Implemented block quotes

Render.go

@@ -10,30 +10,29 @@ var (
 	headerEnd   = []string{"</h1>", "</h2>", "</h3>", "</h4>", "</h5>", "</h6>"}
 )
 
+type renderer struct {
+	out            strings.Builder
+	paragraphLevel int
+	quoteLevel     int
+}
+
 // Render creates HTML from the supplied markdown text.
 func Render(markdown string) string {
 	var (
-		out       = strings.Builder{}
-		paragraph = strings.Builder{}
+		r         renderer
 		i         = 0
 		lineStart = 0
 	)
 
-	flush := func() {
-		if paragraph.Len() == 0 {
-			return
-		}
-
-		out.WriteString("<p>")
-		writeText(&out, paragraph.String())
-		out.WriteString("</p>")
-		paragraph.Reset()
-	}
-
 	for {
 		if i > len(markdown) {
-			flush()
-			return out.String()
+			r.closeParagraphs()
+
+			for range r.quoteLevel {
+				r.out.WriteString("</blockquote>")
+			}
+
+			return r.out.String()
 		}
 
 		if i != len(markdown) && markdown[i] != '\n' {
@@ -45,33 +44,74 @@ func Render(markdown string) string {
 		lineStart = i + 1
 		i++
 
-		switch {
-		case strings.HasPrefix(line, "#"):
-			flush()
-			space := strings.IndexByte(line, ' ')
-
-			if space > 0 && space <= 6 {
-				out.WriteString(headerStart[space-1])
-				writeText(&out, line[space+1:])
-				out.WriteString(headerEnd[space-1])
-			}
-
-		default:
-			if len(line) == 0 {
-				flush()
-				continue
-			}
-
-			if paragraph.Len() > 0 {
-				paragraph.WriteByte(' ')
-			}
-
-			paragraph.WriteString(line)
-		}
+		r.processLine(line)
 	}
 }
 
-func writeText(out *strings.Builder, text string) {
+func (r *renderer) processLine(line string) {
+	newQuoteLevel := 0
+
+	for strings.HasPrefix(line, ">") {
+		line = strings.TrimSpace(line[1:])
+		newQuoteLevel++
+	}
+
+	if newQuoteLevel > r.quoteLevel {
+		r.closeParagraphs()
+
+		for range newQuoteLevel - r.quoteLevel {
+			r.out.WriteString("<blockquote>")
+		}
+	} else if newQuoteLevel < r.quoteLevel {
+		r.closeParagraphs()
+
+		for range r.quoteLevel - newQuoteLevel {
+			r.out.WriteString("</blockquote>")
+		}
+	}
+
+	r.quoteLevel = newQuoteLevel
+
+	if strings.HasPrefix(line, "#") {
+		r.closeParagraphs()
+		space := strings.IndexByte(line, ' ')
+
+		if space > 0 && space <= 6 {
+			r.out.WriteString(headerStart[space-1])
+			r.writeText(line[space+1:])
+			r.out.WriteString(headerEnd[space-1])
+		}
+
+		return
+	}
+
+	if len(line) == 0 {
+		r.closeParagraphs()
+		return
+	}
+
+	if r.paragraphLevel == 0 {
+		r.out.WriteString("<p>")
+		r.paragraphLevel++
+		r.writeText(line)
+		return
+	}
+
+	r.out.WriteByte(' ')
+	r.writeText(line)
+}
+
+// closeParagraphs closes open paragraphs.
+func (r *renderer) closeParagraphs() {
+	for range r.paragraphLevel {
+		r.out.WriteString("</p>")
+	}
+
+	r.paragraphLevel = 0
+}
+
+// writeText converts inline markdown to HTML.
+func (r *renderer) writeText(markdown string) {
 	var (
 		i          = 0
 		tokenStart = 0
@@ -85,16 +125,16 @@ func writeText(out *strings.Builder, text string) {
 	)
 
 	for {
-		if i == len(text) {
-			out.WriteString(html.EscapeString(text[tokenStart:]))
+		if i == len(markdown) {
+			r.out.WriteString(html.EscapeString(markdown[tokenStart:]))
 			return
 		}
 
-		c := text[i]
+		c := markdown[i]
 
 		switch c {
 		case '[':
-			out.WriteString(html.EscapeString(text[tokenStart:i]))
+			r.out.WriteString(html.EscapeString(markdown[tokenStart:i]))
 			tokenStart = i
 			textStart = i
 		case ']':
@@ -109,14 +149,14 @@ func writeText(out *strings.Builder, text string) {
 			parentheses--
 
 			if parentheses == 0 && textStart >= 0 && textEnd >= 0 && urlStart >= 0 {
-				linkText := text[textStart+1 : textEnd]
-				linkURL := text[urlStart+1 : i]
+				linkText := markdown[textStart+1 : textEnd]
+				linkURL := markdown[urlStart+1 : i]
 
-				out.WriteString("<a href=\"")
-				out.WriteString(formatURL(linkURL))
-				out.WriteString("\">")
-				out.WriteString(html.EscapeString(linkText))
-				out.WriteString("</a>")
+				r.out.WriteString("<a href=\"")
+				r.out.WriteString(sanitizeURL(linkURL))
+				r.out.WriteString("\">")
+				r.out.WriteString(html.EscapeString(linkText))
+				r.out.WriteString("</a>")
 
 				textStart = -1
 				textEnd = -1
@@ -130,7 +170,7 @@ func writeText(out *strings.Builder, text string) {
 	}
 }
 
-func formatURL(linkURL string) string {
+func sanitizeURL(linkURL string) string {
 	if strings.HasPrefix(strings.ToLower(linkURL), "javascript:") {
 		return ""
 	}