hswg: try to order entries by date, reverse order

hswg/main.go

@@ -138,6 +138,19 @@ type Entry struct {
 	backlinks       []string  // what documents link back here
 }
 
+// Published returns the date when the entry was published, or nil if unknown.
+func (e *Entry) Published() *time.Time {
+	if d, ok := e.Metadata.Attributes.GetAsString("date"); !ok {
+		return nil
+	} else if t, err := time.Parse(time.RFC3339, d); err == nil {
+		return &t
+	} else if t, err := time.Parse("2006-01-02", d); err == nil {
+		return &t
+	} else {
+		return nil
+	}
+}
+
 var extRE = regexp.MustCompile(`\.[^/.]*$`)
 
 func stripExtension(path string) string {
@@ -286,6 +299,30 @@ func main() {
 			e.Metadata.LastUpdated, e.PathSource))
 	}
 
+	// Reorder entries reversely, primarily by date, secondarily by filename.
+	ordered := []*Entry{}
+	for _, e := range entries {
+		ordered = append(ordered, e)
+	}
+
+	sort.Slice(ordered, func(i, j int) bool {
+		a, b := ordered[i], ordered[j]
+		p1, p2 := a.Published(), b.Published()
+		if p1 == nil && p2 != nil {
+			return true
+		}
+		if p1 == nil && p2 == nil {
+			return a.PathSource > b.PathSource
+		}
+		if p2 == nil {
+			return false
+		}
+		if p1.Equal(*p2) {
+			return a.PathSource > b.PathSource
+		}
+		return p2.Before(*p1)
+	})
+
 	// Execute a template from the standard input.
 	var input []byte
 	if input, err = ioutil.ReadAll(os.Stdin); err != nil {
@@ -294,7 +331,7 @@ func main() {
 
 	// TODO(p): Splitting content to categories would be nice.
 	t, err := template.New("-").Parse(string(input))
-	if err = t.Execute(os.Stdout, entries); err != nil {
+	if err = t.Execute(os.Stdout, ordered); err != nil {
 		log.Fatalln(err)
 	}
 }