TODO F#

gistfile1.fs

type IStore =
    abstract member GetState : unit -> Async<'T>
    abstract member SaveState: 'T -> Async<unit>
    
type IServiceProvider =
    abstract member Resolve : unit -> 'T

type GetTodoListQuery = unit
type AddCommand = { Title: string; }
type RemoveCommand = { Id: Id; }
type CompleteCommand = { Id: Id; }

type Command =
    | Add of AddCommand
    | Remove of RemoveCommand
    | Complete of CompleteCommand

type Query =
    | GetState of GetTodoListQuery
    
let handleAdd (store: IStore) (cmd: AddCommand) =
    async {
        let! state = store.GetState()
        let todo = Todo.create cmd.Title
        let newState = state |> Todo.add todo
        do! store.SaveState newState   
    }
    
let handleRemove (store: IStore) (cmd: RemoveCommand) =
    async {
        let! state = store.GetState()
        let newState = state |> Todo.remove cmd.Id
        do! store.SaveState newState   
    }
    
let handleComplete (store: IStore) (cmd: CompleteCommand) =
    async {
        let! state = store.GetState()
        let newState = state |> Todo.complete cmd.Id
        do! store.SaveState newState   
    }
    
let handleGetState (store: IStore) (cmd: GetTodoListQuery) =
    async {
        return! store.GetState()
    }


let mutable providerResolver: Func<IServiceProvider> = null
let dep = providerResolver.Invoke()
     
let CommandHandler (cmd) =
    async {
        do! match cmd with
            | Add s -> handleAdd (dep.Resolve()) s
            | Remove s -> handleRemove (dep.Resolve()) s
            | Complete s -> handleComplete (dep.Resolve()) s
            
        return ()
    }

let QueryHandler (query) =
    async {
        return! match query with
                | GetState s -> handleGetState (dep.Resolve()) s
    }

//------------usage example------------// 

type HttRequest =
    abstract member ExtractCmd : unit -> Command
    
type HttpResponse =
    static member Ok() = 200
    
let processRequest (ctx: HttRequest) =
    async {
        let cmd = ctx.ExtractCmd()
        do! CommandHandler cmd
        return HttpResponse.Ok()
    }