Some initial playing with Dune Trader game

scratch/DuneTrader.fsx

@@ -0,0 +1,105 @@
+#load "SketchUI.fsx"
+open SketchUI
+let r = System.Random()
+type City = Urik | Balik | Tyr
+type Goods = Spice | Lumber | Metal
+type Model = {
+    city: City
+    money: int
+    goods: Map<Goods, int>
+    }
+type Msg =
+    | Goto of City
+    | Buy of Goods * int
+    | Sell of Goods * int
+let price = function
+    | Lumber, (Tyr | Balik) -> 10
+    | Lumber, Urik -> 17
+    | Spice, (Tyr | Urik) -> 15
+    | Spice, Balik -> 10
+    | Metal, Tyr -> 30
+    | Metal, (Balik | Urik) -> 45
+
+let bulk = function
+    | Lumber -> 10
+    | Spice -> 5
+    | Metal -> 1
+
+exception UserError of string
+let cant msg = UserError $"Can't because {msg}" |> raise
+
+let init _ = { city = Tyr; money = 100; goods = [(Spice, 10); (Lumber, 5)] |> Map.ofList }
+let update msg model =
+    match msg with
+    | Goto city ->
+        if city = model.city then model
+        else
+            let cost = model.goods |> Seq.sumBy (fun (KeyValue(good, amt)) -> amt * bulk good)
+            { model with city = city; money = model.money - cost }
+    | Buy (good, amount) ->
+        let cost = price (good, model.city) * amount
+        if cost > model.money then cant $"That costs {cost} and you only have {model.money}"
+        { model with money = model.money - cost; goods = model.goods |> Map.change good (function None -> Some amount | Some x -> Some (x + amount)) }
+    | Sell (good, amount) ->
+        match model.goods.TryFind good with
+        | Some qty ->
+            if qty < amount then cant $"You only have {qty} of {good}"
+            { model with money = model.money + price (good, model.city) * amount; goods = model.goods |> Map.add good (qty - amount) }
+        | None ->
+            cant $"You don't have any {good}"
+
+let view model =
+    let goods = model.goods |> Map.toList |> List.sortBy fst |> List.map (fun (good, amt) -> $"{good}: {amt}") |> String.oxfordJoin
+    $"""
+    City: {model.city}
+    Money: {model.money}
+    Stuff: {goods}
+    """
+
+let send', state = connect init update view
+let send msg = try send' msg with UserError msg -> printfn "%s" msg
+let buy good amount = send (Buy (good, amount))
+let sell good amount = send (Sell (good, amount))
+let travel city = send (Goto city)
+
+printfn "%s" (view state.Value)
+
+sell Lumber 5
+buy Metal 10
+buy Metal 5
+sell Spice 10
+buy Metal 5
+travel Balik
+sell Metal 10
+buy Spice 20
+buy Lumber 20
+travel Tyr
+sell Spice 20
+sell Lumber 20
+buy Metal 8
+travel Balik
+sell Metal 8
+buy Spice 20
+travel Tyr
+sell Spice 20
+travel Balik
+buy Spice 35
+travel Tyr
+sell Spice 35
+buy Metal 10
+travel Balik
+sell Metal 10
+// Metal is the only profitable material! Everything else costs too much to move between cities!
+travel Tyr
+buy Metal 10
+travel Balik
+sell Metal 10
+travel Tyr
+buy Metal 10
+travel Balik
+sell Metal 10
+travel Tyr
+buy Metal 20
+travel Balik
+sell Metal 20
+// there should also be fixed costs of travelling, so that travelling empty isn't free