chromedp: add links extract example

chromedp/links/main.go

@@ -0,0 +1,137 @@
+// Copyright 2023-2025 Lightpanda (Selecy SAS)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"log/slog"
+	"os"
+
+	"github.com/chromedp/cdproto/cdp"
+	"github.com/chromedp/chromedp"
+)
+
+const (
+	exitOK   = 0
+	exitFail = 1
+)
+
+// main starts interruptable context and runs the program.
+func main() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := run(ctx, os.Args, os.Stdout, os.Stderr)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		os.Exit(exitFail)
+	}
+
+	os.Exit(exitOK)
+}
+
+const (
+	CdpWSDefault = "ws://127.0.0.1:9222"
+)
+
+func run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
+	// declare runtime flag parameters.
+	flags := flag.NewFlagSet(args[0], flag.ExitOnError)
+	flags.SetOutput(stderr)
+
+	var (
+		verbose = flags.Bool("verbose", false, "enable debug log level")
+		cdpws   = flags.String("cdp", env("CDPCLI_WS", CdpWSDefault), "cdp ws to connect")
+	)
+
+	// usage func declaration.
+	exec := args[0]
+	flags.Usage = func() {
+		fmt.Fprintf(stderr, "usage: %s <url>]\n", exec)
+		fmt.Fprintf(stderr, "chromedp fetch an url and extracts all links.\n")
+		fmt.Fprintf(stderr, "\nCommand line options:\n")
+		flags.PrintDefaults()
+		fmt.Fprintf(stderr, "\nEnvironment vars:\n")
+		fmt.Fprintf(stderr, "\tCDPCLI_WS\tdefault %s\n", CdpWSDefault)
+	}
+	if err := flags.Parse(args[1:]); err != nil {
+		return err
+	}
+
+	if *verbose {
+		slog.SetLogLoggerLevel(slog.LevelDebug)
+	}
+
+	args = flags.Args()
+	if len(args) != 1 {
+		return errors.New("url is required")
+	}
+	url := args[0]
+
+	ctx, cancel := chromedp.NewRemoteAllocator(ctx,
+		*cdpws, chromedp.NoModifyURL,
+	)
+	defer cancel()
+
+	// build context options
+	var opts []chromedp.ContextOption
+	if *verbose {
+		opts = append(opts, chromedp.WithDebugf(log.Printf))
+	}
+
+	ctx, cancel = chromedp.NewContext(ctx, opts...)
+	defer cancel()
+
+	// ensure the first tab is created
+	if err := chromedp.Run(ctx); err != nil {
+		return fmt.Errorf("new tab: %w", err)
+	}
+
+	err := chromedp.Run(ctx, chromedp.Navigate(url))
+	if err != nil {
+		return fmt.Errorf("navigate %s: %w", url, err)
+	}
+
+	var a []*cdp.Node
+	if err := chromedp.Run(ctx, chromedp.Nodes(`a[href]`, &a)); err != nil {
+		return fmt.Errorf("get links: %w", err)
+	}
+
+	links := make([]string, 0, len(a))
+	for _, aa := range a {
+		v, ok := aa.Attribute("href")
+		if ok {
+			links = append(links, v)
+		}
+	}
+
+	fmt.Fprintf(os.Stdout, "%v", links)
+
+	return nil
+}
+
+// env returns the env value corresponding to the key or the default string.
+func env(key, dflt string) string {
+	val, ok := os.LookupEnv(key)
+	if !ok {
+		return dflt
+	}
+
+	return val
+}