Added first, last, random filters

2 files changed, 85 insertions, 2 deletions

diff --git a/README.md b/README.md
index 773f233..a04c9de 100644
--- a/README.md
+++ b/README.md
@@ -158,6 +158,35 @@ Payload {
 })
 ```
 
+## Special filters
+
+- first (gets first N posts)
+- last (gets last N posts)
+- random (gets random N posts)
+
+```html
+<!-- First 10 pages -->
+{{ range first 10 .Pages }}
+  {{ if and (eq .Type "post") (not .Draft) }}
+    <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
+  {{ end }}
+{{ end }}
+
+<!-- Last 10 pages -->
+{{ range last 10 .Pages }}
+  {{ if and (eq .Type "post") (not .Draft) }}
+    <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
+  {{ end }}
+{{ end }}
+
+<!-- Random 10 pages -->
+{{ range random 10 .Pages }}
+  {{ if and (eq .Type "post") (not .Draft) }}
+    <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
+  {{ end }}
+{{ end }}
+```
+
 ## License
 
 [jbmafp](https://github.com/mitjafelicijan/jbmafp) was written by [Mitja
diff --git a/main.go b/main.go
index 8440286..2824041 100644
--- a/main.go
+++ b/main.go
@@ -5,10 +5,12 @@ import (
 	"fmt"
 	"html/template"
 	"log"
+	"math/rand"
 	"net/http"
 	"os"
 	"path"
 	"path/filepath"
+	"reflect"
 	"sort"
 	"strings"
 	"time"
@@ -87,6 +89,50 @@ var EmbedTemplatePost string
 //go:embed "files/index.xml"
 var EmbedTemplateFeed string
 
+// firstN returns the first n items of a slice.
+func firstN(n int, items interface{}) interface{} {
+	v := reflect.ValueOf(items)
+	if v.Kind() != reflect.Slice {
+		panic("firstN: not a slice")
+	}
+	if v.Len() < n {
+		return items
+	}
+	return v.Slice(0, n).Interface()
+}
+
+// lastN returns the last n items of any slice.
+func lastN(n int, items interface{}) interface{} {
+	v := reflect.ValueOf(items)
+	if v.Kind() != reflect.Slice {
+		panic("lastN: not a slice")
+	}
+	l := v.Len()
+	if l < n {
+		return items
+	}
+	return v.Slice(l-n, l).Interface()
+}
+
+// randomN returns n random items of any slice.
+func randomN(n int, items interface{}) interface{} {
+	v := reflect.ValueOf(items)
+	if v.Kind() != reflect.Slice {
+		panic("randomN: not a slice")
+	}
+	l := v.Len()
+	if l < n {
+		return items
+	}
+	rand.Seed(time.Now().UnixNano())
+	indices := rand.Perm(l)[:n]
+	result := reflect.MakeSlice(v.Type(), n, n)
+	for i, idx := range indices {
+		result.Index(i).Set(v.Index(idx))
+	}
+	return result.Interface()
+}
+
 // Function to clean HTML tags using bluemonday.
 func cleanHTMLTags(htmlString string) string {
 	p := bluemonday.StrictPolicy()
@@ -284,7 +330,11 @@ func buildProject(projectRoot string) {
 			templates = append([]string{templatePathname}, templates...)
 			templates = append([]string{baseTemplatePathname}, templates...)
 
-			t, err := template.ParseFiles(templates...)
+			t, err := template.New("base.html").Funcs(template.FuncMap{
+				"first":  firstN,
+				"last":   lastN,
+				"random": randomN,
+			}).ParseFiles(templates...)
 			if err != nil {
 				panic(err)
 			}
@@ -335,7 +385,11 @@ func buildProject(projectRoot string) {
 		templates = append([]string{templatePathname}, templates...)
 		templates = append([]string{baseTemplatePathname}, templates...)
 
-		t, err := template.ParseFiles(templates...)
+		t, err := template.New("base.html").Funcs(template.FuncMap{
+			"first":  firstN,
+			"last":   lastN,
+			"random": randomN,
+		}).ParseFiles(templates...)
 		if err != nil {
 			panic(err)
 		}