Begin basics of block validation

lighthouse/state/chain_config.rs

@@ -2,6 +2,7 @@ pub struct ChainConfig {
     pub cycle_length: u8,
     pub shard_count: u16,
     pub min_committee_size: u64,
+    pub genesis_time: u64,
 }
 
 impl ChainConfig {
@@ -10,6 +11,7 @@ impl ChainConfig {
             cycle_length: 8,
             shard_count: 1024,
             min_committee_size: 128,
+            genesis_time: 1537488655,   // arbitrary
         }
     }
 }

lighthouse/state/mod.rs

@@ -5,6 +5,7 @@ extern crate bytes;
 extern crate ssz;
 
 use super::utils;
+use super::db;
 
 pub mod active_state;
 pub mod attestation_record;

lighthouse/state/transition/mod.rs

@@ -1,4 +1,5 @@
-use super::super::utils::types::Hash256;
+use super::utils::types::Hash256;
+use super::db;
 
 mod attestation_parent_hashes;
 mod shuffling;

lighthouse/state/transition/validate_block.rs

@@ -0,0 +1,56 @@
+use super::block::SszBlock;
+use super::Logger;
+use super::db::{
+    BlockStore,
+    PoWChainStore,
+};
+
+pub enum BlockStatus {
+    NewBlock,
+    KnownBlock,
+    UnknownPoWChainRef,
+}
+
+pub enum SszBlockValidationError {
+    SszInvalid,
+    FutureSlot,
+}
+
+macro_rules! valid_if {
+    ($cond:expr, $val:expr) => {
+        if ($cond)
+            return Ok($val);
+        }
+    };
+}
+
+macro_rules! invalid_if {
+    ($cond:expr, $val:expr) => {
+        if ($cond)
+            return Err($val);
+        }
+    };
+}
+
+fn slot_from_time()
+
+
+pub fn validate_ssz_block(b: &SszBlock,
+                          expected_slot: &u64,
+                          block_store: &BlockStore,
+                          pow_store: &PoWChainStore,
+                          log: &Logger)
+    -> Result<BlockStatus, SszBlockValidationError>
+{
+    valid_if!(block_store.block_exists(b.block_hash()),
+              BlockStatus::KnownBlock);
+
+    invalid_if!(b.slot_number() > expected_slot,
+                SszBlockValidationError::FutureSlot);
+
+    invalid_if!(pow_store.block_hash_exists(b.pow_chain_ref()) == false,
+                SszBlockValidationError::UnknownPoWChainRef);
+
+    // Do validation here
+    Ok(BlockStatus::NewBlock)
+}