module NoImportingEverything exposing (rule)

{-|

@docs rule

-}

import Elm.Syntax.Exposing as Exposing
import Elm.Syntax.Import exposing (Import)
import Elm.Syntax.Node as Node exposing (Node)
import Review.Rule as Rule exposing (Error, Rule)
import Set exposing (Set)


{-| Forbids importing everything from a module.

When you import everything from a module, it becomes harder to know where a function
or a type comes from. The official guide even
[recommends against importing everything](https://guide.elm-lang.org/webapps/modules.html#using-modules).

    config =
        [ NoImportingEverything.rule []
        ]

Teams often have an agreement on the list of imports from which it is okay to expose everything, so
you can configure a list of exceptions.

    config =
        [ NoImportingEverything.rule [ "Html", "Some.Module" ]
        ]


## Fail

    import A exposing (..)
    import A as B exposing (..)


## Success

    import A as B exposing (B(..), C, d)

    -- If configured with `[ "Html" ]`
    import Html exposing (..)


## Try it out

You can try this rule out by running the following command:

```bash
elm-review --template jfmengels/elm-review-common/example --rules NoImportingEverything
```

-}
rule : List String -> Rule
rule exceptions =
    Rule.newModuleRuleSchema "NoImportingEverything" ()
        |> Rule.withSimpleImportVisitor (importVisitor <| exceptionsToSet exceptions)
        |> Rule.fromModuleRuleSchema


exceptionsToSet : List String -> Set (List String)
exceptionsToSet exceptions =
    exceptions
        |> List.map (String.split ".")
        |> Set.fromList


importVisitor : Set (List String) -> Node Import -> List (Error {})
importVisitor exceptions node =
    if Set.member (moduleName node) exceptions then
        []

    else
        case
            Node.value node
                |> .exposingList
                |> Maybe.map Node.value
        of
            Just (Exposing.All range) ->
                [ Rule.error
                    { message = "Prefer listing what you wish to import and/or using qualified imports"
                    , details = [ "When you import everything from a module it becomes harder to know where a function or a type comes from." ]
                    }
                    { start = { row = range.start.row, column = range.start.column - 1 }
                    , end = { row = range.end.row, column = range.end.column + 1 }
                    }
                ]

            _ ->
                []


moduleName : Node Import -> List String
moduleName node =
    node
        |> Node.value
        |> .moduleName
        |> Node.value