module NoUnused.Dependencies exposing (rule)

{-| Forbid the use of dependencies that are never used in your project.


# Rule

@docs rule

-}

import Dict exposing (Dict)
import Elm.Package
import Elm.Project exposing (Project)
import Elm.Syntax.Import exposing (Import)
import Elm.Syntax.ModuleName exposing (ModuleName)
import Elm.Syntax.Node as Node exposing (Node)
import Elm.Syntax.Range exposing (Range)
import Review.Project.Dependency as Dependency exposing (Dependency)
import Review.Rule as Rule exposing (Error, Rule)
import Set exposing (Set)


{-| Forbid the use of dependencies that are never used in your project.

A dependency is considered unused if none of its modules are imported in the project.

    config =
        [ NoUnused.Dependencies.rule
        ]


## Try it out

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

```bash
elm-review --template jfmengels/review-unused/example --rules NoUnused.Dependencies
```

-}
rule : Rule
rule =
    Rule.newProjectRuleSchema "NoUnused.Dependencies" initialProjectContext
        |> Rule.withElmJsonProjectVisitor elmJsonVisitor
        |> Rule.withDependenciesProjectVisitor dependenciesVisitor
        |> Rule.withModuleVisitor moduleVisitor
        |> Rule.withModuleContext
            { fromProjectToModule = fromProjectToModule
            , fromModuleToProject = fromModuleToProject
            , foldProjectContexts = foldProjectContexts
            }
        |> Rule.withFinalProjectEvaluation finalEvaluationForProject
        |> Rule.fromProjectRuleSchema


moduleVisitor : Rule.ModuleRuleSchema {} ModuleContext -> Rule.ModuleRuleSchema { hasAtLeastOneVisitor : () } ModuleContext
moduleVisitor schema =
    schema
        |> Rule.withImportVisitor importVisitor


dependenciesVisitor : Dict String Dependency -> ProjectContext -> ( List nothing, ProjectContext )
dependenciesVisitor dependencies projectContext =
    let
        moduleNameToDependency : Dict String String
        moduleNameToDependency =
            dependencies
                |> Dict.toList
                |> List.concatMap
                    (\( packageName, dependency ) ->
                        List.map (\{ name } -> ( name, packageName )) (Dependency.modules dependency)
                    )
                |> Dict.fromList
    in
    ( [], { projectContext | moduleNameToDependency = moduleNameToDependency } )



-- CONTEXT


type alias ProjectContext =
    { moduleNameToDependency : Dict String String
    , directProjectDependencies : Set String
    , importedModuleNames : Set String
    , elmJsonKey : Maybe Rule.ElmJsonKey
    }


type alias ModuleContext =
    Set String


initialProjectContext : ProjectContext
initialProjectContext =
    { moduleNameToDependency = Dict.empty
    , directProjectDependencies = Set.empty
    , importedModuleNames = Set.empty
    , elmJsonKey = Nothing
    }


fromProjectToModule : Rule.ModuleKey -> Node ModuleName -> ProjectContext -> ModuleContext
fromProjectToModule _ _ projectContext =
    projectContext.importedModuleNames


fromModuleToProject : Rule.ModuleKey -> Node ModuleName -> ModuleContext -> ProjectContext
fromModuleToProject _ _ importedModuleNames =
    { moduleNameToDependency = Dict.empty
    , directProjectDependencies = Set.empty
    , importedModuleNames = importedModuleNames
    , elmJsonKey = Nothing
    }


foldProjectContexts : ProjectContext -> ProjectContext -> ProjectContext
foldProjectContexts newContext previousContext =
    { moduleNameToDependency = previousContext.moduleNameToDependency
    , directProjectDependencies = previousContext.directProjectDependencies
    , importedModuleNames = Set.union previousContext.importedModuleNames newContext.importedModuleNames
    , elmJsonKey = previousContext.elmJsonKey
    }



-- PROJECT VISITORS


elmJsonVisitor : Maybe { elmJsonKey : Rule.ElmJsonKey, project : Project } -> ProjectContext -> ( List nothing, ProjectContext )
elmJsonVisitor maybeProject projectContext =
    case maybeProject of
        Just { elmJsonKey, project } ->
            let
                directProjectDependencies : Set String
                directProjectDependencies =
                    case project of
                        Elm.Project.Package { deps } ->
                            deps
                                |> List.map (Tuple.first >> Elm.Package.toString)
                                |> Set.fromList

                        Elm.Project.Application { depsDirect } ->
                            depsDirect
                                |> List.map (Tuple.first >> Elm.Package.toString)
                                |> Set.fromList
            in
            ( []
            , { projectContext
                | elmJsonKey = Just elmJsonKey
                , directProjectDependencies =
                    Set.filter ((/=) "elm/core") directProjectDependencies
              }
            )

        Nothing ->
            ( [], projectContext )



-- IMPORT VISITOR


importVisitor : Node Import -> ModuleContext -> ( List nothing, ModuleContext )
importVisitor node importedModuleNames =
    ( []
    , Set.insert (moduleNameForImport node) importedModuleNames
    )


moduleNameForImport : Node Import -> String
moduleNameForImport node =
    node
        |> Node.value
        |> .moduleName
        |> Node.value
        |> String.join "."



-- FINAL EVALUATION


finalEvaluationForProject : ProjectContext -> List (Error { useErrorForModule : () })
finalEvaluationForProject projectContext =
    case projectContext.elmJsonKey of
        Just elmJsonKey ->
            projectContext.importedModuleNames
                |> Set.toList
                |> List.filterMap (\importedModuleName -> Dict.get importedModuleName projectContext.moduleNameToDependency)
                |> Set.fromList
                |> Set.diff projectContext.directProjectDependencies
                |> Set.toList
                |> List.map (error elmJsonKey)

        Nothing ->
            []


error : Rule.ElmJsonKey -> String -> Error scope
error elmJsonKey packageName =
    Rule.errorForElmJson elmJsonKey
        (\elmJson ->
            { message = "Unused dependency `" ++ packageName ++ "`"
            , details =
                [ "To remove it, I recommend running the following command:"
                , "    elm-json uninstall " ++ packageName
                ]
            , range = findPackageNameInElmJson packageName elmJson
            }
        )


findPackageNameInElmJson : String -> String -> Range
findPackageNameInElmJson packageName elmJson =
    elmJson
        |> String.lines
        |> List.indexedMap Tuple.pair
        |> List.filterMap
            (\( row, line ) ->
                case String.indexes ("\"" ++ packageName ++ "\"") line of
                    [] ->
                        Nothing

                    column :: _ ->
                        Just
                            { start =
                                { row = row + 1
                                , column = column + 2
                                }
                            , end =
                                { row = row + 1
                                , column = column + String.length packageName + 2
                                }
                            }
            )
        |> List.head
        |> Maybe.withDefault { start = { row = 1, column = 1 }, end = { row = 10000, column = 1 } }