{-# LANGUAGE OverloadedStrings #-}

-- | Description : @ToJSON@ for Messages
--
-- This module contains the @ToJSON@ instance for @Message@.
module IHaskell.IPython.Message.Writer (ToJSON(..)) where

import           Data.Aeson
import           Data.Map (Map)
import           Data.Text (Text, pack)
import           Data.Monoid (mempty)

import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString as B
import           Data.Text.Encoding

import           IHaskell.IPython.Types

-- Convert message bodies into JSON.
instance ToJSON Message where
  toJSON KernelInfoReply { versionList = vers, language = language } =
    object ["protocol_version" .= string "5.0"  -- current protocol version, major and minor
           , "language_version" .= vers, "language" .= language]

  toJSON ExecuteReply { status = status, executionCounter = counter, pagerOutput = pager } =
    object
      [ "status" .= show status
      , "execution_count" .= counter
      , "payload" .=
        if null pager
          then []
          else map mkObj pager
      , "user_variables" .= emptyMap
      , "user_expressions" .= emptyMap
      ]
    where
      mkObj o = object
                  [ "source" .= string "page"
                  , "line" .= Number 0
                  , "data" .= object [displayDataToJson o]
                  ]
  toJSON PublishStatus { executionState = executionState } =
    object ["execution_state" .= executionState]
  toJSON PublishStream { streamType = streamType, streamContent = content } =
    object ["data" .= content, "name" .= streamType]
  toJSON PublishDisplayData { source = src, displayData = datas } =
    object
      ["source" .= src, "metadata" .= object [], "data" .= object (map displayDataToJson datas)]

  toJSON PublishOutput { executionCount = execCount, reprText = reprText } =
    object
      [ "data" .= object ["text/plain" .= reprText]
      , "execution_count" .= execCount
      , "metadata" .= object []
      ]
  toJSON PublishInput { executionCount = execCount, inCode = code } =
    object ["execution_count" .= execCount, "code" .= code]
  toJSON (CompleteReply _ matches start end metadata status) =
    object
      [ "matches" .= matches
      , "cursor_start" .= start
      , "cursor_end" .= end
      , "metadata" .= metadata
      , "status" .= if status
                      then string "ok"
                      else "error"
      ]
  toJSON i@InspectReply{} =
    object
      [ "status" .= if inspectStatus i
                      then string "ok"
                      else "error"
      , "data" .= object (map displayDataToJson . inspectData $ i)
      , "metadata" .= object []
      , "found" .= inspectStatus i
      ]

  toJSON ShutdownReply { restartPending = restart } =
    object ["restart" .= restart]

  toJSON ClearOutput { wait = wait } =
    object ["wait" .= wait]

  toJSON RequestInput { inputPrompt = prompt } =
    object ["prompt" .= prompt]

  toJSON req@CommOpen{} =
    object ["comm_id" .= commUuid req, "target_name" .= commTargetName req, "data" .= commData req]

  toJSON req@CommData{} =
    object ["comm_id" .= commUuid req, "data" .= commData req]

  toJSON req@CommClose{} =
    object ["comm_id" .= commUuid req, "data" .= commData req]

  toJSON req@HistoryReply{} =
    object ["history" .= map tuplify (historyReply req)]
    where
      tuplify (HistoryReplyElement sess linum res) = (sess, linum, case res of
                                                                     Left inp         -> toJSON inp
                                                                     Right (inp, out) -> toJSON out)

  toJSON body = error $ "Do not know how to convert to JSON for message " ++ show body

-- | Print an execution state as "busy", "idle", or "starting".
instance ToJSON ExecutionState where
  toJSON Busy = String "busy"
  toJSON Idle = String "idle"
  toJSON Starting = String "starting"

-- | Print a stream as "stdin" or "stdout" strings.
instance ToJSON StreamType where
  toJSON Stdin = String "stdin"
  toJSON Stdout = String "stdout"

-- | Convert a MIME type and value into a JSON dictionary pair.
displayDataToJson :: DisplayData -> (Text, Value)
displayDataToJson (DisplayData mimeType dataStr) =
  pack (show mimeType) .= String dataStr

----- Constants -----
emptyMap :: Map String String
emptyMap = mempty

emptyList :: [Int]
emptyList = []

ints :: [Int] -> [Int]
ints = id

string :: String -> String
string = id