# `ChatMessage`

One message in a conversation with a model: who wrote it and what it says, sent `{"role": "user", "content": "..."}`.

[AI](types.md#ai); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its fields, `ChatMessage { role: ...  content: ... }`.

## Fields

| Field | Type |
|---|---|
| `role` | [`ChatRole`](type-chat-role.md) |
| `content` | `Text` |

## Text, JSON and storage

It has no single text form, so `text.from` and `text.parse` don't take it. JSON sends an object of its parts.

| JSON |
|---|
| `{"role":"system","content":"Answer in British English."}` |
| `{"role":"user","content":"Summarise this page.\nThanks"}` |
| `{"role":"assistant","content":""}` |

It is stored in 2 columns, each named for the field, `_` and its suffix. This is `{"role":"user","content":"Summarise this page.\nThanks"}`:

| Column | Type | Holds |
|---|---|---|
| `<field>_role` | `text` | `'user'` |
| `<field>_content` | `text` | `E'Summarise this page.\nThanks'` |

## Shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `{"role":"system","content":"Answer in British English."}` | `system: Answer in British English.` |
| `{"role":"user","content":"Summarise this page.\nThanks"}` | `"user: Summarise this page.\nThanks"` |
| `{"role":"assistant","content":""}` | `assistant: ` |

## Operations

It has the contract's own operations: `text.format`, `json.read`, `json.write` and `==`. It isn't ordered, so `<` and sorting don't take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.