telegramfmt: text formatting TG -> Matrix

Signed-off-by: Sumner Evans <sumner.evans@automattic.com>

pkg/connector/telegramfmt/html.go

@@ -0,0 +1,115 @@
+// mautrix-telegram - A Matrix-Telegram puppeting bridge.
+// Copyright (C) 2024 Sumner Evans
+//
+// 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 telegramfmt
+
+import (
+	"fmt"
+	"strings"
+	"unicode/utf16"
+)
+
+func (m Mention) Format(message string) string {
+	return fmt.Sprintf(`<a href="%s">%s</a>`, m.MXID.URI().MatrixToURL(), m.Name)
+}
+
+func (s Style) Format(message string) string {
+	switch s.Type {
+	case StyleBold:
+		return fmt.Sprintf("<strong>%s</strong>", message)
+	case StyleItalic:
+		return fmt.Sprintf("<em>%s</em>", message)
+	case StyleSpoiler:
+		return fmt.Sprintf("<span data-mx-spoiler>%s</span>", message)
+	case StyleStrikethrough:
+		return fmt.Sprintf("<del>%s</del>", message)
+	case StyleCode:
+		if strings.ContainsRune(message, '\n') {
+			// This is somewhat incorrect, as it won't allow inline text before/after a multiline monospace-formatted string.
+			return fmt.Sprintf("<pre><code>%s</code></pre>", message)
+		}
+		return fmt.Sprintf("<code>%s</code>", message)
+	case StyleUnderline:
+		return fmt.Sprintf("<u>%s</u>", message)
+	case StyleBlockquote:
+		return fmt.Sprintf("<blockquote>%s</blockquote>", message)
+	case StylePre:
+		if s.Language != "" {
+			return fmt.Sprintf("<pre><code class='language-%s'>%s</code></pre>", s.Language, message)
+		} else {
+			return fmt.Sprintf("<pre><code>%s</code></pre>", message)
+		}
+	case StyleEmail:
+		return fmt.Sprintf(`<a href='mailto:%s'>%s</a>`, message, message)
+	case StyleTextURL:
+		if strings.HasPrefix(s.URL, "https://matrix.to/#") {
+			return s.URL
+		}
+		return fmt.Sprintf(`<a href='%s'>%s</a>`, s.URL, message)
+	case StyleURL:
+		if strings.HasPrefix(s.URL, "https://matrix.to/#") {
+			return s.URL
+		}
+		return fmt.Sprintf(`<a href='%s'>%s</a>`, s.URL, message)
+	case StyleCustomEmoji:
+		if s.Emoji != "" {
+			return s.Emoji
+		} else {
+			return fmt.Sprintf(
+				`<img data-mx-emoticon data-mau-animated-emoji src="%s" height="32" width="32" alt="%s" title="%s"/>`,
+				s.EmojiURI, message, message,
+			)
+		}
+	case StyleBotCommand:
+		return fmt.Sprintf("<font color='#3771bb'>%s</font>", message)
+	case StyleHashtag:
+		return fmt.Sprintf("<font color='#3771bb'>%s</font>", message)
+	case StyleCashtag:
+		return fmt.Sprintf("<font color='#3771bb'>%s</font>", message)
+	case StylePhone:
+		return fmt.Sprintf("<font color='#3771bb'>%s</font>", message)
+	default:
+		return message
+	}
+}
+
+type UTF16String []uint16
+
+func NewUTF16String(s string) UTF16String {
+	return utf16.Encode([]rune(s))
+}
+
+func (u UTF16String) String() string {
+	return string(utf16.Decode(u))
+}
+
+func (lrt *LinkedRangeTree) Format(message UTF16String, ctx formatContext) string {
+	if lrt == nil || lrt.Node == nil {
+		return ctx.TextToHTML(message.String())
+	}
+	head := message[:lrt.Node.Start]
+	headStr := ctx.TextToHTML(head.String())
+	inner := message[lrt.Node.Start:lrt.Node.End()]
+	tail := message[lrt.Node.End():]
+	ourCtx := ctx
+	if lrt.Node.Value.IsCode() {
+		ourCtx.IsInCodeblock = true
+	}
+	childMessage := lrt.Child.Format(inner, ourCtx)
+	formattedChildMessage := lrt.Node.Value.Format(childMessage)
+	siblingMessage := lrt.Sibling.Format(tail, ctx)
+	return headStr + formattedChildMessage + siblingMessage
+}