Added ABI parser; Added Filter creator from Event defs

.ghci

@@ -0,0 +1 @@
+:set prompt "> "

src/Network/Ethereum/ContractAbi.hs

@@ -0,0 +1,60 @@
+{-# LANGUAGE TemplateHaskell #-}
+-- |
+-- Module      :  Network.Ethereum.ContractAbi
+-- Copyright   :  Alexander Krupenkin 2016
+-- License     :  BSD3
+--
+-- Maintainer  :  mail@akru.me
+-- Stability   :  experimental
+-- Portability :  POSIX / WIN32
+--
+-- Ethereum smart contract utils.
+--
+module Network.Ethereum.ContractAbi where
+
+import qualified Data.Text as T
+import Data.Char (toLower)
+import Data.Monoid ((<>))
+import Data.Text (Text)
+import Data.Aeson.TH
+
+data FunctionArg = FunctionArgs
+  { funArgName :: Text
+  , funArgType :: Text
+  } deriving Show
+
+$(deriveJSON (defaultOptions { fieldLabelModifier = map toLower . drop 6 }) ''FunctionArg)
+
+data EventArg = EventArg
+  { eveArgName    :: Text
+  , eveArgType    :: Text
+  , eveArgIndexed :: Bool
+  } deriving Show
+
+$(deriveJSON (defaultOptions { fieldLabelModifier = map toLower . drop 6 }) ''EventArg)
+
+data Method = Constructor { conInputs :: [FunctionArg] }
+
+            | Function { funName      :: Text
+                       , funInputs    :: [FunctionArg]
+                       , funOutputs   :: Maybe [FunctionArg] }
+
+            | Event { eveName      :: Text
+                    , eveInputs    :: [EventArg]
+                    , eveAnonymous :: Bool }
+  deriving Show
+
+$(deriveJSON (defaultOptions {
+    sumEncoding = defaultTaggedObject { tagFieldName = "type" }
+  , constructorTagModifier = map toLower
+  , fieldLabelModifier = map toLower . drop 3 }) ''Method)
+
+type ContractABI = [Method]
+
+events :: ContractABI -> [Method]
+events = filter (\x -> case x of Event _ _ _ -> True; _ -> False)
+
+eventSignature :: Method -> Text
+eventSignature event = eveName event <> "(" <> args event <> ")"
+  where args = T.init . foldMap (<> ",") . inputTypes
+        inputTypes = fmap eveArgType . filter eveArgIndexed . eveInputs

src/Network/Ethereum/Web3/Api.hs

@@ -30,7 +30,7 @@ getBalance = remote "eth_getBalance"
 
 data Filter = Filter
   { filterAddress   :: Maybe Text
-  , filterTopics    :: Maybe Value
+  , filterTopics    :: Maybe [Maybe Text]
   , filterFromBlock :: Maybe Text
   , filterToBlock   :: Maybe Text
   } deriving Show

src/Network/Ethereum/Web3/Util.hs

@@ -0,0 +1,28 @@
+-- |
+-- Module      :  Network.Ethereum.Web3.Utils
+-- Copyright   :  Alexander Krupenkin 2016
+-- License     :  BSD3
+--
+-- Maintainer  :  mail@akru.me
+-- Stability   :  experimental
+-- Portability :  POSIX / WIN32
+--
+-- Web3 utility.
+--
+module Network.Ethereum.Web3.Util where
+
+import Network.Ethereum.ContractAbi (Method, eventSignature)
+import Network.Ethereum.Web3.Api (Filter(..), sha3)
+import Network.Ethereum.Web3.Types (Web3)
+import Data.HexString (toText, fromBytes)
+import Data.Text.Encoding (encodeUtf8)
+import Data.Monoid ((<>))
+import Data.Text (Text)
+
+type Address = Text
+
+eventFilter :: Address -> Method -> Web3 Filter
+eventFilter addr event = do
+    topic0 <- sha3 (hex $ eventSignature event)
+    return (Filter (Just addr) (Just [Just topic0, Nothing]) Nothing Nothing)
+  where hex = ("0x" <>) . toText . fromBytes . encodeUtf8

web3.cabal

@@ -19,14 +19,17 @@ source-repository head
 library
   hs-source-dirs:      src
   exposed-modules:     Network.Ethereum.Web3
+                     , Network.Ethereum.ContractAbi
   other-modules:       Network.Ethereum.Web3.Api
+                     , Network.Ethereum.Web3.Util
                      , Network.Ethereum.Web3.Types
                      , Network.Ethereum.Web3.JsonRpc
   build-depends:       base >= 4.5 && <4.10
                      , mtl
                      , text
                      , aeson
                      , vector
+                     , hexstring
                      , bytestring
                      , http-client
                      , transformers