Add public song comments with reactions and timestamped notes

[Copilot]

Extends the existing UserNote system to support public comments, reactions, and clickable timestamps for seeking to specific song positions. Backed by Parse Server with real-time sync.

Data Layer

Realm (Local)

• Extended UserNoteModel with IsPublic, TimestampMs, AuthorId, AuthorUsername, ReactionsJson
• UserNoteModelView adds computed properties for timestamp display and reaction totals

Parse (Cloud)

• New SongComment class with full feature parity plus Reactions (emoji → count) and ReactionUsers (emoji → user IDs) dictionaries
• ACL enforces write-restricted-to-author, public-read-if-public

Service Layer

ISongCommentService / ParseSongCommentService:

• Standard CRUD with public/private filtering
• Reaction management (add/remove/toggle) with duplicate prevention
• Live query subscriptions via ParseLiveQueryClient
• Bidirectional sync between Realm and Parse
• Helper methods extracted to eliminate duplication in reaction logic

SongCommentMapper:

• Converts between Realm embedded objects and Parse cloud objects
• Handles reaction serialization (simple "emoji:count,emoji:count" format for Realm)

ViewModel

SongCommentsViewModel:

• Observable collections for public/private/all comments
• Commands: create, update, delete, toggle reaction, seek to timestamp, sync
• Integrates with BaseViewModel.SeekTrackPosition() for playback control
• Timestamp picker uses AudioService.CurrentPosition

Android UI

SongNotesRecyclerViewAdapter (enhanced):

• Timestamp chip with click-to-seek
• Four reaction buttons with counts (👍🔥❤️😢)
• Visibility indicator (public/private)
• Author attribution

SongCommentDialogFragment:

• Multi-line text input
• Public/Private toggle via Material chips
• "Use Current Position" button for timestamp
• Edit and Create modes

Example Usage

// Load comments for a song
await commentsViewModel.LoadCommentsForSongAsync(song);

// Create timestamped comment
commentsViewModel.NewCommentText = "Epic guitar solo!";
commentsViewModel.NewCommentTimestamp = 92340; // 1:32.340
commentsViewModel.NewCommentIsPublic = true;
await commentsViewModel.CreateCommentCommand.ExecuteAsync(null);

// Toggle reaction
await commentsViewModel.ToggleReactionCommand.ExecuteAsync(
    (commentId: "abc123", reactionType: "fire")
);

// Seek to timestamp (triggered by tapping timestamp badge)
await commentsViewModel.OnTimestampClickCommand.ExecuteAsync(timestampMs);

Parse Server Setup Required

Database indexes needed:

• {songId: 1, isPublic: 1} (compound)
• {songId: 1, timestampMs: 1} (compound)
• {author: 1}

CLP: Public read where isPublic == true, authenticated create, author-only update/delete.

Cloud Code for atomic reactions recommended (user can currently react multiple times if Parse updates race).

Not Included

• WinUI implementation (architecture ready, ViewModel reusable)
• Threaded replies, typing indicators, moderation tools (documented as future work)

See SONG_COMMENTS_IMPLEMENTATION.md for Parse setup, security considerations, and API reference.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>
Feature Request: Public Song Comments, Reactions & Timestamped Notes (Parse-backed and realm too)</issue_title>
<issue_description>

Problem

Dimmer currently supports UserNote attached to a song (IList) mainly for personal annotations and search reverse-lookup.
There is no unified, cross-platform way to:

Expose public comments

React to comments

Attach clickable timestamps that trigger playback/sample events

Keep UI parity across Android & WinUI 3

This limits social/emotional interaction during listening, which is a core engagement driver.

---

Proposed Solution

Extend the existing UserNote concept into a first-class Song Comment system, backed by Parse Server and shared UI logic across platforms.

---

Data Model (Parse)

Song

{
"objectId": "...",
"title": "...",
"artist": "...",
"userNotes": [Pointer]
}

UserNote (extended)

{
"objectId": "...",
"song": Pointer,
"author": Pointer<_User>,
"text": "string",
"timestampMs": 92340, // nullable
"isPublic": true,
"reactions": {
"like": 12,
"fire": 3,
"sad": 1
},
"createdAt": "Date"
}

Notes:

timestampMs == null → general comment

Public notes act as song comments

Private notes remain personal/search-only

---

Functional Requirements

CRUD

Create / edit / delete own notes

Toggle isPublic

Fetch:

All public notes for a song

User’s private notes

Timestamp Interaction

Timestamp rendered as clickable UI

On click:

Seek playback to timestampMs

Fire OnSongSampleRequested(timestampMs)

Reactions

Lightweight reaction system (no separate class initially)

Atomic increment via Parse Cloud Code

---

UI / UX Parity (Android & WinUI 3)

Now Playing – Comments Section

Scrollable list

Timestamp badge (if present)

Reaction buttons

Live highlight when playback crosses timestamp

Fragments / Views

Android: Fragment / Compose

WinUI 3: Page / UserControl

Shared ViewModel logic (MVVM)

---

Parse Considerations

CLP:

Public read if isPublic == true

Write restricted to author

Index on:

song

isPublic

timestampMs

---

Benefits

Enables real-time emotional sharing

No third-party ToS risk (YouTube/SoundCloud)

Reuses existing UserNote system

Scales naturally with Parse

---

Out of Scope (for now)

Threaded replies (but to be very heavily considered)

Live typing indicators

Moderation tooling

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Feature Request: Public Song Comments, Reactions & Timestamped Notes (Parse-backed and realm too) #319

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