Write the Genesis block in the BlockStorage

Move the loading code into a separate load() method,
and get rid of the empty() method.

Loading should ideally never be done in the constructor.

Fixes #286

source/agora/node/BlockStorage.d

@@ -46,12 +46,15 @@ public interface IBlockStorage
 
     /***************************************************************************
 
-        Returns:
-            true if the storage is empty (height index was not loaded)
+        Load the block storage. If there was nothing to load,
+        a Genesis block will be added to the ledger. In this case the calling
+        code should treat the block as new and update the set of UTXOs, etc.
+
+        If the blockchain data is corrupt the application will be halted.
 
     ***************************************************************************/
 
-    public bool isEmpty ();
+    public void load ();
 
     /***************************************************************************
 
@@ -185,24 +188,28 @@ public class BlockStorage : IBlockStorage
 
         this.height_idx = new IndexHeight();
         this.hash_idx = new IndexHash();
-
-        if (!this.path.exists)
-            mkdirRecurse(this.path);
-
-        if (!this.loadAllIndexes())
-            assert(0);
     }
 
     /***************************************************************************
 
-        Returns:
-            true if the storage is empty (height index was not loaded)
+        Load the blockchain from the storage
 
     ***************************************************************************/
 
-    public bool isEmpty ()
+    public void load ()
     {
-        return this.height_idx.length == 0;
+        if (!this.path.exists)
+            mkdirRecurse(this.path);
+
+        if (!this.loadAllIndexes())
+            assert(0);
+
+        // Add Genesis if the storage is empty
+        if (this.height_idx.length == 0)
+        {
+            if (!this.saveBlock(GenesisBlock))
+                assert(0);
+        }
     }
 
     /***************************************************************************
@@ -962,14 +969,13 @@ public class MemBlockStorage : IBlockStorage
 
     /***************************************************************************
 
-        Returns:
-            true if the storage is empty (height index was not loaded)
+        Adds the genesis block to the in-memory blockchain storage.
 
     ***************************************************************************/
 
-    public bool isEmpty ()
+    public void load ()
     {
-        return this.height_idx.length == 0;
+        this.saveBlock(GenesisBlock);
     }
 
     /***************************************************************************

source/agora/node/Ledger.d

@@ -47,13 +47,7 @@ public class Ledger
     {
         this.pool = pool;
         this.storage = storage;
-
-        // add the genesis block
-        if (this.storage.isEmpty())
-        {
-            this.storage.saveBlock(GenesisBlock);
-            assert(!this.storage.isEmpty());  // sanity check
-        }
+        this.storage.load();
 
         // ensure latest checksum can be read
         if (!this.storage.readLastBlock(this.last_block))

tests/unit/BlockStorage.d

@@ -108,6 +108,7 @@ private void main ()
 
     //  Verify index data that is already stored.
     BlockStorage other = new BlockStorage(path);
+    other.load();
 
     foreach (height; iota(count).randomCover(rnd))
     {

tests/unit/BlockStorageChecksum.d

@@ -51,7 +51,6 @@ private void writeBlocks (string path)
 
     const(Block)[] blocks;
     blocks ~= GenesisBlock;
-    storage.saveBlock(blocks[$ - 1]);
 
     foreach (block_idx; 0 .. BlockCount)
     {

tests/unit/BlockStorageMultiTx.d

@@ -44,10 +44,10 @@ private void main ()
 
     BlockStorage.removeIndexFile(path);
     BlockStorage storage = new BlockStorage(path);
+    storage.load();
     const(Block)[] blocks;
 
     blocks ~= GenesisBlock;
-    storage.saveBlock(blocks[$ - 1]);
 
     // We can use a random keypair because blocks are not validated
     auto gen_key_pair = KeyPair.random();