func main1()

in publicsuffix/gen.go [128:254]
121 lines of code
62 McCabe index (conditional complexity)

func main1() error {
	flag.Parse()
	if nodesBitsTextLength+nodesBitsTextOffset+nodesBitsICANN+nodesBitsChildren > 32 {
		return fmt.Errorf("not enough bits to encode the nodes table")
	}
	if childrenBitsLo+childrenBitsHi+childrenBitsNodeType+childrenBitsWildcard > 32 {
		return fmt.Errorf("not enough bits to encode the children table")
	}
	if *version == "" {
		if *url != defaultURL {
			return fmt.Errorf("-version was not specified, and the -url is not the default one")
		}
		sha, date, err := gitCommit()
		if err != nil {
			return err
		}
		*version = fmt.Sprintf("publicsuffix.org's public_suffix_list.dat, git revision %s (%s)", sha, date)
	}
	var r io.Reader = os.Stdin
	if *url != "" {
		res, err := http.Get(*url)
		if err != nil {
			return err
		}
		if res.StatusCode != http.StatusOK {
			return fmt.Errorf("bad GET status for %s: %s", *url, res.Status)
		}
		r = res.Body
		defer res.Body.Close()
	}

	var root node
	icann := false
	br := bufio.NewReader(r)
	for {
		s, err := br.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				break
			}
			return err
		}
		s = strings.TrimSpace(s)
		if strings.Contains(s, "BEGIN ICANN DOMAINS") {
			if len(rules) != 0 {
				return fmt.Errorf(`expected no rules before "BEGIN ICANN DOMAINS"`)
			}
			icann = true
			continue
		}
		if strings.Contains(s, "END ICANN DOMAINS") {
			icann, numICANNRules = false, len(rules)
			continue
		}
		if s == "" || strings.HasPrefix(s, "//") {
			continue
		}
		s, err = idna.ToASCII(s)
		if err != nil {
			return err
		}
		if !validSuffixRE.MatchString(s) {
			return fmt.Errorf("bad publicsuffix.org list data: %q", s)
		}

		if *subset {
			switch {
			case s == "ac.jp" || strings.HasSuffix(s, ".ac.jp"):
			case s == "ak.us" || strings.HasSuffix(s, ".ak.us"):
			case s == "ao" || strings.HasSuffix(s, ".ao"):
			case s == "ar" || strings.HasSuffix(s, ".ar"):
			case s == "arpa" || strings.HasSuffix(s, ".arpa"):
			case s == "cy" || strings.HasSuffix(s, ".cy"):
			case s == "dyndns.org" || strings.HasSuffix(s, ".dyndns.org"):
			case s == "jp":
			case s == "kobe.jp" || strings.HasSuffix(s, ".kobe.jp"):
			case s == "kyoto.jp" || strings.HasSuffix(s, ".kyoto.jp"):
			case s == "om" || strings.HasSuffix(s, ".om"):
			case s == "uk" || strings.HasSuffix(s, ".uk"):
			case s == "uk.com" || strings.HasSuffix(s, ".uk.com"):
			case s == "tw" || strings.HasSuffix(s, ".tw"):
			case s == "zw" || strings.HasSuffix(s, ".zw"):
			case s == "xn--p1ai" || strings.HasSuffix(s, ".xn--p1ai"):
				// xn--p1ai is Russian-Cyrillic "рф".
			default:
				continue
			}
		}

		rules = append(rules, s)

		nt, wildcard := nodeTypeNormal, false
		switch {
		case strings.HasPrefix(s, "*."):
			s, nt = s[2:], nodeTypeParentOnly
			wildcard = true
		case strings.HasPrefix(s, "!"):
			s, nt = s[1:], nodeTypeException
		}
		labels := strings.Split(s, ".")
		for n, i := &root, len(labels)-1; i >= 0; i-- {
			label := labels[i]
			n = n.child(label)
			if i == 0 {
				if nt != nodeTypeParentOnly && n.nodeType == nodeTypeParentOnly {
					n.nodeType = nt
				}
				n.icann = n.icann && icann
				n.wildcard = n.wildcard || wildcard
			}
			labelsMap[label] = true
		}
	}
	labelsList = make([]string, 0, len(labelsMap))
	for label := range labelsMap {
		labelsList = append(labelsList, label)
	}
	sort.Strings(labelsList)

	if err := generate(printReal, &root, "table.go"); err != nil {
		return err
	}
	if err := generate(printTest, &root, "table_test.go"); err != nil {
		return err
	}
	return nil
}