302 lines
9.4 KiB
Go
302 lines
9.4 KiB
Go
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// Copyright (c) 2020 Tulir Asokan
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package format
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import (
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"fmt"
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"math"
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"strconv"
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"strings"
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"golang.org/x/net/html"
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"maunium.net/go/mautrix/id"
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)
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type Context map[string]interface{}
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type TextConverter func(string, Context) string
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type CodeBlockConverter func(code, language string, ctx Context) string
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type PillConverter func(displayname, mxid, eventID string, ctx Context) string
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func DefaultPillConverter(displayname, mxid, eventID string, _ Context) string {
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switch {
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case len(mxid) == 0, mxid[0] == '@':
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// User link, always just show the displayname
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return displayname
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case len(eventID) > 0:
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// Event ID link, always just show the link
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return fmt.Sprintf("https://matrix.to/#/%s/%s", mxid, eventID)
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case mxid[0] == '!' && displayname == mxid:
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// Room ID link with no separate display text, just show the link
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return fmt.Sprintf("https://matrix.to/#/%s", mxid)
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case mxid[0] == '#':
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// Room alias link, just show the alias
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return mxid
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default:
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// Other link (e.g. room ID link with display text), show text and link
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return fmt.Sprintf("%s (https://matrix.to/#/%s)", displayname, mxid)
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}
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}
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// HTMLParser is a somewhat customizable Matrix HTML parser.
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type HTMLParser struct {
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PillConverter PillConverter
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TabsToSpaces int
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Newline string
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HorizontalLine string
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BoldConverter TextConverter
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ItalicConverter TextConverter
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StrikethroughConverter TextConverter
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UnderlineConverter TextConverter
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MonospaceBlockConverter CodeBlockConverter
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MonospaceConverter TextConverter
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}
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// TaggedString is a string that also contains a HTML tag.
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type TaggedString struct {
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string
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tag string
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}
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func (parser *HTMLParser) getAttribute(node *html.Node, attribute string) string {
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for _, attr := range node.Attr {
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if attr.Key == attribute {
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return attr.Val
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}
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}
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return ""
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}
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// Digits counts the number of digits in a non-negative integer.
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func Digits(num int) int {
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return int(math.Floor(math.Log10(float64(num))) + 1)
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}
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func (parser *HTMLParser) listToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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ordered := node.Data == "ol"
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taggedChildren := parser.nodeToTaggedStrings(node.FirstChild, stripLinebreak, ctx)
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counter := 1
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indentLength := 0
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if ordered {
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start := parser.getAttribute(node, "start")
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if len(start) > 0 {
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counter, _ = strconv.Atoi(start)
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}
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longestIndex := (counter - 1) + len(taggedChildren)
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indentLength = Digits(longestIndex)
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}
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indent := strings.Repeat(" ", indentLength+2)
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var children []string
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for _, child := range taggedChildren {
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if child.tag != "li" {
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continue
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}
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var prefix string
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// TODO make bullets and numbering configurable
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if ordered {
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indexPadding := indentLength - Digits(counter)
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prefix = fmt.Sprintf("%d. %s", counter, strings.Repeat(" ", indexPadding))
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} else {
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prefix = "* "
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}
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str := prefix + child.string
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counter++
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parts := strings.Split(str, "\n")
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for i, part := range parts[1:] {
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parts[i+1] = indent + part
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}
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str = strings.Join(parts, "\n")
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children = append(children, str)
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}
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return strings.Join(children, "\n")
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}
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func (parser *HTMLParser) basicFormatToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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str := parser.nodeToTagAwareString(node.FirstChild, stripLinebreak, ctx)
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switch node.Data {
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case "b", "strong":
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if parser.BoldConverter != nil {
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return parser.BoldConverter(str, ctx)
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}
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return fmt.Sprintf("**%s**", str)
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case "i", "em":
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if parser.ItalicConverter != nil {
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return parser.ItalicConverter(str, ctx)
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}
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return fmt.Sprintf("_%s_", str)
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case "s", "del", "strike":
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if parser.StrikethroughConverter != nil {
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return parser.StrikethroughConverter(str, ctx)
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}
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return fmt.Sprintf("~~%s~~", str)
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case "u", "ins":
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if parser.UnderlineConverter != nil {
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return parser.UnderlineConverter(str, ctx)
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}
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case "tt", "code":
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if parser.MonospaceConverter != nil {
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return parser.MonospaceConverter(str, ctx)
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}
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return fmt.Sprintf("`%s`", str)
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}
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return str
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}
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func (parser *HTMLParser) headerToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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children := parser.nodeToStrings(node.FirstChild, stripLinebreak, ctx)
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length := int(node.Data[1] - '0')
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prefix := strings.Repeat("#", length) + " "
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return prefix + strings.Join(children, "")
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}
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func (parser *HTMLParser) blockquoteToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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str := parser.nodeToTagAwareString(node.FirstChild, stripLinebreak, ctx)
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childrenArr := strings.Split(strings.TrimSpace(str), "\n")
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// TODO make blockquote prefix configurable
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for index, child := range childrenArr {
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childrenArr[index] = "> " + child
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}
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return strings.Join(childrenArr, "\n")
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}
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func (parser *HTMLParser) linkToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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str := parser.nodeToTagAwareString(node.FirstChild, stripLinebreak, ctx)
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href := parser.getAttribute(node, "href")
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if len(href) == 0 {
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return str
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}
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if parser.PillConverter != nil {
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parsedMatrix, err := id.ParseMatrixURIOrMatrixToURL(href)
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if err == nil && parsedMatrix != nil {
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return parser.PillConverter(str, parsedMatrix.PrimaryIdentifier(), parsedMatrix.SecondaryIdentifier(), ctx)
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}
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}
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if str == href {
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return str
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}
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return fmt.Sprintf("%s (%s)", str, href)
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}
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func (parser *HTMLParser) tagToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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switch node.Data {
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case "blockquote":
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return parser.blockquoteToString(node, stripLinebreak, ctx)
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case "ol", "ul":
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return parser.listToString(node, stripLinebreak, ctx)
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case "h1", "h2", "h3", "h4", "h5", "h6":
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return parser.headerToString(node, stripLinebreak, ctx)
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case "br":
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return parser.Newline
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case "b", "strong", "i", "em", "s", "strike", "del", "u", "ins", "tt", "code":
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return parser.basicFormatToString(node, stripLinebreak, ctx)
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case "a":
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return parser.linkToString(node, stripLinebreak, ctx)
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case "p":
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return parser.nodeToTagAwareString(node.FirstChild, stripLinebreak, ctx)
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case "hr":
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return parser.HorizontalLine
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case "pre":
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var preStr, language string
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if node.FirstChild != nil && node.FirstChild.Type == html.ElementNode && node.FirstChild.Data == "code" {
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class := parser.getAttribute(node.FirstChild, "class")
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if strings.HasPrefix(class, "language-") {
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language = class[len("language-"):]
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}
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preStr = parser.nodeToString(node.FirstChild.FirstChild, false, ctx)
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} else {
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preStr = parser.nodeToString(node.FirstChild, false, ctx)
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}
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if parser.MonospaceBlockConverter != nil {
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return parser.MonospaceBlockConverter(preStr, language, ctx)
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}
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if len(preStr) == 0 || preStr[len(preStr)-1] != '\n' {
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preStr += "\n"
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}
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return fmt.Sprintf("```%s\n%s```", language, preStr)
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default:
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return parser.nodeToTagAwareString(node.FirstChild, stripLinebreak, ctx)
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}
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}
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func (parser *HTMLParser) singleNodeToString(node *html.Node, stripLinebreak bool, ctx Context) TaggedString {
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switch node.Type {
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case html.TextNode:
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if stripLinebreak {
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node.Data = strings.Replace(node.Data, "\n", "", -1)
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}
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return TaggedString{node.Data, "text"}
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case html.ElementNode:
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return TaggedString{parser.tagToString(node, stripLinebreak, ctx), node.Data}
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case html.DocumentNode:
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return TaggedString{parser.nodeToTagAwareString(node.FirstChild, stripLinebreak, ctx), "html"}
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default:
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return TaggedString{"", "unknown"}
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}
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}
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func (parser *HTMLParser) nodeToTaggedStrings(node *html.Node, stripLinebreak bool, ctx Context) (strs []TaggedString) {
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for ; node != nil; node = node.NextSibling {
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strs = append(strs, parser.singleNodeToString(node, stripLinebreak, ctx))
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}
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return
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}
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var BlockTags = []string{"p", "h1", "h2", "h3", "h4", "h5", "h6", "ol", "ul", "pre", "blockquote", "div", "hr", "table"}
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func (parser *HTMLParser) isBlockTag(tag string) bool {
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for _, blockTag := range BlockTags {
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if tag == blockTag {
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return true
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}
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}
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return false
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}
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func (parser *HTMLParser) nodeToTagAwareString(node *html.Node, stripLinebreak bool, ctx Context) string {
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strs := parser.nodeToTaggedStrings(node, stripLinebreak, ctx)
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var output strings.Builder
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for _, str := range strs {
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tstr := str.string
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if parser.isBlockTag(str.tag) {
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tstr = fmt.Sprintf("\n%s\n", tstr)
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}
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output.WriteString(tstr)
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}
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return strings.TrimSpace(output.String())
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}
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func (parser *HTMLParser) nodeToStrings(node *html.Node, stripLinebreak bool, ctx Context) (strs []string) {
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for ; node != nil; node = node.NextSibling {
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strs = append(strs, parser.singleNodeToString(node, stripLinebreak, ctx).string)
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}
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return
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}
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func (parser *HTMLParser) nodeToString(node *html.Node, stripLinebreak bool, ctx Context) string {
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return strings.Join(parser.nodeToStrings(node, stripLinebreak, ctx), "")
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}
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// Parse converts Matrix HTML into text using the settings in this parser.
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func (parser *HTMLParser) Parse(htmlData string, ctx Context) string {
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if parser.TabsToSpaces >= 0 {
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htmlData = strings.Replace(htmlData, "\t", strings.Repeat(" ", parser.TabsToSpaces), -1)
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}
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node, _ := html.Parse(strings.NewReader(htmlData))
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return parser.nodeToTagAwareString(node, true, ctx)
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}
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// HTMLToText converts Matrix HTML into text with the default settings.
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func HTMLToText(html string) string {
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return (&HTMLParser{
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TabsToSpaces: 4,
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Newline: "\n",
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HorizontalLine: "\n---\n",
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PillConverter: DefaultPillConverter,
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}).Parse(html, make(Context))
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}
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