fixes for review comments

libraries/shared/watcher/contract_watcher.go

@@ -0,0 +1,77 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// Contract watcher is built with a more generic interface
+// that allows offloading more of the operational logic to
+// the transformers, allowing them to act more dynamically
+// Built to work primarily with the contract_watcher packaging
+package watcher
+
+import (
+	"fmt"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
+	"github.com/vulcanize/vulcanizedb/pkg/core"
+	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
+)
+
+type ContractWatcher struct {
+	Transformers []transformer.ContractTransformer
+	DB           *postgres.DB
+	BlockChain   core.BlockChain
+}
+
+func NewContractWatcher(db *postgres.DB, bc core.BlockChain) ContractWatcher {
+	return ContractWatcher{
+		DB:         db,
+		BlockChain: bc,
+	}
+}
+
+func (watcher *ContractWatcher) AddTransformers(inits interface{}) error {
+	initializers, ok := inits.([]transformer.ContractTransformerInitializer)
+	if !ok {
+		return fmt.Errorf("initializers of type %T, not %T", inits, []transformer.ContractTransformerInitializer{})
+	}
+
+	watcher.Transformers = make([]transformer.ContractTransformer, 0, len(initializers))
+	for _, initializer := range initializers {
+		t := initializer(watcher.DB, watcher.BlockChain)
+		watcher.Transformers = append(watcher.Transformers, t)
+	}
+
+	for _, transformer := range watcher.Transformers {
+		err := transformer.Init()
+		if err != nil {
+			log.Print("Unable to initialize transformer:", transformer.GetConfig().Name, err)
+			return err
+		}
+	}
+	return nil
+}
+
+func (watcher *ContractWatcher) Execute(interface{}) error {
+	for _, transformer := range watcher.Transformers {
+		err := transformer.Execute()
+		if err != nil {
+			log.Error("Unable to execute transformer:", transformer.GetConfig().Name, err)
+			return err
+		}
+	}
+	return nil
+}