move link extraction to a common location

analysis/links.go

+// Extract links from HTML/CSS content.
+
+package analysis
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+
+	"github.com/PuerkitoBio/goquery"
+)
+
+var (
+	urlcssRx = regexp.MustCompile(`background.*:.*url\(["']?([^'"\)]+)["']?\)`)
+
+	linkMatches = []struct {
+		tag  string
+		attr string
+	}{
+		{"a", "href"},
+		{"link", "href"},
+		{"img", "src"},
+		{"script", "src"},
+	}
+)
+
+func GetLinks(resp *http.Response) ([]*url.URL, error) {
+	var outlinks []string
+
+	ctype := resp.Header.Get("Content-Type")
+	if strings.HasPrefix(ctype, "text/html") {
+		doc, err := goquery.NewDocumentFromResponse(resp)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, lm := range linkMatches {
+			doc.Find(fmt.Sprintf("%s[%s]", lm.tag, lm.attr)).Each(func(i int, s *goquery.Selection) {
+				val, _ := s.Attr(lm.attr)
+				outlinks = append(outlinks, val)
+			})
+		}
+	} else if strings.HasPrefix(ctype, "text/css") {
+		if data, err := ioutil.ReadAll(resp.Body); err == nil {
+			for _, val := range urlcssRx.FindAllStringSubmatch(string(data), -1) {
+				outlinks = append(outlinks, val[1])
+			}
+		}
+	}
+
+	// Uniquify and parse outbound links.
+	var result []*url.URL
+	links := make(map[string]*url.URL)
+	for _, val := range outlinks {
+		if linkurl, err := resp.Request.URL.Parse(val); err == nil {
+			links[linkurl.String()] = linkurl
+		}
+	}
+	for _, link := range links {
+		result = append(result, link)
+	}
+
+	return result, nil
+}

cmd/crawl/crawl.go

@@ -10,15 +10,13 @@ import (
 	"io/ioutil"
 	"log"
 	"net/http"
-	"net/url"
 	"os"
-	"regexp"
 	"strconv"
 	"strings"
 
 	"git.autistici.org/ale/crawl"
+	"git.autistici.org/ale/crawl/analysis"
 	"git.autistici.org/ale/crawl/warc"
-	"github.com/PuerkitoBio/goquery"
 )
 
 var (
@@ -27,53 +25,15 @@ var (
 	depth        = flag.Int("depth", 10, "maximum link depth")
 	validSchemes = flag.String("schemes", "http,https", "comma-separated list of allowed protocols")
 	outputFile   = flag.String("output", "crawl.warc.gz", "output WARC file")
-
-	urlcssRx = regexp.MustCompile(`background.*:.*url\(["']?([^'"\)]+)["']?\)`)
 )
 
-var linkMatches = []struct {
-	tag  string
-	attr string
-}{
-	{"a", "href"},
-	{"link", "href"},
-	{"img", "src"},
-	{"script", "src"},
-}
-
 func extractLinks(c *crawl.Crawler, u string, depth int, resp *http.Response, err error) error {
-	var outlinks []string
-
-	ctype := resp.Header.Get("Content-Type")
-	if strings.HasPrefix(ctype, "text/html") {
-		doc, err := goquery.NewDocumentFromResponse(resp)
-		if err != nil {
-			return err
-		}
-
-		for _, lm := range linkMatches {
-			doc.Find(fmt.Sprintf("%s[%s]", lm.tag, lm.attr)).Each(func(i int, s *goquery.Selection) {
-				val, _ := s.Attr(lm.attr)
-				outlinks = append(outlinks, val)
-			})
-		}
-	} else if strings.HasPrefix(ctype, "text/css") {
-		if data, err := ioutil.ReadAll(resp.Body); err == nil {
-			for _, val := range urlcssRx.FindAllStringSubmatch(string(data), -1) {
-				outlinks = append(outlinks, val[1])
-			}
-		}
+	links, err := analysis.GetLinks(resp)
+	if err != nil {
+		return err
 	}
 
-	// Uniquify and parse outbound links.
-	links := make(map[string]*url.URL)
-	for _, val := range outlinks {
-		if linkurl, err := resp.Request.URL.Parse(val); err == nil {
-			links[linkurl.String()] = linkurl
-		}
-	}
 	for _, link := range links {
-		//log.Printf("%s -> %s", u, link.String())
 		c.Enqueue(link, depth+1)
 	}
 

cmd/links/links.go

@@ -6,14 +6,12 @@ package main
 
 import (
 	"flag"
-	"fmt"
 	"log"
 	"net/http"
-	"net/url"
 	"strings"
 
 	"git.autistici.org/ale/crawl"
-	"github.com/PuerkitoBio/goquery"
+	"git.autistici.org/ale/crawl/analysis"
 )
 
 var (
@@ -23,41 +21,16 @@ var (
 	validSchemes = flag.String("schemes", "http,https", "comma-separated list of allowed protocols")
 )
 
-var linkMatches = []struct {
-	tag  string
-	attr string
-}{
-	{"a", "href"},
-	{"link", "href"},
-	{"img", "src"},
-	{"script", "src"},
-}
-
 func extractLinks(c *crawl.Crawler, u string, depth int, resp *http.Response, err error) error {
-	if !strings.HasPrefix(resp.Header.Get("Content-Type"), "text/html") {
-		return nil
-	}
-
-	doc, err := goquery.NewDocumentFromResponse(resp)
+	links, err := analysis.GetLinks(resp)
 	if err != nil {
 		return err
 	}
 
-	links := make(map[string]*url.URL)
-
-	for _, lm := range linkMatches {
-		doc.Find(fmt.Sprintf("%s[%s]", lm.tag, lm.attr)).Each(func(i int, s *goquery.Selection) {
-			val, _ := s.Attr(lm.attr)
-			if linkurl, err := resp.Request.URL.Parse(val); err == nil {
-				links[linkurl.String()] = linkurl
-			}
-		})
-	}
-
 	for _, link := range links {
-		//log.Printf("%s -> %s", u, link.String())
 		c.Enqueue(link, depth+1)
 	}
+
 	return nil
 }