3 files changed, 96 insertions, 59 deletions

diff --git a/README.md b/README.md
index df1417d..e2dbd71 100644
--- a/README.md
+++ b/README.md
@@ -163,28 +163,43 @@ Payload {
 - first (gets first N posts)
 - last (gets last N posts)
 - random (gets random N posts)
+- filterbytype (get just the posts with specific type)
 
 ```html
 <!-- First 10 pages -->
-{{ range first 10 .Pages }}
+{{ range .Pages | first 10 }}
   {{ if and (eq .Type "post") (not .Draft) }}
     <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
   {{ end }}
 {{ end }}
 
 <!-- Last 10 pages -->
-{{ range last 10 .Pages }}
+{{ range .Pages | last 10 }}
   {{ if and (eq .Type "post") (not .Draft) }}
     <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
   {{ end }}
 {{ end }}
 
 <!-- Random 10 pages -->
-{{ range random 10 .Pages }}
+{{ range .Pages | random 10 }}
   {{ if and (eq .Type "post") (not .Draft) }}
     <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
   {{ end }}
 {{ end }}
+
+<!-- Filter by type -->
+{{ range .Pages | filterbytype "post" }}
+  {{ if not .Draft }}
+    <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
+  {{ end }}
+{{ end }}
+
+<!-- Chain multiple together -->
+{{ range .Pages | filterbytype "post" | random 20 | first 5 }}
+  {{ if not .Draft }}
+    <li><a href="{{ .RelPermalink }}">{{ .Title }}</a></li>
+  {{ end }}
+{{ end }}
 ```
 
 ## Additional material
diff --git a/filters.go b/filters.go
new file mode 100644
index 0000000..bb57599
--- /dev/null
+++ b/filters.go
@@ -0,0 +1,69 @@
+package main
+
+import (
+        "math/rand"
+        "reflect"
+        "time"
+)
+
+// 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()
+}
+
+// filterByType filters pages by their type.
+func filterByType(pageType string, pages interface{}) interface{} {
+        v := reflect.ValueOf(pages)
+        if v.Kind() != reflect.Slice {
+                panic("filterByType: not a slice")
+        }
+
+        var filtered []interface{}
+        for i := 0; i < v.Len(); i++ {
+                page := v.Index(i).Interface().(Page)
+                if page.Type == pageType {
+                        filtered = append(filtered, page)
+                }
+        }
+        return filtered
+}
+
diff --git a/main.go b/main.go
index 2824041..9871d1c 100644
--- a/main.go
+++ b/main.go
@@ -5,12 +5,10 @@ import (
         "fmt"
         "html/template"
         "log"
-        "math/rand"
         "net/http"
         "os"
         "path"
         "path/filepath"
-        "reflect"
         "sort"
         "strings"
         "time"
@@ -89,50 +87,6 @@ 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()
@@ -318,6 +272,13 @@ func buildProject(projectRoot string) {
                 return
         }
 
+        filters := template.FuncMap{
+                "first":  firstN,
+                "last":   lastN,
+                "random": randomN,
+                "filterbytype": filterByType,
+        }
+
         // Generate HTML files for all pages.
         for _, page := range pages {
                 outFilepath := path.Join(projectRoot, "public", page.Meta["url"].(string))
@@ -330,11 +291,7 @@ func buildProject(projectRoot string) {
                         templates = append([]string{templatePathname}, templates...)
                         templates = append([]string{baseTemplatePathname}, templates...)
 
-                        t, err := template.New("base.html").Funcs(template.FuncMap{
-                                "first":  firstN,
-                                "last":   lastN,
-                                "random": randomN,
-                        }).ParseFiles(templates...)
+                        t, err := template.New("base.html").Funcs(filters).ParseFiles(templates...)
                         if err != nil {
                                 panic(err)
                         }
@@ -385,11 +342,7 @@ func buildProject(projectRoot string) {
                 templates = append([]string{templatePathname}, templates...)
                 templates = append([]string{baseTemplatePathname}, templates...)
 
-                t, err := template.New("base.html").Funcs(template.FuncMap{
-                        "first":  firstN,
-                        "last":   lastN,
-                        "random": randomN,
-                }).ParseFiles(templates...)
+                t, err := template.New("base.html").Funcs(filters).ParseFiles(templates...)
                 if err != nil {
                         panic(err)
                 }