Render posts completely using common rendering methods

The aim is to reduce reliance on custom logic in the handlers for every
protocol, eventually outsourcing all of it into `render.Methods`,
leaving each protocol to simply direct calls to the correct template.

1 files changed, 48 insertions, 36 deletions

diff --git a/src/http/tpl.go b/src/http/tpl.go
index 24f2453..c623f2e 100644
--- a/src/http/tpl.go
+++ b/src/http/tpl.go
@@ -1,9 +1,12 @@
 package http
 
 import (
+	"bytes"
 	"embed"
+	"errors"
 	"fmt"
 	"html/template"
+	"io"
 	"io/fs"
 	"net/http"
 	"net/url"
@@ -12,6 +15,8 @@ import (
 	"time"
 
 	"dev.mediocregopher.com/mediocre-blog.git/src/http/apiutil"
+	"dev.mediocregopher.com/mediocre-blog.git/src/post"
+	"dev.mediocregopher.com/mediocre-blog.git/src/render"
 )
 
 //go:embed tpl
@@ -105,77 +110,84 @@ func (a *api) tplFuncs() template.FuncMap {
 	}
 }
 
-func (a *api) parseTpl(name, tplBody string) (*template.Template, error) {
-
-	tpl := template.New(name)
+func (a *api) emptyTpl() *template.Template {
+	tpl := template.New("")
 	tpl = tpl.Funcs(a.tplFuncs())
 	tpl = tpl.Funcs(template.FuncMap(a.postPreprocessFuncs().ToFuncMap()))
-
-	var err error
-
-	if tpl, err = tpl.Parse(tplBody); err != nil {
-		return nil, err
-	}
-
-	return tpl, nil
+	return tpl
 }
 
-func (a *api) mustParseTpl(name string) *template.Template {
-	return template.Must(a.parseTpl(name, mustReadTplFile(name)))
+func mustParseTpl(tpl *template.Template, name string) *template.Template {
+	return template.Must(tpl.New(name).Parse(mustReadTplFile(name)))
 }
 
 func (a *api) mustParseBasedTpl(name string) *template.Template {
-	tpl := a.mustParseTpl(name)
-	tpl = template.Must(tpl.New("gemini-cta.html").Parse(mustReadTplFile("gemini-cta.html")))
-	tpl = template.Must(tpl.New("base.html").Parse(mustReadTplFile("base.html")))
+	tpl := a.emptyTpl()
+	tpl = mustParseTpl(tpl, "gemini-cta.html")
+	tpl = mustParseTpl(tpl, "base.html")
+	tpl = mustParseTpl(tpl, name)
 	return tpl
 }
 
 type tplData struct {
+	*render.Methods
 	Payload interface{}
 	Title   string
 }
 
-func newTPLData(r *http.Request, payload interface{}) tplData {
+// WithTitlePrefix returns a copy of tplData but with the given string prefixed
+// to the page title. This is intended for use within templates, when nesting
+// the base template.
+func (d tplData) WithTitlePrefix(prefix string) tplData {
+	d.Title = prefix + " - " + d.Title
+	return d
+}
+
+func (a *api) newTPLData(r *http.Request, payload interface{}) tplData {
 	return tplData{
+		Methods: render.NewMethods(
+			r.Context(),
+			r.URL,
+			a.params.PublicURL,
+			a.params.GeminiGatewayURL,
+			a.params.PostStore,
+			a.postPreprocessFuncs(),
+		),
 		Payload: payload,
 		Title:   "mediocregopher's lil web corner",
 	}
 }
 
-type executeTemplateOpt func(*tplData)
-
-func executeTemplateWithTitlePrefix(prefix string) executeTemplateOpt {
-	return func(d *tplData) {
-		d.Title = prefix + " - " + d.Title
-	}
-}
-
 // executeTemplate expects to be the final action in an http.Handler
-func executeTemplate(
-	rw http.ResponseWriter, r *http.Request,
-	tpl *template.Template, payload interface{},
-	opts ...executeTemplateOpt,
+func (a *api) executeTemplate(
+	rw http.ResponseWriter,
+	r *http.Request,
+	tpl *template.Template,
+	payload interface{},
 ) {
 
-	tplData := newTPLData(r, payload)
+	tplData := a.newTPLData(r, payload)
 
-	for _, opt := range opts {
-		opt(&tplData)
-	}
+	buf := new(bytes.Buffer)
 
-	if err := tpl.Execute(rw, tplData); err != nil {
+	err := tpl.Execute(buf, tplData)
+	if errors.Is(err, post.ErrPostNotFound) {
+		http.Error(rw, "Post not found", 404)
+		return
+	} else if err != nil {
 		apiutil.InternalServerError(
 			rw, r, fmt.Errorf("rendering template: %w", err),
 		)
 		return
 	}
+
+	io.Copy(rw, buf)
 }
 
 func (a *api) executeRedirectTpl(
 	rw http.ResponseWriter, r *http.Request, url string,
 ) {
-	executeTemplate(rw, r, a.redirectTpl, struct {
+	a.executeTemplate(rw, r, a.redirectTpl, struct {
 		URL string
 	}{
 		URL: url,
@@ -188,7 +200,7 @@ func (a *api) renderDumbTplHandler(tplName string) http.Handler {
 
 	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 
-		tplData := newTPLData(r, nil)
+		tplData := a.newTPLData(r, nil)
 
 		if err := tpl.Execute(rw, tplData); err != nil {
 			apiutil.InternalServerError(