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https://github.com/leanprover-community/lean4web

The Lean 4 web editor
https://github.com/leanprover-community/lean4web

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The Lean 4 web editor

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[![GitHub license](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](https://github.com/leanprover-community/lean4web/blob/main/LICENSE)

[![(Runtime) Build and Test](https://github.com/leanprover-community/lean4web/actions/workflows/build.yml/badge.svg)](https://github.com/leanprover-community/lean4web/actions/workflows/build.yml)



# Lean 4 Web



This is a web version of Lean 4. The official lean playground is hosted at [live.lean-lang.org](https://live.lean-lang.org), while [lean.math.hhu.de](https://lean.math.hhu.de) hosts a development server testing newer features.



In contrast to the [Lean 3 web editor](https://github.com/leanprover-community/lean-web-editor), in this web editor, the Lean server is

running on a web server, and not in the browser.



## Contribution



If you experience any problems, or have feature requests, please open an issue here!

PRs are welcome as well.



## Security

Providing the use access to a Lean instance running on the server is a severe security risk.

That is why we start the Lean server using [Bubblewrap](https://github.com/containers/bubblewrap).



If bubblewrap is not installed, the server will start without a container and produce a warning.

You can also opt-out of using bubblewrap by setting `NODE_ENV=development`.



## Documentation



### URL arguments



The website parses arguments of the form `https://myserver.com/#arg1=value1&arg2=value2`.

The recognised arguments are:



- `code=`: plain text code.

  (overwrites `codez`)

- `codez=`: compressed code using [LZ-string](https://www.npmjs.com/package/lz-string).

- `url=`: a URL where the content is loaded from.

  (overwrites `code` and `codez`).

- `project=`: the Lean project used by the server to evaluate the code. This has the be the name

  of one of the projects the server defines in their config.



The server will automatically only write one of `code`, `codez`, and `url` based on the following

logic:



1. if the code matches the one from the loaded URL, use `url`

2. if the preferences say no comression, use `code`

3. otherwise use `codez` or `code` depending on which results in a shorter URL.



## Build Instructions



We have set up the project on a Ubuntu Server 22.10.

Here are the installation instructions:



Install NPM (don't use `apt-get` since it will give you an outdated version of npm):

```

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.2/install.sh | bash

source ~/.bashrc

nvm install node npm

```



Now, install `git` and clone this repository:

```

sudo apt-get install git

git clone --recurse-submodules https://github.com/leanprover-community/lean4web.git

```



note that `--recurse-submodules` is needed to load the predefined projects in `Projects/`. (on an existing clone, you can call `git submodule init` and `git submodule update`)



Install Bubblewrap:

```

sudo apt-get install bubblewrap

```



Navigate into the cloned repository, install, and

compile:

```

cd lean4web

npm install

npm run build

```



Now the server can be started using

```

PORT=8080 npm run production

```



To set the locations of SSL certificates, use the following environment variables:

```

SSL_CRT_FILE=/path/to/crt_file.cer SSL_KEY_FILE=/path/to/private_ssl_key.pem PORT=8080 npm run production

```



### Cronjob



Optionally, you can set up a cronjob to regularly update the mathlib version.

To do so, run

```

crontab -e

```

and add the following lines, where all paths must be adjusted appropriately:

```

# Need to set PATH manually:

SHELL=/usr/bin/bash

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/home/USER/.elan/bin:/home/USER/.nvm/versions/node/v20.8.0/bin/



# Update server (i.e. mathlib) of lean4web and delete mathlib cache

*  */6 * * * cd /home/USER/lean4web && npm run build_server 2>&1 1>/dev/null | logger -t lean4web

40 2   * * * rm -rf /home/USER/.cache/mathlib/

```



Note that with this setup, you will still have to manage the lean toolchains manually, as they will slowly fill up your space (~0.9GB per new toolchain): see `elan toolchain --help` for infos.



In addition, we use Nginx and pm2 to manage our server.



#### Managing toolchains



Running and updating the server periodically might accumulate Lean toolchains.



To delete unused toolchains automatically, you can use the

[elan-cleanup tool](https://github.com/JLimperg/elan-cleanup) and set up a

cron-job with `crontab -e` and adding the following line, which runs once a month and

deletes any unused toolchains:



```

30 2 1 * * /PATH/TO/elan-cleanup/build/bin/elan-cleanup | logger -t lean-cleanup

```



You can see installed lean toolchains with `elan toolchain list`

and check the size of `~/.elan`.



### Legal information



Depending on the GDPR and laws applying to your server, you will need to provide the following

information:



- `client/config/config.tsx`, `serverCountry`: where your server is located.

- `client/config/config.tsx`, `contactDetails`: used in privacy policy & impressum

- `client/config/config.tsx`, `impressum`: further legal notes



if `contactDetails` or `impressum` are not `null`, you will see an item `Impressum` in

the dropdown menu containing that information.



Further, you might need to add the impressum manually to `index.html`

for people with javascript disabled!



## Development Instructions



Install [npm](https://www.npmjs.com/) and clone this repository. Inside the repository, run:



1. `npm install`, to install dependencies

2. `npm run build_server`, to build contained lean projects under `Projects/` (or run `lake build` manually inside any lean project)

3. `npm start`, to start the server.



The project can be accessed via http://localhost:3000. (Internally, websocket requests to `ws://localhost:3000/`websockets will be forwarded to a Lean server running on port 8080.)



## Running different projects

You can run any lean project through the webeditor by cloning them to the `Projects/` folder. See [Adding Projects](Projects/README.md) for further instructions.