path: root/Readme.md

# walint: lint & adjust workadventure maps

### Overview & Components

`walint` is intended as a linter for workadventure maps that checks for common
errors (such as non-existent map entrypoints or missing asset files) and makes
suggestions to improve accessability.

It can also *adjust* maps — e.g. to automatically insert property values or help
enforce an event's map policies (among other things, this is used to resolve 
special inter-assembly `world://` links).

`walint-mapserver` is a minimal implementation of a server that periodically
fetches, lints, and adjusts maps from a set of git repositories, writing them
to a path that can then be served by a webserver. It can be used as a (very
simple) replacement for rc3's hub and mapservice at smaller events — to get
started, manually list all map repositories in `config.toml`, then visit 
`localhost:8080/admin/overview`.


## Installing

### From the CI pipeline

Gitlab [automatically builds a version](https://git.cccv.de/hub/walint/-/jobs)
of `walint` each time something is pushed to this repository. The resulting
binary should work fine on most linux systems, especially if they're vaguely
debian-like.

In case you get an incomprehensible or confusing error when executing it, try 
running `ldd walint` and see if anything is marked as not found, then install it.

### Build using stack

This uses a lockfile to pin versions of dependencies (as well as `ghc`, the haskell
compiler). You will need [the haskell stack](https://docs.haskellstack.org/en/stable/README/).

Then just run

```
stack build
```

If you lack `ghc` in the correct version and don't know how to install it, you can
pass it `--install-ghc` to take care of that for you (note that on NixOS, `stack` may
use a fitting `ghc` derivation if it finds one, even without `--install-ghc`).

To install into your `$PATH`, use

```
stack install
```

Alternatively, run `walint` via stack:

```
stack run -- walint [options as normal]
```

However, in this case stack will re-check files every time to ensure your build
is up to date with the sources, increasing startup time.

### Build using cabal

You can, but probably should not. Beware of older Aeson versions!

## Usage
``` sh
walint --config-file config.json --repository path \
      [--out path] [--json] [--pretty] [--entrypoint main.json]

```

### Options
 - `--repository`: path to a map repository
 - `--entrypoint`: entrypoint of a map repository, i.e. a tiled map in its root
   directory. `walint` will lint all maps reachable from it. If not given, it
   defaults to `main.json`
 - `--lintLevel`: limit output only to messages that have at most the given
   level. Valid levels are `Info`, `Suggestion`, `Warning`, `Forbidden`, `Error`,
   `Fatal`. Defaults to `Suggestion` if not given.
 - `--json`: print output as json instead of the normal more human-friendly format
 - `--pretty`: if used with `--json`, insert line breaks and indentation to make
   the output more readable. Otherwise no effect.
 - `--out path`: write the linted & adjusted repository to the given path. Any
   json written to this path will be minimised, and *only those maps and assets
   which are reachable from the entrypoint* will be writen at all. If not given,
   `walint` will only run the linter and do nothing else. If `walint` encounters
   any references to local map assets which are not present in the repository, 
   or if the map generates lints above the maximum lint level, it will instead
   exit with code 1 without touching the output path at all.
 - `--config-file file`: path to a configuation file. Required (for now).
 - `--config json`: takes a string which should contain a json object conforming
   to the same schema as the configuration file, except that all keys are 
   optional. Keys given here will override whatever values are set in the 
   configuration file.

## Configuation
Take a look at `config.json` for an example. Most keys are required, and do not
have default values. In `config.json`, all possible keys are given.

Most options should be reasonably self-explanatory. Note that `MaxLintLevel`
differs from the option `--lintLevel`: the latter merely determines what is
*printed* (in case json output is not enabled), the former determines the 
maximum lint level allowed before the linter rejects the map and does not
copy it to the path given to `--out`.

### Uri Schemas

`walint` supports (limited) rewriting of URIs contained in the map json via
the `UriSchemas` option, which takes a map from uri schemas to a rule describing
what to do with such links, depending on the scope in which they appear.

`walint` takes a very reductive view or URIs: `schema://domain/tail`

#### Rewrite Rules

For now there are three types of such rules:
 - `schema: {"scope":[scopes]}`: if in a scope listed in `scopes`, allow any
   links of the given `schema`
 - `schema: {"scope":[scopes], "allowed":[allowed], "blocked":[blocked], "prefix":prefix}`: 
   if in a scope listed in `scopes`, prefix any URIs of the given `schema` with
   the given `prefix`, unless the URI's domain occurs in `allowed` (in which case
   leave it untouched), or it occurs in `blocked`, in which
   case it will be rejected as a lint error.
 - `schema: {"scope":[scopes], "subst":{domain: prefix, ...}}`: if in a scope
   listed in `scopes` and given a URI with the domain `domain`, concatenate 
   `prefix` with the tail of this URI.

In case an URI is encountered and there is no applicable rule, it will be rejected
(note that this means you'll have to explicitly allow `https://` for links!)

There are currently three possible scopes: `map` applies to tiled map links 
(i.e. `exitUrl`), `website` to `openWebsite`, `audio` to `playAudio`.


## Output
By default `walint` prints lints in a hopefully human-readable manner. Its exit
code will be 1 if the maximum lint level set in its config was exceeded, and 0
otherwise. Only in the latter case will it write out an adjusted map respository
to the path passed to `--out`. If the path given to `--out` already exists, 
`walint` will print its normal output but refuse to write anything to that path,
and exit with code 2.

If the `--json` option is given, output to stdout will be printed as json, which
should conform to the following schema (here defined in a quasi-haskell syntax):

```haskell
-- | The main output type. All json output will conform to it.
type Output =
  { severity :: Level
  -- ^ the maximum Lint level that occurred
  , badges :: List Badge
  -- ^ a list of badges occurring in any of the maps
  , result :: Result
  -- ^ detailed lints in a structured way
  , resultText :: String
  -- ^ all lints in a human-readable text block
  }

-- | A detailed description of which errors occurred
type Result = 
  { mapLints :: Map FilePath MapLint
  -- ^ an object of per-map lints. Each key is a filepath from the repository's root
  , missingAssets :: List Asset
  -- ^ a list of missing assets
  , missingDeps :: List Entrypoint
  -- ^ a list of other missing dependencies (for now, just entrypoints)
  }

-- | An object containing map lints
type MapLint =
  { general :: List Lint 
  -- ^ general lints (most often empty)
  , layer :: Map Message Where
  -- ^ an object of per-layer lints. Each key is a lint message
  , tileset :: Map Message Where
  -- ^ an object of per-tileset lints. Again, each key is a lint message
  }

-- | Further desription of a single lint
type Where =
  { in :: List String
  -- ^ where did this lint occur? (list of layers / tileset names)
  , level :: Level
  -- ^ what is this lint's level?
  }
  
-- | Valid lint levels. Encoded as strings, listed in ascending order here.
data Level = Info | Suggestion | Warning | Forbidden | Error | Fatal


-- | description of a single (missing) asset
type Asset =
  { asset :: FilePath
  -- ^ the filename, as referenced somewhere within the repository
  , neededBy :: List FilePath
  -- ^ list of filenames of maps which reference this asset
  }

-- | description of a single (missing) entrypoint
type Entrypoint =
  { entrypoint :: String
  -- ^ the entrypoint, as a string, e.g. path/to/map#entrypoint
  , neededBy :: List FilePath 
  -- ^ list of filenames of maps which reference this entrypoint
  }

-- | Lints that don't come grouped by place (for now, just those in generalLints)
type Lint = 
  { level :: Level
  -- ^ this lint's level
  , msg :: String
  -- ^ a human-readable (single-line) message
  }

type Badge =
  { type :: AreaType 
  -- ^ type of the badge's area
  , token :: String
  -- ^ this badge's token
  , x :: Number
  -- ^ x position on the map
  , y :: Number
  -- ^ y position on the map
  , width :: Maybe Number
  -- ^ width of the rectangle/ellipse (not present if type=point)
  , height :: Maybe Number
  -- ^ height of the rectangle/ellipse (not present if type=point)
  }

-- | types of "areas" for badges, encoded as lower-cased strings
data AreaType = Point | Rectangle | Ellipse
```