# Chat Protocol

This document describes a simple chat protocol. To re-generate the source files,
run `go run ./cmd/hopp-generate examples/chat/protocol.md examples/chat/protocol`

## Messages

### 0000 Error
| Tag | Name        | Type   | Required |
| --: | ----------- | ------ | -------- |
|   0 | Code        | U16    | Yes      |
|   1 | Description | String | No       |

Error is sent by a party when the other party has done something erroneous. The
valid error codes are:

- 0: General, unspecified error 

The description field, if specified, determines a human-readable error to be
shown to the user. The sending party must immediately close the transaction
after this message is sent.

### 0001 Success
Success is sent by a party when it has successfully completed a task given to it
by the other party. The sending party must immediately close the transaction
after this message is sent.

### 0100 UpdateProfile
| Tag | Name     | Type   | Required |
| --: | -------- | ------ | -------- |
|   0 | Nickname | String | No       |

UpdateProfile is sent by the client in a new transaction to update the profile
details that will be shown to other connected clients.

### 0200 Join
| Tag | Name     | Type   | Required |
| --: | -------- | ------ | -------- |
|   0 | Room     | String | Yes      |

Join is sent by the client when it wishes to join a room. It must begin a new
transaction, and that transaction will persist while the user is in that room.
Messages having to do with the room will be sent along this transaction. To
leave the room, the client must close the transaction.

### 0201 Chat
| Tag | Name     | Type   | Required |
| --: | -------- | ------ | -------- |
|   0 | Nickname | String | No       |
|   1 | Content  | String | Yes      |

Chat is sent by the client when it wishes to post a message to the room. It is
also relayed by the server to other clients to notify them of the message. It
must be sent within a room transaction.

### 0300 JoinNotify
| Tag | Name     | Type   | Required |
| --: | -------- | ------ | -------- |
|   0 | Nickname | String | No       |

JoinNotify is sent by the server when another client joins the room. It must be
sent within a room transaction.

### 0301 LeaveNotify
| Tag | Name     | Type   | Required |
| --: | -------- | ------ | -------- |
|   0 | Nickname | String | No       |

LeaveNotify is sent by the server when another client leaves the room. It must
be sent within a room transaction.