Implement preprocessing of post bodies for gemini

src/gmi/gmi.go

@@ -119,6 +119,21 @@ func (a *api) Shutdown(ctx context.Context) error {
 	return a.srv.Shutdown(ctx)
 }
 
+func indexMiddleware(h gemini.Handler) gemini.Handler {
+
+	return gemini.HandlerFunc(func(
+		ctx context.Context,
+		rw gemini.ResponseWriter,
+		r *gemini.Request,
+	) {
+		if strings.HasSuffix(r.URL.Path, "/") {
+			r.URL.Path += "index.gmi"
+		}
+
+		h.ServeGemini(ctx, rw, r)
+	})
+}
+
 func postsMiddleware(tplHandler gemini.Handler) gemini.Handler {
 
 	return gemini.HandlerFunc(func(
@@ -156,7 +171,10 @@ func (a *api) handler() (gemini.Handler, error) {
 	mux.Handle("/posts/", postsMiddleware(tplHandler))
 	mux.Handle("/", tplHandler)
 
-	h := mux
+	var h gemini.Handler
+
+	h = mux
+	h = indexMiddleware(h)
 
 	// TODO logging
 	// TODO caching

src/gmi/tpl.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"io/fs"
 	"net/url"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"text/template"
@@ -25,6 +26,11 @@ type rendererGetPostsRes struct {
 	HasMore bool
 }
 
+type rendererGetPostSeriesNextPreviousRes struct {
+	Next     *post.StoredPost
+	Previous *post.StoredPost
+}
+
 type renderer struct {
 	url       *url.URL
 	postStore post.Store
@@ -43,6 +49,80 @@ func (r renderer) GetPostByID(id string) (post.StoredPost, error) {
 	return p, nil
 }
 
+func (r renderer) GetPostSeriesNextPrevious(p post.StoredPost) (rendererGetPostSeriesNextPreviousRes, error) {
+
+	seriesPosts, err := r.postStore.GetBySeries(p.Series)
+	if err != nil {
+		return rendererGetPostSeriesNextPreviousRes{}, fmt.Errorf(
+			"fetching posts for series %q: %w", p.Series, err,
+		)
+	}
+
+	var (
+		res       rendererGetPostSeriesNextPreviousRes
+		foundThis bool
+	)
+
+	for i := range seriesPosts {
+
+		seriesPost := seriesPosts[i]
+
+		if seriesPost.ID == p.ID {
+			foundThis = true
+			continue
+		}
+
+		if !foundThis {
+			res.Next = &seriesPost
+			continue
+		}
+
+		res.Previous = &seriesPost
+		break
+	}
+
+	return res, nil
+}
+
+func (r renderer) PostBody(p post.StoredPost) (string, error) {
+
+	preprocessFuncs := post.PreprocessFunctions{
+		BlogURL: func(path string) string {
+			return filepath.Join("/", path)
+		},
+		AssetURL: func(id string) string {
+			return filepath.Join("/assets", id)
+		},
+		PostURL: func(id string) string {
+			return filepath.Join("/posts", id)
+		},
+		StaticURL: func(path string) string {
+			return filepath.Join("/static", path)
+		},
+		Image: func(args ...string) (string, error) {
+
+			var (
+				id    = args[0]
+				descr = "Image"
+			)
+
+			if len(args) > 1 {
+				descr = args[1]
+			}
+
+			return fmt.Sprintf("=> %s %s", filepath.Join("/assets", id), descr), nil
+		},
+	}
+
+	buf := new(bytes.Buffer)
+
+	if err := p.PreprocessBody(buf, preprocessFuncs); err != nil {
+		return "", fmt.Errorf("preprocessing post body: %w", err)
+	}
+
+	return buf.String(), nil
+}
+
 func (r renderer) GetQueryValue(key, def string) string {
 	v := r.url.Query().Get(key)
 	if v == "" {
@@ -97,10 +177,6 @@ func (a *api) tplHandler() (gemini.Handler, error) {
 		r *gemini.Request,
 	) {
 
-		if strings.HasSuffix(r.URL.Path, "/") {
-			r.URL.Path += "index.gmi"
-		}
-
 		tplPath := strings.TrimPrefix(r.URL.Path, "/")
 
 		ctx = mctx.Annotate(ctx,

src/gmi/tpl/index.gmi

@@ -1,3 +1,3 @@
-# Index
+# mediocregopher's lil web corner
 
-=> /posts/index.gmi See all posts
+=> /posts/ See all posts

src/gmi/tpl/posts/index.gmi

@@ -1,10 +1,10 @@
 # mediocregopher's Posts
 
 {{ $page := .GetQueryIntValue "page" 0 -}}
-{{ $getPostsRes := .GetPosts $page 20 -}}
+{{ $getPostsRes := .GetPosts $page 15 -}}
 
 {{ if gt $page 0 -}}
-=> /posts.gmi?page={{ .Add $page -1 }} Previous Page
+=> /posts/?page={{ .Add $page -1 }} Previous Page
 
 {{ end -}}
 
@@ -14,5 +14,8 @@
 {{ end -}}
 
 {{ if $getPostsRes.HasMore -}}
-=> /posts.gmi?page={{ .Add $page 1 }} Next page
-{{ end -}}
+=> /posts/?page={{ .Add $page 1 }} Next page
+{{ end }}
+================================================================================
+
+=> / Home

src/gmi/tpl/posts/post.gmi

@@ -6,4 +6,28 @@
 > {{ $post.Description }}
 {{ end -}}
 
-{{ $post.Body }}
+{{ .PostBody $post }}
+
+--------------------------------------------------------------------------------
+
+Published {{ $post.PublishedAt.Format "2006-01-02" }}
+
+{{- if $post.Series }}
+
+This post is part of a series!
+
+{{ $seriesNextPrev := .GetPostSeriesNextPrevious $post -}}
+
+{{ if $seriesNextPrev.Next -}}
+=> /posts/{{ $seriesNextPrev.Next.ID }}.gmi Next: {{ $seriesNextPrev.Next.Title }}
+{{ end -}}
+
+{{ if $seriesNextPrev.Previous -}}
+=> /posts/{{ $seriesNextPrev.Previous.ID }}.gmi Previously: {{ $seriesNextPrev.Previous.Title }}
+{{ end -}}
+
+{{ end }}
+================================================================================
+
+=> /posts/ More posts
+=> /       Home

src/http/posts.go

@@ -21,68 +21,43 @@ import (
 	"github.com/mediocregopher/mediocre-go-lib/v2/mctx"
 )
 
-func (a *api) parsePostBody(p post.Post) (*txttpl.Template, error) {
-	tpl := txttpl.New("root")
-	tpl = tpl.Funcs(txttpl.FuncMap(a.tplFuncs()))
+func (a *api) postPreprocessFuncImage(args ...string) (string, error) {
 
-	tpl = txttpl.Must(tpl.New("image.html").Parse(mustReadTplFile("image.html")))
+	var (
+		id    = args[0]
+		descr = "TODO"
+	)
 
-	if p.Format == post.FormatMarkdown {
-		tpl = tpl.Funcs(txttpl.FuncMap{
-			"Image": func(id string) (string, error) {
-
-				tplPayload := struct {
-					ID        string
-					Descr     string
-					Resizable bool
-				}{
-					ID: id,
-					// I could use variadic args to make this work, I think
-					Descr:     "TODO: proper alt text",
-					Resizable: isImgResizable(id),
-				}
-
-				buf := new(bytes.Buffer)
-				if err := tpl.ExecuteTemplate(buf, "image.html", tplPayload); err != nil {
-					return "", err
-				}
-
-				return buf.String(), nil
-			},
-		})
+	if len(args) > 1 {
+		descr = args[1]
 	}
 
-	if p.Format == post.FormatGemtext {
-		tpl = tpl.Funcs(txttpl.FuncMap{
-			"Image": func(id, descr string) (string, error) {
+	tpl := txttpl.New("image.html")
 
-				tplPayload := struct {
-					ID        string
-					Descr     string
-					Resizable bool
-				}{
-					ID:        id,
-					Descr:     descr,
-					Resizable: isImgResizable(id),
-				}
+	tpl.Funcs(txttpl.FuncMap{
+		"AssetURL": func(id string) string {
+			return a.assetURL(id, false)
+		},
+	})
 
-				buf := new(bytes.Buffer)
-				if err := tpl.ExecuteTemplate(buf, "image.html", tplPayload); err != nil {
-					return "", err
-				}
+	tpl = txttpl.Must(tpl.Parse(mustReadTplFile("image.html")))
 
-				return buf.String(), nil
-			},
-		})
+	tplPayload := struct {
+		ID        string
+		Descr     string
+		Resizable bool
+	}{
+		ID:        id,
+		Descr:     descr,
+		Resizable: isImgResizable(id),
 	}
 
-	tpl, err := tpl.New(p.ID + "-body.html").Parse(p.Body)
-
-	if err != nil {
-		return nil, err
+	buf := new(bytes.Buffer)
+	if err := tpl.ExecuteTemplate(buf, "image.html", tplPayload); err != nil {
+		return "", err
 	}
 
-	return tpl, nil
+	return buf.String(), nil
 }
 
 type postTplPayload struct {
@@ -93,15 +68,27 @@ type postTplPayload struct {
 
 func (a *api) postToPostTplPayload(storedPost post.StoredPost) (postTplPayload, error) {
 
-	bodyTpl, err := a.parsePostBody(storedPost.Post)
-	if err != nil {
-		return postTplPayload{}, fmt.Errorf("parsing post body as template: %w", err)
+	preprocessFuncs := post.PreprocessFunctions{
+		BlogURL: func(path string) string {
+			return a.blogURL(path, false)
+		},
+		AssetURL: func(id string) string {
+			return a.assetURL(id, false)
+		},
+		PostURL: func(id string) string {
+			return a.postURL(id, false)
+		},
+		StaticURL: func(path string) string {
+			path = filepath.Join("static", path)
+			return a.blogURL(path, false)
+		},
+		Image: a.postPreprocessFuncImage,
 	}
 
 	bodyBuf := new(bytes.Buffer)
 
-	if err := bodyTpl.Execute(bodyBuf, nil); err != nil {
-		return postTplPayload{}, fmt.Errorf("executing post body as template: %w", err)
+	if err := storedPost.PreprocessBody(bodyBuf, preprocessFuncs); err != nil {
+		return postTplPayload{}, fmt.Errorf("preprocessing post body: %w", err)
 	}
 
 	if storedPost.Format == post.FormatGemtext {

src/post/preprocess.go

@@ -0,0 +1,66 @@
+package post
+
+import (
+	"fmt"
+	"io"
+	"text/template"
+)
+
+// PreprocessFunctions are functions which can be used by posts themselves to
+// interleave dynamic content into their bodies. Usually this is used for
+// properly constructing URLs, but also for things like displaying images.
+type PreprocessFunctions struct {
+
+	// BlogURL returns the given string, rooted to the blog's base url (which
+	// may or may not include path components itself).
+	//
+	// The given path should not have a leading slash.
+	BlogURL func(path string) string
+
+	// AssetURL returns the URL of the asset with the given ID.
+	AssetURL func(id string) string
+
+	// PostURL returns the URL of the post with the given ID.
+	PostURL func(id string) string
+
+	// StaticURL returns the URL of a file being served from the static
+	// directory. The given path should _not_ include the prefixed 'static/'
+	// path element.
+	StaticURL func(path string) string
+
+	// Image returns a string which should be inlined into the post body in
+	// order to display an.
+	//
+	// The first argument to Image _must_ be the ID of an image asset. The
+	// second argument _may_ be a description of the image which will be used as
+	// alt text, or possibly displayed to the user with the image.
+	Image func(args ...string) (string, error)
+}
+
+// PreprocessBody 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 (p Post) PreprocessBody(into io.Writer, funcs PreprocessFunctions) error {
+
+	tpl := template.New("")
+
+	tpl.Funcs(template.FuncMap{
+		"BlogURL":   funcs.BlogURL,
+		"AssetURL":  funcs.AssetURL,
+		"PostURL":   funcs.PostURL,
+		"StaticURL": funcs.StaticURL,
+		"Image":     funcs.Image,
+	})
+
+	tpl, err := tpl.Parse(p.Body)
+
+	if err != nil {
+		return fmt.Errorf("parsing post body as template: %w", err)
+	}
+
+	if err := tpl.Execute(into, nil); err != nil {
+		return fmt.Errorf("executing post body as template: %w", err)
+	}
+
+	return nil
+}