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// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
package sanitizer
import (
"fmt"
"strconv"
"strings"
)
type ImageCandidate struct {
ImageURL string
Descriptor string
}
type ImageCandidates []*ImageCandidate
func (c ImageCandidates) String() string {
var htmlCandidates []string
for _, imageCandidate := range c {
var htmlCandidate string
if imageCandidate.Descriptor != "" {
htmlCandidate = fmt.Sprintf(`%s %s`, imageCandidate.ImageURL, imageCandidate.Descriptor)
} else {
htmlCandidate = imageCandidate.ImageURL
}
htmlCandidates = append(htmlCandidates, htmlCandidate)
}
return strings.Join(htmlCandidates, ", ")
}
// ParseSrcSetAttribute returns the list of image candidates from the set.
// https://html.spec.whatwg.org/#parse-a-srcset-attribute
func ParseSrcSetAttribute(attributeValue string) (imageCandidates ImageCandidates) {
unparsedCandidates := strings.Split(attributeValue, ", ")
for _, unparsedCandidate := range unparsedCandidates {
if candidate, err := parseImageCandidate(unparsedCandidate); err == nil {
imageCandidates = append(imageCandidates, candidate)
}
}
return imageCandidates
}
func parseImageCandidate(input string) (*ImageCandidate, error) {
input = strings.TrimSpace(input)
parts := strings.Split(strings.TrimSpace(input), " ")
nbParts := len(parts)
if nbParts > 2 || nbParts == 0 {
return nil, fmt.Errorf(`srcset: invalid number of descriptors`)
}
if nbParts == 2 {
if !isValidWidthOrDensityDescriptor(parts[1]) {
return nil, fmt.Errorf(`srcset: invalid descriptor`)
}
return &ImageCandidate{ImageURL: parts[0], Descriptor: parts[1]}, nil
}
return &ImageCandidate{ImageURL: parts[0]}, nil
}
func isValidWidthOrDensityDescriptor(value string) bool {
if value == "" {
return false
}
lastChar := value[len(value)-1:]
if lastChar != "w" && lastChar != "x" {
return false
}
_, err := strconv.ParseFloat(value[0:len(value)-1], 32)
return err == nil
}
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