Canonical blocks (#108)

* Update Block w/ newest Block

* Add cascading delete to blocks and transactions tables

* Add handling for new conflicting blocks

* Command line version of sliding window n behind HEAD

pkg/observers/blockchain_db_observer.go

@@ -14,5 +14,5 @@ func NewBlockchainDbObserver(repository repositories.Repository) BlockchainDbObs
 }
 
 func (observer BlockchainDbObserver) NotifyBlockAdded(block core.Block) {
-	observer.repository.CreateBlock(block)
+	observer.repository.CreateOrUpdateBlock(block)
 }

pkg/observers/blockchain_logging_observer.go

@@ -1,18 +1,32 @@
 package observers
 
 import (
-	"fmt"
+	"os"
+	"text/template"
+
 	"time"
 
 	"github.com/8thlight/vulcanizedb/pkg/core"
 )
 
+const blockAddedTemplate = `
+    New block was added: {{.Number}}
+    Time: {{.Time | unix_time}}
+    Gas Limit: {{.GasLimit}}
+    Gas Used: {{.GasUsed}}
+    Number of Transactions {{.Transactions | len}}
+
+`
+
+var funcMap = template.FuncMap{
+	"unix_time": func(n int64) time.Time {
+		return time.Unix(n, 0)
+	},
+}
+var tmp = template.Must(template.New("window").Funcs(funcMap).Parse(blockAddedTemplate))
+
 type BlockchainLoggingObserver struct{}
 
 func (blockchainObserver BlockchainLoggingObserver) NotifyBlockAdded(block core.Block) {
-	fmt.Printf("New block was added: %d\n"+
-		"\tTime: %v\n"+
-		"\tGas Limit: %d\n"+
-		"\tGas Used: %d\n"+
-		"\tNumber of Transactions %d\n", block.Number, time.Unix(block.Time, 0), block.GasLimit, block.GasUsed, len(block.Transactions))
+	tmp.Execute(os.Stdout, block)
 }