From 6d9d8fb6054356ecc2c5cbe4ad643324137773b4 Mon Sep 17 00:00:00 2001
From: Leonardo Yvens <leoyvens@gmail.com>
Date: Wed, 13 May 2020 17:24:08 -0300
Subject: [PATCH] Support eth_call by block hash

---
 src/api/eth.rs      |  4 ++--
 src/contract/mod.rs | 44 +++++++++++++++++++++++++++++++++++++++-----
 src/types/block.rs  | 10 +++++++---
 3 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/src/api/eth.rs b/src/api/eth.rs
index 6ba39d6d..3799ac9d 100644
--- a/src/api/eth.rs
+++ b/src/api/eth.rs
@@ -39,9 +39,9 @@ impl<T: Transport> Eth<T> {
     }
 
     /// Call a constant method of contract without changing the state of the blockchain.
-    pub fn call(&self, req: CallRequest, block: Option<BlockNumber>) -> CallFuture<Bytes, T::Out> {
+    pub fn call(&self, req: CallRequest, block: Option<BlockId>) -> CallFuture<Bytes, T::Out> {
         let req = helpers::serialize(&req);
-        let block = helpers::serialize(&block.unwrap_or(BlockNumber::Latest));
+        let block = helpers::serialize(&block.unwrap_or(BlockNumber::Latest.into()));
 
         CallFuture::new(self.transport.execute("eth_call", vec![req, block]))
     }
diff --git a/src/contract/mod.rs b/src/contract/mod.rs
index 5b8ebe8b..595b543c 100644
--- a/src/contract/mod.rs
+++ b/src/contract/mod.rs
@@ -5,7 +5,7 @@ use ethabi;
 use crate::api::{Eth, Namespace};
 use crate::confirm;
 use crate::contract::tokens::{Detokenize, Tokenize};
-use crate::types::{Address, BlockNumber, Bytes, CallRequest, TransactionCondition, TransactionRequest, H256, U256};
+use crate::types::{Address, BlockId, Bytes, CallRequest, TransactionCondition, TransactionRequest, H256, U256};
 use crate::Transport;
 use std::{collections::HashMap, hash::Hash, time};
 
@@ -222,7 +222,7 @@ impl<T: Transport> Contract<T> {
     where
         R: Detokenize,
         A: Into<Option<Address>>,
-        B: Into<Option<BlockNumber>>,
+        B: Into<Option<BlockId>>,
         P: Tokenize,
     {
         self.abi
@@ -256,7 +256,7 @@ mod tests {
     use crate::api::{self, Namespace};
     use crate::helpers::tests::TestTransport;
     use crate::rpc;
-    use crate::types::{Address, BlockNumber, H256, U256};
+    use crate::types::{Address, BlockId, BlockNumber, H256, U256};
     use crate::Transport;
     use futures::Future;
 
@@ -276,7 +276,13 @@ mod tests {
 
             // when
             token
-                .query("name", (), None, Options::default(), BlockNumber::Number(1.into()))
+                .query(
+                    "name",
+                    (),
+                    None,
+                    Options::default(),
+                    BlockId::Number(BlockNumber::Number(1.into())),
+                )
                 .wait()
                 .unwrap()
         };
@@ -293,6 +299,34 @@ mod tests {
         assert_eq!(result, "Hello World!".to_owned());
     }
 
+    #[test]
+    fn should_call_constant_function_by_hash() {
+        // given
+        let mut transport = TestTransport::default();
+        transport.set_response(rpc::Value::String("0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000c48656c6c6f20576f726c64210000000000000000000000000000000000000000".into()));
+
+        let result: String = {
+            let token = contract(&transport);
+
+            // when
+            token
+                .query("name", (), None, Options::default(), BlockId::Hash(H256::default()))
+                .wait()
+                .unwrap()
+        };
+
+        // then
+        transport.assert_request(
+            "eth_call",
+            &[
+                "{\"data\":\"0x06fdde03\",\"to\":\"0x0000000000000000000000000000000000000001\"}".into(),
+                "{\"blockHash\":\"0x0000000000000000000000000000000000000000000000000000000000000000\"}".into(),
+            ],
+        );
+        transport.assert_no_more_requests();
+        assert_eq!(result, "Hello World!".to_owned());
+    }
+
     #[test]
     fn should_query_with_params() {
         // given
@@ -311,7 +345,7 @@ mod tests {
                     Options::with(|options| {
                         options.gas_price = Some(10_000_000.into());
                     }),
-                    BlockNumber::Latest,
+                    BlockId::Number(BlockNumber::Latest),
                 )
                 .wait()
                 .unwrap()
diff --git a/src/types/block.rs b/src/types/block.rs
index 8ee8bdae..953f9607 100644
--- a/src/types/block.rs
+++ b/src/types/block.rs
@@ -1,5 +1,5 @@
 use crate::types::{Bytes, H160, H2048, H256, H64, U256, U64};
-use serde::{Deserialize, Serialize, Serializer};
+use serde::{ser::SerializeStruct, Deserialize, Serialize, Serializer};
 
 /// The block header type returned from RPC calls.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
@@ -144,7 +144,7 @@ impl Serialize for BlockNumber {
 }
 
 /// Block Identifier
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub enum BlockId {
     /// By Hash
     Hash(H256),
@@ -158,7 +158,11 @@ impl Serialize for BlockId {
         S: Serializer,
     {
         match *self {
-            BlockId::Hash(ref x) => serializer.serialize_str(&format!("0x{}", x)),
+            BlockId::Hash(ref x) => {
+                let mut s = serializer.serialize_struct("BlockIdEip1898", 1)?;
+                s.serialize_field("blockHash", &format!("{:?}", x))?;
+                s.end()
+            }
             BlockId::Number(ref num) => num.serialize(serializer),
         }
     }