internal/api: factor out common renderer things

Change-Id: I5d8a579913942bcdea664af675ff2ef29888281c
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/761400
TryBot-Bypass: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Ethan Lee <ethanalee@google.com>

3 files changed, 44 insertions, 53 deletions

diff --git a/internal/api/api.go b/internal/api/api.go
index cf771e82..fbc00e61 100644
--- a/internal/api/api.go
+++ b/internal/api/api.go
@@ -104,11 +104,11 @@ func ServePackage(w http.ResponseWriter, r *http.Request, ds internal.DataSource
 			var sb strings.Builder
 			switch params.Doc {
 			case "text":
-				r = &textRenderer{fset: gpkg.Fset, w: &sb}
+				r = newTextRenderer(gpkg.Fset, &sb)
 			case "md", "markdown":
-				r = &markdownRenderer{fset: gpkg.Fset, w: &sb}
+				r = newMarkdownRenderer(gpkg.Fset, &sb)
 			case "html":
-				return errors.New("unimplemented")
+				r = newHTMLRenderer(gpkg.Fset, &sb)
 			default:
 				return fmt.Errorf("%w: bad doc format: need one of 'text', 'md', 'markdown' or 'html'", derrors.InvalidArgument)
 			}
diff --git a/internal/api/render.go b/internal/api/render.go
index f8d9dbc7..4001f6ca 100644
--- a/internal/api/render.go
+++ b/internal/api/render.go
@@ -2,10 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// TODO(jba)? Consider rendering notes separately. Now they appear
-// with the doc for each symbol, which is probably better for LLMs,
-// but be open to evidence to the contrary.
-
 package api
 
 import (
@@ -42,13 +38,34 @@ type renderer interface {
 	emitExample(ex *doc.Example)
 }
 
+type commonRenderer struct {
+	fset *token.FileSet
+	w    io.Writer
+	err  error
+}
+
+func (r *commonRenderer) printf(format string, args ...any) {
+	if r.err != nil {
+		return
+	}
+	if _, err := fmt.Fprintf(r.w, format, args...); err != nil {
+		r.err = err
+	}
+}
+
+func (r *commonRenderer) end() error { return r.err }
+
 type textRenderer struct {
-	fset    *token.FileSet
-	w       io.Writer
+	commonRenderer
 	pkg     *doc.Package
 	parser  *comment.Parser
 	printer *comment.Printer
-	err     error
+}
+
+func newTextRenderer(fset *token.FileSet, w io.Writer) *textRenderer {
+	return &textRenderer{
+		commonRenderer: commonRenderer{fset: fset, w: w},
+	}
 }
 
 func (r *textRenderer) start(pkg *doc.Package) {
@@ -71,8 +88,6 @@ func (r *textRenderer) start(pkg *doc.Package) {
 	r.printf("\n")
 }
 
-func (r *textRenderer) end() error { return r.err }
-
 func (r *textRenderer) startSection(name string) {
 	r.printf("%s\n\n", strings.ToUpper(name))
 }
@@ -141,24 +156,18 @@ func (r *textRenderer) emitExample(ex *doc.Example) {
 	r.printf("\n")
 }
 
-// TODO(jba): consolidate this function to avoid duplication.
-func (r *textRenderer) printf(format string, args ...any) {
-	if r.err != nil {
-		return
-	}
-	if _, err := fmt.Fprintf(r.w, format, args...); err != nil {
-		r.err = err
-	}
-}
-
 type markdownRenderer struct {
-	fset    *token.FileSet
-	w       io.Writer
+	commonRenderer
 	pkg     *doc.Package
 	parser  *comment.Parser
 	printer *comment.Printer
 	caser   cases.Caser
-	err     error
+}
+
+func newMarkdownRenderer(fset *token.FileSet, w io.Writer) *markdownRenderer {
+	return &markdownRenderer{
+		commonRenderer: commonRenderer{fset: fset, w: w},
+	}
 }
 
 func (r *markdownRenderer) start(pkg *doc.Package) {
@@ -178,8 +187,6 @@ func (r *markdownRenderer) start(pkg *doc.Package) {
 	r.printf("\n")
 }
 
-func (r *markdownRenderer) end() error { return r.err }
-
 func (r *markdownRenderer) startSection(name string) {
 	if name == "" {
 		return
@@ -239,24 +246,19 @@ func (r *markdownRenderer) emitExample(ex *doc.Example) {
 	r.printf("\n")
 }
 
-func (r *markdownRenderer) printf(format string, args ...any) {
-	if r.err != nil {
-		return
-	}
-	if _, err := fmt.Fprintf(r.w, format, args...); err != nil {
-		r.err = err
-	}
-}
-
 type htmlRenderer struct {
-	fset    *token.FileSet
-	w       io.Writer
+	commonRenderer
 	pkg     *doc.Package
 	parser  *comment.Parser
 	printer *comment.Printer
 	caser   cases.Caser
 	buf     strings.Builder
-	err     error
+}
+
+func newHTMLRenderer(fset *token.FileSet, w io.Writer) *htmlRenderer {
+	return &htmlRenderer{
+		commonRenderer: commonRenderer{fset: fset, w: w},
+	}
 }
 
 func (r *htmlRenderer) start(pkg *doc.Package) {
@@ -276,8 +278,6 @@ func (r *htmlRenderer) start(pkg *doc.Package) {
 	r.printf("\n")
 }
 
-func (r *htmlRenderer) end() error { return r.err }
-
 func (r *htmlRenderer) startSection(name string) {
 	if name == "" {
 		return
@@ -338,15 +338,6 @@ func (r *htmlRenderer) emitExample(ex *doc.Example) {
 	r.printf("\n")
 }
 
-func (r *htmlRenderer) printf(format string, args ...any) {
-	if r.err != nil {
-		return
-	}
-	if _, err := fmt.Fprintf(r.w, format, args...); err != nil {
-		r.err = err
-	}
-}
-
 // renderDoc renders the documentation for dpkg using the given renderer.
 func renderDoc(dpkg *doc.Package, r renderer, examples bool) error {
 	r.start(dpkg)
diff --git a/internal/api/render_test.go b/internal/api/render_test.go
index fdfb8612..5cc826d1 100644
--- a/internal/api/render_test.go
+++ b/internal/api/render_test.go
@@ -77,7 +77,7 @@ func testRenderDoc(t *testing.T, examples bool) {
 		})
 	}
 
-	check(t, "text", &textRenderer{fset: decoded.Fset, w: &sb})
-	check(t, "markdown", &markdownRenderer{fset: decoded.Fset, w: &sb})
-	check(t, "html", &htmlRenderer{fset: decoded.Fset, w: &sb})
+	check(t, "text", newTextRenderer(decoded.Fset, &sb))
+	check(t, "markdown", newMarkdownRenderer(decoded.Fset, &sb))
+	check(t, "html", newHTMLRenderer(decoded.Fset, &sb))
 }