feat: client-side post previews

* refactor compose form

src/kaiteki/lib/fediverse/model/post/draft.dart

@@ -1,10 +1,11 @@
+import "package:equatable/equatable.dart";
 import "package:kaiteki/fediverse/model/attachment.dart";
 import "package:kaiteki/fediverse/model/formatting.dart";
 import "package:kaiteki/fediverse/model/post/post.dart";
 import "package:kaiteki/fediverse/model/visibility.dart";
 import "package:kaiteki/model/file.dart";
 
-class PostDraft {
+class PostDraft extends Equatable {
   final String content;
   final Visibility visibility;
   final Formatting formatting;
@@ -13,6 +14,9 @@ class PostDraft {
   final List<Attachment> attachments;
   final String? language;
 
+  bool get isEmpty =>
+      content.isEmpty && subject?.isNotEmpty != true && attachments.isEmpty;
+
   const PostDraft({
     required this.subject,
     required this.content,
@@ -42,6 +46,17 @@ class PostDraft {
       language: language ?? this.language,
     );
   }
+
+  @override
+  List<Object?> get props => [
+        subject,
+        content,
+        visibility,
+        formatting,
+        replyTo,
+        attachments,
+        language,
+      ];
 }
 
 class AttachmentDraft {

src/kaiteki/lib/text/elements.dart

@@ -23,20 +23,22 @@ abstract class Element extends Equatable {
   }
 
   const Element({this.text, this.children});
+
+  bool has(bool Function(Element element) predicate) {
+    return predicate(this) || children?.any(predicate) == true;
+  }
 }
 
 typedef ReplacementElementBuilder = Element Function(String text);
 
 class TextElement extends Element {
-  @override
-  final String? text;
   final TextElementStyle? style;
 
   const TextElement(
-    this.text, {
+    String? text, {
     this.style,
     super.children,
-  });
+  }) : super(text: text);
 
   List<Element> cut(int index, int length, ReplacementElementBuilder builder) {
     final text = this.text;

src/kaiteki/lib/text/rendering_extensions.dart

@@ -75,18 +75,25 @@ Emoji? resolveEmoji(
 ]) {
   final adapter = ref.read(adapterProvider);
 
+  if (emojis == null) debugPrint("No emojis were provided");
+
   if (emojis != null) {
-    return emojis.firstWhereOrNull((e) => e.short == input);
+    final emoji = emojis.firstWhereOrNull((e) => e.short == input);
+    if (emoji == null) debugPrint("Couldn't find $input in provided emojis");
+    return emoji;
   }
 
   if (adapter is MisskeyAdapter) {
     final url = buildEmojiUriManual(adapter.instance, input, remoteHost);
+    debugPrint("Returning mkv13 emoji based on static url: $url");
     return CustomEmoji(
       short: input,
       url: url,
       instance: remoteHost ?? adapter.instance,
     );
   }
 
+  debugPrint("Couldn't resolve emoji $input");
+
   return null;
 }

src/kaiteki/lib/text/text_renderer.dart

@@ -109,7 +109,10 @@ class TextRenderer {
     final name = element.name;
     final emoji = context?.emojiResolver?.call(name);
 
-    if (emoji == null) return TextSpan(text: ":$name:");
+    if (emoji == null) {
+      debugPrint("Couldn't resolve emoji $name");
+      return TextSpan(text: ":$name:");
+    }
 
     // FIXME(Craftplacer): Change this piece widget into an EmojiSpan. Added Builder to fix scaling with inherited font size.
     return WidgetSpan(