New RSS support, and improvements to http-get.

* Add a new `feeds` command.
  * Show the RSS-feeds linked in the given URL.
* Update `get-http` command.
  * Default to `https://` if no protocol is specified.

This is WIP unless or until I have documentation.

Author: skx

cmd_feeds.go

@@ -0,0 +1,134 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/skx/subcommands"
+	"golang.org/x/net/html"
+)
+
+// Structure for our options and state.
+type feedsCommand struct {
+
+	// We embed the NoFlags option, because we accept no command-line flags.
+	subcommands.NoFlags
+}
+
+// ErrNoFeeds is used if no feeds are found in a remote URL
+var ErrNoFeeds = errors.New("NO-FEED")
+
+// Info returns the name of this subcommand.
+func (t *feedsCommand) Info() (string, string) {
+	return "feeds", `Extract RSS feeds from remote URLS.
+
+Details:
+
+This command fetches the contents of the specified URL, much like
+the 'http-get' command would, and extracts any specified RSS feed
+from the contents of that remote URL.
+
+Examples:
+
+  $ sysbox feeds https://blog.steve.fi/`
+}
+
+func (t *feedsCommand) FindFeeds(base string) ([]string, error) {
+
+	ret := []string{}
+
+	if !strings.HasPrefix(base, "http") {
+		base = "https://" + base
+	}
+
+	// Make the request
+	response, err := http.Get(base)
+	if err != nil {
+		return ret, err
+	}
+
+	// Get the body.
+	defer response.Body.Close()
+
+	z := html.NewTokenizer(response.Body)
+
+	for {
+		tt := z.Next()
+		switch tt {
+		case html.ErrorToken:
+			err := z.Err()
+			if err == io.EOF {
+				if len(ret) > 0 {
+					return ret, nil
+				}
+				return ret, ErrNoFeeds
+			}
+			return ret, fmt.Errorf("%s", z.Err())
+		case html.StartTagToken, html.SelfClosingTagToken:
+			t := z.Token()
+			if t.Data == "link" {
+				isRSS := false
+				u := ""
+				for _, attr := range t.Attr {
+					if attr.Key == "type" && (attr.Val == "application/rss+xml" || attr.Val == "application/atom+xml") {
+						isRSS = true
+					}
+
+					if attr.Key == "href" {
+						u = attr.Val
+					}
+				}
+				if isRSS {
+					if !strings.HasPrefix(u, "http") {
+						u, _ = url.JoinPath(base, u)
+					}
+					ret = append(ret, u)
+				}
+			}
+		}
+	}
+
+	// Nothing found?
+	if len(ret) == 0 {
+		return ret, ErrNoFeeds
+	}
+	return ret, nil
+}
+
+// Execute is invoked if the user specifies `feeds` as the subcommand.
+func (t *feedsCommand) Execute(args []string) int {
+
+	// Ensure we have only a single URL
+	if len(args) != 1 {
+		fmt.Printf("Usage: feeds URL\n")
+		return 1
+	}
+
+	// The URL
+	url := args[0]
+
+	// We'll default to https if the protocol isn't specified.
+	if !strings.HasPrefix(url, "http") {
+		url = "https://" + url
+	}
+
+	out, err := t.FindFeeds(url)
+	if err != nil {
+		if err == ErrNoFeeds {
+			fmt.Printf("No Feeds found in %s\n", url)
+		} else {
+			fmt.Printf("Error processing %s: %s\n", url, err)
+			return 1
+		}
+	} else {
+		for _, x := range out {
+			fmt.Printf("%s\n", x)
+		}
+	}
+
+	return 0
+}

cmd_http_get.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"sort"
+	"strings"
 )
 
 // Structure for our options and state.
@@ -51,10 +52,18 @@ func (hg *httpGetCommand) Execute(args []string) int {
 		return 1
 	}
 
+	// The URL
+	url := args[0]
+
+	// We'll default to https if the protocol isn't specified.
+	if !strings.HasPrefix(url, "http") {
+		url = "https://" + url
+	}
+
 	// Make the request
-	response, err := http.Get(args[0])
+	response, err := http.Get(url)
 	if err != nil {
-		fmt.Printf("error: %s", err.Error())
+		fmt.Printf("error fetching %s: %s", url, err.Error())
 		return 1
 	}
 

main.go

@@ -41,6 +41,7 @@ func main() {
 	subcommands.Register(&envTemplateCommand{})
 	subcommands.Register(&execSTDINCommand{})
 	subcommands.Register(&expectCommand{})
+	subcommands.Register(&feedsCommand{})
 	subcommands.Register(&findCommand{})
 	subcommands.Register(&fingerdCommand{})
 	subcommands.Register(&html2TextCommand{})