Add methods for collection the watch session API auth map

Refs #53

src/cljs/wish/providers.cljs

@@ -214,3 +214,18 @@
       (throw (js/Error. (str "No provider instance for " sheet-id
                                "(" provider-id " / " pro-sheet-id ")"))))))
 
+(defn watch-auth-map
+  "Given a collection of sheet IDs, generate an appropate
+   auth-map for use with the wish-server watch session API"
+  [sheet-ids]
+  (->> sheet-ids
+       (map (comp first unpack-id))
+       (into #{})
+       (reduce
+         (fn [m provider-id]
+           (if-let [auth (some-> provider-id
+                                 (provider-key :inst)
+                                 (provider/watch-auth))]
+             (assoc m provider-id auth)
+             m))
+         {})))

src/cljs/wish/providers/caching.cljs

@@ -140,7 +140,11 @@
             (swap! dirty?-storage disj file-id))
 
           ; return the result as-is
-          result))))
+          result)))
+
+  (watch-auth [this]
+    ; delegate
+    (provider/watch-auth base)))
 
 (defn with-caching [base-provider]
   (let [cache-id (keyword (str (name (provider/id base-provider))

src/cljs/wish/providers/core.cljs

@@ -50,7 +50,12 @@
      The original `data` *may* be provided, which you can use to
      update `:name`, for example, but it may also be omitted.
      `data-str` is in the same string format that should be
-     returned by `load-raw`."))
+     returned by `load-raw`.")
+
+  (watch-auth
+    [this]
+    "Generate the auth data needed to watch changes to files provided
+     by this provider, or nil if that's not supported by this provider"))
 
 (defn signed-out-err?
   "Check if the given error was caused by not being signed into the provider"

src/cljs/wish/providers/gdrive.cljs

@@ -217,12 +217,15 @@
           (.-currentUser)
           (.get)))
 
+(defn- auth-response []
+  (some-> (current-user)
+          (.getAuthResponse)))
+
 (defn- access-token
   "When logged in, get the current user's access token"
   []
-  (-> (current-user)
-      (.getAuthResponse)
-      (.-access_token)))
+  (some-> (auth-response)
+          (.-access_token)))
 
 (defn- update-signin-status!
   [signed-in?]
@@ -519,7 +522,12 @@
           data-str))
 
       ; not ready? don't try
-      (to-chan [[(js/Error. "No network; unable to save sheet") nil]]))))
+      (to-chan [[(js/Error. "No network; unable to save sheet") nil]])))
+
+  (watch-auth [this]
+    (when-let [resp (auth-response)]
+      {:id_token (.-id_token resp)
+       :access_token (access-token)})))
 
 (defn create-provider []
   (->GDriveProvider))

src/cljs/wish/providers/wish.cljs

@@ -60,7 +60,11 @@
     (to-chan [[(js/Error. "Not implemented") nil]]))
 
   (save-sheet [this file-id data data-str]
-    (to-chan [[(js/Error. "Not implemented") nil]])))
+    (to-chan [[(js/Error. "Not implemented") nil]]))
+
+  (watch-auth [this]
+    ; not supported:
+    nil))
 
 (defn create-provider []
   (->WishProvider))