indexer: support data exporting/forwarding (#103)

To support more effective and flexible blockchain info exploring, we add
`indexer` package, defines the flow of indexer dameon, and integrate
into dex.Dexon fullnode.

For more export options, we use Golang built-in `plugin` package to
support mulitple implementations.

1 files changed, 35 insertions, 0 deletions

diff --git a/indexer/config.go b/indexer/config.go
new file mode 100644
index 000000000..3b626272a
--- /dev/null
+++ b/indexer/config.go
@@ -0,0 +1,35 @@
+package indexer
+
+import (
+	"plugin"
+)
+
+// Config is data sources related configs struct.
+type Config struct {
+	// Used by dex/backend init flow.
+	Enable bool
+
+	// Plugin path for building components.
+	Plugin string
+}
+
+// NewIndexerFromConfig initialize exporter according to given config.
+func NewIndexerFromConfig(bc ReadOnlyBlockChain, c Config) (idx Indexer) {
+	if c.Plugin == "" {
+		// default
+		return
+	}
+
+	plug, err := plugin.Open(c.Plugin)
+	if err != nil {
+		panic(err)
+	}
+
+	symbol, err := plug.Lookup(NewIndexerFuncName)
+	if err != nil {
+		panic(err)
+	}
+
+	idx = symbol.(NewIndexerFunc)(bc, c)
+	return
+}