From a0c3a990ed65466414214606e03257cc372e188e Mon Sep 17 00:00:00 2001
From: Hans Svensson <hans.svensson@quviq.com>
Date: Tue, 18 Jun 2019 10:08:57 +0200
Subject: [PATCH] Add function_name_from_function_hash to aeb_fate_abi

---
 src/aeb_fate_abi.erl  | 27 ++++++++++++++++++++++++++-
 src/aeb_fate_code.erl |  3 +++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/aeb_fate_abi.erl b/src/aeb_fate_abi.erl
index 91f05b2..fc19b0a 100644
--- a/src/aeb_fate_abi.erl
+++ b/src/aeb_fate_abi.erl
@@ -9,7 +9,11 @@
 %%%-------------------------------------------------------------------
 -module(aeb_fate_abi).
 
--export([ create_calldata/2 ]).
+-export([ create_calldata/2
+        , function_name_from_function_hash/2
+        , get_function_hash_from_calldata/1 ]).
+
+-include("../include/aeb_fate_data.hrl").
 
 %%%===================================================================
 %%% API
@@ -21,3 +25,24 @@ create_calldata(FunName, Args) ->
     {ok, aeb_fate_encoding:serialize(
            aeb_fate_data:make_tuple({FunctionId,
                                      aeb_fate_data:make_tuple(list_to_tuple(Args))}))}.
+
+-spec function_name_from_function_hash(any(), aeb_fate_code:fcode()) ->
+    {ok, term()} | {error, term()}.
+function_name_from_function_hash(<<SymbolHash:4/binary, _:28/binary>>, FateCode) ->
+    function_name_from_function_hash(SymbolHash, FateCode);
+function_name_from_function_hash(SymbolHash = <<_:4/binary>>, FateCode) ->
+    Symbols = aeb_fate_code:symbols(FateCode),
+    case maps:get(SymbolHash, Symbols, undefined) of
+        undefined -> {error, no_function_matching_function_hash};
+        Function  -> {ok, Function}
+    end.
+
+-spec get_function_hash_from_calldata(binary()) ->
+    {ok, binary()} | {error, term()}.
+get_function_hash_from_calldata(CallData) ->
+    try ?FATE_TUPLE_ELEMENTS(aeb_fate_encoding:deserialize(CallData)) of
+        [FunHash, _Args] -> {ok, FunHash};
+        _                -> {error, bad_calldata}
+    catch _:_ ->
+        {error, bad_calldata}
+    end.
diff --git a/src/aeb_fate_code.erl b/src/aeb_fate_code.erl
index a60858b..d5289d9 100644
--- a/src/aeb_fate_code.erl
+++ b/src/aeb_fate_code.erl
@@ -39,6 +39,9 @@
 
 -define(HASH_BYTES, 32).
 
+-type fcode() :: #fcode{}.
+-export_type([fcode/0]).
+
 %%%===================================================================
 %%% API
 %%%===================================================================