feat(frontend): online dots on private chats, deleted last message struck through, back from a chat goes through history

frontend/src/lib/components/ChatHeader.svelte

@@ -29,8 +29,11 @@
   const isDm = $derived(chatId > 0);
   const chat = $derived(chats.byId(chatId));
   const discovered = $derived(discover.get(chatId));
+  const DONE_DURATION = 2500;
+
   let peer = $state<PeerView | null>(null);
   let backfilling = $state(false);
+  let backfilled = $state(false);
 
   async function backfill() {
     if (backfilling) {
@@ -39,7 +42,10 @@
     backfilling = true;
     try {
       await enqueueBackfill(chatId, true);
-      toasts.success(t("chat.backfill.started"));
+      backfilled = true;
+      setTimeout(() => {
+        backfilled = false;
+      }, DONE_DURATION);
     } catch {
       toasts.error(t("chat.backfill.failed"));
     } finally {
@@ -48,6 +54,10 @@
   }
 
   function back() {
+    if (page.state.inApp) {
+      history.back();
+      return;
+    }
     const target = new URL(page.url.href);
     target.pathname = "/app";
     goto(withoutMessage(target));
@@ -216,14 +226,15 @@
       <Icon name="stats" />
     </Button>
     <Button
-      aria-label={t("chat.backfill")}
+      aria-label={backfilled ? t("chat.backfill.started") : t("chat.backfill")}
       loading={backfilling}
       onclick={backfill}
       round
       smaller
+      title={backfilled ? t("chat.backfill.started") : t("chat.backfill")}
       variant="translucent"
     >
-      <Icon name="cloud-download" />
+      <Icon name={backfilled ? "check" : "cloud-download"} />
     </Button>
   </div>
 </header>
@@ -287,8 +298,13 @@
   }
 
   .subtitle {
+    overflow: hidden;
+    display: block;
+
     font-size: 0.8125rem;
     color: var(--color-text-secondary);
+    text-overflow: ellipsis;
+    white-space: nowrap;
 
     &.online {
       color: var(--color-primary);

frontend/src/lib/components/ChatList.svelte

@@ -76,6 +76,22 @@
     }
   });
 
+  $effect(() => {
+    const id = activeChatId;
+    untrack(() => {
+      const index = list.findIndex((chat) => chat.chat_id === id);
+      if (index === -1 || viewport === null) {
+        return;
+      }
+      const top = index * rowHeight;
+      if (top < viewport.scrollTop) {
+        viewport.scrollTop = top;
+      } else if (top + rowHeight > viewport.scrollTop + viewport.clientHeight) {
+        viewport.scrollTop = top + rowHeight - viewport.clientHeight;
+      }
+    });
+  });
+
   function measure(el: HTMLElement) {
     ({ scrollTop } = el);
     if (el.scrollTop + el.clientHeight >= el.scrollHeight - SCROLL_THRESHOLD) {

frontend/src/lib/components/ChatListItem.svelte

@@ -4,9 +4,11 @@
   import Avatar from "#lib/components/ui/Avatar.svelte";
   import ContextMenu from "#lib/components/ui/ContextMenu.svelte";
   import ContextMenuItem from "#lib/components/ui/ContextMenuItem.svelte";
+  import Icon from "#lib/components/ui/Icon.svelte";
   import { formatListDate } from "#lib/format/datetime.js";
   import { t } from "#lib/i18n/locale.svelte.js";
   import { accounts } from "#lib/stores/accounts.svelte.js";
+  import { online } from "#lib/stores/online.svelte.js";
   import { peers } from "#lib/stores/peers.svelte.js";
   import { policyUi } from "#lib/stores/policy.svelte.js";
   import { type RightPanel, ui } from "#lib/stores/ui.svelte.js";
@@ -31,6 +33,14 @@
         ? t("chat.deletedAccount")
         : t("chat.fallbackTitle", { id: chat.chat_id }))
   );
+  const person = $derived(chat.chat_id > 0 && !chat.is_bot);
+  const isOnline = $derived(person && online.isOnline(chat.chat_id));
+
+  $effect(() => {
+    if (person) {
+      online.watch(chat.chat_id);
+    }
+  });
   const avatarKind = $derived(chat.chat_id > 0 ? "peer" : "chat");
   const ownId = $derived(accounts.selected?.tg_user_id ?? null);
   const showSender = $derived(
@@ -74,12 +84,14 @@
       class:selected
       use:ripple
     >
+      <span class="avatar" class:online={isOnline}>
         <Avatar
           avatar={{ id: chat.chat_id, kind: avatarKind }}
           colorKey={chat.chat_id}
           hasAvatar={chat.has_avatar}
           name={title}
         />
+      </span>
       <div class="info">
         <div class="info-row">
           <h3 class="title">{title}</h3>
@@ -90,7 +102,13 @@
             {#if senderPrefix}
               <span class="sender">{senderPrefix}</span>
             {/if}
+            {#if chat.last_deleted}
+              <span class="deleted-mark" title={t("chat.deletedPreview")}
+                ><Icon name="delete" size="1rem" /></span
+              ><s class="deleted-text">{preview}</s>
+            {:else}
               {preview}
+            {/if}
           </span>
         </div>
       </div>
@@ -147,11 +165,15 @@
 
     @media (hover: hover) {
       &:hover {
+        --online-ring: var(--color-chat-hover);
+
         background-color: var(--color-chat-hover);
       }
     }
 
     &.selected {
+      --online-ring: var(--color-chat-active);
+
       background-color: var(--color-chat-active);
 
       .title,
@@ -163,6 +185,37 @@
     }
   }
 
+  .avatar {
+    position: relative;
+    display: flex;
+    flex-shrink: 0;
+
+    &.online::after {
+      content: "";
+
+      position: absolute;
+      right: 0.0625rem;
+      bottom: 0.0625rem;
+
+      width: 0.875rem;
+      height: 0.875rem;
+      border: 2px solid var(--online-ring, var(--color-background));
+      border-radius: 50%;
+
+      background-color: var(--color-green);
+    }
+  }
+
+  .deleted-mark {
+    display: inline-flex;
+    margin-inline-end: 0.1875rem;
+    vertical-align: -0.1875rem;
+  }
+
+  .deleted-text {
+    text-decoration: line-through;
+  }
+
   .info {
     overflow: hidden;
     flex: 1;

frontend/src/lib/stores/chats.svelte.ts

@@ -14,6 +14,7 @@ import { folders } from "#lib/stores/folders.svelte.js";
 const POLL_INTERVAL = 1500;
 const POLL_MAX = 12;
 const PAGE_SIZE = 40;
+const CHANNEL_IDS = -1_000_000_000_000;
 const ALL = "all";
 const EMPTY: Chat[] = [];
 
@@ -159,7 +160,29 @@ function createChats() {
     }
   }
 
+  function applyDelete(chatId: number | null, ids: number[]) {
+    for (const bucket of Object.values(buckets)) {
+      for (const chat of bucket.list) {
+        const inScope =
+          chatId === null
+            ? chat.chat_id > CHANNEL_IDS
+            : chat.chat_id === chatId;
+        if (
+          inScope &&
+          chat.last_message_id !== null &&
+          ids.includes(chat.last_message_id)
+        ) {
+          chat.last_deleted = true;
+        }
+      }
+    }
+  }
+
   function applyEvent(event: LiveEvent) {
+    if (event.type === "delete") {
+      applyDelete(event.chat_id, event.message_ids);
+      return;
+    }
     if (event.type !== "message") {
       return;
     }
@@ -174,6 +197,8 @@ function createChats() {
       }
       seenChat = true;
       existing.last_date = message.date;
+      existing.last_deleted = message.deleted_at !== null;
+      existing.last_message_id = message.message_id;
       existing.last_sender_id = message.sender_id;
       existing.last_text = message.text;
       existing.message_count += 1;