perf(sanitizer): minor simplifications of the sanitizer

- Factorize some conditions
- Remove useless `default` case and move the return at the end of the functions
- Use strings.CutPrefix instead of strings.HasPrefix + strings.TrimPrefix
- Use switch-case constructs instead of slices.Contains, as this reduces the
  complexity of the functions and allows them to be inlined, as well as helping
  the compiler to optimize them, as it sucks at interprocedural optimizations.

internal/reader/sanitizer/sanitizer.go

@@ -322,15 +322,20 @@ func sanitizeAttributes(parsedBaseUrl *url.URL, baseURL, tagName string, attribu
 			value = "http://www.w3.org/1998/Math/MathML"
 		}
 
-		if tagName == "img" && attribute.Key == "fetchpriority" {
-			if !isValidFetchPriorityValue(value) {
-				continue
-			}
-		}
-
-		if tagName == "img" && attribute.Key == "decoding" {
-			if !isValidDecodingValue(value) {
-				continue
+		if tagName == "img" {
+			switch attribute.Key {
+			case "fetchpriority":
+				if !isValidFetchPriorityValue(value) {
+					continue
+				}
+			case "decoding":
+				if !isValidDecodingValue(value) {
+					continue
+				}
+			case "width", "height":
+				if isImageLargerThanLayout || !isPositiveInteger(value) {
+					continue
+				}
 			}
 		}
 
@@ -338,12 +343,6 @@ func sanitizeAttributes(parsedBaseUrl *url.URL, baseURL, tagName string, attribu
 			value = sanitizeSrcsetAttr(baseURL, value)
 		}
 
-		if tagName == "img" && (attribute.Key == "width" || attribute.Key == "height") {
-			if isImageLargerThanLayout || !isPositiveInteger(value) {
-				continue
-			}
-		}
-
 		if isExternalResourceAttribute(attribute.Key) {
 			switch {
 			case tagName == "iframe":
@@ -511,11 +510,11 @@ func rewriteIframeURL(link string) string {
 
 	switch strings.TrimPrefix(u.Hostname(), "www.") {
 	case "youtube.com":
-		if strings.HasPrefix(u.Path, "/embed/") {
+		if pathWithoutEmbed, ok := strings.CutPrefix(u.Path, "/embed/"); ok {
 			if len(u.RawQuery) > 0 {
-				return config.Opts.YouTubeEmbedUrlOverride() + strings.TrimPrefix(u.Path, "/embed/") + "?" + u.RawQuery
+				return config.Opts.YouTubeEmbedUrlOverride() + pathWithoutEmbed + "?" + u.RawQuery
 			}
-			return config.Opts.YouTubeEmbedUrlOverride() + strings.TrimPrefix(u.Path, "/embed/")
+			return config.Opts.YouTubeEmbedUrlOverride() + pathWithoutEmbed
 		}
 	case "player.vimeo.com":
 		// See https://help.vimeo.com/hc/en-us/articles/12426260232977-About-Player-parameters
@@ -534,9 +533,8 @@ func isBlockedTag(tagName string) bool {
 	switch tagName {
 	case "noscript", "script", "style":
 		return true
-	default:
-		return false
 	}
+	return false
 }
 
 func sanitizeSrcsetAttr(baseURL, value string) string {
@@ -581,11 +579,17 @@ func getIntegerAttributeValue(name string, attributes []html.Attribute) int {
 }
 
 func isValidFetchPriorityValue(value string) bool {
-	allowedValues := []string{"high", "low", "auto"}
-	return slices.Contains(allowedValues, value)
+	switch value {
+	case "high", "low", "auto":
+		return true
+	}
+	return false
 }
 
 func isValidDecodingValue(value string) bool {
-	allowedValues := []string{"sync", "async", "auto"}
-	return slices.Contains(allowedValues, value)
+	switch value {
+	case "sync", "async", "auto":
+		return true
+	}
+	return false
 }