# Presenters (Strict)

This document defines the **Presenter** boundary for `apps/website`.

Presenters exist to prevent responsibility drift into:

- server routes
- Page Queries
- Templates

## 1) Definition

A **Presenter** is a deterministic, side-effect free transformation between website presentation models.

Allowed transformations:

- Page DTO → ViewData
- Page DTO → ViewModel
- ViewModel → ViewData

## 2) Non-negotiable rules

1. Presenters MUST be deterministic.
2. Presenters MUST be side-effect free.
3. Presenters MUST NOT perform HTTP.
4. Presenters MUST NOT call API clients.
5. Presenters MUST NOT access cookies/headers.
6. Presenters MAY use Display Objects.
7. Presenters MUST NOT import Templates.

## 3) Where Presenters run

Presenters run in **client code only**.

Presenters MUST be defined in `'use client'` modules.

If a computation affects routing decisions (redirect, notFound), it belongs in a Page Query or server route composition, not in a Presenter.

## 4) Relationship to Display Objects

Display Objects implement reusable formatting/mapping.

Rules:

- Presenters may orchestrate Display Objects.
- Display Object instances MUST NOT appear in ViewData.

See [`DISPLAY_OBJECTS.md`](docs/architecture/website/DISPLAY_OBJECTS.md:1) and [`VIEW_DATA.md`](docs/architecture/website/VIEW_DATA.md:1).

## 5) Canonical placement in this repo (strict)

Presenters MUST live colocated with ViewModels under:

- `apps/website/lib/view-models/**`

Reason: this repo already treats `apps/website/lib/view-models/**` as the client-only presentation module boundary.