module Main where

  ----------------Imports----------------

  import System.Environment (getArgs)
  import Data.Yaml (ParseException, decodeEither')
  import Data.Aeson (encode, encodeFile)

  import qualified Data.ByteString.Char8 as BS
  import Workflow (Workflow, buildData)
  import Export
  import Data.Maybe (fromJust, isNothing)
  import Data.Either (isLeft, fromLeft, fromRight)
  import Control.Exception (throw)

  ---------------------------------------


  ----------------Methods----------------  

  -- | Required command line arguments:
  -- 1. A workflow source file (YAML)
  -- 2. A graph data target file (JSON) 
  main :: IO ()
  main = getArgs >>= process >>= finish where
    process :: [String] -> IO Bool
    process args = if   length args /= 2
                   then print "Please provide (1) a source and (2) a target file" >> return True
                   else generateJSON args >> return False
    finish :: Bool -> IO ()
    finish abort = if abort then return () else print "Done."
         


  -- | Imports the YAML document specified in the first command line argument and
  --   exports the graph data to the JSON file specified in the second argument.
  generateJSON :: [String] -> IO ()
  generateJSON args = do
    content <- BS.readFile (head args)
    let decoded = decodeEither' content :: Either ParseException Workflow
    if isLeft decoded then throw (fromLeft undefined decoded) else do
      let yaml = fromRight undefined decoded
      -- let GData (nodeData, edgeData) = buildData yaml
      -- putStrLn $ "\nNode Data:\n\n" ++ show nodeData
      -- putStrLn $ "\nEdge Data:\n\n" ++ show edgeData
      -- encodeFile (last args) $ GData (nodeData, edgeData)
      encodeFile (last args) $ buildData yaml

  ---------------------------------------

-- https://stackoverflow.com/questions/59903779/how-to-parse-json-with-field-of-optional-and-variant-type-in-haskell
-- https://stackoverflow.com/questions/21292428/reading-yaml-lists-of-objects-in-haskell