From f2d2b620fa453865962b5debd91535cd7718297c Mon Sep 17 00:00:00 2001
From: Richard Patel <terorie@alphakevin.club>
Date: Sat, 27 Oct 2018 04:08:32 +0200
Subject: [PATCH] Simple queue crawler

---
 crawl.go | 185 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 185 insertions(+)
 create mode 100644 crawl.go

diff --git a/crawl.go b/crawl.go
new file mode 100644
index 0000000..9e030e3
--- /dev/null
+++ b/crawl.go
@@ -0,0 +1,185 @@
+package main
+
+import (
+	"github.com/PuerkitoBio/goquery"
+	"github.com/sirupsen/logrus"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	nConns = 100
+)
+
+var client = http.DefaultClient
+var wait sync.WaitGroup
+
+var visited int64
+
+var in chan<- url.URL
+var out <-chan url.URL
+
+func main() {
+	if len(os.Args) != 2 {
+		println("Usage: ./crawl <url>")
+		os.Exit(1)
+	}
+
+	in, out = makeInfinite()
+	
+	go func() {
+		var visitedLast int64 = 0
+		for range time.NewTicker(time.Second).C {
+			visitedNow := atomic.LoadInt64(&visited)
+			logrus.
+				WithField("per_second", visitedNow - visitedLast).
+				WithField("total", visitedNow).
+				Info("Tick")
+			visitedLast = visitedNow
+		}
+	}()
+
+	base, _ := url.Parse(os.Args[1])
+	in <- *base
+	wait.Add(nConns)
+	for i := 0; i < nConns; i++ {
+		go worker()
+	}
+	wait.Wait()
+}
+
+func worker() {
+	for u := range out {
+		if strings.HasSuffix(u.Path, "/") {
+			// Dir
+			links := listDir(u)
+			for _, sub := range links {
+				subrefi, err := url.Parse(sub)
+				subref := *subrefi
+				if err != nil { continue }
+
+				in <- *u.ResolveReference(&subref)
+			}
+		} else {
+			// File
+			// TODO check file
+		}
+	}
+	wait.Done()
+}
+
+func listDir(u url.URL) (links []string) {
+	//logrus.Infof("Visiting %s", u)
+	atomic.AddInt64(&visited, 1)
+
+	res, err := client.Get(u.String())
+	if err != nil {
+		logrus.Error(err)
+		return
+	}
+	defer res.Body.Close()
+
+	doc, err := goquery.NewDocumentFromReader(res.Body)
+	if err != nil {
+		logrus.Error(err)
+		return
+	}
+
+	doc.Find("a[href]").Each(func(_ int, s *goquery.Selection) {
+		href, _ := s.Attr("href")
+		text := s.Text()
+
+		if href == "." {
+			return
+		}
+
+		for _, entry := range blackList {
+			if strings.Contains(href, entry) {
+				return
+			}
+		}
+
+		for _, entry := range fileNameBlackList {
+			if strings.Contains(text, entry) {
+				return
+			}
+		}
+
+		links = append(links, href)
+	})
+
+	return
+}
+
+func makeInfinite() (chan<- url.URL, <-chan url.URL) {
+	in := make(chan url.URL)
+	out := make(chan url.URL)
+	// Set up in and out queues
+	go func() {
+		var inQueue []url.URL
+		outCh := func() chan url.URL {
+			if len(inQueue) == 0 {
+				return nil
+			}
+			return out
+		}
+		for len(inQueue) > 0 || in != nil {
+			if len(inQueue) == 0 {
+				v, ok := <-in
+				if !ok {
+					in = nil
+				} else {
+					inQueue = append(inQueue, v)
+				}
+			} else {
+				select {
+				case v, ok := <-in:
+					if !ok {
+						in = nil
+					} else {
+						inQueue = append(inQueue, v)
+					}
+				case outCh() <- inQueue[0]:
+					inQueue = inQueue[1:]
+				}
+			}
+		}
+		close(out)
+	}()
+	return in, out
+}
+
+var blackList = [...]string {
+	"?C=N&O=D",
+	"?C=M&O=A",
+	"?C=S&O=A",
+	"?C=D&O=A",
+	"?C=N;O=D",
+	"?C=M;O=A",
+	"?C=M&O=D",
+	"?C=S;O=A",
+	"?C=S&O=D",
+	"?C=D;O=A",
+	"?MA",
+	"?SA",
+	"?DA",
+	"?ND",
+	"?C=N&O=A",
+	"?C=N&O=A",
+	"?M=A",
+	"?N=D",
+	"?S=A",
+	"?D=A",
+}
+
+var fileNameBlackList = [...]string {
+	"Parent Directory",
+	" Parent Directory",
+	"../",
+}
+