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RealTimeChat NextGen v4.0

RealTimeChat NextGen v4.0 is a high-concurrency real-time communication and collaboration suite built in Java 21 LTS (Virtual Threads, FlatLaf Dark Swing GUI, H2 SQL persistence, embedded HTTP Webhook server, and TCP JSON sockets). It brings Discord-grade workflows including Optimistic UI, threads, live reactions, presence detection, cursor pagination, offline queuing/resync, bitfield permissions, Markdown + Piston code execution, slash commands, search filters, clipboard image paste, OpenGraph previews, PCM voice rooms, a collaborative whiteboard, and ECDH + AES-256-GCM end-to-end encrypted direct messages.

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Key Features

Phase 1: Real-Time Experience, Presence & Customization

• Custom Uploadable & Resizable Avatars: Upload local PNG/JPG/GIF/WebP photos, zoom/pan crop interactively inside AvatarCropDialog, preview circular avatars across chat messages, member sidebar, and profile cards.
• Structured Profile Customization: Multi-line biography editor enforced at 240 characters with live counter (0/240), vector avatar presets (cyber-neon, synthwave, cosmic, emerald, sunset, bot-matrix, golden, retro-pixel), and banner themes/hex colors.
• Optimistic UI & Message Lifecycle: Local tempId SENDING state with reduced opacity, real-time server MESSAGE_ACK assigning permanent DB id & timestamp, and red ERROR cards with Retry / Delete actions after 8s timeout.
• Throttled Typing Indicators: Client-side 2.5s emission throttle (TYPING_START / TYPING_STOP) and receiver 3.0s auto-debounce cleared immediately upon message delivery.
• Nested Replies & Thread Side Panel: Clickable quote previews (replyToId) jumping to parent messages, plus a dedicated Discord-style side drawer (ThreadSidePanel) scoped by threadParentId.
• Advanced Presence System: Automatic inactivity monitor (IDLE), notification suppression (DND), heartbeat offline tracking (OFFLINE), and custom status text/tag.
• Delta Emoji Reactions: Incremental REACTION_ADD / REACTION_REMOVE broadcasts updating grouped counters live.

Phase 2: Scalability, Persistence & Access Control

• H2 Embedded SQL Database: Persistent tables (user_profiles, channels, messages, webhooks) replacing volatile RAM history.
• Cursor-Based Pagination & Feed Virtualization: beforeId / afterId keyset queries (no OFFSET) powering smooth upward infinite scroll without viewport jump and sliding-window card pruning.
• Offline FIFO Queue & Reconnect Resync: Automatic exponential-backoff reconnect (autoReconnect), local queuing of messages composed while disconnected, and automatic afterId gap filling upon reconnect.
• Channel Lifecycle & Bitfield RBAC Permissions: Create/delete text or voice channels dynamically with bitmask permissions (VIEW_CHANNEL, SEND_MESSAGES, MANAGE_MESSAGES, ADMINISTRATOR, MANAGE_CHANNELS, MANAGE_ROLES, MANAGE_WEBHOOKS, CREATE_THREADS, VOICE_CONNECT) and per-channel user overrides enforced on both server and client UI.

Phase 3: Technical Tools, Commands & Search

• Rich Markdown & Piston Code Runner: Renders **bold**, *italic*, `inline`, ~~strike~~, @mentions, auto-linked URLs, and fenced code blocks with Copy button and Run > execution against the Piston API (stdout/stderr).
• Slash (/) Autocomplete Engine & Polls: Live popup suggestions for /poll Question | Opt1 | Opt2 (real-time vote tallies), /roll [NdM], /shrug, /clear, /join, /createchannel, /deletechannel, /search, /status, /w, /bio, and /whiteboard.
• Channel Webhooks (POST /api/webhooks/{id}/{token}): Embedded com.sun.net.httpserver.HttpServer (tcpPort + 1, default 5001) accepting external JSON payloads and broadcasting rich embeds into channels, with /api/health.
• Advanced Search with Modifiers: Filter queries parsed via from:user, in:#channel, has:link, has:file, and keywords with click-to-jump navigation.

Phase 4: Media, Collaboration & Security

• Direct Clipboard Paste (Ctrl+V): Intercepts clipboard images, displays removable strip previews, scales/compresses via JPEG encoding (ImageUtils), and renders inline clickable lightboxes.
• Async OpenGraph Previews: Background metadata extraction (og:title, og:description, og:image, og:site_name) with SSRF private-IP/localhost filtering pushing MESSAGE_EMBED_UPDATE patches.
• PCM Voice Channels & Collaborative Whiteboard: Low-latency 16 kHz mono audio rooms (javax.sound.sampled) with RMS speaking indicators and Mute/Deafen controls, plus real-time synchronized drawing canvas (WhiteboardDialog) and WEBRTC_SIGNAL relay.
• End-to-End Encrypted DMs (E2EE): Ephemeral/session ECDH (secp256r1) key exchange deriving AES-256-GCM secrets via SHA-256; private message ciphertext + iv remain opaque to the server and H2 database.

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Network Architecture

flowchart TD
    subgraph Clients ["Dual Clients (GUI & CLI)"]
        GUI["ChatGuiClient (FlatLaf Dark + Voice + Whiteboard + E2EE)"]
        CLI["ChatConsoleClient (Interactive Terminal CLI)"]
    end

    subgraph Server ["RealTimeChat NextGen Server"]
        TCP["ServerSocket :5000 (Virtual Threads + TokenBucket)"]
        HTTP["WebhookHttpServer :5001 (REST /api/webhooks/{id}/{token})"]
        Core["ChatRoom (RBAC Bitfields, Channels, Presence, Bot, E2EE Relay)"]
        DB[("H2 Embedded SQL (./data/realtimechat)")]
        OG["OpenGraphService (Async + SSRF Guard)"]
    end

    GUI <-->|TCP JSON / E2EE| TCP
    CLI <-->|TCP JSON| TCP
    TCP --> Core
    HTTP -->|Embed Broadcast| Core
    Core <--> DB
    Core --> OG

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Build & Execution

Prerequisites

• Java Development Kit (JDK) 21 LTS+
• Apache Maven 3.9+

Compile, Run Tests & Package Fat JAR

mvn clean test package

Produces shaded executable JAR at target/realtimechat-1.0.0.jar (10.56 MB with FlatLaf, Jackson, H2, and multi-resolution window icons).

Run Server & Client

# Server (TCP :5000 + Webhook HTTP :5001 + ./data/realtimechat H2 DB)
java -cp target/realtimechat-1.0.0.jar com.danicaju.chat.server.ChatServer 5000

# Desktop GUI Client
java -jar target/realtimechat-1.0.0.jar

# Terminal CLI Client
java -cp target/realtimechat-1.0.0.jar com.danicaju.chat.client.ChatConsoleClient

Docker Deployment

docker build -t realtimechat:latest .
docker run -d --name realtimechat-server -p 5000:5000 -p 5001:5001 realtimechat:latest

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Testing & Quality Assurance

Verified with 103 automated JUnit 5 tests across 15 test suites:

• ChatRoomTest (32): Concurrency, case-insensitive user checks, channel switching/creation/deletion, bitfield overrides, history bounds.
• MessageTest (16): JSON roundtrip, forward compatibility, rich factory payloads.
• RealTimeBotTest (14): Summarization, math parser (^, sqrt, precedence), diagnostics, computing topics.
• ChatServerIntegrationTest (11): Live TCP handshakes, multi-channel isolation, typing events, rate limiter, reactive profiles.
• DatabaseManagerTest (5): H2 persistence, keyset cursor pagination (beforeId/afterId), threads, reactions, webhooks, filtered search.
• PhaseOneToFourIntegrationTest (4): Live TCP/HTTP tests covering Optimistic ACK, threads, reactions, DND presence, bitfield SEND_MESSAGES denial, polls, REST webhooks, offline FIFO queue & reconnect afterId resync, and ECDH+AES-GCM E2EE opaque storage.
• TokenBucketRateLimiterTest (4) & UserProfileTest (4): Flooding defense and 240-char bio/profile validation.
• SlashCommandHelperTest (3), ImageUtilsAndMarkdownTest (2), OpenGraphServiceTest (2), E2EECryptoTest (2), PermissionTest (2), PistonClientTest (1), SearchQueryParserTest (1).

[INFO] Tests run: 103, Failures: 0, Errors: 0, Skipped: 0
[INFO] BUILD SUCCESS

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_{Developed by Daniel Casado Juan | Universitat de les Illes Balears (UIB)}