1 files changed, 46 insertions, 6 deletions
diff --git a/shard/lib/app/pagestore.ex b/shard/lib/app/pagestore.ex
index 3cda51d..0cbb10a 100644
--- a/shard/lib/app/pagestore.ex
+++ b/shard/lib/app/pagestore.ex
@@ -7,12 +7,29 @@ defmodule SApp.PageStore do
 
   Uses an ETS table of:
   
-    { page_id, why_have_it }         -- waiting for data
-    { page_id, why_have_it, data }   -- once we have the data
+      { page_id, why_have_it }         # waiting for data
+      { page_id, why_have_it, data }   # once we have the data
 
-  why_have_it := :root
-               | {:req_by, some_other_page_id}
-               | {:cached, expiry_date}
+      why_have_it := :root
+                   | {:req_by, some_other_page_id}
+                   | {:cached, expiry_date}
+
+  TODO: at the moment we are trying to pull all missing pages at once from our peers.
+  This can work for metadata that isn't too big but won't work with bigger objects.
+  Have a smart strategy where we limit the number of requests currently in-flight but
+  still make sure everything gets pulled in. This will also pave the way to selectively
+  pulling in pages, for instance if we have a function to give them a priority score and
+  a maximum stored page count.
+
+  A `SApp.PageStore` can be used as a `SData.PageStore` in the following way:
+
+      %SApp.PageStore{pid: store_pid}
+
+  or:
+
+      %SApp.PageStore{pid: store_pid, prefer_ask: [connection_pid, ...]}
+
+  In the second case, missing pages will be requested first to the specified peers.
   """
 
   use GenServer
@@ -25,6 +42,9 @@ defmodule SApp.PageStore do
   @max_failures 4         # Maximum of peers that reply not_found before we abandon
 
   defmodule State do
+    @moduledoc"""
+    Internal state struct of pagestore process.
+    """
     defstruct [:shard_id, :path, :netgroup, :store, :reqs, :retries, :store_path]
   end
 
@@ -258,7 +278,7 @@ defmodule SApp.PageStore do
     {:noreply, state}
   end
 
-  def ask_random_peers(state, key) do
+  defp ask_random_peers(state, key) do
     SNet.Group.broadcast(state.netgroup, {state.shard_id, state.path, {:get, key}}, nmax: 3)
   end
 
@@ -289,4 +309,24 @@ defmodule SApp.PageStore do
       store ## DO SOMETHING???
     end
   end
+
+  # ====================
+  # PAGE STORE INTERFACE
+  # ====================
+
+  @doc"""
+  Returns `true` if the page store currently stores the specified root page
+  and all its dependencies, recursively.
+  """
+  def have_rec?(pid, root) do
+    GenServer.call(pid, {:have_rec, root})
+  end
+
+  @doc"""
+  Define the set of root pages we are interested in. This will start pulling in
+  the defined pages and all their dependencies recursively if we don't have them.
+  """
+  def set_roots(pid, roots) do
+    GenServer.cast(pid, {:set_roots, roots})
+  end
 end