html: Make textToHTML accept an io.Reader

Use gemini.ParseLines to convert the Gemini text to HTML in one pass.

format.go

@@ -4,8 +4,6 @@ import (
 	"bytes"
 	pathpkg "path"
 	"strings"
-
-	"git.sr.ht/~adnano/go-gemini"
 )
 
 // Format represents an output format.
@@ -31,8 +29,7 @@ func FormatHTML(p *Page, cfg *Config) (path string, content []byte) {
 	path = pathpkg.Join(p.Path, "index.html")
 
 	r := strings.NewReader(p.Content)
-	text := gemini.ParseText(r)
-	content = textToHTML(text)
+	content = textToHTML(r)
 
 	// html template context
 	type htmlCtx struct {

html.go

@@ -4,73 +4,79 @@ import (
 	"bytes"
 	"fmt"
 	"html"
+	"io"
 
 	"git.sr.ht/~adnano/go-gemini"
 )
 
 // textToHTML returns the Gemini text response as HTML.
-func textToHTML(text gemini.Text) []byte {
-	var b bytes.Buffer
-	var pre bool
-	var list bool
-	for _, l := range text {
-		if _, ok := l.(gemini.LineListItem); ok {
-			if !list {
-				list = true
-				b.WriteString("<ul>\n")
+func textToHTML(r io.Reader) []byte {
+	buf := &bytes.Buffer{}
+	hw := &HTMLWriter{
+		out: buf,
 	}
-		} else if list {
-			list = false
-			b.WriteString("</ul>\n")
+	defer hw.Finish()
+	gemini.ParseLines(r, hw.Handle)
+	return buf.Bytes()
 }
-		switch l.(type) {
+
+type HTMLWriter struct {
+	out  io.Writer
+	pre  bool
+	list bool
+}
+
+func (h *HTMLWriter) Handle(line gemini.Line) {
+	if _, ok := line.(gemini.LineListItem); ok {
+		if !h.list {
+			h.list = true
+			fmt.Fprint(h.out, "<ul>\n")
+		}
+	} else if h.list {
+		h.list = false
+		fmt.Fprint(h.out, "</ul>\n")
+	}
+	switch line := line.(type) {
 	case gemini.LineLink:
-			link := l.(gemini.LineLink)
-			url := html.EscapeString(link.URL)
-			name := html.EscapeString(link.Name)
+		url := html.EscapeString(line.URL)
+		name := html.EscapeString(line.Name)
 		if name == "" {
 			name = url
 		}
-			fmt.Fprintf(&b, "<p><a href='%s'>%s</a></p>\n", url, name)
+		fmt.Fprintf(h.out, "<p><a href='%s'>%s</a></p>\n", url, name)
 	case gemini.LinePreformattingToggle:
-			pre = !pre
-			if pre {
-				b.WriteString("<pre>\n")
+		h.pre = !h.pre
+		if h.pre {
+			fmt.Fprint(h.out, "<pre>\n")
 		} else {
-				b.WriteString("</pre>\n")
+			fmt.Fprint(h.out, "</pre>\n")
 		}
 	case gemini.LinePreformattedText:
-			text := string(l.(gemini.LinePreformattedText))
-			fmt.Fprintf(&b, "%s\n", html.EscapeString(text))
+		fmt.Fprintf(h.out, "%s\n", html.EscapeString(string(line)))
 	case gemini.LineHeading1:
-			text := string(l.(gemini.LineHeading1))
-			fmt.Fprintf(&b, "<h1>%s</h1>\n", html.EscapeString(text))
+		fmt.Fprintf(h.out, "<h1>%s</h1>\n", html.EscapeString(string(line)))
 	case gemini.LineHeading2:
-			text := string(l.(gemini.LineHeading2))
-			fmt.Fprintf(&b, "<h2>%s</h2>\n", html.EscapeString(text))
+		fmt.Fprintf(h.out, "<h2>%s</h2>\n", html.EscapeString(string(line)))
 	case gemini.LineHeading3:
-			text := string(l.(gemini.LineHeading3))
-			fmt.Fprintf(&b, "<h3>%s</h3>\n", html.EscapeString(text))
+		fmt.Fprintf(h.out, "<h3>%s</h3>\n", html.EscapeString(string(line)))
 	case gemini.LineListItem:
-			text := string(l.(gemini.LineListItem))
-			fmt.Fprintf(&b, "<li>%s</li>\n", html.EscapeString(text))
+		fmt.Fprintf(h.out, "<li>%s</li>\n", html.EscapeString(string(line)))
 	case gemini.LineQuote:
-			text := string(l.(gemini.LineQuote))
-			fmt.Fprintf(&b, "<blockquote>%s</blockquote>\n", html.EscapeString(text))
+		fmt.Fprintf(h.out, "<blockquote>%s</blockquote>\n", html.EscapeString(string(line)))
 	case gemini.LineText:
-			text := string(l.(gemini.LineText))
-			if text == "" {
-				b.WriteString("<br>\n")
+		if line == "" {
+			fmt.Fprint(h.out, "<br>\n")
 		} else {
-				fmt.Fprintf(&b, "<p>%s</p>\n", html.EscapeString(text))
+			fmt.Fprintf(h.out, "<p>%s</p>\n", html.EscapeString(string(line)))
 		}
 	}
 }
-	if pre {
-		b.WriteString("</pre>\n")
+
+func (h *HTMLWriter) Finish() {
+	if h.pre {
+		fmt.Fprint(h.out, "</pre>\n")
 	}
-	if list {
-		b.WriteString("</ul>\n")
+	if h.list {
+		fmt.Fprint(h.out, "</ul>\n")
 	}
-	return b.Bytes()
 }