json-autotype-0.2.2.0: GenerateJSONParser.hs

{-# LANGUAGE TemplateHaskell, ScopedTypeVariables, OverloadedStrings #-}
{-# LANGUAGE DeriveGeneric, StandaloneDeriving, ViewPatterns #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Main where

import           Control.Applicative
import           Data.Maybe
import           System.Exit
import           System.IO                 (stdin, stderr, stdout, IOMode(..))
import           System.FilePath           (splitExtension)
import           Control.Monad             (forM_, when)
import qualified Data.ByteString.Lazy.Char8 as BSL
import qualified Data.HashMap.Strict        as Map
import           Data.Aeson
import qualified Data.Text                  as Text
import qualified Data.Text.IO               as Text
import           Data.Text                 (Text)
import           Text.PrettyPrint.GenericPretty (pretty)

import           Data.Aeson.AutoType.Pretty
import           Data.Aeson.AutoType.Type
import           Data.Aeson.AutoType.Extract
import           Data.Aeson.AutoType.Format
import           Data.Aeson.AutoType.CodeGen
import           Data.Aeson.AutoType.Util
import           HFlags

fst3 ::  (t, t1, t2) -> t
fst3 (a, _, _) = a

-- * Command line flags
defineFlag "outputFilename"  defaultOutputFilename "Write output to the given file"
defineFlag "suggest"         True                  "Suggest candidates for unification"
defineFlag "autounify"       True                  "Automatically unify suggested candidates"
defineFlag "debug"           False                 "Set this flag to see more debugging info"
defineFlag "fakeFlag"        True                  "Ignore this flag - it doesn't exist!!!"

-- Tracing is switched off:
myTrace :: String -> IO ()
myTrace msg = if flags_debug
                then putStrLn msg
                else return ()

-- | Report an error to error output.
report   :: Text -> IO ()
report    = Text.hPutStrLn stderr

-- | Report an error and terminate the program.
fatal    :: Text -> IO ()
fatal msg = do report msg
               exitFailure

extractTypeFromJSONFile :: FilePath -> IO (Maybe Type)
extractTypeFromJSONFile inputFilename =
      withFileOrHandle inputFilename ReadMode stdin $ \hIn ->
        -- First we decode JSON input into Aeson's Value type
        do bs <- BSL.hGetContents hIn
           Text.hPutStrLn stderr $ "Processing " `Text.append` Text.pack (show inputFilename)
           myTrace ("Decoded JSON: " ++ pretty (decode bs :: Maybe Value))
           case decode bs of
             Nothing -> do report $ "Cannot decode JSON input from " `Text.append` Text.pack (show inputFilename)
                           return Nothing
             Just v  -> do -- If decoding JSON was successful...
               -- We extract type structure from the JSON value.
               let t        = extractType v
               myTrace $ "Type: " ++ pretty t
               return $ Just t

-- | Take a set of JSON input filenames, Haskell output filename, and generate module parsing these JSON files.
generateHaskellFromJSONs :: [FilePath] -> FilePath -> IO ()
generateHaskellFromJSONs inputFilenames outputFilename =
    forM_ inputFilenames $ \inputFilename -> do
      -- Read type from each file
      typeForEachFile  <- catMaybes <$> mapM extractTypeFromJSONFile inputFilenames
      -- Unify all input types
      let finalType = foldr1 unifyTypes typeForEachFile
      -- We split different dictionary labels to become different type trees (and thus different declarations.)
      let splitted = splitTypeByLabel "TopLevel" finalType
      myTrace $ "SPLITTED: " ++ pretty splitted
      assertM $ not $ any hasNonTopTObj $ Map.elems splitted
      -- We compute which type labels are candidates for unification
      let uCands = unificationCandidates splitted
      myTrace $ "CANDIDATES:\n" ++ pretty uCands
      when flags_suggest $ forM_ uCands $ \cs -> do
                             putStr "-- "
                             Text.putStrLn $ "=" `Text.intercalate` cs
      -- We unify the all candidates or only those that have been given as command-line flags.
      let unified = if flags_autounify
                      then unifyCandidates uCands splitted
                      else splitted
      myTrace $ "UNIFIED:\n" ++ pretty unified
      -- We start by writing module header
      writeHaskellModule outputFilename unified

main :: IO ()
main = do filenames <- $initHFlags "json-autotype -- automatic type and parser generation from JSON"
          -- TODO: should integrate all inputs into single type set!!!
          generateHaskellFromJSONs filenames flags_outputFilename