More basic modules for errors and parsers

1 files changed, 70 insertions, 0 deletions

diff --git a/src/Hakyll/Error.hs b/src/Hakyll/Error.hs
new file mode 100644
index 0000000..3ca29d3
--- /dev/null
+++ b/src/Hakyll/Error.hs
@@ -0,0 +1,70 @@
+module Hakyll.Error
+    ( ErrorConv (..)
+    , throwErr
+    , CompilerError
+    ) where
+
+import Prolog
+import Text.Parsec.Error
+
+class ErrorConv c err where
+    toErr :: c -> err
+
+type CompilerError c = ErrorConv c [String]
+
+instance ErrorCnv err err where
+    toErr = id
+
+-- instance Functor f => ErrorCnv c err => ErrorCnv (f c) (f err) where
+--     toErr = fmap toErr
+
+instance Applicative f => ErrorCnv c err => ErrorCnv c (f err) where
+    toErr = pure . toErr
+
+throwErr :: (MonadError err m, ErrorConv c err) => c -> m a
+throwErr = throwError . toErr
+
+liftErr :: (MonadError err m, ErrorConv c err) => Either c a -> m a
+liftErr = either throwErr pure
+
+squashErr :: (MonadError err m, ErrorConv c err) => m (Either c a) -> m a
+squashErr = (>>= liftErr)
+
+instance ErrorConv Message String where
+    toErr = messageString
+
+instance ErrorConv ParseError [String] where
+    toErr = fmap messageString . errorMessages
+
+
+-- class CompilerError c where
+--     toCompilerError :: c -> [String]
+--     default toCompilerError :: Exception c => c -> [String]
+--     toCompilerError = pure . displayException
+
+--     toCompilerErrors :: [c] -> [String]
+--     toCompilerErrors = (>>= toCompilerError)
+
+-- instance CompilerError c => CompilerError [c] where
+--     toCompilerError = toCompilerErrors
+
+
+-- throwCompilerError :: (MonadError [String] m, CompilerError c) => c -> m a
+-- throwCompilerError = throwError . toCompilerError
+
+-- liftCompilerError :: (MonadError [String] m, CompilerError c) => Either c a -> m a
+-- liftCompilerError = either throwError pure
+
+-- squashCompilerError :: (MonadError [String] m, CompilerError c) => m (Either c a) -> m a
+-- squashCompilerError = (>>= liftCompilerError)
+
+-- instance CompilerError Char where
+--     toCompilerError = pure . pure
+--     toCompilerErrors = pure
+
+-- instance CompilerError Message where
+--     toCompilerError = pure . messageString
+--     toCompilerErrors = fmap messageString
+
+-- instance CompilerError ParseError where
+--     toCompilerError = toCompilerErrors . errorMessages