Add support for multiple executor backends. Create Executor interface and allow executors to register themselves with the application. Update README (Todo list).

common/executors.go

@@ -0,0 +1,40 @@
+package common
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/munnerz/plex-elastic-transcoder/executors"
+
+	log "github.com/Sirupsen/logrus"
+)
+
+type ExecutorFactory struct {
+	Create        func(executors.Job) executors.Executor
+}
+
+var executorFactories map[string]ExecutorFactory
+
+func CreateExecutor(j executors.Job) executors.Executor {
+	// TODO: Some sort of executor selection algorithm
+	for _, e := range executorFactories {
+		// TODO: Here, run the create command defined in the factory
+		return e.Create(j)
+		// Hacky way to dispatch to the first executor
+	}
+	panic("No executors registered!")
+}
+
+func RegisterExecutor(name string, e ExecutorFactory) error {
+	if executorFactories == nil {
+		executorFactories = make(map[string]ExecutorFactory)
+	}
+
+	if _, ok := executorFactories[name]; ok {
+		return errors.New(fmt.Sprintf("Executor already registered: %s", name))
+	}
+
+	log.Print("Registered executor: ", name)
+	executorFactories[name] = e
+	return nil
+}