A tool to generate HTML code from Elm source in the terminal using [QuickJS](https://bellard.org/quickjs/).

# Requirements

* depends only on elm compiler, quickjs cli and a posix shell
* do not alter elm compiler
* do not alter quickjs cli
* do not patch elm compiler output
* provide acceptable performances (500ms for a big script)


# Design

QuickJS (Qjs) is a [JavaScript runtime](https://en.wikipedia.org/wiki/List_of_JavaScript_engines), similar to V8 or SpiderMonkey, but lighter and faster.

As any runtime, Qjs can interpret JavaScript code, but it is not a web browser. It has no concept of an HTML document.

To bridge this gap, we add a minimal [DOM](https://dom.spec.whatwg.org/) implementation.

Next, we concatenate this with the Elm JavaScript output and an app launcher snippet, then ask Qjs to interpret all of it.

## Limitations

* No event loop
* Hence, no [TEA](https://guide.elm-lang.org/architecture/); no `update` can be triggered
* Hence, no Time, no Random, no Http
* Nodes can only have one parent (this should always be the case)
* Does not scale well : creating thousands of Nodes consumes a [lot of RAM](#Performances)


# Usage

1. Clone this repository and navigate into your local copy
2. Run `elm init`.
3. Create `src/Hello.elm` with the following content:

```elm
module Hello exposing(main)

import Html exposing (text)

main = text "Hello World!"
```

4. Run `./elmscript.sh src/Hello.elm`

This produces the expected output:

```text
Hello World!
```

## passing input

Input content can be passed to the script via the standard input. The content is then passed to the Elm script as "flags". The script must then use `Browser.element` and implement `init flags` function.


Create `src/Greet.elm` with the following content:

```elm
module Greet exposing (main)

import Browser
import Html exposing (text)


main =
  Browser.element
    { init = \f -> (f, Cmd.none)
    , update = \m _ -> (m, Cmd.none)
    , view = \m -> text ("hello " ++ m)
    , subscriptions = always Sub.none
    }
```

Run `./elmscript.sh src/Greet.elm <<< 'Elm'`

This produces the expected output:  `hello Elm`.


I's even more natural when passing file :

* run `elm install elm-explorations/markdown`
* create `src/MdRender.elm` with the following content:

```elm
module MdRender exposing (main)

import Browser
import Html.Attributes exposing (class)
import Markdown

main =
  Browser.element
    { init = \s -> (s, Cmd.none)
    , update = \m c -> (m, Cmd.none)
    , view = \m -> Markdown.toHtml [class "content"] m
    , subscriptions = always Sub.none
    }

```

* run `./elmscript.sh src/MdRender.elm < README.md > README.html`



## Performances

Acceptable for small scripts : 250ms on a modest x86_64 CPU and 64MB RAM for a 500 records into a table ; but is does not scale well as everything is loaded before processing ; no streaming contrary to the usual Unix way.

Generate 500k "li" loop took 17s and 900MB RAM.


# Prior Work

There are more complete tools for generating static sites with Elm:

* [elm-pages](https://elm-pages.com/)
* [elmstatic](https://korban.net/elm/elmstatic)
* [elm-starter](https://github.com/lucamug/elm-starter)
* [siteelm](https://github.com/nikueater/siteelm)

You should probably consider using one of them instead of this one. :)