{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}

-- Copyright (C) 2012 John Millikin <jmillikin@gmail.com>
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program.  If not, see <http://www.gnu.org/licenses/>.

module Main
  ( main ) where

import qualified CPython as Py
import qualified CPython.Types.Module as Py
import qualified CPython.Protocols.Object as Py
import qualified CPython.Protocols.Number as Py
import qualified CPython.Types.Dictionary as PyDict
import qualified CPython.Types.List as PyList
import qualified CPython.Types.Tuple as PyTuple
import qualified CPython.Types.Unicode as PyUnicode
import qualified CPython.Types.Integer as PyInt
import qualified CPython.Types.Exception as PyExc
import Data.Text()
import Control.Monad(guard)
import Data.Maybe(fromMaybe)
import Control.Exception(handle, SomeException)

main :: IO ()
main = verboseExc $ handle pyExceptionHandler $ do
  Py.initialize
  testingSomePythonEvaluation
  Py.finalize
  where
    pyExceptionHandler :: PyExc.Exception -> IO ()
    pyExceptionHandler exception = handle pyExceptionHandlerWithoutPythonTraceback $ do
        tracebackModule <- Py.importModule "traceback"
        print_exc <- PyUnicode.toUnicode "print_exception" >>= Py.getAttribute tracebackModule
        kwargs <- PyDict.new
        args <- case PyExc.exceptionTraceback exception of
          Just tb -> PyTuple.toTuple [PyExc.exceptionType exception, PyExc.exceptionValue exception, tb]
          _ -> PyTuple.toTuple [PyExc.exceptionType exception, PyExc.exceptionValue exception]
        _ <- Py.call print_exc args kwargs
        return ()
    pyExceptionHandlerWithoutPythonTraceback :: PyExc.Exception -> IO ()
    pyExceptionHandlerWithoutPythonTraceback exception = do
        print exception
        putStrLn "Unexpected Python exception (Please report a bug)"

    verboseExc ioAction = handleEverything (\exc -> print exc >> error "Unexpected error") ioAction

    handleEverything :: (SomeException -> IO a) -> IO a -> IO a
    handleEverything = handle

testingSomePythonEvaluation :: IO ()
testingSomePythonEvaluation = do
    testList <- traverse toObj [1, 10, 100, 42] >>= PyList.toList >>= (return . Py.toObject)
    builtinsModule <- Py.importModule "builtins"
    sumFunc <- PyUnicode.toUnicode "sum" >>= Py.getAttribute builtinsModule
    args <- PyTuple.toTuple [testList]
    kwargs <- PyDict.new
    result <- Py.call sumFunc args kwargs >>= castToNumber >>= Py.toInteger >>= PyInt.fromInteger
    guard $ result == 153
  where
    castToNumber obj = do x <- Py.castToNumber obj
                          return $ fromMaybe (error "not a number returned from the sum") x
    toObj integer = fmap Py.toObject $ PyInt.toInteger integer