Filter random added.

Random returns a random item out of the input slice.

filters.go

@@ -3,6 +3,7 @@ package pongo2addons
 import (
 	"bytes"
 	"fmt"
+	"math/rand"
 	"regexp"
 	"strings"
 	"time"
@@ -22,6 +23,7 @@ func init() {
 	pongo2.RegisterFilter("filesizeformat", filterFilesizeformat)
 	pongo2.RegisterFilter("truncatesentences", filterTruncatesentences)
 	pongo2.RegisterFilter("truncatesentences_html", filterTruncatesentencesHTML)
+	pongo2.RegisterFilter("random", filterRandom)
 
 	// Markup
 	pongo2.RegisterFilter("markdown", filterMarkdown)
@@ -218,6 +220,24 @@ func filterTruncatesentencesHTML(in *pongo2.Value, param *pongo2.Value) (*pongo2
 	return pongo2.AsSafeValue(newOutput.String()), nil
 }
 
+func filterRandom(in *pongo2.Value, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
+	if !in.CanSlice() {
+		return nil, &pongo2.Error {
+			Sender: "filter:random",
+			OrigError: error.New("input is not sliceable"),
+		}
+	}
+	
+	if in.Len() <= 0 {
+		return nil, &pongo2.Error {
+			Sender: "filter:random",
+			OrigError: error.New("input slice is empty"),
+		}	
+	}
+	
+	return in.Index(rand.Intn(in.Len())), nil
+}
+
 func filterTimeuntilTimesince(in *pongo2.Value, param *pongo2.Value) (*pongo2.Value, *pongo2.Error) {
 	basetime, isTime := in.Interface().(time.Time)
 	if !isTime {