page-writer-no-buffer

nikolaydubina · nikolaydubina · commit c015457f4e20 · 2023-03-18T17:27:55.000+08:00
diff --git a/html_default_page.go b/html_default_page.go
@@ -4,25 +4,65 @@ import (
 	"bytes"
 	_ "embed"
 	"io"
-	"strings"
 )
 
 //go:embed html_default_page.html
-var DefaultHTMLPageTemplate string
+var defaultPageTemplate []byte
 
-func MarshalHTML(v any) []byte {
+var DefaultPageMarshaler = PageMarshaler{
+	Title:            "htmljson",
+	Template:         defaultPageTemplate,
+	TemplateTitleKey: `{{.Title}}`,
+	TemplateJSONKey:  `{{.HTMLJSON}}`,
+	Marshaler:        &DefaultMarshaler,
+}
+
+// PageMarshaler encodes JSON via marshaller into HTML page by placing Title and content appropriately.
+type PageMarshaler struct {
+	Title            string
+	Template         []byte
+	TemplateTitleKey string
+	TemplateJSONKey  string
+
+	Marshaler interface {
+		MarshalTo(w io.Writer, v any) error
+	}
+
+	idxTitle    int
+	idxHTMLJSON int
+}
+
+func (m *PageMarshaler) Marshal(v any) []byte {
 	b := bytes.Buffer{}
-	MarshalHTMLTo(&b, v)
+	m.MarshalTo(&b, v)
 	return b.Bytes()
 }
 
-func MarshalHTMLTo(w io.Writer, v any) (written int64, err error) {
-	var b bytes.Buffer
-	b.Grow(1000)
+func (m *PageMarshaler) parseTemplate() {
+	if m.idxTitle == 0 || m.idxHTMLJSON == 0 {
+		m.idxTitle = bytes.Index(m.Template, []byte(m.TemplateTitleKey))
+		m.idxHTMLJSON = bytes.Index(m.Template, []byte(m.TemplateJSONKey))
+	}
+}
+
+func (m *PageMarshaler) MarshalTo(w io.Writer, v any) error {
+	m.parseTemplate()
+
+	var s int
+
+	if f := m.idxTitle; f > 0 {
+		w.Write(m.Template[s:f])
+		s = f + len(m.TemplateTitleKey)
+		w.Write([]byte(m.Title))
+	}
+
+	if f := m.idxHTMLJSON; f > 0 {
+		w.Write(m.Template[s:f])
+		s = f + len(m.TemplateJSONKey)
+		m.Marshaler.MarshalTo(w, v)
+	}
 
-	jsonHTML := DefaultMarshaler.Marshal(v)
-	b.WriteString(strings.ReplaceAll(DefaultHTMLPageTemplate, `{{.HTMLJSON}}`, string(jsonHTML)))
+	w.Write(m.Template[s:])
 
-	n, err := w.Write(b.Bytes())
-	return int64(n), err
+	return nil
 }
diff --git a/html_default_page.html b/html_default_page.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html>
 <head>
-<title>htmljson</title>
+<title>{{.Title}}</title>
 <style> 
 
 /* Colors from Apple https://developer.apple.com/design/human-interface-guidelines/foundations/color
diff --git a/html_default_page_test.go b/html_default_page_test.go
@@ -20,7 +20,7 @@ func TestMarshalHTML(t *testing.T) {
 	var v any
 	json.Unmarshal(exampleJSON, &v)
 
-	h := htmljson.MarshalHTML(v)
+	h := htmljson.DefaultPageMarshaler.Marshal(v)
 
 	os.WriteFile("testdata/example-page.out.html", h, 0666)
 	if strings.TrimSpace(examplePageHTML) != strings.TrimSpace(string(h)) {
@@ -50,7 +50,10 @@ func TestMarshalHTML_Color(t *testing.T) {
 		Row:   htmljson.DefaultRowHTML{Padding: 4}.Marshal,
 	}
 
-	htmlPage := strings.ReplaceAll(htmljson.DefaultHTMLPageTemplate, `{{.HTMLJSON}}`, string(s.Marshal(v)))
+	m := htmljson.DefaultPageMarshaler
+	m.Marshaler = &s
+
+	htmlPage := m.Marshal(v)
 
 	os.WriteFile("testdata/example-page-color.out.html", []byte(htmlPage), 0666)
 	if strings.TrimSpace(examplePageColorHTML) != strings.TrimSpace(string(htmlPage)) {
