# `Expresso.Check.Session`
[🔗](https://github.com/rellen/expresso/blob/main/lib/expresso/check/session.ex#L1)

Runs `--check=browser`: the checks of the page in Playwright, and the keys of the presenter

`--check=browser` runs each check of `--check=a11y`, and then it uses the
presenter as the presenter does, with real key presses. It needs Node, the
npm packages `playwright` and `axe-core`, the Chromium of Playwright, and
the Hex package `playwright_ex`. `find/2` finds them.

`run/4` writes a copy of the document with axe-core to a temporary
directory, and opens it in a page of 1920 × 1080:

1. With `?check=a11y`, the page runs the layout check and axe-core.
   `assets/src/check.ts` gives the rules.
2. With no query, the session presses the key of the next step from the
   first step to the last step. After each key, the slide and the step that
   show must be the next entry of the list of the steps.
3. The session opens the menu, the list of keys, the overview and the
   handout view with their keys. Each view must open. The menu and the list
   of keys must take the focus, and `Escape` must close them and give the
   focus back.
4. Each error of the script of the page, and each `console.error`, during
   the steps 2 and 3 is a problem too.

The keys come from the program of `Expresso.Presenter.Default`, so the
check presses the keys that the list of keys of the deck shows.

# `tools`

```elixir
@type tools() :: %{cli: Path.t(), axe: Path.t()}
```

The tools of the session: the Playwright CLI and the axe-core file

# `find`

```elixir
@spec find([Path.t()], %{required(String.t()) => String.t()}) ::
  {:ok, tools()} | {:error, String.t()}
```

Find the tools of `--check=browser`

The function looks for each tool in this sequence, and it returns the error
of the first tool that it does not find:

  1. The Hex package `playwright_ex`.
  2. Node, as `node` on the `PATH`.
  3. The npm package `playwright`. The variable `EXPRESSO_PLAYWRIGHT` in
     `env` gives the path of its `cli.js`. Without it, the function looks
     for `node_modules/playwright/cli.js` in each directory of
     `directories`, in each parent of them, and in the directory of
     `Expresso.Check.Tools`.
  4. axe-core, as `Expresso.Check.Browser.find_axe/2` finds it.

# `key`

```elixir
@spec key(Expresso.Presenter.Program.t(), atom(), tuple()) :: String.t()
```

Return the key of a mode of a program that runs a command

A binding with more than one key gives the key that the list of keys shows
first in this sense: a letter before another key, and a short name before
a long name.

    iex> deck = Expresso.Builder.deck([Expresso.Builder.slide("one", elements: [])], name: "k")
    iex> program = Expresso.Presenter.Program.compile(Expresso.Presenter.Definition.presenter(), deck)
    iex> Expresso.Check.Session.key(program, :present, {:step, 1})
    "j"
    iex> Expresso.Check.Session.key(program, :present, {:set, :menu, true})
    "m"

# `run`

```elixir
@spec run(String.t(), Expresso.Deck.t(), tools(), keyword()) ::
  {:ok, [{{Expresso.Check.size(), :light | :dark | nil}, map()}]}
  | {:error, String.t()}
```

Run the checks of the page and the keys of the presenter on a document

`deck` gives the list of the steps and the program of the keys. The option
`:schemes` gives the variants of the theme, such as `[:light, :dark]`, and
`[nil]` by default for the variant of the document. The option `:sizes`
gives the sizes of the page, such as `[{1280, 720}]`, and
`[{1920, 1080}]` by default. The page runs its checks one time for each
size and each variant, and the keys run one time, at the first size and in
the first variant.

The function returns a list with a tuple `{{size, scheme}, result}` for
each size and each variant. A result holds the result of the page, as
`Expresso.Check.Browser.decode/1` returns it. The first result also holds
the problems of the keys and of the script in `:session`. The option `:env`
gives the environment, and `EXPRESSO_CHROMIUM` in it gives a different
browser than the Chromium of Playwright.

---

*Consult [api-reference.md](api-reference.md) for complete listing*