deploy: 06a1bdf735

vendor/gopl.io/ch5/findlinks2/main.go

@@ -0,0 +1,69 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 125.
+
+// Findlinks2 does an HTTP GET on each URL, parses the
+// result as HTML, and prints the links within it.
+//
+// Usage:
+//	findlinks url ...
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+
+	"golang.org/x/net/html"
+)
+
+// visit appends to links each link found in n, and returns the result.
+func visit(links []string, n *html.Node) []string {
+	if n.Type == html.ElementNode && n.Data == "a" {
+		for _, a := range n.Attr {
+			if a.Key == "href" {
+				links = append(links, a.Val)
+			}
+		}
+	}
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		links = visit(links, c)
+	}
+	return links
+}
+
+//!+
+func main() {
+	for _, url := range os.Args[1:] {
+		links, err := findLinks(url)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "findlinks2: %v\n", err)
+			continue
+		}
+		for _, link := range links {
+			fmt.Println(link)
+		}
+	}
+}
+
+// findLinks performs an HTTP GET request for url, parses the
+// response as HTML, and extracts and returns the links.
+func findLinks(url string) ([]string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		resp.Body.Close()
+		return nil, fmt.Errorf("getting %s: %s", url, resp.Status)
+	}
+	doc, err := html.Parse(resp.Body)
+	resp.Body.Close()
+	if err != nil {
+		return nil, fmt.Errorf("parsing %s as HTML: %v", url, err)
+	}
+	return visit(nil, doc), nil
+}
+
+//!-