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metadata.go
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metadata.go
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// This file is part of go-trafilatura, Go package for extracting readable
// content, comments and metadata from a web page. Source available in
// <https://github.com/markusmobius/go-trafilatura>.
//
// Copyright (C) 2021 Markus Mobius
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Code in this file is ported from <https://github.com/adbar/trafilatura>
// which available under Apache 2.0 license.
package trafilatura
import (
"fmt"
"regexp"
"strings"
"time"
"unicode"
"unicode/utf8"
"github.com/forPelevin/gomoji"
"github.com/go-shiori/dom"
"github.com/markusmobius/go-htmldate"
"github.com/markusmobius/go-trafilatura/internal/etree"
"github.com/markusmobius/go-trafilatura/internal/selector"
"golang.org/x/net/html"
"golang.org/x/text/cases"
"golang.org/x/text/language"
)
var (
rxCommaSeparator = regexp.MustCompile(`\s*[,;]\s*`)
rxTitleCleaner = regexp.MustCompile(`(?i)^(.+)?\s+[–•·—|⁄*⋆~‹«<›»>:-]\s+(.+)$`) // part without dots?
rxJsonSymbol = regexp.MustCompile(`[{\\}]`)
rxNameJson = regexp.MustCompile(`(?i)"name\\?":\s*\\?"([^"\\]+)`)
rxUrlCheck = regexp.MustCompile(`(?i)https?://`)
rxSitenameFinder = regexp.MustCompile(`(?i)https?://(?:www\.|w[0-9]+\.)?([^/]+)`)
rxHtmlStripTag = regexp.MustCompile(`(?i)(<!--.*?-->|<[^>]*>)`)
rxCategoryHref = regexp.MustCompile(`(?i)/categor(?:y|ies)/`)
rxTagHref = regexp.MustCompile(`(?i)/tags?/`)
rxCcLicense = regexp.MustCompile(`(?i)/(by-nc-nd|by-nc-sa|by-nc|by-nd|by-sa|by|zero)/([1-9]\.[0-9])`)
rxCcLicenseText = regexp.MustCompile(`(?i)(cc|creative commons) (by-nc-nd|by-nc-sa|by-nc|by-nd|by-sa|by|zero) ?([1-9]\.[0-9])?`)
rxAuthorPrefix = regexp.MustCompile(`(?i)^([a-zäöüß]+(ed|t))? ?(written by|words by|words|by|von|from) `)
rxAuthorDigits = regexp.MustCompile(`(?i)\pN.+?$`)
rxAuthorSocialMedia = regexp.MustCompile(`(?i)@\S+`)
rxAuthorSpaceChars = regexp.MustCompile(`(?i)[._+]`)
rxAuthorNickname = regexp.MustCompile(`(?i)["‘({\[’\'][^"]+?[‘’"\')\]}]`)
rxAuthorSpecialChars = regexp.MustCompile(`(?i)[^\pL\pM\pN_]+$|[:()?*$#!%/<>{}~¿]`)
rxAuthorPreposition = regexp.MustCompile(`(?i)\b\s+(am|on|for|at|in|to|from|of|via|with|—|-|–)\s+(.*)`)
rxAuthorEmail = regexp.MustCompile(`(?i)\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b`)
rxAuthorSeparator = regexp.MustCompile(`(?i)/|;|,|\||&|(?:^|[^\pL\pM\pN_])[u|a]nd(?:$|[^\pL\pM\pN_])`)
rxAuthorHTML = regexp.MustCompile(`(?i)<[^>]+>`)
metaNameAuthor = sliceToMap(
"article:author", "atc-metaauthor", "author", "authors", "byl", "citation_author",
"creator", "dc.creator", "dc.creator.aut", "dc:creator",
"dcterms.creator", "dcterms.creator.aut", "dcsext.author", "parsely-author",
"rbauthors", "sailthru.author", "shareaholic:article_author_name") // questionable: twitter:creator
metaNameTitle = sliceToMap(
"citation_title", "dc.title", "dcterms.title", "fb_title",
"headline", "parsely-title", "sailthru.title", "shareaholic:title",
"rbtitle", "title", "twitter:title")
metaNameDescription = sliceToMap(
"dc.description", "dc:description",
"dcterms.abstract", "dcterms.description",
"description", "sailthru.description", "twitter:description")
metaNamePublisher = sliceToMap(
"article:publisher", "citation_journal_title", "copyright",
"dc.publisher", "dc:publisher", "dcterms.publisher",
"publisher", "sailthru.publisher", "rbpubname", "twitter:site") // questionable: citation_publisher
metaNameTag = sliceToMap(
"citation_keywords", "dcterms.subject", "keywords", "parsely-tags",
"shareaholic:keywords", "tags")
metaNameImage = sliceToMap(
"image", "og:image", "og:image:url", "og:image:secure_url",
"twitter:image", "twitter:image:src")
// metaNameUrl = sliceToMap("rbmainurl", "twitter:url")
fastHtmlDateOpts = &htmldate.Options{UseOriginalDate: true, SkipExtensiveSearch: true}
extensiveHtmlDateOpts = &htmldate.Options{UseOriginalDate: true, SkipExtensiveSearch: false}
)
// Metadata is the metadata of the page.
type Metadata struct {
Title string
Author string
URL string
Hostname string
Description string
Sitename string
Date time.Time
Categories []string
Tags []string
ID string
Fingerprint string
License string
Language string
Image string
PageType string
}
func extractMetadata(doc *html.Node, opts Options) Metadata {
// Extract metadata from <meta> tags
metadata := examineMeta(doc)
metadata.Author = removeBlacklistedAuthors(metadata.Author, opts)
// TODO: in original trafilatura, if author name is a single word,
// it's regarded as invalid and author name will be set to empty.
// However, in some Asia country there are case hwere the name is
// only a single word, so I decided to not implement it here.
// Extract metadata from JSON-LD and override
metadata = extractJsonLd(opts, doc, metadata)
metadata.Author = removeBlacklistedAuthors(metadata.Author, opts)
// Try extracting from DOM element using selectors
// Title
if metadata.Title == "" {
metadata.Title = extractDomTitle(doc)
}
// Author
if metadata.Author == "" {
metadata.Author = extractDomAuthor(doc)
metadata.Author = removeBlacklistedAuthors(metadata.Author, opts)
}
// URL
if metadata.URL == "" {
metadata.URL = extractDomURL(doc)
}
// Validate URL
// If URL exist, it must be absolute. If not absolute, just remove it.
if metadata.URL != "" {
validURL, isAbs := validateURL(metadata.URL, opts.OriginalURL)
if validURL != "" && isAbs {
metadata.URL = validURL
} else {
metadata.URL = ""
}
}
// If URL not found but original URL specified, just use that.
if metadata.URL == "" && opts.OriginalURL != nil {
metadata.URL = opts.OriginalURL.String()
}
// Hostname
if metadata.URL != "" {
metadata.Hostname = getDomainURL(metadata.URL)
}
// Image
if metadata.Image == "" {
metadata.Image = extractDomImage(doc)
}
// Validate image URL, it must be absolute. If not absolute, just remove it.
if metadata.Image != "" {
validURL, isAbs := validateURL(metadata.Image, opts.OriginalURL)
if validURL != "" && isAbs {
metadata.Image = validURL
} else {
metadata.Image = ""
}
}
// Publish date
if opts.HtmlDateOverride != nil { // User has his own HtmlDate result
if opts.HtmlDateOverride.HasTime {
metadata.Date = opts.HtmlDateOverride.DateTime
}
} else {
var optsPointer *htmldate.Options
switch {
case opts.HtmlDateOptions != nil: // User has his own HtmlDate options
optsPointer = opts.HtmlDateOptions
case opts.HtmlDateMode == Default:
if opts.EnableFallback {
optsPointer = extensiveHtmlDateOpts
} else {
optsPointer = fastHtmlDateOpts
}
case opts.HtmlDateMode == Fast:
optsPointer = fastHtmlDateOpts
case opts.HtmlDateMode == Extensive:
optsPointer = extensiveHtmlDateOpts
case opts.HtmlDateMode == Disabled:
optsPointer = nil
}
if optsPointer != nil {
htmlDateOpts := *optsPointer
htmlDateOpts.URL = metadata.URL
publishDate, err := htmldate.FromDocument(doc, htmlDateOpts)
if err == nil && !publishDate.IsZero() {
metadata.Date = publishDate.DateTime
}
}
}
// Sitename
if metadata.Sitename == "" {
metadata.Sitename = extractDomSitename(doc)
}
if metadata.Sitename != "" {
// Scrap Twitter ID
metadata.Sitename = strings.TrimPrefix(metadata.Sitename, "@")
// Capitalize
firstRune := getRune(metadata.Sitename, 0)
if !strings.Contains(metadata.Sitename, ".") && !unicode.IsUpper(firstRune) {
metadata.Sitename = cases.Title(language.English).String(metadata.Sitename)
}
} else if metadata.URL != "" {
matches := rxSitenameFinder.FindStringSubmatch(metadata.URL)
if len(matches) > 0 {
metadata.Sitename = matches[1]
}
}
// Categories
if len(metadata.Categories) == 0 {
metadata.Categories = extractDomCategories(doc)
}
if len(metadata.Categories) != 0 {
metadata.Categories = cleanCatTags(metadata.Categories)
}
// Tags
if len(metadata.Tags) == 0 {
metadata.Tags = extractDomTags(doc)
}
if len(metadata.Tags) != 0 {
metadata.Tags = cleanCatTags(metadata.Tags)
}
// License
metadata.License = extractLicense(doc)
return metadata
}
// examineMeta search meta tags for relevant information
func examineMeta(doc *html.Node) Metadata {
// Bootstrap metadata from OpenGraph tags
metadata := extractOpenGraphMeta(doc)
// If all OpenGraph metadata have been assigned, we can return it
if metadata.Title != "" && metadata.Author != "" &&
metadata.URL != "" && metadata.Description != "" &&
metadata.Sitename != "" && metadata.Image != "" && metadata.PageType != "" {
return metadata
}
// Scan all <meta> nodes that has attribute "content"
var tmpSitename string
for _, node := range dom.QuerySelectorAll(doc, "head meta[content]") {
// Make sure content is not empty
content := dom.GetAttribute(node, "content")
content = rxHtmlStripTag.ReplaceAllString(content, "")
content = html.UnescapeString(content)
content = trim(content)
if content == "" {
continue
}
// Handle property attribute
property := dom.GetAttribute(node, "property")
property = trim(property)
if property != "" {
switch {
case strings.HasPrefix(property, "og:"):
// We already handle OpenGraph before
case property == "article:tag":
metadata.Tags = append(metadata.Tags, content)
case strIn(property, "author", "article:author"):
metadata.Author = normalizeAuthors(metadata.Author, content)
case property == "article:publisher":
metadata.Sitename = strOr(metadata.Sitename, content)
case inMap(property, metaNameImage):
metadata.Image = strOr(metadata.Image, content)
}
continue
}
// Handle name attribute
name := dom.GetAttribute(node, "name")
name = strings.ToLower(name)
name = trim(name)
if name != "" {
if inMap(name, metaNameAuthor) {
content = rxHtmlStripTag.ReplaceAllString(content, "")
metadata.Author = normalizeAuthors(metadata.Author, content)
} else if inMap(name, metaNameTitle) {
metadata.Title = strOr(metadata.Title, content)
} else if inMap(name, metaNameDescription) {
metadata.Description = strOr(metadata.Description, content)
} else if inMap(name, metaNamePublisher) {
metadata.Sitename = strOr(metadata.Sitename, content)
} else if strIn(name, "twitter:site", "application-name") || strings.Contains(name, "twitter:app:name") {
tmpSitename = content
} else if name == "twitter:url" {
if isAbs, _ := isAbsoluteURL(content); metadata.URL == "" && isAbs {
metadata.URL = content
}
} else if inMap(name, metaNameTag) { // "page-topic"
metadata.Tags = append(metadata.Tags, content)
}
continue
}
// Handle itemprop attribute
itemprop := dom.GetAttribute(node, "itemprop")
itemprop = trim(itemprop)
if itemprop != "" {
switch itemprop {
case "author":
metadata.Author = normalizeAuthors(metadata.Author, content)
case "description":
metadata.Description = strOr(metadata.Description, content)
case "headline":
metadata.Title = strOr(metadata.Title, content)
}
continue
}
}
// Use temporary site name if necessary
if metadata.Sitename == "" && tmpSitename != "" {
metadata.Sitename = tmpSitename
}
// Clean up author and tags
metadata.Author = validateMetadataName(metadata.Author)
metadata.Categories = uniquifyLists(metadata.Categories...)
metadata.Tags = uniquifyLists(metadata.Tags...)
return metadata
}
// extractOpenGraphMeta search meta tags following the OpenGraph guidelines (https://ogp.me/)
func extractOpenGraphMeta(doc *html.Node) Metadata {
var metadata Metadata
// Scan all <meta> nodes whose property starts with "og:"
for _, node := range dom.QuerySelectorAll(doc, `meta[property^="og:"]`) {
// Get property name
propName := dom.GetAttribute(node, "property")
propName = trim(propName)
// Make sure node has content attribute
content := dom.GetAttribute(node, "content")
content = html.UnescapeString(content)
content = trim(content)
if content == "" {
continue
}
// Fill metadata
switch propName {
case "og:site_name":
metadata.Sitename = content
case "og:title":
metadata.Title = content
case "og:description":
metadata.Description = content
case "og:author", "og:article:author":
metadata.Author = normalizeAuthors("", content)
case "og:image", "og:image:url", "og:image:secure_url":
metadata.Image = content
case "og:url":
if isAbs, _ := isAbsoluteURL(content); isAbs {
metadata.URL = content
}
case "og:article:tag":
metadata.Tags = uniquifyLists(content)
case "og:type":
metadata.PageType = content
}
}
return metadata
}
func validateMetadataName(name string) string {
if name == "" {
return name
}
if !strings.Contains(name, " ") || strings.HasPrefix(name, "http") {
return ""
}
// Make sure author doesn't contain JSON symbols (in case JSON+LD has wrong format)
if rxJsonSymbol.MatchString(name) {
return ""
}
return name
}
func examineTitleElement(doc *html.Node) (title, first, second string) {
titleNode := dom.QuerySelector(doc, "head > title")
if titleNode != nil {
title = dom.TextContent(titleNode)
title = trim(title)
matches := rxTitleCleaner.FindStringSubmatch(title)
if len(matches) > 0 {
first, second = matches[1], matches[2]
}
}
return
}
// extractDomTitle returns the document title from DOM elements.
func extractDomTitle(doc *html.Node) string {
// If there are only one H1, use it as title
h1Nodes := dom.QuerySelectorAll(doc, "h1")
if len(h1Nodes) == 1 {
title := trim(dom.TextContent(h1Nodes[0]))
if title != "" {
return title
}
}
// Look for title using several CSS selectors
title := extractDomMetaSelectors(doc, 200, selector.MetaTitle)
if title != "" {
return title
}
// Look in <title> tag
title, first, second := examineTitleElement(doc)
if first != "" && !strings.Contains(first, ".") {
title = first
} else if second != "" && !strings.Contains(second, ".") {
title = second
}
if title != "" {
return title
}
// If still not found, just use the first H1 as it is
if len(h1Nodes) > 0 {
title := dom.TextContent(h1Nodes[0])
return trim(title)
}
// If STILL not found, use the first H2 as it is
h2Node := dom.QuerySelector(doc, "h2")
if h2Node != nil {
title := dom.TextContent(h2Node)
return trim(title)
}
return ""
}
// extractDomAuthor returns the document author from DOM elements.
func extractDomAuthor(doc *html.Node) string {
clone := dom.Clone(doc, true)
clone = pruneUnwantedNodes(clone, selector.MetaAuthorDiscard)
author := extractDomMetaSelectors(clone, 120, selector.MetaAuthor)
if author != "" {
return normalizeAuthors("", author)
}
return ""
}
// extractDomURL extracts the document URL from the canonical <link>.
func extractDomURL(doc *html.Node) string {
var url string
// Try canonical link first
linkNode := dom.QuerySelector(doc, `link[rel="canonical"][href]`)
if linkNode == nil {
// Now try default language link
linkNode = dom.QuerySelector(doc, `link[rel="alternate"][hreflang="x-default"]`)
}
if linkNode != nil {
if href := trim(dom.GetAttribute(linkNode, "href")); href != "" {
url = href
}
}
// Add domain name if it's missing
if url != "" && strings.HasPrefix(url, "/") {
for _, node := range dom.QuerySelectorAll(doc, "head meta[content]") {
nodeName := trim(dom.GetAttribute(node, "name"))
nodeProperty := trim(dom.GetAttribute(node, "property"))
attrType := strOr(nodeName, nodeProperty)
if attrType == "" {
continue
}
if strings.HasPrefix(attrType, "og:") || strings.HasPrefix(attrType, "twitter:") {
nodeContent := trim(dom.GetAttribute(node, "content"))
if baseURL := getBaseURL(nodeContent); baseURL != "" {
url = baseURL + url
break
}
}
}
}
// If default URL is not specified, just give up
return url
}
// extractDomSitename extracts the name of a site from the main title (if it exists).
func extractDomSitename(doc *html.Node) string {
_, first, second := examineTitleElement(doc)
if first != "" && strings.Contains(first, ".") {
return first
} else if second != "" && strings.Contains(second, ".") {
return second
}
return ""
}
// extractDomCategories returns the categories of the document.
func extractDomCategories(doc *html.Node) []string {
categories := []string{}
// Try using selectors
for _, query := range selector.MetaCategories {
for _, node := range selector.QueryAll(doc, query) {
href := trim(dom.GetAttribute(node, "href"))
if href != "" && rxCategoryHref.MatchString(href) {
if text := trim(dom.TextContent(node)); text != "" {
categories = append(categories, text)
}
}
}
if len(categories) > 0 {
break
}
}
// Fallback
if len(categories) == 0 {
selectors := []string{
`head meta[property="article:section"]`,
`head meta[name*="subject"]`}
mergedSelector := strings.Join(selectors, ", ")
for _, node := range dom.QuerySelectorAll(doc, mergedSelector) {
if content := trim(dom.GetAttribute(node, "content")); content != "" {
categories = append(categories, content)
}
}
}
return uniquifyLists(categories...)
}
// extractDomTags returns the tags of the document.
func extractDomTags(doc *html.Node) []string {
tags := []string{}
// Try using selectors
for _, query := range selector.MetaTags {
for _, node := range selector.QueryAll(doc, query) {
href := trim(dom.GetAttribute(node, "href"))
if href != "" && rxTagHref.MatchString(href) {
if text := trim(dom.TextContent(node)); text != "" {
tags = append(tags, text)
}
}
}
if len(tags) > 0 {
break
}
}
return uniquifyLists(tags...)
}
// extractDomImage returns the hero image of the document using Twitter meta tags.
func extractDomImage(doc *html.Node) string {
for _, node := range dom.QuerySelectorAll(doc, `meta[property^="twitter:"]`) {
content := trim(dom.GetAttribute(node, "content"))
property := trim(dom.GetAttribute(node, "property"))
if (property == "twitter:image" || property == "twitter:image:src") && content != "" {
return content
}
}
return ""
}
func cleanCatTags(catTags []string) []string {
cleanedEntries := []string{}
for _, entry := range catTags {
for _, item := range rxCommaSeparator.Split(entry, -1) {
if item = trim(item); item != "" {
cleanedEntries = append(cleanedEntries, item)
}
}
}
return cleanedEntries
}
func extractDomMetaSelectors(doc *html.Node, limit int, queries []selector.Rule) string {
for _, query := range queries {
for _, node := range selector.QueryAll(doc, query) {
text := etree.IterText(node, " ")
text = trim(text)
lenText := utf8.RuneCountInString(text)
if lenText > 2 && lenText < limit {
return text
}
}
}
return ""
}
// extractLicense search the HTML code for license information and parse it.
func extractLicense(doc *html.Node) string {
// Look for links labeled as license
for _, a := range dom.QuerySelectorAll(doc, `a[rel="license"][href]`) {
if result := parseLicenseElement(a, false); result != "" {
return result
}
}
// Probe footer elements for CC links
selector := `footer a[href], div[class*="footer"] a[href], div[id*="footer"] a[href]`
for _, node := range dom.QuerySelectorAll(doc, selector) {
if result := parseLicenseElement(node, true); result != "" {
return result
}
}
return ""
}
// parseLicenseElement probes a link for identifiable free license cues.
// Parse the href attribute first and then the link text.
func parseLicenseElement(node *html.Node, strict bool) string {
// Check in href for CC license
if href := trim(dom.GetAttribute(node, "href")); href != "" {
if parts := rxCcLicense.FindStringSubmatch(href); len(parts) > 0 {
return fmt.Sprintf("CC %s %s", strings.ToUpper(parts[1]), parts[2])
}
}
// Check in text
if text := trim(etree.Text(node)); text != "" {
if !strict {
return text
}
if parts := rxCcLicenseText.FindStringSubmatch(text); len(parts) > 0 {
return parts[0]
}
}
return ""
}
func normalizeAuthors(authors string, input string) string {
if rxUrlCheck.MatchString(input) || rxAuthorEmail.MatchString(input) {
return authors
}
// Clean up input string
input = trim(input)
input = html.UnescapeString(input)
input = gomoji.RemoveEmojis(input)
input = rxAuthorDigits.ReplaceAllString(input, "")
input = rxAuthorSocialMedia.ReplaceAllString(input, "")
input = rxAuthorSpaceChars.ReplaceAllString(input, " ")
// Fix HTML entities
if strings.Contains(input, "&#") || strings.Contains(input, "&") {
input = html.UnescapeString(input)
}
// Remove HTML tags
input = rxAuthorHTML.ReplaceAllString(input, "")
// Prepare list of current authors
listAuthor := strings.Split(authors, "; ")
if len(listAuthor) == 1 && listAuthor[0] == "" {
listAuthor = []string{}
}
// Track the existing authors
tracker := sliceToMap(listAuthor...)
// Save the new authors
for _, a := range rxAuthorSeparator.Split(input, -1) {
// Clean the author
a = rxAuthorNickname.ReplaceAllString(a, "")
a = rxAuthorSpecialChars.ReplaceAllString(a, "")
a = rxAuthorPrefix.ReplaceAllString(a, "")
a = rxAuthorPreposition.ReplaceAllString(a, "")
a = trim(a)
// Stop if author is empty, or single word but too long.
// The max length 23 is taken from ISO IEC-7813.
length := utf8.RuneCountInString(a)
hasDash := strings.Contains(a, "-")
hasSpace := strings.Contains(a, " ")
if length == 0 || (!hasDash && !hasSpace && length >= 50) {
continue
}
// If necessary, convert to title
if !unicode.IsUpper(getRune(a, 0)) || strings.ToLower(a) == a {
a = cases.Title(language.English).String(a)
}
// Save to list
_, tracked := tracker[a]
if !strings.Contains(authors, a) && !tracked {
tracker[a] = struct{}{}
listAuthor = append(listAuthor, a)
}
}
return strings.Join(listAuthor, "; ")
}
func removeBlacklistedAuthors(current string, opts Options) string {
if current == "" {
return current
}
blacklisted := make(map[string]struct{})
for _, ab := range opts.BlacklistedAuthors {
blacklisted[strings.ToLower(ab)] = struct{}{}
}
var allowedAuthors []string
for _, author := range strings.Split(current, ";") {
author = strings.TrimSpace(author)
if _, exist := blacklisted[strings.ToLower(author)]; !exist {
allowedAuthors = append(allowedAuthors, author)
}
}
if len(allowedAuthors) > 0 {
return strings.Join(allowedAuthors, "; ")
}
return ""
}