Merge pull request #5 from tucnak/patch-1

Filter random for slices

README.md

@@ -3,7 +3,7 @@
 [![Build Status](https://travis-ci.org/flosch/pongo2-addons.svg?branch=master)](https://travis-ci.org/flosch/pongo2-addons)
 [![Gratipay](http://img.shields.io/badge/gratipay-support%20pongo-brightgreen.svg)](https://gratipay.com/flosch/)
 
-Official filter and tag add-ons for [pongo2](https://github.com/flosch/pongo2). Since this package uses 
+Official filter and tag add-ons for [pongo2](https://github.com/flosch/pongo2). Since this package uses
 3rd-party-libraries, it's in its own package.
 
 ## How to install and use
@@ -24,10 +24,11 @@ All additional filters/tags will be registered automatically.
      - **[filesizeformat](https://docs.djangoproject.com/en/dev/ref/templates/builtins/#filesizeformat)** (human-readable filesize; takes bytes as input)
      - **[slugify](https://docs.djangoproject.com/en/dev/ref/templates/builtins/#slugify)** (creates a slug for a given input)
      - **truncatesentences** / **truncatesentences_html** (returns the first X sentences [like truncatechars/truncatewords]; please provide X as a parameter)
+     - **random** (returns a random element of the input slice)
 
   - Markup
      - **markdown**
-  
+
   - Humanize
      - **[intcomma](https://docs.djangoproject.com/en/dev/ref/contrib/humanize/#intcomma)** (put decimal marks into the number)
      - **[ordinal](https://docs.djangoproject.com/en/dev/ref/contrib/humanize/#ordinal)** (convert integer to its ordinal as string)

filters.go

@@ -3,6 +3,7 @@ package pongo2addons
 import (
 	"bytes"
 	"fmt"
+	"math/rand"
 	"regexp"
 	"strings"
 	"time"
@@ -17,11 +18,14 @@ import (
 )
 
 func init() {
+	rand.Seed(time.Now().UTC().UnixNano())
+
 	// Regulars
 	pongo2.RegisterFilter("slugify", filterSlugify)
 	pongo2.RegisterFilter("filesizeformat", filterFilesizeformat)
 	pongo2.RegisterFilter("truncatesentences", filterTruncatesentences)
 	pongo2.RegisterFilter("truncatesentences_html", filterTruncatesentencesHTML)
+	pongo2.RegisterFilter("random", filterRandom)
 
 	// Markup
 	pongo2.RegisterFilter("markdown", filterMarkdown)
@@ -218,6 +222,24 @@ 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: errors.New("input is not sliceable"),
+		}
+	}
+
+	if in.Len() <= 0 {
+		return nil, &pongo2.Error{
+			Sender:    "filter:random",
+			OrigError: errors.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 {

filters_test.go

@@ -89,4 +89,10 @@ func (s *TestSuite1) TestFilters(c *C) {
 	c.Assert(getResult("{{ text|truncatesentences_html:3 }}", pongo2.Context{
 		"text": `<div class="test"><ul><li>This is a first sentence with a 4.50 number.</li><li>The second one is even more fun! Isn't it?</li><li>Last sentence, okay.</li></ul></div>`}),
 		Equals, `<div class="test"><ul><li>This is a first sentence with a 4.50 number.</li><li>The second one is even more fun! Isn't it?</li></ul></div>`)
+
+	// Random
+	c.Assert(getResult("{{ array|random }}",
+		pongo2.Context{"array": []int{42}}),
+		Equals, "42")
+
 }