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formatter.go
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formatter.go
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// mautrix-discord - A Matrix-Discord puppeting bridge.
// Copyright (C) 2023 Tulir Asokan
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package main
import (
"fmt"
"regexp"
"strings"
"github.com/bwmarrin/discordgo"
"github.com/yuin/goldmark"
"github.com/yuin/goldmark/extension"
"github.com/yuin/goldmark/parser"
"github.com/yuin/goldmark/util"
"go.mau.fi/util/variationselector"
"golang.org/x/exp/slices"
"maunium.net/go/mautrix/event"
"maunium.net/go/mautrix/format"
"maunium.net/go/mautrix/format/mdext"
"maunium.net/go/mautrix/id"
)
// escapeFixer is a hacky partial fix for the difference in escaping markdown, used with escapeReplacement
//
// Discord allows escaping with just one backslash, e.g. \__a__,
// but standard markdown requires both to be escaped (\_\_a__)
var escapeFixer = regexp.MustCompile(`\\(__[^_]|\*\*[^*])`)
func escapeReplacement(s string) string {
return s[:2] + `\` + s[2:]
}
// indentableParagraphParser is the default paragraph parser with CanAcceptIndentedLine.
// Used when disabling CodeBlockParser (as disabling it without a replacement will make indented blocks disappear).
type indentableParagraphParser struct {
parser.BlockParser
}
var defaultIndentableParagraphParser = &indentableParagraphParser{BlockParser: parser.NewParagraphParser()}
func (b *indentableParagraphParser) CanAcceptIndentedLine() bool {
return true
}
var removeFeaturesExceptLinks = []any{
parser.NewListParser(), parser.NewListItemParser(), parser.NewHTMLBlockParser(), parser.NewRawHTMLParser(),
parser.NewSetextHeadingParser(), parser.NewThematicBreakParser(),
parser.NewCodeBlockParser(),
}
var removeFeaturesAndLinks = append(removeFeaturesExceptLinks, parser.NewLinkParser())
var fixIndentedParagraphs = goldmark.WithParserOptions(parser.WithBlockParsers(util.Prioritized(defaultIndentableParagraphParser, 500)))
var discordExtensions = goldmark.WithExtensions(extension.Strikethrough, mdext.SimpleSpoiler, mdext.DiscordUnderline, ExtDiscordEveryone, ExtDiscordTag)
var discordRenderer = goldmark.New(
goldmark.WithParser(mdext.ParserWithoutFeatures(removeFeaturesAndLinks...)),
fixIndentedParagraphs, format.HTMLOptions, discordExtensions,
)
var discordRendererWithInlineLinks = goldmark.New(
goldmark.WithParser(mdext.ParserWithoutFeatures(removeFeaturesExceptLinks...)),
fixIndentedParagraphs, format.HTMLOptions, discordExtensions,
)
func (portal *Portal) renderDiscordMarkdownOnlyHTML(text string, allowInlineLinks bool) string {
text = escapeFixer.ReplaceAllStringFunc(text, escapeReplacement)
var buf strings.Builder
ctx := parser.NewContext()
ctx.Set(parserContextPortal, portal)
renderer := discordRenderer
if allowInlineLinks {
renderer = discordRendererWithInlineLinks
}
err := renderer.Convert([]byte(text), &buf, parser.WithContext(ctx))
if err != nil {
panic(fmt.Errorf("markdown parser errored: %w", err))
}
return format.UnwrapSingleParagraph(buf.String())
}
const formatterContextPortalKey = "fi.mau.discord.portal"
const formatterContextAllowedMentionsKey = "fi.mau.discord.allowed_mentions"
const formatterContextInputAllowedMentionsKey = "fi.mau.discord.input_allowed_mentions"
func appendIfNotContains(arr []string, newItem string) []string {
for _, item := range arr {
if item == newItem {
return arr
}
}
return append(arr, newItem)
}
func (br *DiscordBridge) pillConverter(displayname, mxid, eventID string, ctx format.Context) string {
if len(mxid) == 0 {
return displayname
}
if mxid[0] == '#' {
alias, err := br.Bot.ResolveAlias(id.RoomAlias(mxid))
if err != nil {
return displayname
}
mxid = alias.RoomID.String()
}
if mxid[0] == '!' {
portal := br.GetPortalByMXID(id.RoomID(mxid))
if portal != nil {
if eventID == "" {
//currentPortal := ctx[formatterContextPortalKey].(*Portal)
return fmt.Sprintf("<#%s>", portal.Key.ChannelID)
//if currentPortal.GuildID == portal.GuildID {
//} else if portal.GuildID != "" {
// return fmt.Sprintf("<#%s:%s:%s>", portal.Key.ChannelID, portal.GuildID, portal.Name)
//} else {
// // TODO is mentioning private channels possible at all?
//}
} else if msg := br.DB.Message.GetByMXID(portal.Key, id.EventID(eventID)); msg != nil {
guildID := portal.GuildID
if guildID == "" {
guildID = "@me"
}
return fmt.Sprintf("https://discord.com/channels/%s/%s/%s", guildID, msg.DiscordProtoChannelID(), msg.DiscordID)
}
}
} else if mxid[0] == '@' {
allowedMentions, _ := ctx.ReturnData[formatterContextInputAllowedMentionsKey].([]id.UserID)
if allowedMentions != nil && !slices.Contains(allowedMentions, id.UserID(mxid)) {
return displayname
}
mentions := ctx.ReturnData[formatterContextAllowedMentionsKey].(*discordgo.MessageAllowedMentions)
parsedID, ok := br.ParsePuppetMXID(id.UserID(mxid))
if ok {
mentions.Users = appendIfNotContains(mentions.Users, parsedID)
return fmt.Sprintf("<@%s>", parsedID)
}
mentionedUser := br.GetUserByMXID(id.UserID(mxid))
if mentionedUser != nil && mentionedUser.DiscordID != "" {
mentions.Users = appendIfNotContains(mentions.Users, mentionedUser.DiscordID)
return fmt.Sprintf("<@%s>", mentionedUser.DiscordID)
}
}
return displayname
}
const discordLinkPattern = `https?://[^<\p{Zs}\x{feff}]*[^"'),.:;\]\p{Zs}\x{feff}]`
// Discord links start with http:// or https://, contain at least two characters afterwards,
// don't contain < or whitespace anywhere, and don't end with "'),.:;]
//
// Zero-width whitespace is mostly in the Format category and is allowed, except \uFEFF isn't for some reason
var discordLinkRegex = regexp.MustCompile(discordLinkPattern)
var discordLinkRegexFull = regexp.MustCompile("^" + discordLinkPattern + "$")
var discordMarkdownEscaper = strings.NewReplacer(
`\`, `\\`,
`_`, `\_`,
`*`, `\*`,
`~`, `\~`,
"`", "\\`",
`|`, `\|`,
`<`, `\<`,
`#`, `\#`,
)
func escapeDiscordMarkdown(s string) string {
submatches := discordLinkRegex.FindAllStringIndex(s, -1)
if submatches == nil {
return discordMarkdownEscaper.Replace(s)
}
var builder strings.Builder
offset := 0
for _, match := range submatches {
start := match[0]
end := match[1]
builder.WriteString(discordMarkdownEscaper.Replace(s[offset:start]))
builder.WriteString(s[start:end])
offset = end
}
builder.WriteString(discordMarkdownEscaper.Replace(s[offset:]))
return builder.String()
}
var matrixHTMLParser = &format.HTMLParser{
TabsToSpaces: 4,
Newline: "\n",
HorizontalLine: "\n---\n",
ItalicConverter: func(s string, ctx format.Context) string {
return fmt.Sprintf("*%s*", s)
},
UnderlineConverter: func(s string, ctx format.Context) string {
return fmt.Sprintf("__%s__", s)
},
TextConverter: func(s string, ctx format.Context) string {
if ctx.TagStack.Has("pre") || ctx.TagStack.Has("code") {
// If we're in a code block, don't escape markdown
return s
}
return escapeDiscordMarkdown(s)
},
SpoilerConverter: func(text, reason string, ctx format.Context) string {
if reason != "" {
return fmt.Sprintf("(%s) ||%s||", reason, text)
}
return fmt.Sprintf("||%s||", text)
},
LinkConverter: func(text, href string, ctx format.Context) string {
if text == href {
return text
} else if !discordLinkRegexFull.MatchString(href) {
return fmt.Sprintf("%s (%s)", escapeDiscordMarkdown(text), escapeDiscordMarkdown(href))
}
return fmt.Sprintf("[%s](%s)", escapeDiscordMarkdown(text), href)
},
}
func (portal *Portal) parseMatrixHTML(content *event.MessageEventContent) (string, *discordgo.MessageAllowedMentions) {
allowedMentions := &discordgo.MessageAllowedMentions{
Parse: []discordgo.AllowedMentionType{},
Users: []string{},
RepliedUser: true,
}
if content.Format == event.FormatHTML && len(content.FormattedBody) > 0 {
ctx := format.NewContext()
ctx.ReturnData[formatterContextPortalKey] = portal
ctx.ReturnData[formatterContextAllowedMentionsKey] = allowedMentions
if content.Mentions != nil {
ctx.ReturnData[formatterContextInputAllowedMentionsKey] = content.Mentions.UserIDs
}
return variationselector.FullyQualify(matrixHTMLParser.Parse(content.FormattedBody, ctx)), allowedMentions
} else {
return variationselector.FullyQualify(escapeDiscordMarkdown(content.Body)), allowedMentions
}
}