gistfile1.txt

data Error = ParsingError | IncompleteDataError | IncorrectDataError String
  deriving (Show, Eq)

data Person = Person { firstName :: String, lastName :: String, age :: Int }
  deriving (Show, Eq)

parsePerson :: String -> Either Error Person

parsePerson = validatePerson . buildPerson (Right $ Person "" "" (-1)) . parse where
  trim = unwords . words
  parse = map (map trim . splitOn "=") . splitOn "\n"
  isNumber = (== 0) . length . dropWhile isDigit

  buildPerson result         []     = result
  buildPerson error@(Left _) _      = error
  buildPerson (Right person) (x:xs) = buildPerson (addAttribute person x) xs

  addAttribute person ("firstName":[value])
    = Right person { firstName = value }
  addAttribute person ("lastName":[value])
    = Right person { lastName = value }
  addAttribute person ("age":[value])
    | isNumber value = Right person { age = read value :: Int }
    | otherwise      = Left $ IncorrectDataError value
  addAttribute person attribute
    | length (filter (/= "") attribute) /= 2 = Left ParsingError
    | otherwise = Right person

  validatePerson person@(Right (Person fName lName age))
    | fName == "" || lName == "" || age == (-1) = Left IncompleteDataError
    | otherwise = person
  validatePerson error = error


parsePersonSpecs = [
    (1, "firstName = John\nlastName = Connor\nage = 30", Right (Person {firstName = "John", lastName = "Connor", age = 30})),
    (2, "firstName = John Smith\nlastName = Connor\nage = 30\nasde=as11", Right (Person {firstName = "John Smith", lastName = "Connor", age = 30})),
    (3, "firstName=Barbarian\nlastName=Conn On\nage=30", Right (Person {firstName = "Barbarian", lastName = "Conn On", age = 30})),
    (4, "firstName=Barbarian\nlastName=Conn On\nage=30\ng dsfsd", Left ParsingError),
    (5, "firstName=Barbarian\nlastName=Conn On\nage=30\ng dsfsd\n drrr", Left ParsingError),
    (6, "firstName=Barbarian\nlastName=Conn On", Left IncompleteDataError),
    (7, " firstName = John\nlastName = Connor\nage = 2f8 ", Left (IncorrectDataError "2f8")),
    (8, "firstName = John Smith\nlastName = Connor\nage = 3d0\nasde=", Left ParsingError)
  ]

runSpecs []     _ = []
runSpecs (x:xs) f = runSpec x : runSpecs xs f where
  runSpec (id,input,expected) = (id, f input == expected)

runSpecById [] _ _  = Left "spec not found"
runSpecById ((specId,input,expected):xs) f id
  | specId == id = Right $ (("expected",expected),("actual",f input),("passed", f input == expected)) 
  | otherwise    = runSpecById xs f id

runParsePersonSpecs = runSpecs parsePersonSpecs parsePerson
runParsePersonSpec  = runSpecById parsePersonSpecs parsePerson



parsePerson' = (buildPerson (Right $ Person "" "" 0)) .
               (checkAttrsPresence ["firstName", "lastName", "age"] []) .
               (validateData []) . parse where

  trim = unwords . words
  parse = map (filter (/= "") . map trim . splitOn "=") . splitOn "\n"
  isNumber = (== 0) . length . dropWhile isDigit

  validateData acc [] = Right acc
  validateData acc (x:xs)
    | length x /= 2 = Left ParsingError
    | otherwise     = validateData (x:acc) xs

  checkAttrsPresence _ _ error@(Left _) = error
  checkAttrsPresence attrs filtered (Right [])
    | length attrs > 0 = Left IncompleteDataError
    | otherwise        = Right filtered
  checkAttrsPresence attrs filtered (Right (x:xs))
    = checkAttrsPresence (filter (/= head x) attrs)
                         (x:filtered) (Right xs)

  buildPerson _ _  = Right [1]
  buildPerson error@(Left _) _  = error
  buildPerson person (Right []) = person
  buildPerson (Right person) (Right (x:xs))
    = buildPerson (addAttribute person x) (Right xs)

  addAttribute person ("age":[value])
    | isNumber value = Right person { age = read value :: Int }
    | otherwise      = Left $ IncorrectDataError value
  addAttribute person (attr:[value])
    | attr == "firstName" = Right person { firstName = value }
    | attr == "lastName"  = Right person { lastName = value }
    | otherwise           = Right person