1 files changed, 35 insertions, 3 deletions
diff --git a/src/render/methods.go b/src/render/methods.go
index ee22dfd..2b8675b 100644
--- a/src/render/methods.go
+++ b/src/render/methods.go
@@ -5,11 +5,13 @@ import (
 	"context"
 	"fmt"
 	"html/template"
+	"io"
 	"net/url"
 	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
+	txttpl "text/template"
 
 	"dev.mediocregopher.com/mediocre-blog.git/src/gmi/gemtext"
 	"dev.mediocregopher.com/mediocre-blog.git/src/post"
@@ -196,11 +198,41 @@ func (m *Methods) GetPostSeriesNextPrevious(
 	return res, nil
 }
 
-func (m *Methods) PostGemtextBody(p post.StoredPost) (string, error) {
+type preprocessPostPayload struct {
+	RootURL URLBuilder
+	image   func(args ...string) (string, error)
+}
+
+func (p preprocessPostPayload) Image(args ...string) (string, error) {
+	return p.image(args...)
+}
+
+// preprocessPostBody interprets the Post's Body as a text template which may
+// use any of the functions found in PreprocessFunctions (all must be set). It
+// executes the template and writes the result to the given writer.
+func (m *Methods) preprocessPostBody(into io.Writer, p post.Post) error {
+	tpl := txttpl.New("")
+
+	tpl, err := tpl.Parse(p.Body)
+	if err != nil {
+		return fmt.Errorf("parsing post body as template: %w", err)
+	}
+
+	err = tpl.Execute(into, preprocessPostPayload{
+		RootURL: m.RootURL(),
+		image:   m.preprocessFuncs.Image,
+	})
+	if err != nil {
+		return fmt.Errorf("executing post body as template: %w", err)
+	}
 
+	return nil
+}
+
+func (m *Methods) PostGemtextBody(p post.StoredPost) (string, error) {
 	buf := new(bytes.Buffer)
 
-	if err := p.PreprocessBody(buf, m.preprocessFuncs); err != nil {
+	if err := m.preprocessPostBody(buf, p.Post); err != nil {
 		return "", fmt.Errorf("preprocessing post body: %w", err)
 	}
 
@@ -222,7 +254,7 @@ func (m *Methods) PostGemtextBody(p post.StoredPost) (string, error) {
 func (m *Methods) PostHTMLBody(p post.StoredPost) (template.HTML, error) {
 	bodyBuf := new(bytes.Buffer)
 
-	if err := p.PreprocessBody(bodyBuf, m.preprocessFuncs); err != nil {
+	if err := m.preprocessPostBody(bodyBuf, p.Post); err != nil {
 		return "", fmt.Errorf("preprocessing post body: %w", err)
 	}