3 files changed, 194 insertions, 14 deletions
diff --git a/srv/src/post/post.go b/srv/src/post/post.go
index bdc48af..5835995 100644
--- a/srv/src/post/post.go
+++ b/srv/src/post/post.go
@@ -5,7 +5,6 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
-	"path"
 	"regexp"
 	"strings"
 	"time"
@@ -37,6 +36,12 @@ type Post struct {
 	Body        string
 }
 
+// HTTPPath returns the relative URL path of the StoredPost, when querying it
+// over HTTP.
+func (p Post) HTTPPath() string {
+	return fmt.Sprintf("%s.html", p.ID)
+}
+
 // StoredPost is a Post which has been stored in a Store, and has been given
 // some extra fields as a result.
 type StoredPost struct {
@@ -46,19 +51,6 @@ type StoredPost struct {
 	LastUpdatedAt time.Time
 }
 
-// URL returns the relative URL of the StoredPost.
-func (p StoredPost) URL() string {
-	return path.Join(
-		fmt.Sprintf(
-			"%d/%0d/%0d",
-			p.PublishedAt.Year(),
-			p.PublishedAt.Month(),
-			p.PublishedAt.Day(),
-		),
-		p.ID+".html",
-	)
-}
-
 // Store is used for storing posts to a persistent storage.
 type Store interface {
 
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)
+}
diff --git a/srv/src/post/renderer_test.go b/srv/src/post/renderer_test.go
new file mode 100644
index 0000000..5c01cd2
--- /dev/null
+++ b/srv/src/post/renderer_test.go
@@ -0,0 +1,92 @@
+package post
+
+import (
+	"bytes"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMarkdownBodyToHTML(t *testing.T) {
+
+	tests := []struct {
+		body string
+		exp  string
+	}{
+		{
+			body: `
+# Foo
+`,
+			exp: `<h1 id="foo">Foo</h1>`,
+		},
+		{
+			body: `
+this is a body
+
+this is another
+`,
+			exp: `
+<p>this is a body</p>
+
+<p>this is another</p>`,
+		},
+		{
+			body: `this is a [link](somewhere.html)`,
+			exp:  `<p>this is a <a href="somewhere.html" target="_blank">link</a></p>`,
+		},
+	}
+
+	for i, test := range tests {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+
+			outB := mdBodyToHTML([]byte(test.body))
+			out := string(outB)
+
+			// just to make the tests nicer
+			out = strings.TrimSpace(out)
+			test.exp = strings.TrimSpace(test.exp)
+
+			assert.Equal(t, test.exp, out)
+		})
+	}
+}
+
+func TestMarkdownToHTMLRenderer(t *testing.T) {
+
+	r := NewMarkdownToHTMLRenderer()
+
+	post := RenderablePost{
+		StoredPost: StoredPost{
+			Post: Post{
+				ID:          "foo",
+				Title:       "Foo",
+				Description: "Bar.",
+				Body:        "This is the body.",
+				Series:      "baz",
+			},
+			PublishedAt: time.Now(),
+		},
+
+		SeriesPrevious: &StoredPost{
+			Post: Post{
+				ID:    "foo-prev",
+				Title: "Foo Prev",
+			},
+		},
+
+		SeriesNext: &StoredPost{
+			Post: Post{
+				ID:    "foo-next",
+				Title: "Foo Next",
+			},
+		},
+	}
+
+	buf := new(bytes.Buffer)
+	err := r.Render(buf, post)
+	assert.NoError(t, err)
+	t.Log(buf.String())
+}