commit b832bd2ec001f9a8ddb38d94ad518f7484faf6c1
Author: Nhân <hi@imnhan.com>
Date:   Mon Aug 21 23:54:41 2023 +0700

    og:image must be full url apparently
    
    Discord preview wouldn't work otherwise.

diff --git a/docs/_s4g/theme/base.tmpl b/docs/_s4g/theme/base.tmpl
index f27d1ad..710d06d 100644
--- a/docs/_s4g/theme/base.tmpl
+++ b/docs/_s4g/theme/base.tmpl
@@ -15,12 +15,12 @@
     <meta property="og:description" content="{{.Post.Description}}" />
     <meta name="twitter:description" content="{{.Post.Description}}" />
   {{- end -}}
-  {{- if .Post.Thumb -}}
-    <meta property="og:image" content="{{.Post.Thumb}}" />
-    <meta name="twitter:image" content="{{.Post.Thumb}}" />
+  {{- if .Post.OpenGraphImage -}}
+    <meta property="og:image" content="{{.Post.OpenGraphImage}}" />
+    <meta name="twitter:image" content="{{.Post.OpenGraphImage}}" />
   {{- else if .Site.DefaultThumb -}}
-    <meta property="og:image" content="{{.Site.Root}}{{.Site.DefaultThumb}}" />
-    <meta name="twitter:image" content="{{.Site.Root}}{{.Site.DefaultThumb}}" />
+    <meta property="og:image" content="{{.Site.Address}}{{.Site.Root}}{{.Site.DefaultThumb}}" />
+    <meta name="twitter:image" content="{{.Site.Address}}{{.Site.Root}}{{.Site.DefaultThumb}}" />
   {{- end }}
   {{- if .Site.AuthorTwitter -}}
     <meta name="twitter:site" content="{{.Site.AuthorTwitter}}" />
diff --git a/main.go b/main.go
index 1209e75..17c4b12 100644
--- a/main.go
+++ b/main.go
@@ -261,13 +261,17 @@ type Article struct {
 	OutputPath string
 	DjotBody   []byte
 	ArticleMetadata
-	WebPath       string
-	TemplatePaths []string
+	WebPath        string
+	TemplatePaths  []string
+	OpenGraphImage string
 }
 
-func (a *Article) ComputeDerivedFields(root string) {
+func (a *Article) ComputeDerivedFields(addr, root string) {
 	a.WebPath = computeWebPath(root, a.OutputPath)
 	a.TemplatePaths = computeTemplatePaths(a.Path, a.Templates)
+	if a.Thumb != "" {
+		a.OpenGraphImage = addr + root + filepath.Dir(a.Path) + "/" + a.Thumb
+	}
 }
 
 func computeWebPath(root string, outputPath string) string {
@@ -393,7 +397,7 @@ func findArticles(fsys writablefs.FS, site *SiteMetadata) (map[string]Article, e
 			DjotBody:        bodyText,
 			ArticleMetadata: meta,
 		}
-		article.ComputeDerivedFields(site.Root)
+		article.ComputeDerivedFields(site.Address, site.Root)
 		result[article.Path] = article
 		return nil
 	})
diff --git a/theme/base.tmpl b/theme/base.tmpl
index f27d1ad..710d06d 100644
--- a/theme/base.tmpl
+++ b/theme/base.tmpl
@@ -15,12 +15,12 @@
     <meta property="og:description" content="{{.Post.Description}}" />
     <meta name="twitter:description" content="{{.Post.Description}}" />
   {{- end -}}
-  {{- if .Post.Thumb -}}
-    <meta property="og:image" content="{{.Post.Thumb}}" />
-    <meta name="twitter:image" content="{{.Post.Thumb}}" />
+  {{- if .Post.OpenGraphImage -}}
+    <meta property="og:image" content="{{.Post.OpenGraphImage}}" />
+    <meta name="twitter:image" content="{{.Post.OpenGraphImage}}" />
   {{- else if .Site.DefaultThumb -}}
-    <meta property="og:image" content="{{.Site.Root}}{{.Site.DefaultThumb}}" />
-    <meta name="twitter:image" content="{{.Site.Root}}{{.Site.DefaultThumb}}" />
+    <meta property="og:image" content="{{.Site.Address}}{{.Site.Root}}{{.Site.DefaultThumb}}" />
+    <meta name="twitter:image" content="{{.Site.Address}}{{.Site.Root}}{{.Site.DefaultThumb}}" />
   {{- end }}
   {{- if .Site.AuthorTwitter -}}
     <meta name="twitter:site" content="{{.Site.AuthorTwitter}}" />