module Parser (
  parse, -- exporta essa função (publica)
)
where

import AST -- importa o arquivo AST.hs

-- uso do apóstrofo como convenção de função que será auxiliar da publica
parse' :: String -> Either String (AST, String)
parse' :: String -> Either String (AST, String)
parse' [] = (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right ([], []) -- String Vazia = FIM

-- começando com o loop pra ter menos dor de cabeça depois
parse' (Char
']' : String
resto) = (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right ([], Char
']' Char -> String -> String
forall a. a -> [a] -> [a]
: String
resto)
parse' (Char
'[' : String
resto) =
  case String -> Either String (AST, String)
parse' String
resto of
    Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err -- retorno de erro
    Right (AST
astLoop, String
restoFora) ->
      -- resto de fora do loop e o ast de dentro
      case String
restoFora of
        [] -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
"Erro: loop '[' nao foi fechado!"
        (Char
']' : String
restoDepoisDoLoop) ->
          case String -> Either String (AST, String)
parse' String
restoDepoisDoLoop of
            Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
            -- Finalmente, joga o 'astLoop' dentro do Loop do AST e continua com o parser'
            Right (AST
astFinal, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (AST -> Cmd
Loop AST
astLoop Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astFinal, String
strFinal)
        String
_ -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
"Erro de sintaxe: ']' esperado para fechar o loop."
--
-- lidando com os outros caracteres
parse' (Char
c : String
resto) =
  case Char
c of
    Char
'+' ->
      case String -> Either String (AST, String)
parse' String
resto of
        Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
        Right (AST
astResto, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (Cmd
Incr Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astResto, String
strFinal)
    Char
'-' ->
      case String -> Either String (AST, String)
parse' String
resto of
        Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
        Right (AST
astResto, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (Cmd
Decr Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astResto, String
strFinal)
    Char
'>' ->
      case String -> Either String (AST, String)
parse' String
resto of
        Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
        Right (AST
astResto, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (Cmd
Next Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astResto, String
strFinal)
    Char
'<' ->
      case String -> Either String (AST, String)
parse' String
resto of
        Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
        Right (AST
astResto, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (Cmd
Prev Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astResto, String
strFinal)
    Char
'.' ->
      case String -> Either String (AST, String)
parse' String
resto of
        Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
        Right (AST
astResto, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (Cmd
Print Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astResto, String
strFinal)
    Char
',' ->
      case String -> Either String (AST, String)
parse' String
resto of
        Left String
err -> String -> Either String (AST, String)
forall a b. a -> Either a b
Left String
err
        Right (AST
astResto, String
strFinal) -> (AST, String) -> Either String (AST, String)
forall a b. b -> Either a b
Right (Cmd
Input Cmd -> AST -> AST
forall a. a -> [a] -> [a]
: AST
astResto, String
strFinal)
    Char
_ -> String -> Either String (AST, String)
parse' String
resto -- Ignora caracteres inválidos como se fossem comentários

-- ! FUNÇÃO PARSE PÚBLICA ! --
parse :: String -> Either String AST
parse :: String -> Either String AST
parse String
input =
  case String -> Either String (AST, String)
parse' String
input of
    Left String
err -> String -> Either String AST
forall a b. a -> Either a b
Left String
err
    -- se o resto for null, significa que o bendito parse' analisou tudo sem sobrar código
    Right (AST
ast, String
resto) ->
      if String -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null String
resto -- tentei usar guards, mas só funciona com if-then-else
        then
          AST -> Either String AST
forall a b. b -> Either a b
Right AST
ast
        else
          String -> Either String AST
forall a b. a -> Either a b
Left String
"Erro de Sintaxe"