Implemented links

Render.go

@@ -25,7 +25,7 @@ func Render(markdown string) string {
 		}
 
 		out.WriteString("<p>")
-		out.WriteString(html.EscapeString(paragraph.String()))
+		writeText(&out, paragraph.String())
 		out.WriteString("</p>")
 		paragraph.Reset()
 	}
@@ -52,7 +52,7 @@ func Render(markdown string) string {
 
 			if space > 0 && space <= 6 {
 				out.WriteString(headerStart[space-1])
-				out.WriteString(html.EscapeString(line[space+1:]))
+				writeText(&out, line[space+1:])
 				out.WriteString(headerEnd[space-1])
 			}
 
@@ -69,3 +69,70 @@ func Render(markdown string) string {
 		}
 	}
 }
+
+func writeText(out *strings.Builder, text string) {
+	var (
+		i          = 0
+		tokenStart = 0
+	)
+
+	var (
+		textStart   = -1
+		textEnd     = -1
+		urlStart    = -1
+		parentheses = 0
+	)
+
+	for {
+		if i == len(text) {
+			out.WriteString(html.EscapeString(text[tokenStart:]))
+			return
+		}
+
+		c := text[i]
+
+		switch c {
+		case '[':
+			out.WriteString(html.EscapeString(text[tokenStart:i]))
+			tokenStart = i
+			textStart = i
+		case ']':
+			textEnd = i
+		case '(':
+			if parentheses == 0 {
+				urlStart = i
+			}
+
+			parentheses++
+		case ')':
+			parentheses--
+
+			if parentheses == 0 && textStart >= 0 && textEnd >= 0 && urlStart >= 0 {
+				linkText := text[textStart+1 : textEnd]
+				linkURL := text[urlStart+1 : i]
+
+				out.WriteString("<a href=\"")
+				out.WriteString(formatURL(linkURL))
+				out.WriteString("\">")
+				out.WriteString(html.EscapeString(linkText))
+				out.WriteString("</a>")
+
+				textStart = -1
+				textEnd = -1
+				urlStart = -1
+
+				tokenStart = i + 1
+			}
+		}
+
+		i++
+	}
+}
+
+func formatURL(linkURL string) string {
+	if strings.HasPrefix(strings.ToLower(linkURL), "javascript:") {
+		return ""
+	}
+
+	return html.EscapeString(linkURL)
+}