Handle events

- Adds interfaces for developers to build handlers that update data in
response to log events
- Resolves #29

libraries/shared/watcher_test.go

@@ -0,0 +1,69 @@
+package shared_test
+
+import (
+	"errors"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"github.com/vulcanize/vulcanizedb/libraries/shared"
+	"github.com/vulcanize/vulcanizedb/pkg/core"
+	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
+)
+
+type MockHandler struct {
+	executeWasCalled bool
+	executeError     error
+}
+
+func (mh *MockHandler) Execute() error {
+	if mh.executeError != nil {
+		return mh.executeError
+	}
+	mh.executeWasCalled = true
+	return nil
+}
+
+func fakeHandlerInitializer(db *postgres.DB, blockchain core.ContractDataFetcher) shared.Handler {
+	return &MockHandler{}
+}
+
+var _ = Describe("Watcher", func() {
+	It("Adds handlers", func() {
+		watcher := shared.Watcher{}
+
+		watcher.AddHandlers([]shared.HandlerInitializer{fakeHandlerInitializer})
+
+		Expect(len(watcher.Handlers)).To(Equal(1))
+		Expect(watcher.Handlers).To(ConsistOf(&MockHandler{}))
+	})
+
+	It("Adds handlers from multiple sources", func() {
+		watcher := shared.Watcher{}
+
+		watcher.AddHandlers([]shared.HandlerInitializer{fakeHandlerInitializer})
+		watcher.AddHandlers([]shared.HandlerInitializer{fakeHandlerInitializer})
+
+		Expect(len(watcher.Handlers)).To(Equal(2))
+	})
+
+	It("Executes each handler", func() {
+		watcher := shared.Watcher{}
+		fakeHandler := &MockHandler{}
+		watcher.Handlers = []shared.Handler{fakeHandler}
+
+		watcher.Execute()
+
+		Expect(fakeHandler.executeWasCalled).To(BeTrue())
+	})
+
+	It("Returns an error if handler returns an error", func() {
+		watcher := shared.Watcher{}
+		fakeHandler := &MockHandler{executeError: errors.New("Something bad happened")}
+		watcher.Handlers = []shared.Handler{fakeHandler}
+
+		err := watcher.Execute()
+
+		Expect(err).To(HaveOccurred())
+		Expect(fakeHandler.executeWasCalled).To(BeFalse())
+	})
+})