Added StateChain append condition

src/chain/Cargo.toml

@@ -13,6 +13,7 @@ lru = "0.1.13"
 rlp = "0.3.0"
 parking_lot = "0.7.1"
 hex = "0.3.2"
+patricia-trie = "0.3.0"
 account = { path = "../account" }
 crypto = { path = "../crypto" }
 events = { path = "../events" }

src/chain/src/state_chain/block.rs

@@ -38,6 +38,9 @@ use std::sync::Arc;
 use std::net::SocketAddr;
 use std::str;
 use rlp::{Rlp, RlpStream};
+use persistence::{Codec, BlakeDbHasher};
+use patricia_trie::TrieDBMut;
+use hashdb::HashDB;
 
 lazy_static! {
     /// Atomic reference count to state chain genesis block
@@ -147,7 +150,43 @@ impl Block for StateBlock {
         Some(Box::new(fun))
     }
 
-    fn append_condition(_block: Arc<StateBlock>, chain_state: Self::ChainState) -> Result<Self::ChainState, ChainErr> {
+    fn append_condition(block: Arc<StateBlock>, mut chain_state: Self::ChainState) -> Result<Self::ChainState, ChainErr> {
+        let pool_state = &mut chain_state.pool_state;
+
+        if block.epoch != pool_state.epoch {
+            return Err(ChainErr::BadAppendCondition);
+        }
+
+        // Validate and apply each event in the block
+        for event in block.events.iter().cloned() {
+            let node_id = event.node_id();
+
+            // TODO: Handle different errors
+            if pool_state.account_sent_by_validator(&node_id).is_err() {
+                return Err(ChainErr::BadAppendCondition);
+            }
+
+            let raw_root_hash = chain_state.db.retrieve(PersistentDb::ROOT_HASH_KEY).unwrap();
+            let mut root_hash_slice = [0; 32];
+
+            root_hash_slice.copy_from_slice(&raw_root_hash);
+
+            let mut root = Hash(root_hash_slice);
+
+            {
+                let mut trie = TrieDBMut::<BlakeDbHasher, Codec>::new(&mut chain_state.db, &mut root);
+
+                if event.validate_apply(&mut trie).is_err() {
+                    return Err(ChainErr::BadAppendCondition);
+                }
+            }
+
+            let root = root.0.to_vec();
+
+            // Update root hash entry
+            chain_state.db.put(PersistentDb::ROOT_HASH_KEY, &root);
+        }
+
         Ok(chain_state)
     }
 

src/crypto/src/hash.rs

@@ -16,9 +16,8 @@
   along with the Purple Library. If not, see <http://www.gnu.org/licenses/>.
 */
 
-use blake2_rfc::blake2b::{blake2b, Blake2b};
+use blake2_rfc::blake2b::blake2b;
 use blake_hasher::BlakeHasher;
-use byteorder::{LittleEndian, WriteBytesExt};
 use crc32fast::Hasher as CrcHasher;
 use hashdb::Hasher;
 use quickcheck::Arbitrary;

src/events/src/lib.rs

@@ -50,6 +50,9 @@ use crypto::Hash;
 use crypto::NodeId;
 use std::hash::Hash as HashTrait;
 use std::hash::Hasher;
+use persistence::Codec;
+use patricia_trie::TrieDBMut;
+use persistence::BlakeDbHasher;
 
 #[derive(Clone, Debug)]
 pub enum Event {
@@ -84,6 +87,10 @@ impl HashTrait for Event {
 }
 
 impl Event {
+    pub fn validate_apply(&self, trie: &mut TrieDBMut<BlakeDbHasher, Codec>) -> Result<(), ()> {
+        unimplemented!();
+    }
+
     pub fn stamp(&self) -> Stamp {
         match *self {
             Event::Heartbeat(ref event) => event.stamp.clone(),

src/persistence/src/persistent_db.rs

@@ -98,6 +98,8 @@ pub struct PersistentDb {
 }
 
 impl PersistentDb {
+    pub const ROOT_HASH_KEY: &'static [u8] = b"root_hash";
+
     pub fn new(db_ref: Arc<DB>, cf_name: Option<&'static str>) -> PersistentDb {
         if !is_initialized() {
             panic!("Persistence module not initialized! Call `persistence::init()` before using anything");
@@ -203,7 +205,13 @@ impl PersistentDb {
                     Operation::Put(ref val) => Some(val.clone()),
                     Operation::Remove => None,
                 },
-                None => self.get_db(key),
+                None => match self.get_db(key) {
+                    Some(res) => Some(res),
+                    None => match key {
+                        Self::ROOT_HASH_KEY => Some(Hash::NULL_RLP.0.to_vec()),
+                        _ => None
+                    }
+                },
             }
         } else {
             let result = self.memory_db.get(key);