Ted Unangst
5 years ago
parent
1813bb7c39
commit
1f3e7a8479
@ -1,196 +0,0 @@
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//
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// Copyright (c) 2019 Ted Unangst <tedu@tedunangst.com>
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//
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// Permission to use, copy, modify, and distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice appear in all copies.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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package main
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import (
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"fmt"
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"html/template"
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"io"
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"log"
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"net/url"
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"regexp"
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"sort"
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"strings"
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"golang.org/x/net/html"
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)
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var permittedtags = []string{
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"div", "h1", "h2", "h3", "h4", "h5", "h6",
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"table", "thead", "tbody", "th", "tr", "td", "colgroup", "col",
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"p", "br", "pre", "code", "blockquote", "q",
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"samp", "mark", "ins", "dfn", "cite", "abbr", "address",
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"strong", "em", "b", "i", "s", "u", "sub", "sup", "del", "tt", "small",
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"ol", "ul", "li", "dl", "dt", "dd",
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}
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var permittedattr = []string{"colspan", "rowspan"}
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var bannedtags = []string{"script", "style"}
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func init() {
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sort.Strings(permittedtags)
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sort.Strings(permittedattr)
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sort.Strings(bannedtags)
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}
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func contains(array []string, tag string) bool {
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idx := sort.SearchStrings(array, tag)
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return idx < len(array) && array[idx] == tag
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}
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func getattr(node *html.Node, attr string) string {
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for _, a := range node.Attr {
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if a.Key == attr {
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return a.Val
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}
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}
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return ""
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}
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func hasclass(node *html.Node, class string) bool {
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return strings.Contains(" "+getattr(node, "class")+" ", " "+class+" ")
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}
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func writetag(w io.Writer, node *html.Node) {
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io.WriteString(w, "<")
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io.WriteString(w, node.Data)
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for _, attr := range node.Attr {
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if contains(permittedattr, attr.Key) {
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fmt.Fprintf(w, ` %s="%s"`, attr.Key, html.EscapeString(attr.Val))
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}
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}
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io.WriteString(w, ">")
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}
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func render(w io.Writer, node *html.Node) {
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if node.Type == html.ElementNode {
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tag := node.Data
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switch {
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case tag == "a":
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href := getattr(node, "href")
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hrefurl, err := url.Parse(href)
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if err != nil {
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href = "#BROKEN-" + href
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} else {
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href = hrefurl.String()
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}
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fmt.Fprintf(w, `<a href="%s" rel=noreferrer>`, html.EscapeString(href))
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case tag == "img":
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div := replaceimg(node)
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if div != "skip" {
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io.WriteString(w, div)
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}
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case tag == "span":
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case tag == "iframe":
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src := html.EscapeString(getattr(node, "src"))
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fmt.Fprintf(w, `<iframe src="<a href="%s">%s</a>">`, src, src)
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case contains(permittedtags, tag):
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writetag(w, node)
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case contains(bannedtags, tag):
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return
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}
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} else if node.Type == html.TextNode {
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io.WriteString(w, html.EscapeString(node.Data))
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}
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for c := node.FirstChild; c != nil; c = c.NextSibling {
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render(w, c)
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}
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if node.Type == html.ElementNode {
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tag := node.Data
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if tag == "a" || (contains(permittedtags, tag) && tag != "br") {
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fmt.Fprintf(w, "</%s>", tag)
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}
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if tag == "p" || tag == "div" {
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io.WriteString(w, "\n")
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}
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}
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}
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func replaceimg(node *html.Node) string {
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src := getattr(node, "src")
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alt := getattr(node, "alt")
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//title := getattr(node, "title")
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if hasclass(node, "Emoji") && alt != "" {
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return html.EscapeString(alt)
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}
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return html.EscapeString(fmt.Sprintf(`<img src="%s">`, src))
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}
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func cleannode(node *html.Node) template.HTML {
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var buf strings.Builder
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render(&buf, node)
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return template.HTML(buf.String())
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}
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func cleanstring(shtml string) template.HTML {
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reader := strings.NewReader(shtml)
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body, err := html.Parse(reader)
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if err != nil {
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log.Printf("error parsing html: %s", err)
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return ""
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}
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return cleannode(body)
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}
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func textonly(w io.Writer, node *html.Node) {
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switch node.Type {
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case html.ElementNode:
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tag := node.Data
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switch {
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case tag == "a":
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href := getattr(node, "href")
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fmt.Fprintf(w, `<a href="%s">`, href)
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case tag == "img":
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io.WriteString(w, "<img>")
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case contains(bannedtags, tag):
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return
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}
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case html.TextNode:
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io.WriteString(w, node.Data)
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}
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for c := node.FirstChild; c != nil; c = c.NextSibling {
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textonly(w, c)
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}
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if node.Type == html.ElementNode {
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tag := node.Data
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if tag == "a" {
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fmt.Fprintf(w, "</%s>", tag)
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}
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if tag == "p" || tag == "div" {
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io.WriteString(w, "\n")
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}
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}
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}
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var re_whitespaceeater = regexp.MustCompile("[ \t\r]*\n[ \t\r]*")
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var re_blanklineeater = regexp.MustCompile("\n\n+")
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var re_tabeater = regexp.MustCompile("[ \t]+")
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func htmltotext(shtml template.HTML) string {
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reader := strings.NewReader(string(shtml))
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body, _ := html.Parse(reader)
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var buf strings.Builder
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textonly(&buf, body)
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rv := buf.String()
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rv = re_whitespaceeater.ReplaceAllLiteralString(rv, "\n")
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rv = re_blanklineeater.ReplaceAllLiteralString(rv, "\n\n")
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rv = re_tabeater.ReplaceAllLiteralString(rv, " ")
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for len(rv) > 0 && rv[0] == '\n' {
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rv = rv[1:]
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}
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return rv
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}
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