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package main
import (
"fmt"
"sync"
"time"
)
type Fetcher interface {
Fetch(url string) (body string, urls []string, err error)
}
type fakeFetcher map[string]*fakeResult
type fakeResult struct {
body string
urls []string
}
func (f fakeFetcher) Fetch(url string) (string, []string, error) {
if res, ok := f[url]; ok {
return res.body, res.urls, nil
}
return "", nil, fmt.Errorf("not found: %s", url)
}
func addToMap(url string) {
mux.Lock()
crawlMap[url] = url
mux.Unlock()
}
func Crawl(url string, depth int, fetcher Fetcher) {
if depth <= 0 {
return
}
body, urls, err := fetcher.Fetch(url)
if err != nil {
fmt.Println(err)
return
}
addToMap(url)
fmt.Printf("found: %s %q\n", url, body)
for _, u := range urls {
if _, ok := crawlMap[u]; !ok {
addToMap(u)
go Crawl(u, depth-1, fetcher)
}
}
return
}
func main() {
go Crawl("http://golang.org/", 4, fetcher)
time.Sleep(time.Second * 5)
fmt.Println("Crawling finished")
}
var mux = sync.Mutex{}
var crawlMap = make(map[string]string)
var fetcher = fakeFetcher{
"http://golang.org/": &fakeResult{
"The Go Programming Language",
[]string{
"http://golang.org/pkg/",
"http://golang.org/cmd/",
},
},
"http://golang.org/pkg/": &fakeResult{
"Packages",
[]string{
"http://golang.org/",
"http://golang.org/cmd/",
"http://golang.org/pkg/fmt/",
"http://golang.org/pkg/os/",
},
},
"http://golang.org/pkg/fmt/": &fakeResult{
"Package fmt",
[]string{
"http://golang.org/",
"http://golang.org/pkg/",
},
},
"http://golang.org/pkg/os/": &fakeResult{
"Package os",
[]string{
"http://golang.org/",
"http://golang.org/pkg/",
},
},
}
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