{-#LANGUAGE TemplateHaskell #-}
module Text.HPaco.Writers.PHP
    ( writePHP
    , defPHPWriterOptions
    , WrapMode (..)
    )
where

import Control.Monad.RWS
import Data.FileEmbed
import Data.List (intersperse)
import Data.Maybe
import Data.Typeable
import Data.Char
import Text.HPaco.AST.AST
import Text.HPaco.AST.Expression
import Text.HPaco.AST.Statement
import Text.HPaco.Writer
import Text.HPaco.Writers.Internal.WrapMode
import Text.HPaco.Writers.Internal.CodeWriter
import qualified Data.ByteString.Char8 as BS8
import qualified Data.Map as M

data OutputMode = PHP | Html

type ScopeMap = [M.Map String String]

defPHPWriterOptions =
    defaultWriterOptions { woWriteFunc = "print" }

data PHPWriterState =
    PHPWriterState { pwsIndent :: Int
                   , pwsLocalScope :: ScopeMap
                   , pwsNextLocalVariableID :: Integer
                   , pwsAST :: AST
                   , pwsOutputMode :: OutputMode
                   , pwsEscapeFilters :: [String -> String]
                   }

defaultPHPWriterState =
    PHPWriterState { pwsIndent = 0
                   , pwsLocalScope = []
                   , pwsNextLocalVariableID = 0
                   , pwsAST = defAST
                   , pwsOutputMode = Html
                   , pwsEscapeFilters = []
                   }

instance CodeWriterState PHPWriterState where
    cwsGetIndent = pwsIndent
    cwsSetIndent f s = s { pwsIndent = f }
    cwsGetFilters = pwsEscapeFilters
    cwsSetFilters f s = s { pwsEscapeFilters = f }

type PWS = RWS WriterOptions String PHPWriterState

writePHP :: WriterOptions -> Writer
writePHP opts ast =
    runCodeWriter (writeAST ast) opts defaultPHPWriterState { pwsAST = ast}

writeAST :: AST -> PWS ()
writeAST ast = do
    writeHeader ast
    writeStatement $ astRootStatement ast
    writeFooter

getOutputMode :: PWS OutputMode
getOutputMode = gets pwsOutputMode

-- Unsafe, because it doesn't take care of writing appropriate PHP
-- open/close tags for you. Should only be used when the PHP tags have been
-- written using other means already.
unsafeSetOutputMode :: OutputMode -> PWS ()
unsafeSetOutputMode m =
    modify (\s -> s { pwsOutputMode = m })

setOutputMode :: OutputMode -> PWS ()
setOutputMode m = do
    m0 <- getOutputMode
    unsafeSetOutputMode m
    case (m0, m) of
        (Html, PHP) -> write "<?php "
        (PHP, Html) -> write " ?>\n"
        otherwise -> return ()

withOutputMode :: OutputMode -> PWS a -> PWS a
withOutputMode m a = do
    m0 <- getOutputMode
    setOutputMode m
    x <- a
    setOutputMode m0
    return x

pushScope :: PWS ()
pushScope = modify (\s -> s { pwsLocalScope = M.empty:pwsLocalScope s })

popScope :: PWS ()
popScope = modify (\s -> s { pwsLocalScope = tail (pwsLocalScope s) })

getScope :: PWS ScopeMap
getScope = gets pwsLocalScope

setScope :: ScopeMap -> PWS ()
setScope newScope = modify (\s -> s { pwsLocalScope = newScope })

scopeResolve :: String -> PWS (Maybe String)
scopeResolve key = do
    scopeStack <- gets pwsLocalScope
    return $ resolve key scopeStack
    where
        resolve key scopes =
            let mr = mapMaybe (M.lookup key) scopes
            in if null mr then Nothing else (Just . head) mr

resolveVariable :: String -> PWS String
resolveVariable key = do
    strid <- scopeResolve key
    return $ maybe key toVarname strid

maybeResolveVariable :: String -> PWS (Maybe String)
maybeResolveVariable key = do
    strid <- scopeResolve key
    return $ maybe Nothing (Just . toVarname) strid

nextVarID :: PWS Integer
nextVarID = do
    id <- gets pwsNextLocalVariableID
    modify (\s -> s { pwsNextLocalVariableID = 1 + pwsNextLocalVariableID s })
    return id

toVarname :: String -> String
toVarname i = "_lv" ++ i

defineVariable :: String -> PWS String
defineVariable key = do
    vidInt <- nextVarID
    let vid = show vidInt ++ "_" ++ sanitizeIdentifier key
    scope <- gets pwsLocalScope >>= \x -> return $ head x
    let scope' =  M.insert key vid . M.delete key $ scope
    modify (\s -> s { pwsLocalScope = scope':tail (pwsLocalScope s) })
    return vid

-- Filter an arbitrary string to become a valid PHP identifier tail
sanitizeIdentifier :: String -> String
sanitizeIdentifier str =
    map sanitizeIdentifierChar str
    where
        sanitizeIdentifierChar c =
            if isAlphaNum c
                then c
                else '_'

writePreamble :: PWS ()
writePreamble = do
    let src = BS8.unpack $(embedFile "snippets/php/preamble.php")
    unsafeSetOutputMode PHP
    write src

writeHeader :: AST -> PWS ()
writeHeader ast = do
    templateName <- woTemplateName `liftM` ask
    includePreamble <- woIncludePreamble `liftM` ask
    wrapMode <- woWrapMode `liftM` ask

    when includePreamble writePreamble

    setOutputMode PHP

    case wrapMode of
        WrapFunction -> do
            let funcName =
                    if null templateName
                        then "runTemplate"
                        else "runTemplate_" ++ templateName
            writeLn $ "function " ++ funcName ++ "($context) {"
            withIndent $ writeDefs $ astDefs ast
            pushIndent
        WrapClass -> do
            let className =
                    if null templateName
                        then "Template"
                        else "Template_" ++ templateName
            writeLn $ "class " ++ className ++ " {"
            writeDefs $ astDefs ast
            pushIndent
            writeLn $ "public function __invoke($context) {"
            pushIndent
        otherwise -> writeDefs $ astDefs ast
    pushScope
    vid <- defineVariable "."
    writeLn "if (isset($context)) {"
    withIndent $ writeVarAssignment vid $ write "$context"
    writeLn "}"
    writeLn "else {"
    withIndent $ writeVarAssignment vid $ write "array()"
    writeLn "}"
    writeLn "$_scope = array();"
    writePushScope

writeVar vid = do
    write "$"
    write $ toVarname vid

writeVarAssignment vid rhs = writeAssignment (writeVar vid) rhs

writeAssignment lhs rhs = do
    writeIndent
    lhs
    write " = "
    rhs
    write ";"
    endl
    
writeDefs defs = do
    mapM_ writeDef defs

writeUnsetVar id = do
    writeIndent
    write "unset($"
    write $ toVarname id
    write ");";
    endl

withSealedScope inner = do
    outerScope <- getScope
    setScope []
    result <- inner
    setScope outerScope
    return result

writeDef (ident, stmt) = do
    setOutputMode PHP
    wrapMode <- woWrapMode `liftM` ask
    writeIndent
    case wrapMode of
        WrapClass -> write "private static $_macro_"
        otherwise -> write "$_macro_"
    write ident
    write " = '"
    endl
    withFilter evalQuoteString $ withIndent $ writeStatement stmt
    setOutputMode PHP
    writeLn "';"

writePushScope = writePushScopeVar "."

writePushScopeVar var = do
    vid <- resolveVariable var
    let str = if var == "."
                then
                    "$_scope = new _S($" ++ vid ++ ", $_scope);"
                else
                    "$_scope = new _S(array('" ++ var ++ "' => $" ++ vid ++ "), $_scope);"
    writeLn str

writePopScope =
    writeLn "if ($_scope instanceof _S) { $_scope = $_scope->p; } else { $_scope = array(); }"

writeFooter :: PWS ()
writeFooter = do
    wrapMode <- woWrapMode `liftM` ask

    case wrapMode of
        WrapFunction -> do
            popIndent
            writeLn "}"
        WrapClass -> do
            popIndent
            writeLn "}"
            popIndent
            writeLn "}"
        otherwise -> return ()

writeIndentedStatement :: Statement -> PWS ()
writeIndentedStatement stmt = do
    writeStatement stmt

writeStatement :: Statement -> PWS ()
writeStatement stmt = do
    -- writeIndent >> write "/* " >> write (show stmt) >> write " */" >> endl
    case stmt of
        StatementSequence ss -> mapM_ writeStatement ss
        PrintStatement expr -> do
            writeIndent
            write "print"
            withParens $
                case expr of
                    EscapeExpression _ _ -> writeExpression expr
                    StringLiteral _ -> writeExpression expr
                    IntLiteral _ -> writeExpression expr
                    FloatLiteral _ -> writeExpression expr
                    otherwise -> do
                        write "_f"
                        withParens $ writeExpression expr
            write ";"
            endl
        NullStatement -> return ()
        IfStatement { } -> writeIf stmt
        LetStatement identifier expr stmt -> writeLet identifier expr stmt
        ForStatement iter identifier expr stmt -> writeFor iter identifier expr stmt
        SwitchStatement masterExpr branches -> writeSwitch masterExpr branches
        CallStatement identifier -> do
            wrapMode <- woWrapMode `liftM` ask
            writeIndent
            write "eval("
            when (wrapMode == WrapClass) $ write "self::"
            write "$_macro_"
            write identifier
            write ");"
            endl
        SourcePositionStatement fn ln -> do
            c <- asks woSourcePositionComments
            when c $ do
                writeIndent
                write "/* "
                write fn
                write ":"
                write $ show ln
                write " */"
                endl

writeIf :: Statement -> PWS ()
writeIf (IfStatement cond true false) = do
    writeIndent
    write "if ("
    writeExpression cond
    write ") {"
    endl
    withIndent $ writeStatement true
    writeLn "}"
    if false == NullStatement
        then return ()
        else do
                writeLn "else {"
                withIndent $ writeStatement false
                writeLn "}"

writeLet :: String -> Expression -> Statement -> PWS ()
writeLet identifier expr stmt = do
    pushScope
    id <- defineVariable identifier

    writeVarAssignment id $ writeExpression expr

    writePushScopeVar identifier

    writeStatement stmt

    writeUnsetVar id

    popScope
    writePopScope


writeFor :: Maybe String -> String -> Expression -> Statement -> PWS ()
writeFor iter identifier expr stmt = do
    pushScope

    writeAssignment (write "$_iteree") (writeExpression expr)

    writeLn "if (is_array($_iteree) || ($_iteree instanceof Traversable)) {"

    id <- defineVariable identifier
    withIndent $ do
        writeIndent
        write "foreach ($_iteree as $"
        case iter of
            Just k -> do
                kid <- defineVariable k
                write $ toVarname kid
                write " => $"
            otherwise -> return ()
        write $ toVarname id
        write ") {"
        endl

        withIndent $ do
            writePushScopeVar identifier
            writeStatement stmt
            writePopScope

        writeLn "}"

        writeUnsetVar id

    writeLn "}"

    popScope

writeSwitch :: Expression -> [(Expression, Statement)] -> PWS ()
writeSwitch masterExpr branches = do
    writeIndent
    write "switch ("
    writeExpression masterExpr
    write ") {"
    endl
    withIndent $
        mapM writeSwitchBranch branches
    writeLn "}"
    where
        writeSwitchBranch :: (Expression, Statement) -> PWS ()
        writeSwitchBranch (expr, stmt) = do
            writeIndent
            write "case "
            writeExpression expr
            write ":"
            endl
            withIndent $ do
                writeStatement stmt
                writeLn "break;"

writeExpression :: Expression -> PWS ()
writeExpression expr =
    case expr of
        StringLiteral str -> write $ singleQuoteString str

        IntLiteral i -> write $ show i
        FloatLiteral i -> write $ show i

        BooleanLiteral b -> write $ if b then "TRUE" else "FALSE"

        ListExpression items -> do
            write "array("
            sequence_ $
                intersperse (write ", ") $
                map writeExpression items
            write ")"

        AListExpression items -> do
            write "array("
            sequence_ $
                intersperse (write ", ") $
                map writeElem items
            write ")"
            where
                writeElem (key, value) = do
                writeExpression key
                write " => "
                writeExpression value

        VariableReference vn -> do
            vid <- maybeResolveVariable vn
            write $ maybe
                ("_r($_scope, '" ++ vn ++ "')")
                (\v -> "(isset($" ++ v ++ ") ? $" ++ v ++ " : _r($_scope, '" ++ vn ++ "'))")
                vid

        EscapeExpression mode e -> do
            let escapefunc =
                    case mode of
                        EscapeHTML -> "htmlspecialchars"
                        EscapeURL -> "rawurlencode"
            write escapefunc
            write "(_f("
            writeExpression e
            write "))"

        BinaryExpression (Flipped op) left right ->
            writeExpression $ BinaryExpression op right left

        BinaryExpression OpMember left right -> do
            write "_r("
            writeExpressionPair left right
            write ")"

        BinaryExpression OpInList left right -> do
            write "_in("
            writeExpressionPair left right
            write ")"

        BinaryExpression o left right -> do
            let opstr = case o of
                            OpPlus -> "+"
                            OpMinus -> "-"
                            OpMul -> "*"
                            OpDiv -> "/"
                            OpMod -> "%"
                            OpEquals -> "==="
                            OpLooseEquals -> "=="
                            OpNotEquals -> "!=="
                            OpLooseNotEquals -> "!="
                            OpGreater -> ">"
                            OpLess -> "<"
                            OpNotGreater -> "<="
                            OpNotLess -> ">="
                            OpBooleanAnd -> "&&"
                            OpBooleanOr -> "||"
                            OpBooleanXor -> " xor "
            withParens $ do
                writeExpression left
                write opstr
                writeExpression right

        UnaryExpression o e -> do
            let opstr = case o of
                            OpNot -> "!"
            withParens $ do
                write opstr
                withParens $ writeExpression e

        FunctionCallExpression fn args -> do
            write "_call("
            writeExpression fn
            write ", array("
            mapM_ (\e -> writeExpression e >> write ", ") args
            write "))"

writeExpressionPair :: Expression -> Expression -> PWS ()
writeExpressionPair lhs rhs = do
    writeExpression lhs
    write ","
    writeExpression rhs

singleQuoteString :: String -> String
singleQuoteString str =
    "\"" ++ escape str ++ "\""
    where
        escapeChar '\"' = "\\\""
        escapeChar '\n' = "\\n"
        escapeChar '\t' = "\\t"
        escapeChar '\r' = "\\r"
        escapeChar '$' = "\\$"
        escapeChar x = [x]
        escape = concat . map escapeChar

evalQuoteString :: String -> String
evalQuoteString =
    concat . map escapeChar
    where
        escapeChar '\'' = "\\\'"
        escapeChar x = [x]