landed the email and URL rewriters

htmlcheck/rewriter.go

@@ -9,8 +9,13 @@
 // The htmlcheck package contains the HTML Checker.
 package htmlcheck
 
-import "net/url"
+import (
+	"net/mail"
+	"net/url"
+	"strings"
+)
 
+// markupData holds the return from rewriters.
 type markupData struct {
 	beginMarkup string
 	text        string
@@ -18,14 +23,117 @@ type markupData struct {
 	rescan      bool
 }
 
+// rewriterServices is an interface that provides services to rewriters.
 type rewriterServices interface {
 	rewriterAttrValue(string) string
 	rewriterContextValue(string) any
-	addExternalRef(url.URL)
+	addExternalRef(*url.URL)
 	addInternalRef(string)
 }
 
+// rewriter is the interface for components that rewrite source text and place markup around it.
 type rewriter interface {
 	Name() string
 	Rewrite(string, rewriterServices) *markupData
 }
+
+// emailRewriter is an implementation of Rewriter that recognizes E-mail addresses.
+type emailRewriter struct{}
+
+// EmailRewriter is a singleton implementration of rewriter for E-mail addresses.
+var EmailRewriter = emailRewriter{}
+
+// Name returns the rewriter's name.
+func (rw *emailRewriter) Name() string {
+	return "email"
+}
+
+/* Rewrite rewrites the given string data and adds markup before and after if needed.
+ * Parameters:
+ *     data - The data to be rewritten.
+ *     svc - Services interface we can use.
+ * Returns:
+ *     Pointer to markup data, or nil.
+ */
+func (rw *emailRewriter) Rewrite(data string, svc rewriterServices) *markupData {
+	_, err := mail.ParseAddress(data)
+	if err != nil {
+		return nil
+	}
+
+	var openA strings.Builder
+	openA.WriteString("<a href=\"mailto:")
+	openA.WriteString(data)
+	openA.WriteString("\"")
+	catenate := svc.rewriterAttrValue("ANCHORTAIL")
+	if catenate != "" {
+		openA.WriteString(" ")
+		openA.WriteString(catenate)
+	}
+	openA.WriteString(">")
+	return &markupData{
+		beginMarkup: openA.String(),
+		text:        data,
+		endMarkup:   "</a>",
+		rescan:      false}
+}
+
+// urlRewriter is an implementation of Rewriter that recognizes URLs.
+type urlRewriter struct{}
+
+// URLRewriter is a singleton implementration of rewriter for URLs.
+var URLRewriter = urlRewriter{}
+
+// Name returns the rewriter's name.
+func (rw *urlRewriter) Name() string {
+	return "url"
+}
+
+/* Rewrite rewrites the given string data and adds markup before and after if needed.
+ * Parameters:
+ *     data - The data to be rewritten.
+ *     svc - Services interface we can use.
+ * Returns:
+ *     Pointer to markup data, or nil.
+ */
+func (rw *urlRewriter) Rewrite(data string, svc rewriterServices) *markupData {
+	url, err := url.Parse(data)
+	if err != nil {
+		secondChance := ""
+		if strings.HasPrefix(data, "www.") {
+			secondChance = "http://" + data
+		} else if strings.HasPrefix(data, "ftp.") {
+			secondChance = "ftp://" + data
+		} else if strings.HasPrefix(data, "gopher.") {
+			secondChance = "gopher://" + data
+		}
+		if secondChance == "" {
+			return nil
+		}
+		url, err = url.Parse(secondChance)
+		if err != nil {
+			return nil
+		}
+	}
+
+	if url.Scheme == "http" || url.Scheme == "https" {
+		svc.addExternalRef(url)
+	}
+
+	var openA strings.Builder
+	openA.WriteString("<a href=\"")
+	openA.WriteString(url.String())
+	openA.WriteString("\"")
+	catenate := svc.rewriterAttrValue("ANCHORTAIL")
+	if catenate != "" {
+		openA.WriteString(" ")
+		openA.WriteString(catenate)
+	}
+	openA.WriteString(">")
+	return &markupData{
+		beginMarkup: openA.String(),
+		text:        data,
+		endMarkup:   "</a>",
+		rescan:      false,
+	}
+}