Add part7

intro/part7/src/Session.elm

@@ -0,0 +1,116 @@
+port module Session
+    exposing
+        ( Session
+        , changes
+        , cred
+        , decode
+        , login
+        , logout
+        , navKey
+        , viewer
+        )
+
+import Browser.Navigation as Nav
+import Json.Decode as Decode exposing (Decoder)
+import Json.Decode.Pipeline exposing (custom, required)
+import Json.Encode as Encode exposing (Value)
+import Profile exposing (Profile)
+import Time
+import Viewer exposing (Viewer)
+import Viewer.Cred as Cred exposing (Cred)
+
+
+
+-- TYPES
+
+
+type Session
+    = LoggedIn Nav.Key Viewer
+    | Guest Nav.Key
+
+
+
+-- INFO
+
+
+viewer : Session -> Maybe Viewer
+viewer session =
+    case session of
+        LoggedIn _ val ->
+            Just val
+
+        Guest _ ->
+            Nothing
+
+
+cred : Session -> Maybe Cred
+cred session =
+    case session of
+        LoggedIn _ val ->
+            Just (Viewer.cred val)
+
+        Guest _ ->
+            Nothing
+
+
+navKey : Session -> Nav.Key
+navKey session =
+    case session of
+        LoggedIn key _ ->
+            key
+
+        Guest key ->
+            key
+
+
+
+-- LOGIN
+
+
+login : Viewer -> Cmd msg
+login newViewer =
+    Viewer.encode newViewer
+        |> Encode.encode 0
+        |> Just
+        |> storeSession
+
+
+
+-- LOGOUT
+
+
+logout : Cmd msg
+logout =
+    storeSession Nothing
+
+
+port storeSession : Maybe String -> Cmd msg
+
+
+
+-- CHANGES
+
+
+changes : (Session -> msg) -> Nav.Key -> Sub msg
+changes toMsg key =
+    onSessionChange (\val -> toMsg (decode key val))
+
+
+port onSessionChange : (Value -> msg) -> Sub msg
+
+
+decode : Nav.Key -> Value -> Session
+decode key value =
+    -- It's stored in localStorage as a JSON String;
+    -- first decode the Value as a String, then
+    -- decode that String as JSON.
+    case
+        Decode.decodeValue Decode.string value
+            |> Result.andThen (Decode.decodeString Viewer.decoder)
+            |> Result.toMaybe
+    of
+        Just decodedViewer ->
+            LoggedIn key decodedViewer
+
+        Nothing ->
+            Guest key