initial feed reader

it reads feeds. who would have thought. it also follows redirects and
searches for feed urls already. seems as if it could be an alternative
with (quite) a bit more work on it.

go/feeds.go

@@ -0,0 +1,114 @@
package main
import (
	"bufio"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"strings"
	"code.google.com/p/cascadia"
	"code.google.com/p/go.net/html"
	feed "github.com/SlyMarbo/rss"
)
func main() {
	feeds, err := ReadConfig("config.txt")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	fmt.Printf("fetching %d feeds...\n", len(*feeds))
	for _, fn := range *feeds {
		fmt.Printf("fetching %s\n", fn)
		fu, err := GetFeedUrl(fn)
		if err != nil {
			fmt.Println(err)
			continue
		}
		fn = fu
		f, err :=  feed.Fetch(fn)
		if err != nil {
			fmt.Println(err)
			continue
		}
		fmt.Printf("%s: %d entries\n", fn, len(f.Items))
		//for _, item := range f.Items {
		//	fmt.Println(item.Title)
		//}
	}
}
func GetFeedUrl(u string) (string, error) {
	resp, err := http.Get(u)
	if err != nil {
		return "", err
	}
	if strings.Contains(resp.Header.Get("Content-Type"), "xml") {
		return u, nil
	}
	tree, err := html.Parse(resp.Body)
	if err != nil {
		return "", err
	}
	sel := cascadia.MustCompile("link[rel=alternate][type*=xml]")
	alt := sel.MatchFirst(tree)
	if alt == nil {
		return "", errors.New("no feed link found")
	}
	altUrl, found := FindAttr("href", alt.Attr)
	if !found {
		return "", errors.New("missing link in alternate")
	}
	return ToAbsolute(resp.Request.URL, altUrl.Val), nil
}
func FindAttr(name string, attributes []html.Attribute) (*html.Attribute, bool) {
	for _, attr := range attributes {
		if attr.Key == name {
			return &attr, true
		}
	}
	return nil, false
}
func ToAbsolute(base *url.URL, rawUrl string) string {
	url, err := url.Parse(rawUrl)
	if err != nil {
		return rawUrl
	}
	return base.ResolveReference(url).String()
}
func ReadConfig(fileName string) (*[]string, error) {
	f, err := os.Open(fileName)
	if err != nil {
		return nil, err
	}
	lines := make([]string, 0)
	r := bufio.NewReader(f)
	line, err := r.ReadString('\n')
	for err == nil {
		line = strings.TrimSpace(line)
		if line != "" && line[0] != '#' && line[0] != ';' {
			lines = append(lines, line)
		}
		line, err = r.ReadString('\n')
	}
	return &lines, nil
}