module PascalParser where

import Text.Parsec.Expr

import Text.Parsec.Char

import Text.Parsec.Token

import Text.Parsec.Language

import Text.Parsec.Prim

import Text.Parsec.Combinator

import Text.Parsec.String

import Control.Monad

import Data.Char

data PascalUnit =

    Program Identifier Implementation

    | Unit Identifier Interface Implementation (Maybe Initialize) (Maybe Finalize)

    deriving Show

data Interface = Interface Uses TypesAndVars

    deriving Show

data Implementation = Implementation Uses TypesAndVars

    deriving Show

data Identifier = Identifier String

    deriving Show

data TypesAndVars = TypesAndVars [TypeVarDeclaration]

    deriving Show

    | FunctionDeclaration Identifier Identifier (Maybe Phrase)

    deriving Show

data TypeDecl = SimpleType Identifier

    | RangeType Range

    | ArrayDecl Range TypeDecl

    deriving Show

    deriving Show

data Initialize = Initialize String

    deriving Show

data Finalize = Finalize String

    deriving Show

data Uses = Uses [Identifier]

    deriving Show

data Phrase = ProcCall Identifier [Expression]

        | IfThenElse Expression Phrase (Maybe Phrase)

        | WhileCycle Expression Phrase

        | RepeatCycle Expression [Phrase]

        | ForCycle Identifier Expression Expression Phrase

        | WithBlock Expression Phrase

        | Phrases [Phrase]

        | SwitchCase Expression [(Expression, Phrase)] (Maybe Phrase)

        | Assignment Reference Expression

    deriving Show

data Expression = Expression String

    | PrefixOp String Expression

    | PostfixOp String Expression

    | BinOp String Expression Expression

    | StringLiteral String

    | NumberLiteral String

    | Reference Reference

    deriving Show

data Reference = ArrayElement Identifier Expression

    | SimpleReference Identifier

    | RecordField Reference Reference

    | Dereference Reference

    deriving Show

pascalLanguageDef

    = emptyDef

    { commentStart   = "(*"

    , commentEnd     = "*)"

    , commentLine    = "//"

    , nestedComments = False

    , identStart     = letter <|> oneOf "_"

    , identLetter    = alphaNum <|> oneOf "_."

    , reservedNames  = [

            "begin", "end", "program", "unit", "interface"

            , "implementation", "and", "or", "xor", "shl"

            , "shr", "while", "do", "repeat", "until", "case", "of"

            , "type", "var", "const", "out", "array"

            , "procedure", "function", "with", "for", "to"

            ]

    , reservedOpNames= [] 

    , caseSensitive  = False   

    }

pas = patch $ makeTokenParser pascalLanguageDef

    where

comments = do

    spaces

    skipMany $ do

        comment

        spaces

pascalUnit = do

    comments

    u <- choice [program, unit]

    comments

    return u

comment = choice [

        char '{' >> manyTill anyChar (try $ char '}')

        , (try $ string "(*") >> manyTill anyChar (try $ string "*)")

        , (try $ string "//") >> manyTill anyChar (try newline)

        ]

iD = do

    i <- liftM Identifier (identifier pas)

    comments

    return i

unit = do

    string "unit" >> comments

    name <- iD

    semi pas

    comments

    int <- interface

    impl <- implementation

    comments

    return $ Unit name int impl Nothing Nothing

reference = buildExpressionParser table term <?> "reference"

    where

    term = comments >> choice [

        parens pas reference 

        , try $ iD >>= \i -> (brackets pas) expression >>= return . ArrayElement i

        , iD >>= return . SimpleReference

        ] <?> "simple reference"

    table = [ 

        [Postfix (char '^' >> return Dereference)]

        , [Infix (char '.' >> return RecordField) AssocLeft]

        ]

    comments

    where

    aVarDecl = do

        when (not endsWithSemi) $

            optional $ choice [

                try $ string "var"

                , try $ string "const"

                , try $ string "out"

                ]

        comments

        comments

constsDecl = do

    comments

    where

    aConstDecl = do

        comments

        optional $ do

            char ':'

            comments

            t <- typeDecl

            return ()

        char '='

        comments

        e <- expression

        comments

typeDecl = choice [

    arrayDecl

    , rangeDecl >>= return . RangeType

    , identifier pas >>= return . SimpleType . Identifier

    ] <?> "type declaration"

    where

    arrayDecl = do

        try $ string "array"

        comments

        char '['

        r <- rangeDecl

        char ']'

        comments

        string "of"

        comments

        t <- typeDecl

        return $ ArrayDecl r t

rangeDecl = choice [

    ] <?> "range declaration"

    varSection,

    constSection,

    funcDecl,

    procDecl

    ]

    where

    varSection = do

        try $ string "var"

        comments

        comments

        return v

    constSection = do

        try $ string "const"

        comments

        c <- constsDecl

        comments

        return c

    procDecl = do

        string "procedure"

        comments

        i <- iD

        optional $ do

            char '('

            varsDecl False

            char ')'

        comments

        char ';'

        b <- if isImpl then

                do

                comments

                comments

                liftM Just functionBody

                else

                return Nothing

        comments

    funcDecl = do

        string "function"

        comments

        i <- iD

        optional $ do

            char '('

            varsDecl False

            char ')'

        comments

        char ':'

        ret <- iD

        comments

        char ';'

        b <- if isImpl then

                do

                comments

                comments

                liftM Just functionBody

                else

                return Nothing

program = do

    string "program"

    comments

    name <- iD

    (char ';')

    comments

    impl <- implementation

    comments

    return $ Program name impl

interface = do

    string "interface"

    comments

    u <- uses

    comments

    comments

    return $ Interface u (TypesAndVars tv)

implementation = do

    string "implementation"

    comments

    u <- uses

    comments

    string "end."

    comments

    return $ Implementation u (TypesAndVars tv)

expression = buildExpressionParser table term <?> "expression"

    where

    term = comments >> choice [

        parens pas $ expression 

        , integer pas >>= return . NumberLiteral . show

        , stringLiteral pas >>= return . StringLiteral

        , try $ funCall

        , reference >>= return . Reference

        ] <?> "simple expression"

    table = [ 

          [Prefix (string "not" >> return (PrefixOp "not"))]

        , [  Infix (char '*' >> return (BinOp "*")) AssocLeft

           , Infix (char '/' >> return (BinOp "/")) AssocLeft

           , Infix (try (string "div") >> return (BinOp "div")) AssocLeft

           , Infix (try (string "mod") >> return (BinOp "mod")) AssocLeft

          ]

        , [  Infix (char '+' >> return (BinOp "+")) AssocLeft

           , Infix (char '-' >> return (BinOp "-")) AssocLeft

           , Prefix (char '-' >> return (PrefixOp "-"))

          ]

        , [  Infix (try (string "<>") >> return (BinOp "<>")) AssocNone

           , Infix (try (string "<=") >> return (BinOp "<=")) AssocNone

           , Infix (try (string ">=") >> return (BinOp ">=")) AssocNone

           , Infix (char '<' >> return (BinOp "<")) AssocNone

           , Infix (char '>' >> return (BinOp ">")) AssocNone

           , Infix (char '=' >> return (BinOp "=")) AssocNone

          ]

        , [  Infix (try $ string "and" >> return (BinOp "and")) AssocLeft

           , Infix (try $ string "or" >> return (BinOp "or")) AssocLeft

           , Infix (try $ string "xor" >> return (BinOp "xor")) AssocLeft

          ]

        ]

phrasesBlock = do

    try $ string "begin"

    comments

    p <- manyTill phrase (try $ string "end")

    comments

    return $ Phrases p

phrase = do

    o <- choice [

        phrasesBlock

        , ifBlock

        , whileCycle

        , repeatCycle

        , switchCase

        , withBlock

        , forCycle

        , (try $ reference >>= \r -> string ":=" >> return r) >>= \r -> expression >>= return . Assignment r

        , procCall

        ]

    optional $ char ';'

    comments

    return o

ifBlock = do

    try $ string "if"

    comments

    e <- expression

    comments

    string "then"

    comments

    o1 <- phrase

    comments

    o2 <- optionMaybe $ do

        try $ string "else"

        comments

        o <- phrase

        comments

        return o

    return $ IfThenElse e o1 o2

whileCycle = do

    try $ string "while"

    comments

    e <- expression

    comments

    string "do"

    comments

    o <- phrase

    return $ WhileCycle e o

withBlock = do

    try $ string "with"

    comments

    e <- expression

    comments

    string "do"

    comments

    o <- phrase

    return $ WithBlock e o

repeatCycle = do

    try $ string "repeat"

    comments

    o <- many phrase

    string "until"

    comments

    e <- expression

    comments

    return $ RepeatCycle e o

forCycle = do

    try $ string "for"

    comments

    i <- iD

    comments

    string ":="

    comments

    e1 <- expression

    comments

    choice [string "to", string "downto"]

    comments

    e2 <- expression

    comments

    string "do"

    comments

    p <- phrase

    comments

    return $ ForCycle i e1 e2 p