Managing opml feeds

feed.go

package main

import (
	"encoding/xml"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strings"
	"text/tabwriter"
)

var usage = `feedst: [options] filename
[options]:
   -c Check. (Default does not check url.)
   -p Print. (Default behaviour.) 
`

type outline struct {
	Title   string    `xml:"title,attr"`
	URL     string    `xml:"htmlUrl,attr"`
	Outline []outline `xml:"outline,omitempty"`
}

type opml struct {
	XMLName  xml.Name  `xml:"opml"`
	Title    string    `xml:"head>title"`
	Outlines []outline `xml:"body>outline"`
}

func main() {
	var c, p bool
	flag.BoolVar(&c, "c", false, "")
	flag.BoolVar(&p, "p", true, "")

	flag.Usage = func() {
		fmt.Fprintf(os.Stdout, "%s", usage)
		os.Exit(1)
	}
	flag.Parse()

	if flag.NArg() < 1 {
		flag.Usage()
	}

	filename := flag.Arg(0)
	opml, err := readFile(filename)
	if err != nil {
		log.Fatal(err)
	}
	extract(opml)
}

func extract(o *opml) {
	w := tabwriter.NewWriter(os.Stdout, 40, 8, 0, ' ', 0)
	var header string
	categories := make(map[string][]outline)
	elementsByCategory := make(map[string]int)
	// Generate header based on category
	for i, e := range o.Outlines {
		categories[e.Title] = e.Outline
		elementsByCategory[e.Title] = len(e.Outline)
		header = header + fmt.Sprintf("%s", strings.ToUpper(e.Title))
		if i < (len(o.Outlines) - 1) {
			header = header + "\t"
		}
	}

	fmt.Fprintln(w, header)
	fmt.Println(elementsByCategory)

	w.Flush()
}
func readFile(filename string) (*opml, error) {

	data, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	opml := new(opml)

	err = xml.Unmarshal(data, &opml)
	if err != nil {
		return nil, fmt.Errorf(fmt.Sprintf("xml.Decode: %s", err))
	}

	return opml, nil
}