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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package followlinks
import (
"net/url"
"regexp"
"strings"
"github.com/PuerkitoBio/goquery"
"github.com/philippta/flyscrape"
)
func init() {
flyscrape.RegisterModule(Module{})
}
type Module struct {
Follow *[]string `json:"follow"`
}
func (Module) ModuleInfo() flyscrape.ModuleInfo {
return flyscrape.ModuleInfo{
ID: "followlinks",
New: func() flyscrape.Module { return new(Module) },
}
}
func (m *Module) Provision(ctx flyscrape.Context) {
if m.Follow == nil {
m.Follow = &[]string{"a[href]"}
}
}
func (m *Module) ReceiveResponse(resp *flyscrape.Response) {
if m.Follow == nil {
return
}
for _, link := range m.parseLinks(string(resp.Body), resp.Request.URL) {
resp.Visit(link)
}
}
func (m *Module) parseLinks(html string, origin string) []string {
if m.Follow == nil {
return nil
}
var links []string
doc, err := goquery.NewDocumentFromReader(strings.NewReader(html))
if err != nil {
return nil
}
originurl, err := url.Parse(origin)
if err != nil {
return nil
}
uniqueLinks := make(map[string]bool)
for _, selector := range *m.Follow {
attr := parseSelectorAttr(selector)
doc.Find(selector).Each(func(i int, s *goquery.Selection) {
link, _ := s.Attr(attr)
parsedLink, err := originurl.Parse(link)
if err != nil || !isValidLink(parsedLink) {
return
}
absLink := parsedLink.String()
if !uniqueLinks[absLink] {
links = append(links, absLink)
uniqueLinks[absLink] = true
}
})
}
return links
}
func isValidLink(link *url.URL) bool {
if link.Scheme != "" && link.Scheme != "http" && link.Scheme != "https" {
return false
}
return true
}
func parseSelectorAttr(sel string) string {
matches := selectorExpr.FindAllString(sel, -1)
if len(matches) == 0 {
return "href"
}
attr := attrExpr.FindString(matches[len(matches)-1])
if attr == "" {
return "href"
}
return attr
}
var (
_ flyscrape.Provisioner = (*Module)(nil)
_ flyscrape.ResponseReceiver = (*Module)(nil)
)
var (
selectorExpr = regexp.MustCompile(`\[(.*?)\]`)
attrExpr = regexp.MustCompile(`[\w-]+`)
)
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