autolink.go

package main

import (
	"html/template"
	"net/url"
	"regexp"
)

var LinkRegex = regexp.MustCompile("(?:\\@[_a-zA-Z0-9]{1,17})|(?:(?:(?:(?:http|https|irc)?:\\/\\/(?:(?:[!$&-.0-9;=?A-Z_a-z]|(?:\\%[a-fA-F0-9]{2}))+(?:\\:(?:[!$&-.0-9;=?A-Z_a-z]|(?:\\%[a-fA-F0-9]{2}))+)?\\@)?)?(?:(?:(?:[a-zA-Z0-9][-a-zA-Z0-9]*\\.)+(?:(?:aero|arpa|asia|a[cdefgilmnoqrstuwxz])|(?:biz|b[abdefghijmnorstvwyz])|(?:cat|com|coop|c[acdfghiklmnoruvxyz])|d[ejkmoz]|(?:edu|e[cegrstu])|f[ijkmor]|(?:gov|g[abdefghilmnpqrstuwy])|h[kmnrtu]|(?:info|int|i[delmnoqrst])|j[emop]|k[eghimnrwyz]|l[abcikrstuvy]|(?:mil|museum|m[acdeghklmnopqrstuvwxyz])|(?:name|net|n[acefgilopruz])|(?:org|om)|(?:pro|p[aefghklmnrstwy])|qa|r[eouw]|s[abcdeghijklmnortuvyz]|(?:tel|travel|t[cdfghjklmnoprtvwz])|u[agkmsyz]|v[aceginu]|w[fs]|y[etu]|z[amw]))|(?:(?:25[0-5]|2[0-4][0-9]|[0-1][0-9]{2}|[1-9][0-9]|[1-9])\\.(?:25[0-5]|2[0-4][0-9]|[0-1][0-9]{2}|[1-9][0-9]|[0-9])\\.(?:25[0-5]|2[0-4][0-9]|[0-1][0-9]{2}|[1-9][0-9]|[0-9])\\.(?:25[0-5]|2[0-4][0-9]|[0-1][0-9]{2}|[1-9][0-9]|[0-9])))(?:\\:\\d{1,5})?)(?:\\/(?:(?:[!#&-;=?-Z_a-z~])|(?:\\%[a-fA-F0-9]{2}))*)?)")

func AutoLink(in string) template.HTML {
	out := LinkRegex.ReplaceAllStringFunc(in, func(src string) string {
		URL, err := url.Parse(src)
		if err != nil {
			return src
		}
		if URL.Scheme == "" {
			URL.Scheme = "http"
		}
		return `<a href="` + URL.String() + `">` + src + `</a>`
	})
	return template.HTML(out)
}

func ScanLinks(in string) []*url.URL {
	rawlinks := LinkRegex.FindAllString(in, -1)
	links := make([]*url.URL, 0)
	for _, rawlink := range rawlinks {
		link, err := url.Parse(rawlink)
		if err != nil {
			continue
		}
		if link.Scheme == "" {
			link.Scheme = "http"
		}
		links = append(links, link)
	}
	return links
}