Custom emoji in markdown rich messages (send + round-trip)

Parse custom emoji into RichText.textCustomEmoji when sending markdown
rich messages, and round-trip them through edit, copy, and paste using a
shared tg://emoji?id=<fileId> markdown-link marker.

- Send: rewrite each customEmoji input attribute into a
  [<alt>](tg://emoji?id=<fileId>) marker before the CommonMark parse, then
  intercept the marker URL afterward to emit .textCustomEmoji. Only rich
  messages are affected; a custom emoji alone stays on the entity path.
- Reverse: InstantPageToMarkdown (whole-message copy + edit reconstruction)
  and InstantPageMultiTextAdapter (selection copy) emit the marker;
  edit-load and chat paste reattach it as a live customEmoji attribute.
- Marker helpers shared in TextFormat/CustomEmojiMarkdownMarker.swift.
- Rich sends now pass inlineStickers so recipients can fetch the files.

Follow-up to verify at runtime: recipient rendering goes out with
Api.InputRichMessage.documents: nil; if recipients see only the fallback
glyph, populate documents: in apiInputRichMessage().

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

submodules/BrowserUI/Sources/BrowserMarkdown.swift

@@ -3,6 +3,7 @@ import UIKit
 import TelegramCore
 import AccountContext
 import InstantPageUI
+import TextFormat
 
 private let markdownPresentationIntentAttribute = NSAttributedString.Key("NSPresentationIntent")
 private let markdownInlinePresentationIntentAttribute = NSAttributedString.Key("NSInlinePresentationIntent")
@@ -1137,11 +1138,41 @@ private func instantPageNeedsRichLayout(_ blocks: [InstantPageBlock]) -> Bool {
     return blocks.contains { !blockIsEntityExpressible($0) }
 }
 
+// Rewrites each `ChatTextInputAttributes.customEmoji` run in the attributed
+// input as a `[<alt>](tg://emoji?id=<fileId>)` markdown link, leaving all other
+// text (and its markdown syntax) verbatim. With no custom emoji present this
+// returns `attributedText.string` unchanged, so non-emoji messages are
+// unaffected. The marker is intercepted post-parse in markdownInlineContent.
+private func markdownSourceInjectingCustomEmojiMarkers(_ attributedText: NSAttributedString) -> String {
+    let nsString = attributedText.string as NSString
+    var result = ""
+    attributedText.enumerateAttribute(ChatTextInputAttributes.customEmoji, in: NSRange(location: 0, length: attributedText.length), options: []) { value, range, _ in
+        let substring = nsString.substring(with: range)
+        if let attribute = value as? ChatTextInputTextCustomEmojiAttribute {
+            // The link text must be non-empty: CommonMark drops `[](url)` (no
+            // run carries the link attribute), which would silently lose the
+            // emoji. Fall back to a space, matching the reattach helper.
+            let alt = substring.isEmpty ? " " : substring
+            result += "[\(escapeCustomEmojiMarkdownAlt(alt))](\(customEmojiMarkdownURL(fileId: attribute.fileId)))"
+        } else {
+            result += substring
+        }
+    }
+    return result
+}
+
 // Returns a RichTextMessageAttribute IFF the markdown in `text` produces an
 // InstantPage block with no entity equivalent. Returns nil (-> send via the
 // regular entity path) for plain text, pre-iOS-15, oversize markdown, or
 // markdown that maps cleanly onto entities.
-public func richMarkdownAttributeIfNeeded(context: AccountContext, text: String) -> RichTextMessageAttribute? {
+public func richMarkdownAttributeIfNeeded(context: AccountContext, attributedText: NSAttributedString) -> RichTextMessageAttribute? {
+    // Custom emoji are rewritten to `[<alt>](tg://emoji?id=...)` link markers
+    // before classification + parse; the markers are intercepted back into
+    // .textCustomEmoji in markdownInlineContent. A link is entity-expressible,
+    // so an emoji-only message still classifies as not-rich (and falls through
+    // to the entity path, where its untouched attribute makes a .CustomEmoji
+    // entity) — custom emoji alone never forces a rich message.
+    let text = markdownSourceInjectingCustomEmojiMarkers(attributedText)
     guard markdownMightNeedRichLayout(text) else {
         return nil
     }
@@ -1688,6 +1719,13 @@ private func markdownInlineContent(from attributedString: NSAttributedString, co
             return
         }
 
+        if let linkUrl = markdownLink(attributes: attributes, documentURL: context.documentURL),
+           let fileId = parseCustomEmojiFileId(fromMarkdownURL: linkUrl) {
+            // `text` is the parsed (already-unescaped) link display text = the alt.
+            fragments.append(.richText(.textCustomEmoji(fileId: fileId, alt: text)))
+            return
+        }
+
         let segments = markdownInlineTextSegments(from: text, formulasByPlaceholder: context.formulasByPlaceholder)
         for segment in segments {
             let baseText: RichText

submodules/BrowserUI/Sources/InstantPageToMarkdown.swift

@@ -1,5 +1,6 @@
 import Foundation
 import TelegramCore
+import TextFormat
 
 /// Reconstructs a markdown source string from an `InstantPage`.
 ///
@@ -125,9 +126,11 @@ private func markdownInline(from richText: RichText) -> String {
         return markdownInline(from: text)
     case let .`subscript`(text):
         return markdownInline(from: text)
+    case let .textCustomEmoji(fileId, alt):
+        return "[\(escapeCustomEmojiMarkdownAlt(alt))](\(customEmojiMarkdownURL(fileId: fileId)))"
     default:
-        // .image, .textCustomEmoji, and the entity cases (.textMention,
-        // .textHashtag, …): fall back to plain text.
+        // .image and the entity cases (.textMention, .textHashtag, …):
+        // fall back to plain text.
         return escapeMarkdown(richText.plainText)
     }
 }

submodules/InstantPageUI/Sources/InstantPageMultiTextAdapter.swift

@@ -282,8 +282,13 @@ private func inlineMarkdown(from slice: NSAttributedString) -> String {
     slice.enumerateAttributes(in: fullRange, options: []) { attributes, range, _ in
         let substring = (slice.string as NSString).substring(with: range)
 
-        // Custom emoji: single-space placeholder with no alt available — drop it.
-        if attributes[ChatTextInputAttributes.customEmoji] != nil {
+        // Custom emoji: emit the shared marker carrying the fileId. The display
+        // placeholder may have no real alt (often a single space), so alt is
+        // best-effort; whole-message copy / edit reconstruction have the true alt.
+        if let emojiAttribute = attributes[ChatTextInputAttributes.customEmoji] as? ChatTextInputTextCustomEmojiAttribute {
+            // Non-empty link text required: CommonMark drops `[](url)` on re-parse.
+            let alt = substring.isEmpty ? " " : substring
+            result += "[\(escapeCustomEmojiMarkdownAlt(alt))](\(customEmojiMarkdownURL(fileId: emojiAttribute.fileId)))"
             return
         }
 

submodules/TelegramUI/Components/Chat/ChatTextInputPanelNode/Sources/ChatTextInputPanelNode.swift

@@ -5301,7 +5301,20 @@ public class ChatTextInputPanelNode: ChatInputPanelNode, ASEditableTextNodeDeleg
                 attributedString = chatInputStateStringFromRTF(data, type: NSAttributedString.DocumentType.rtfd)
             }
         }
-        
+
+        // Rich-message markdown copied to the clipboard is plain text containing
+        // `[<alt>](tg://emoji?id=<fileId>)` emoji markers (no RTF/private type).
+        // Reattach those markers as live custom-emoji attributes so the field
+        // shows the animated emoji (matching the edit-load reconstruction). Only
+        // taken when a marker actually converted, so ordinary text pastes are
+        // unaffected and fall through to default paste.
+        if attributedString == nil, let plainText = pasteboard.string, plainText.contains("tg://emoji?id=") {
+            let reattached = chatInputTextWithReattachedCustomEmoji(plainText)
+            if reattached.string != plainText {
+                attributedString = reattached
+            }
+        }
+
         if let attributedString = attributedString {
             self.interfaceInteraction?.updateTextInputStateAndMode { current, inputMode in
                 if let inputText = current.inputText.mutableCopy() as? NSMutableAttributedString {

submodules/TelegramUI/Sources/Chat/ChatControllerLoadDisplayNode.swift

@@ -1781,7 +1781,7 @@ extension ChatControllerImpl {
                             
                             let inputText: NSAttributedString
                             if let richTextAttribute = message.attributes.first(where: { $0 is RichTextMessageAttribute }) as? RichTextMessageAttribute {
-                                inputText = NSAttributedString(string: markdownStringFromInstantPage(richTextAttribute.instantPage))
+                                inputText = chatInputTextWithReattachedCustomEmoji(markdownStringFromInstantPage(richTextAttribute.instantPage))
                             } else {
                                 inputText = chatInputStateStringWithAppliedEntities(message.text, entities: entities)
                             }
@@ -2214,14 +2214,13 @@ extension ChatControllerImpl {
                 
                 let text = trimChatInputText(convertMarkdownToAttributes(expandedInputStateAttributedString(editMessage.inputState.inputText)))
 
-                let rawEditText = expandedInputStateAttributedString(editMessage.inputState.inputText).string
                 var isSpecialChatContents = false
                 if case .customChatContents = strongSelf.presentationInterfaceState.subject {
                     isSpecialChatContents = true
                 }
                 var richTextAttribute: RichTextMessageAttribute?
                 if !isSpecialChatContents {
-                    richTextAttribute = richMarkdownAttributeIfNeeded(context: strongSelf.context, text: rawEditText)
+                    richTextAttribute = richMarkdownAttributeIfNeeded(context: strongSelf.context, attributedText: expandedInputStateAttributedString(editMessage.inputState.inputText))
                 }
 
                 let entities = generateTextEntities(text.string, enabledTypes: .all, currentEntities: generateChatInputTextEntities(text))

submodules/TelegramUI/Sources/Chat/ChatMessageDisplaySendMessageOptions.swift

@@ -215,8 +215,8 @@ func chatMessageDisplaySendMessageOptions(selfController: ChatControllerImpl, no
             var richTextPreview: ChatSendMessageContextScreenRichTextPreview?
             if case .customChatContents = selfController.presentationInterfaceState.subject {
             } else if mediaPreview == nil,
-                      let plainText = textInputView.attributedText?.string,
-                      let attribute = richMarkdownAttributeIfNeeded(context: selfController.context, text: plainText) {
+                      let attributedText = textInputView.attributedText,
+                      let attribute = richMarkdownAttributeIfNeeded(context: selfController.context, attributedText: attributedText) {
                 richTextPreview = ChatSendMessageRichTextPreview(context: selfController.context, instantPage: attribute.instantPage)
             }
 

submodules/TelegramUI/Sources/ChatControllerNode.swift

@@ -4861,9 +4861,18 @@ class ChatControllerNode: ASDisplayNode, ASScrollViewDelegate {
                 if case .customChatContents = self.chatPresentationInterfaceState.subject {
                     isSpecialChatContents = true
                 }
-                if !isSpecialChatContents, let attribute = richMarkdownAttributeIfNeeded(context: self.context, text: effectiveInputText.string) {
+                if !isSpecialChatContents, let attribute = richMarkdownAttributeIfNeeded(context: self.context, attributedText: effectiveInputText) {
                     let attributes: [MessageAttribute] = [attribute]
-                    messages.append(.message(text: "", attributes: attributes, inlineStickers: [:], mediaReference: nil, threadId: self.chatLocation.threadId, replyToMessageId: self.chatPresentationInterfaceState.interfaceState.replyMessageSubject?.subjectModel, replyToStoryId: nil, localGroupingKey: nil, correlationId: nil, bubbleUpEmojiOrStickersets: []))
+                    var richBubbleUpEmojiOrStickersets: [ItemCollectionId] = []
+                    for (_, packId) in bubbleUpEmojiOrStickersetsById {
+                        if !richBubbleUpEmojiOrStickersets.contains(packId) {
+                            richBubbleUpEmojiOrStickersets.append(packId)
+                        }
+                    }
+                    if richBubbleUpEmojiOrStickersets.count > 1 {
+                        richBubbleUpEmojiOrStickersets.removeAll()
+                    }
+                    messages.append(.message(text: "", attributes: attributes, inlineStickers: inlineStickers, mediaReference: nil, threadId: self.chatLocation.threadId, replyToMessageId: self.chatPresentationInterfaceState.interfaceState.replyMessageSubject?.subjectModel, replyToStoryId: nil, localGroupingKey: nil, correlationId: nil, bubbleUpEmojiOrStickersets: richBubbleUpEmojiOrStickersets))
                     mediaReference = nil
                 } else {
                     for text in breakChatInputText(trimChatInputText(inputText)) {

submodules/TextFormat/Sources/CustomEmojiMarkdownMarker.swift

@@ -0,0 +1,84 @@
+import Foundation
+
+/// The private markdown-link URL that carries a custom emoji's file id between
+/// the send path and the rich-message renderer. Shared by the forward
+/// (compose/send) path and the reverse (copy/edit) converters so the encode and
+/// decode cannot drift. Format: a markdown link `[<alt>](tg://emoji?id=<fileId>)`.
+public func customEmojiMarkdownURL(fileId: Int64) -> String {
+    return "tg://emoji?id=\(fileId)"
+}
+
+/// Backslash-escapes only the characters that would break a marker link's
+/// display text (the `alt`): backslash, the link-text brackets, and newline.
+/// Minimal by design — the forward CommonMark parser unescapes these, so the
+/// alt round-trips. Shared by every site that emits a `[<alt>](tg://emoji?id=…)`
+/// marker so the escaping cannot drift between encoders.
+public func escapeCustomEmojiMarkdownAlt(_ string: String) -> String {
+    var result = ""
+    result.reserveCapacity(string.count)
+    for character in string {
+        switch character {
+        case "\\", "[", "]", "\n":
+            result.append("\\")
+            result.append(character)
+        default:
+            result.append(character)
+        }
+    }
+    return result
+}
+
+/// Parses the file id out of a `tg://emoji?id=<fileId>` marker URL.
+/// Returns nil for any other URL (ordinary links flow through unchanged).
+public func parseCustomEmojiFileId(fromMarkdownURL url: String) -> Int64? {
+    let prefix = "tg://emoji?id="
+    guard url.hasPrefix(prefix) else {
+        return nil
+    }
+    return Int64(url.dropFirst(prefix.count))
+}
+
+/// Regex matching an emitted marker link: `[<alt>](tg://emoji?id=<digits>)`.
+/// `alt` is captured as group 1 (any run of non-`]` chars), the file id as group 2.
+private let customEmojiMarkerRegex = try? NSRegularExpression(
+    pattern: "\\[([^\\]]*)\\]\\(tg://emoji\\?id=(-?\\d+)\\)",
+    options: []
+)
+
+/// Reverse of the forward normalization: takes reconstructed markdown source
+/// (e.g. from `markdownStringFromInstantPage`) and returns an attributed string
+/// where each `tg://emoji?id=` marker link has been turned back into a live
+/// `ChatTextInputAttributes.customEmoji` run (the alt text carrying a
+/// `ChatTextInputTextCustomEmojiAttribute`). Everything else stays verbatim
+/// markdown text. Used to populate the edit compose field so it shows the
+/// animated emoji; on re-save the forward path reads the attribute's fileId back.
+///
+/// `file` is left nil — the renderer resolves the emoji lazily from `fileId`,
+/// and the send path only needs the fileId. Known limitation: an alt containing
+/// a literal `]` is not matched (emoji alts do not contain brackets).
+public func chatInputTextWithReattachedCustomEmoji(_ markdown: String) -> NSAttributedString {
+    let result = NSMutableAttributedString(string: markdown)
+    guard let regex = customEmojiMarkerRegex else {
+        return result
+    }
+    let matches = regex.matches(in: markdown, options: [], range: NSRange(markdown.startIndex..., in: markdown))
+    // Replace from last match to first so the earlier NSRanges stay valid.
+    for match in matches.reversed() {
+        guard match.numberOfRanges == 3 else {
+            continue
+        }
+        guard let altRange = Range(match.range(at: 1), in: markdown),
+              let idRange = Range(match.range(at: 2), in: markdown),
+              let fileId = Int64(markdown[idRange]) else {
+            continue
+        }
+        let alt = String(markdown[altRange])
+        // The attribute must ride on at least one character; use a space if the
+        // alt was emitted empty (selection-copy with no alt available).
+        let displayText = alt.isEmpty ? " " : alt
+        let attribute = ChatTextInputTextCustomEmojiAttribute(interactivelySelectedFromPackId: nil, fileId: fileId, file: nil)
+        let replacement = NSAttributedString(string: displayText, attributes: [ChatTextInputAttributes.customEmoji: attribute])
+        result.replaceCharacters(in: match.range, with: replacement)
+    }
+    return result
+}