Revert "plugins/viewhtml: convert mailto links"

This reverts commit 02faf6174b.

This commit doesn't work, because it's applied to <img> tags. Making it
handle <a> tags doesn't work either because bluemonday will strip any
target="_blank" attributes, making the compose form open in the
<iframe>. Let's just revert this whole commit for now.

plugins/base/routes.go

@@ -431,7 +431,6 @@ func handleCompose(ctx *koushin.Context, msg *OutgoingMessage, draft *messagePat
 
 func handleComposeNew(ctx *koushin.Context) error {
 	// These are common mailto URL query parameters
-	// TODO: cc, bcc
 	return handleCompose(ctx, &OutgoingMessage{
 		To:        strings.Split(ctx.QueryParam("to"), ","),
 		Subject:   ctx.QueryParam("subject"),

plugins/viewhtml/sanitize.go

@@ -70,14 +70,6 @@ var allowedStyles = map[string]bool{
 	"list-style-position": true,
 }
 
-var mailtoParams = []string{
-	"subject",
-	"cc",
-	"bcc",
-	"body",
-	"in-reply-to",
-}
-
 type sanitizer struct {
 	msg *koushinbase.IMAPMessage
 }
@@ -88,31 +80,17 @@ func (san *sanitizer) sanitizeImageURL(src string) string {
 		return "about:blank"
 	}
 
-	switch strings.ToLower(u.Scheme) {
-	case "mailto":
-		mailtoQuery := u.Query()
-
-		composeURL := url.URL{Path: "/compose"}
-		composeQuery := make(url.Values)
-		composeQuery.Set("to", u.Opaque)
-		for _, k := range mailtoParams {
-			if v := mailtoQuery.Get(k); v != "" {
-				composeQuery.Set(k, v)
-			}
-		}
-		composeURL.RawQuery = composeQuery.Encode()
-		return composeURL.String()
-	case "cid":
 	// TODO: mid support?
+	if !strings.EqualFold(u.Scheme, "cid") || san.msg == nil {
+		return "about:blank"
+	}
+
 	part := san.msg.PartByID(u.Opaque)
 	if part == nil || !strings.HasPrefix(part.MIMEType, "image/") {
 		return "about:blank"
 	}
 
 	return part.URL(true).String()
-	default:
-		return "about:blank"
-	}
 }
 
 func (san *sanitizer) sanitizeCSSDecls(decls []*css.Declaration) []*css.Declaration {