Insipx/add block method (#18)

* Fix compile errors

* Fix tests, close #13 BTW

* add block method

* add block_hash method

* add tests for block and block_hash

src/lib.rs

@@ -55,6 +55,8 @@ use crate::{
     rpc::{
         MapStream,
         Rpc,
+        ChainBlock,
+        BlockNumber
     },
     srml::{
         system::{
@@ -183,6 +185,18 @@ impl<T: System + 'static> Client<T> {
         self.fetch(key).map(|value| value.unwrap_or_default())
     }
 
+    /// Get a block hash. By default returns the latest block hash
+    pub fn block_hash(&self, hash: Option<BlockNumber<T>>) -> impl Future<Item = Option<T::Hash>, Error = Error> {
+        self.connect().and_then(|rpc| rpc.block_hash(hash.map(|h| h)))
+    }
+
+    /// Get a block
+    pub fn block<H>(&self, hash: Option<H>) -> impl Future<Item = Option<ChainBlock<T>>, Error = Error>
+        where H: Into<T::Hash> + 'static
+    {
+        self.connect().and_then(|rpc| rpc.block(hash.map(|h| h.into())))
+    }
+
     /// Subscribe to events.
     pub fn subscribe_events(
         &self,
@@ -504,6 +518,22 @@ mod tests {
             .expect("Extrinsic should be included in a block");
     }
 
+    #[test]
+    #[ignore] // requires locally running substrate node
+    fn test_getting_hash() {
+        let (mut rt, client) = test_setup();
+        rt.block_on(client.block_hash(None)).unwrap();
+    }
+
+    #[test]
+    #[ignore] // requires locally running substrate node
+    fn test_getting_block() {
+        let (mut rt, client) = test_setup();
+        rt.block_on(client.block_hash(None).and_then(move |h| {
+            client.block(h)
+        })).unwrap();
+    }
+
     #[test]
     #[ignore] // requires locally running substrate node
     fn test_state_read_free_balance() {