1 files changed, 96 insertions, 0 deletions
diff --git a/srv/src/post/renderer.go b/srv/src/post/renderer.go
new file mode 100644
index 0000000..74acc25
--- /dev/null
+++ b/srv/src/post/renderer.go
@@ -0,0 +1,96 @@
+package post
+
+import (
+	_ "embed"
+	"fmt"
+	"html/template"
+	"io"
+
+	"github.com/gomarkdown/markdown"
+	"github.com/gomarkdown/markdown/html"
+	"github.com/gomarkdown/markdown/parser"
+	"github.com/mediocregopher/blog.mediocregopher.com/srv/tpl"
+)
+
+// RenderablePost is a Post wrapped with extra information necessary for
+// rendering.
+type RenderablePost struct {
+	StoredPost
+	SeriesPrevious, SeriesNext *StoredPost
+}
+
+// NewRenderablePost wraps an existing Post such that it can be rendered.
+func NewRenderablePost(store Store, post StoredPost) (RenderablePost, error) {
+
+	renderablePost := RenderablePost{
+		StoredPost: post,
+	}
+
+	if post.Series != "" {
+
+		seriesPosts, err := store.GetBySeries(post.Series)
+		if err != nil {
+			return RenderablePost{}, fmt.Errorf(
+				"fetching posts for series %q: %w",
+				post.Series, err,
+			)
+		}
+
+		var foundThis bool
+
+		for i := range seriesPosts {
+
+			seriesPost := seriesPosts[i]
+
+			if seriesPost.ID == post.ID {
+				foundThis = true
+				continue
+			}
+
+			if !foundThis {
+				renderablePost.SeriesPrevious = &seriesPost
+				continue
+			}
+
+			renderablePost.SeriesNext = &seriesPost
+			break
+		}
+	}
+
+	return renderablePost, nil
+}
+
+// Renderer takes a Post and renders it to some encoding.
+type Renderer interface {
+	Render(io.Writer, RenderablePost) error
+}
+
+func mdBodyToHTML(body []byte) []byte {
+	parserExt := parser.CommonExtensions | parser.AutoHeadingIDs
+	parser := parser.NewWithExtensions(parserExt)
+
+	htmlFlags := html.CommonFlags | html.HrefTargetBlank
+	htmlRenderer := html.NewRenderer(html.RendererOptions{Flags: htmlFlags})
+
+	return markdown.ToHTML(body, parser, htmlRenderer)
+}
+
+type mdHTMLRenderer struct{}
+
+// NewMarkdownToHTMLRenderer renders Posts from markdown to HTML.
+func NewMarkdownToHTMLRenderer() Renderer {
+	return mdHTMLRenderer{}
+}
+
+func (r mdHTMLRenderer) Render(into io.Writer, post RenderablePost) error {
+
+	data := struct {
+		RenderablePost
+		Body template.HTML
+	}{
+		RenderablePost: post,
+		Body:           template.HTML(mdBodyToHTML([]byte(post.Body))),
+	}
+
+	return tpl.HTML.ExecuteTemplate(into, "post.html", data)
+}