Basics.hs

{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE EmptyDataDeriving #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

-- |
-- Module: Capnp.Basics
-- Description: Handling of "basic" capnp datatypes.
--
-- This module contains phantom types for built-in Cap'n Proto
-- types, analogous to the phantom types generated for structs
-- by the code generator. It also defines applicable type class
-- instances.
module Capnp.Basics where

-- XXX: I(zenhack) don't know how to supply an explicit
-- export list here, since we have instances of data families
-- and I don't know what to call the instances to get all of the
-- constructors.

import qualified Capnp.Classes as C
import qualified Capnp.Errors as E
import qualified Capnp.Message as M
import qualified Capnp.Repr as R
import qualified Capnp.Untyped as U
import Control.Monad (when)
import Control.Monad.Catch (MonadThrow, throwM)
import qualified Data.ByteString as BS
import Data.Default (Default (..))
import Data.Foldable (foldl', for_)
import qualified Data.Text as T
import qualified Data.Text.Encoding as TE
import qualified Data.Vector as V
import Data.Word
import GHC.Generics (Generic)
import GHC.Prim (coerce)

-- | The Cap'n Proto @Text@ type.
data Text

-- | The Cap'n Proto @Data@ type.
data Data

-- | A Cap'n Proto @AnyPointer@, i.e. an arbitrary pointer with unknown schema.
data AnyPointer

-- | A Cap'n Proto @List@ with unknown element type.
data AnyList

-- | A Cap'n Proto struct of unknown type.
data AnyStruct

-- | A Cap'n Proto capability with unknown interfaces.
data Capability

type instance R.ReprFor Data = R.ReprFor (R.List Word8)

type instance R.ReprFor Text = R.ReprFor (R.List Word8)

type instance R.ReprFor AnyPointer = 'R.Ptr 'Nothing

type instance R.ReprFor (Maybe AnyPointer) = 'R.Ptr 'Nothing

type instance R.ReprFor AnyList = 'R.Ptr ('Just ('R.List 'Nothing))

type instance R.ReprFor AnyStruct = 'R.Ptr ('Just 'R.Struct)

type instance R.ReprFor Capability = 'R.Ptr ('Just 'R.Cap)

data instance C.Parsed AnyPointer
  = PtrStruct (C.Parsed AnyStruct)
  | PtrList (C.Parsed AnyList)
  | PtrCap M.Client
  deriving (Show, Eq, Generic)

instance C.Parse (Maybe AnyPointer) (Maybe (C.Parsed AnyPointer)) where
  parse (R.Raw ptr) = case ptr of
    Nothing -> pure Nothing
    Just _ -> Just <$> C.parse (R.Raw ptr :: R.Raw AnyPointer 'M.Const)

  encode msg value =
    R.Raw <$> case value of
      Nothing -> pure Nothing
      Just v -> coerce <$> C.encode msg v

instance C.Parse AnyPointer (C.Parsed AnyPointer) where
  parse (R.Raw ptr) = case ptr of
    Just (U.PtrCap cap) -> PtrCap <$> C.parse (R.Raw cap)
    Just (U.PtrList list) -> PtrList <$> C.parse (R.Raw list)
    Just (U.PtrStruct struct) -> PtrStruct <$> C.parse (R.Raw struct)
    Nothing ->
      throwM $ E.SchemaViolationError "Non-nullable AnyPointer was null"

  encode msg value =
    R.Raw <$> case value of
      PtrCap cap -> Just . U.PtrCap . R.fromRaw <$> C.encode msg cap
      PtrList list -> Just . U.PtrList . R.fromRaw <$> C.encode msg list
      PtrStruct struct -> Just . U.PtrStruct . R.fromRaw <$> C.encode msg struct

instance C.AllocateList AnyPointer where
  type ListAllocHint AnyPointer = Int

instance C.EstimateListAlloc AnyPointer (C.Parsed AnyPointer)

instance C.AllocateList (Maybe AnyPointer) where
  type ListAllocHint (Maybe AnyPointer) = Int

instance C.EstimateListAlloc (Maybe AnyPointer) (Maybe (C.Parsed AnyPointer))

data instance C.Parsed AnyStruct = Struct
  { structData :: V.Vector Word64,
    structPtrs :: V.Vector (Maybe (C.Parsed AnyPointer))
  }
  deriving (Show, Generic)

instance Eq (C.Parsed AnyStruct) where
  -- We define equality specially (rather than just deriving), such that
  -- slices are padded out with the default values of their elements.
  (Struct dl pl) == (Struct dr pr) = sectionEq dl dr && sectionEq pl pr
    where
      sectionEq :: (Eq a, Default a) => V.Vector a -> V.Vector a -> Bool
      sectionEq l r = go 0
        where
          go i
            | i >= length = True
            | otherwise = indexDef i l == indexDef i r && go (i + 1)
          length = max (V.length l) (V.length r)
          indexDef i vec
            | i < V.length vec = vec V.! i
            | otherwise = def

instance C.Parse AnyStruct (C.Parsed AnyStruct) where
  parse (R.Raw s) =
    Struct
      <$> V.generateM
        (fromIntegral $ U.structWordCount s)
        (`U.getData` s)
      <*> V.generateM
        (fromIntegral $ U.structPtrCount s)
        (\i -> U.getPtr i s >>= C.parse . R.Raw)

instance C.AllocateList AnyStruct where
  type ListAllocHint AnyStruct = (Int, R.AllocHint 'R.Struct)

instance C.EstimateListAlloc AnyStruct (C.Parsed AnyStruct) where
  estimateListAlloc structs =
    let len = V.length structs
        !nWords = foldl' max 0 $ map (V.length . structData) $ V.toList structs
        !nPtrs = foldl' max 0 $ map (V.length . structPtrs) $ V.toList structs
     in (len, (fromIntegral nWords, fromIntegral nPtrs))

instance C.EstimateAlloc AnyStruct (C.Parsed AnyStruct) where
  estimateAlloc s =
    ( fromIntegral $ V.length $ structData s,
      fromIntegral $ V.length $ structPtrs s
    )

instance C.Marshal AnyStruct (C.Parsed AnyStruct) where
  marshalInto (R.Raw raw) s = do
    V.iforM_ (structData s) $ \i value -> do
      U.setData value i raw
    V.iforM_ (structPtrs s) $ \i value -> do
      R.Raw ptr <- C.encode (U.message @U.Struct raw) value
      U.setPtr ptr i raw

-- TODO(cleanup): It would be nice if we could reuse Capnp.Repr.Parsed.Parsed
-- here, but that would cause a circular import dependency.
type ParsedList a = V.Vector a

data instance C.Parsed AnyList
  = ListPtr (ParsedList (Maybe (C.Parsed AnyPointer)))
  | ListStruct (ParsedList (C.Parsed AnyStruct))
  | List0 (ParsedList ())
  | List1 (ParsedList Bool)
  | List8 (ParsedList Word8)
  | List16 (ParsedList Word16)
  | List32 (ParsedList Word32)
  | List64 (ParsedList Word64)
  deriving (Show, Eq, Generic)

instance C.Parse AnyList (C.Parsed AnyList) where
  parse (R.Raw list) = case list of
    U.List0 l -> List0 <$> C.parse (R.Raw l)
    U.List1 l -> List1 <$> C.parse (R.Raw l)
    U.List8 l -> List8 <$> C.parse (R.Raw l)
    U.List16 l -> List16 <$> C.parse (R.Raw l)
    U.List32 l -> List32 <$> C.parse (R.Raw l)
    U.List64 l -> List64 <$> C.parse (R.Raw l)
    U.ListPtr l -> ListPtr <$> C.parse (R.Raw l)
    U.ListStruct l -> ListStruct <$> C.parse (R.Raw l)

  encode msg list =
    R.Raw <$> case list of
      List0 l -> U.List0 . R.fromRaw <$> C.encode msg l
      List1 l -> U.List1 . R.fromRaw <$> C.encode msg l
      List8 l -> U.List8 . R.fromRaw <$> C.encode msg l
      List16 l -> U.List16 . R.fromRaw <$> C.encode msg l
      List32 l -> U.List32 . R.fromRaw <$> C.encode msg l
      List64 l -> U.List64 . R.fromRaw <$> C.encode msg l
      ListPtr l -> U.ListPtr . R.fromRaw <$> C.encode msg l
      ListStruct l -> U.ListStruct . R.fromRaw <$> C.encode msg l

instance C.Parse Capability M.Client where
  parse (R.Raw cap) = U.getClient cap
  encode msg client = R.Raw <$> U.appendCap msg client

instance C.Allocate Text where
  type AllocHint Text = Int
  new len msg = R.Raw <$> U.allocList8 msg (len + 1)

instance C.AllocateList Text where
  type ListAllocHint Text = Int

instance C.EstimateListAlloc Text T.Text

instance C.Parse Text T.Text where
  parse (R.Raw list) =
    let len = U.length list
     in if len == 0
          then -- We are somewhat lenient here; technically this is invalid, as there is
          -- no null terminator (see logic below, which is dead code because of
          -- this check. But to avoid this we really need to expose nullability
          -- in the API, so for now we just fudge it.
            pure ""
          else
            ( do
                when (len == 0) $
                  throwM $
                    E.SchemaViolationError
                      "Text is not NUL-terminated (list of bytes has length 0)"
                lastByte <- U.index (len - 1) list
                when (lastByte /= 0) $
                  throwM $
                    E.SchemaViolationError $
                      "Text is not NUL-terminated (last byte is " ++ show lastByte ++ ")"
                bytes <- BS.take (len - 1) <$> U.rawBytes list
                case TE.decodeUtf8' bytes of
                  Left e -> throwM $ E.InvalidUtf8Error e
                  Right v -> pure v
            )
  encode msg value = do
    let bytes = TE.encodeUtf8 value
    raw@(R.Raw untyped) <- C.new @Text (BS.length bytes) msg
    C.marshalInto @Data (R.Raw untyped) bytes
    pure raw

-- Instances for Data
instance C.Parse Data BS.ByteString where
  parse = U.rawBytes . R.fromRaw

instance C.Allocate Data where
  type AllocHint Data = Int
  new len msg = R.Raw <$> U.allocList8 msg len

instance C.EstimateAlloc Data BS.ByteString where
  estimateAlloc = BS.length

instance C.AllocateList Data where
  type ListAllocHint Data = Int

instance C.EstimateListAlloc Data BS.ByteString

instance C.Marshal Data BS.ByteString where
  marshalInto (R.Raw list) bytes =
    for_ [0 .. BS.length bytes - 1] $ \i ->
      U.setIndex (BS.index bytes i) i list

-- Instances for AnyStruct
instance C.Allocate AnyStruct where
  type AllocHint AnyStruct = (Word16, Word16)
  new (nWords, nPtrs) msg = R.Raw <$> U.allocStruct msg nWords nPtrs

-- | Return the underlying buffer containing the text. This does not include the
-- null terminator.
textBuffer :: MonadThrow m => R.Raw Text mut -> m (R.Raw Data mut)
textBuffer (R.Raw list) = R.Raw <$> U.take (U.length list - 1) list

-- | Convert a 'Text' to a 'BS.ByteString', comprising the raw bytes of the text
-- (not counting the NUL terminator).
textBytes :: U.ReadCtx m 'M.Const => R.Raw Text 'M.Const -> m BS.ByteString
textBytes text = do
  R.Raw raw <- textBuffer text
  U.rawBytes raw