInfo <$>! "length"
             <*>? "md5sum"
             <*>! "path"
  {-# INLINE fromBEncode #-}

type Put a = a -> BDict -> BDict

putFileInfoSingle :: Put (FileInfo ByteString)
putFileInfoSingle FileInfo {..} cont =
       "length" .=! fiLength
    .: "md5sum" .=? fiMD5Sum
    .: "name"   .=! fiName
    .: cont

getFileInfoSingle :: Get (FileInfo ByteString)
getFileInfoSingle = do
    FileInfo <$>! "length"
             <*>? "md5sum"
             <*>! "name"

instance BEncode (FileInfo ByteString) where
  toBEncode = toDict . (`putFileInfoSingle` endDict)
  {-# INLINE toBEncode #-}

  fromBEncode = fromDict getFileInfoSingle
  {-# INLINE fromBEncode #-}

instance Pretty (FileInfo BS.ByteString) where
  pretty FileInfo {..} =
       "Path: " <> text (T.unpack (T.decodeUtf8 fiName))
    $$ "Size: " <> text (show fiLength)
    $$ maybe PP.empty ppMD5 fiMD5Sum
   where
    ppMD5 md5 = "MD5 : " <> text (show (Base16.encode md5))

-- | Join file path.
joinFilePath :: FileInfo [ByteString] -> FileInfo ByteString
joinFilePath = fmap (BS.intercalate "/")

{-----------------------------------------------------------------------
--  Original torrent file layout info
-----------------------------------------------------------------------}

-- | Original (found in torrent file) layout info is either:
--
--     * Single file with its /name/.
--
--     * Multiple files with its relative file /paths/.
--
data LayoutInfo
  = SingleFile
    { -- | Single file info.
      liFile     :: !(FileInfo ByteString)
    }
  | MultiFile
    { -- | List of the all files that torrent contains.
      liFiles    :: ![FileInfo [ByteString]]

      -- | The /suggested/ name of the root directory in which to
      -- store all the files.
    , liDirName  :: !ByteString
    } deriving (Show, Read, Eq, Typeable)

$(deriveJSON omitRecordPrefix ''LayoutInfo)

makeLensesFor
  [ ("liFile"   , "singleFile" )
  , ("liFiles"  , "multiFile"  )
  , ("liDirName", "rootDirName")
  ]
  ''LayoutInfo

instance NFData LayoutInfo where
  rnf SingleFile {..} = ()
  rnf MultiFile  {..} = rnf liFiles

getLayoutInfo :: Get LayoutInfo
getLayoutInfo = single <|> multi
  where
    single = SingleFile <$>  getFileInfoSingle
    multi  = MultiFile  <$>! "files" <*>! "name"

putLayoutInfo :: Put LayoutInfo
putLayoutInfo SingleFile {..} = putFileInfoSingle liFile
putLayoutInfo MultiFile  {..} = \ cont ->
     "files" .=! liFiles
  .: "name"  .=! liDirName
  .: cont

instance BEncode LayoutInfo where
  toBEncode   = toDict . (`putLayoutInfo` endDict)
  fromBEncode = fromDict getLayoutInfo

instance Pretty LayoutInfo where
  pretty SingleFile {..} = pretty liFile
  pretty MultiFile  {..} = vcat $ L.map (pretty . joinFilePath) liFiles

-- | Test if this is single file torrent.
isSingleFile :: LayoutInfo -> Bool
isSingleFile SingleFile {} = True
isSingleFile _             = False
{-# INLINE isSingleFile #-}

-- | Test if this is multifile torrent.
isMultiFile :: LayoutInfo -> Bool
isMultiFile MultiFile {} = True
isMultiFile _            = False
{-# INLINE isMultiFile #-}

-- | Get name of the torrent based on the root path piece.
suggestedName :: LayoutInfo -> ByteString
suggestedName (SingleFile FileInfo {..}) = fiName
suggestedName  MultiFile           {..}  = liDirName
{-# INLINE suggestedName #-}

-- | Find sum of sizes of the all torrent files.
contentLength :: LayoutInfo -> FileSize
contentLength SingleFile { liFile  = FileInfo {..} } = fiLength
contentLength MultiFile  { liFiles = tfs           } = L.sum (L.map fiLength tfs)

-- | Get number of all files in torrent.
fileCount :: LayoutInfo -> Int
fileCount SingleFile {..} = 1
fileCount MultiFile  {..} = L.length liFiles

-- | Find number of blocks of the specified size. If torrent size is
-- not a multiple of block size then the count is rounded up.
blockCount :: Int -> LayoutInfo -> Int
blockCount blkSize ci = contentLength ci `sizeInBase` blkSize

{-----------------------------------------------------------------------
--  Flat layout
-----------------------------------------------------------------------}

-- | File layout specifies the order and the size of each file in the
--   storage. Note that order of files is highly important since we
--   coalesce all the files in the given order to get the linear block
--   address space.
--
type FileLayout a = [(FilePath, a)]

-- | Extract files layout from torrent info with the given root path.
flatLayout
  :: FilePath            -- ^ Root path for the all torrent files.
  -> LayoutInfo          -- ^ Torrent content information.
  -> FileLayout FileSize -- ^ The all file paths prefixed with the given root.
flatLayout prefixPath SingleFile { liFile = FileInfo {..} }
    = [(prefixPath </> BC.unpack fiName, fiLength)]
flatLayout prefixPath MultiFile  {..}     = L.map mkPath liFiles
  where   -- TODO use utf8 encoding in name
    mkPath FileInfo {..} = (path, fiLength)
      where
        path = prefixPath </> BC.unpack liDirName
           </> joinPath (L.map BC.unpack fiName)

-- | Calculate offset of each file based on its length, incrementally.
accumPositions :: FileLayout FileSize -> FileLayout (FileOffset, FileSize)
accumPositions = go 0
  where
    go !_ [] = []
    go !offset ((n, s) : xs) = (n, (offset, s)) : go (offset + s) xs

-- | Gives global offset of a content file for a given full path.
fileOffset :: FilePath -> FileLayout FileOffset -> Maybe FileOffset
fileOffset = lookup
{-# INLINE fileOffset #-}

{-----------------------------------------------------------------------
-- Internal utilities
-----------------------------------------------------------------------}

-- | Divide and round up.
sizeInBase :: Integral a => a -> Int -> Int
sizeInBase n b = fromIntegral (n `div` fromIntegral b) + align
  where
    align = if n `mod` fromIntegral b == 0 then 0 else 1
{-# SPECIALIZE sizeInBase :: Int -> Int -> Int #-}
{-# SPECIALIZE sizeInBase :: Integer -> Int -> Int #-}