Merkle list not a separate process, it makes no sense

1 files changed, 67 insertions, 50 deletions

diff --git a/lib/data/merklelist.ex b/lib/data/merklelist.ex
index 727f2a8..71483bd 100644
--- a/lib/data/merklelist.ex
+++ b/lib/data/merklelist.ex
@@ -1,50 +1,45 @@
 defmodule SData.MerkleList do
-  @moduledoc """
+  @moduledoc"""
   A simple Merkle list store.
 
   Future improvements:
-  - When messages are inserted other than at the top, all intermediate hashes
-    change. Keep track of the mapping from old hashes to new hashes so that get
-    requests can work even for hashes that are not valid anymore.
-  - group items in "pages" (bigger bundles)
+    - When messages are inserted other than at the top, all intermediate hashes
+      change. Keep track of the mapping from old hashes to new hashes so that get
+      requests can work even for hashes that are not valid anymore.
+    - group items in "pages" (bigger bundles)
   """
 
-  use GenServer
+  defstruct [:root, :top, :cmp, :store]
 
-  @doc """
-    Start a Merkle List storage process.
+  @doc"""
+  Create a Merkle list store.
 
-
-    `cmp` is a function that compares stored items and provides a total order.
-    It must return:
-      - `:after` if the first argument is more recent
-      - `:duplicate` if the two items are the same
-      - `:before` if the first argument is older
+  `cmp` is a function that compares stored items and provides a total order.
+  It must return:
+    - `:after` if the first argument is more recent
+    - `:duplicate` if the two items are the same
+    - `:before` if the first argument is older
   """
-  def start_link(cmp) do
-    GenServer.start_link(__MODULE__, cmp)
-  end
-
-  def init(cmp) do
+  def new(cmp) do
     root_item = :root
     root_hash = SData.term_hash root_item
-    state = %{
+    state = %SData.MerkleList{
               root:  root_hash,
               top:   root_hash,
               cmp:   cmp,
               store: %{ root_hash => root_item }
             }
-    {:ok, state}
+    state
   end
 
-  defp state_push(item, state) do
+  defp push(state, item) do
     new_item = {item, state.top}
     new_item_hash = SData.term_hash new_item
     new_store = Map.put(state.store, new_item_hash, new_item)
     %{ state | :top => new_item_hash, :store => new_store }
   end
 
-  defp state_pop(state) do
+  defp pop(state) do
     if state.top == state.root do
       :error
     else
@@ -55,59 +50,81 @@ defmodule SData.MerkleList do
     end
   end
 
-  defp insert_many(state, [], _callback) do
+  @doc"""
+  Insert a list of items in the store.
+
+  A callback function may be specified that is called on any item
+  that is sucessfully added, i.e. that wasn't present in the store before.
+  """
+  def insert_many(state, items, callback \\ (fn _ -> nil end)) do
+    items_sorted = Enum.sort(items, fn (x, y) -> state.cmp.(x, y) == :after end)
+    insert_many_aux(state, items_sorted, callback)
+  end
+
+  defp insert_many_aux(state, [], _callback) do
     state
   end
 
-  defp insert_many(state, [item | rest], callback) do
-    case state_pop(state) do
+  defp insert_many_aux(state, [item | rest], callback) do
+    case pop(state) do
       :error ->
-        new_state = state_push(item, insert_many(state, rest, callback))
+        new_state = push(insert_many_aux(state, rest, callback), item)
         callback.(item)
         new_state
       {:ok, front, state_rest} ->
         case state.cmp.(item, front) do
           :after ->
-            new_state = state_push(item, insert_many(state, rest, callback))
+            new_state = push(insert_many_aux(state, rest, callback), item)
             callback.(item)
             new_state
-          :duplicate -> insert_many(state, rest, callback)
-          :before -> state_push(front, insert_many(state_rest, [item | rest], callback))
+          :duplicate -> insert_many_aux(state, rest, callback)
+          :before -> push(insert_many_aux(state_rest, [item | rest], callback), item)
         end
     end
   end
 
-  def handle_cast({:insert, item}, state) do
-    handle_cast({:insert_many, [item]}, state)
-  end
+  @doc"""
+  Insert a single item in the store.
 
-  def handle_cast({:insert_many, items}, state) do
-    handle_cast({:insert_many, items, fn _ -> nil end}, state)
+  A callback function may be specified that is called on the item
+  if it is sucessfully added, i.e. it wasn't present in the store before.
+  """
+  def insert(state, item, callback \\ (fn _ -> nil end)) do
+    insert_many(state, [item], callback)
   end
 
-  def handle_cast({:insert_many, items, callback}, state) do
-    items_sorted = Enum.sort(items, fn (x, y) -> state.cmp.(x, y) == :after end)
-    new_state = insert_many(state, items_sorted, callback)
-    {:noreply, new_state}
-  end
+  @doc"""
+  Read some items from the state.
 
-  def handle_call({:read, qbegin, qlimit}, _from, state) do
+  The two parameters are optional:
+  - qbegin : hash of the first item to read
+  - qlimit : number of items to read
+  """
+  def read(state, qbegin \\ nil, qlimit \\ nil) do
     begin = qbegin || state.top
     limit = qlimit || 20
-    items = get_items_list(state, begin, limit)
-    {:reply, items, state}
+    get_items_list(state, begin, limit)
   end
 
-  def handle_call(:top, _from, state) do
-    {:reply, state.top, state}
+  @doc"""
+  Get the hash of the last item
+  """
+  def top(state) do
+    state.top
   end
 
-  def handle_call(:root, _from, state) do
-    {:reply, state.root, state}
+  @doc"""
+  Get the hash of the root item
+  """
+  def root(state) do
+    state.root
   end
 
-  def handle_call({:has, hash}, _from, state) do
-    {:reply, Map.has_key?(state.store, hash), state}
+  @doc"""
+  Check if the store holds a certain item
+  """
+  def has(state, hash) do
+    Map.has_key?(state.store, hash)
   end
 
   defp get_items_list(state, begin, limit) do
@@ -128,7 +145,7 @@ defmodule SData.MerkleList do
     end
   end
 
-  @doc """
+  @doc"""
     Compare function for timestamped strings
   """
   def cmp_ts_str({ts1, str1}, {ts2, str2}) do