feat: explanation as observer too

cmd/lambda/lambda.go

@@ -7,6 +7,7 @@ import (
 	"git.maximhutz.com/max/lambda/internal/cli"
 	"git.maximhutz.com/max/lambda/internal/config"
 	"git.maximhutz.com/max/lambda/internal/executer"
+	"git.maximhutz.com/max/lambda/internal/explanation"
 	"git.maximhutz.com/max/lambda/internal/performance"
 	"git.maximhutz.com/max/lambda/internal/statistics"
 	"git.maximhutz.com/max/lambda/pkg/convert"
@@ -43,20 +44,23 @@ func main() {
 		logger.Info("compiled lambda expression", "tree", lambda.Stringify(compiled))
 	}
 
-	process := executer.New(options)
+	process := executer.New(options, &compiled)
 	if options.Profile != "" {
 		profiler := performance.Track(options.Profile)
 		process.On("start", profiler.Start)
 		process.On("end", profiler.End)
 	}
 
+	if options.Explanation {
+		explanation.Track(process)
+	}
+
 	statistics := statistics.Track()
 	process.On("start", statistics.Start)
 	process.On("step", statistics.Step)
 	process.On("end", statistics.End)
 
-	process.Run(&compiled)
-	cli.HandleError(err)
+	process.Run()
 
 	fmt.Println(lambda.Stringify(compiled))
 	fmt.Fprint(os.Stderr, statistics.Results.String())