internal/commentfix: create an action to execute

First of a few CLs to refactor the commentfix package to separate
creating actions from executing them.

This moves the logic of what to do for an event (or whether to do
anything) into a separate method.

For #9.

Change-Id: I909b03f1e009437d4aab090821dea7edaaf8cbe4
Reviewed-on: https://go-review.googlesource.com/c/oscar/+/612895
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Zvonimir Pavlinovic <[email protected]>

internal/commentfix/fix.go

@@ -255,6 +255,12 @@ func (f *Fixer) ReplaceURL(pattern, repl string) error {
 	return nil
 }
 
+// An action has all the information needed to edit a GitHub issue or comment.
+type action struct {
+	ic   *issueOrComment
+	body string // new body of issue or comment
+}
+
 // Run applies the configured rewrites to issue texts and comments on GitHub
 // that have been updated since the last call to Run for this fixer with edits enabled
 // (including in different program invocations using the same fixer name).
@@ -296,34 +302,12 @@ func (f *Fixer) Run(ctx context.Context) error {
 		}
 		last = e.DBTime
 
-		if !f.projects[e.Project] {
-			continue
-		}
-		var ic *issueOrComment
-		switch x := e.Typed.(type) {
-		default: // for example, *github.IssueEvent
-			f.slog.Info("fixer skip", "dbtime", e.DBTime, "type", reflect.TypeOf(e.Typed).String())
-			continue
-		case *github.Issue:
-			if x.PullRequest != nil {
-				// Do not edit pull request bodies,
-				// because they turn into commit messages
-				// and cannot contain things like hyperlinks.
-				continue
-			}
-			ic = &issueOrComment{issue: x}
-			f.slog.Info("fixer run issue", "dbtime", e.DBTime, "issue", ic.issue.Number)
-		case *github.IssueComment:
-			ic = &issueOrComment{comment: x}
-			f.slog.Info("fixer run comment", "dbtime", e.DBTime, "url", ic.comment.URL)
-		}
-		if tm, err := time.Parse(time.RFC3339, ic.updatedAt()); err == nil && tm.Before(f.timeLimit) {
-			continue
-		}
-		body, updated := f.Fix(ic.body())
-		if !updated {
+		a := f.newAction(e)
+		if a == nil {
 			continue
 		}
+		ic := a.ic
+		body := a.body
 		live, err := ic.download(ctx, f.github)
 		if err != nil {
 			// unreachable unless github error
@@ -367,6 +351,40 @@ func (f *Fixer) Run(ctx context.Context) error {
 	return nil
 }
 
+// newAction returns an newAction to take on the issue or comment of the event,
+// or nil if there is nothing to do.
+func (f *Fixer) newAction(e *github.Event) *action {
+	if !f.projects[e.Project] {
+		return nil
+	}
+	var ic *issueOrComment
+	switch x := e.Typed.(type) {
+	default: // for example, *github.IssueEvent
+		f.slog.Info("fixer skip", "dbtime", e.DBTime, "type", reflect.TypeOf(e.Typed).String())
+		return nil
+	case *github.Issue:
+		if x.PullRequest != nil {
+			// Do not edit pull request bodies,
+			// because they turn into commit messages
+			// and cannot contain things like hyperlinks.
+			return nil
+		}
+		ic = &issueOrComment{issue: x}
+		f.slog.Info("fixer run issue", "dbtime", e.DBTime, "issue", ic.issue.Number)
+	case *github.IssueComment:
+		ic = &issueOrComment{comment: x}
+		f.slog.Info("fixer run comment", "dbtime", e.DBTime, "url", ic.comment.URL)
+	}
+	if tm, err := time.Parse(time.RFC3339, ic.updatedAt()); err == nil && tm.Before(f.timeLimit) {
+		return nil
+	}
+	body, updated := f.Fix(ic.body())
+	if !updated {
+		return nil
+	}
+	return &action{ic: ic, body: body}
+}
+
 // Latest returns the latest known DBTime marked old by the Fixer's Watcher.
 func (f *Fixer) Latest() timed.DBTime {
 	return f.watcher.Latest()