Files
mautrix-discord/pkg/msgconv/formatter.go
Skip R b5e6db06f8 msgconv: port most of attachment and text message bridging
* Created a separate discordid package to avoid import cycles.
* Implemented attachment bridging. We still need to implement direct
  media, but this will do for now.
* Corrected how encrypted files (e.g. embed images and attachments) were
  bridged. Previously, the URL field would be empty.

Still a lot of missing pieces. Thoughts:

* Mentions to roles and custom emoji are not rendered properly. We need
  to maintain our own DB.
* We might not need the "attachments" leaf package anymore? It's just
  there to avoid an import cycle.

Bridging actual events (i.e. wiring up discordgo's event handlers) is
probably next.
2025-11-26 18:13:07 -08:00

100 lines
4.0 KiB
Go

// mautrix-discord - A Matrix-Discord puppeting bridge.
// Copyright (C) 2024 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 msgconv
import (
"fmt"
"regexp"
"strings"
"github.com/yuin/goldmark"
"github.com/yuin/goldmark/extension"
"github.com/yuin/goldmark/parser"
"github.com/yuin/goldmark/util"
"maunium.net/go/mautrix/bridgev2"
"maunium.net/go/mautrix/format"
"maunium.net/go/mautrix/format/mdext"
)
// 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,
)
// renderDiscordMarkdownOnlyHTML converts Discord-flavored Markdown text to HTML.
//
// After conversion, if the text is surrounded by a single outermost paragraph
// tag, it is unwrapped.
func (mc *MessageConverter) renderDiscordMarkdownOnlyHTML(portal *bridgev2.Portal, text string, allowInlineLinks bool) string {
return format.UnwrapSingleParagraph(mc.renderDiscordMarkdownOnlyHTMLNoUnwrap(portal, text, allowInlineLinks))
}
// renderDiscordMarkdownOnlyHTMLNoUnwrap converts Discord-flavored Markdown text to HTML.
func (mc *MessageConverter) renderDiscordMarkdownOnlyHTMLNoUnwrap(portal *bridgev2.Portal, 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 buf.String()
}
// TODO(skip): Stopping here for now. Continue at formatterContextPortalKey.