Merge pull request #11 from wowica/add-sync-from-option

- Add sync_from option
- Fix client disconnection bug.

examples/chain_sync_client.ex

@@ -17,6 +17,17 @@ defmodule ChainSyncClient do
 
   def start_link(opts) do
     initial_state = [counter: 3]
+    ### See examples below on how to sync
+    ### from different points of the chain:
+    # initial_state = [sync_from: :babbage]
+    # initial_state = [
+    #   sync_from: %{
+    #     point: %{
+    #       slot: 114_127_654,
+    #       id: "b0ff1e2bfc326a7f7378694b1f2693233058032bfb2798be2992a0db8b143099"
+    #     }
+    #   }
+    # ]
     opts = Keyword.merge(opts, initial_state)
     Xogmios.start_chain_sync_link(__MODULE__, opts)
   end

lib/xogmios/chain_sync.ex

@@ -9,9 +9,9 @@ defmodule Xogmios.ChainSync do
               {:ok, :next_block, map()} | {:ok, map()} | {:ok, :close, map()}
 
   def start_link(client, opts) do
-    url = Keyword.fetch!(opts, :url)
-    state = Keyword.merge(opts, handler: client)
-    :websocket_client.start_link(url, client, state)
+    {url, opts} = Keyword.pop(opts, :url)
+    initial_state = Keyword.merge(opts, handler: client)
+    :websocket_client.start_link(url, client, initial_state)
   end
 
   defmacro __using__(_opts) do
@@ -28,7 +28,25 @@ defmodule Xogmios.ChainSync do
           "result" => %{"direction" => "backward", "tip" => tip}
         } = message
 
-        message = Messages.find_intersection(tip["slot"], tip["id"])
+        message =
+          case state[:sync_from] do
+            nil ->
+              # No option passed, sync with current tip
+              Messages.find_intersection(tip["slot"], tip["id"])
+
+            %{point: point} ->
+              # Sync with a specific point
+              Messages.find_intersection(point.slot, point.id)
+
+            cardano_era when cardano_era in [:origin, :byron] ->
+              # Sync with origin
+              Messages.find_origin()
+
+            cardano_era when is_atom(cardano_era) ->
+              # Sync with a particular era bound
+              Messages.last_block_from(cardano_era)
+          end
+
         {:reply, {:text, message}, state}
       end
 

lib/xogmios/chain_sync/connection.ex

@@ -31,7 +31,7 @@ defmodule Xogmios.ChainSync.Connection do
           |> Enum.into(%{})
           |> Map.merge(%{handler: __MODULE__})
 
-        {:once, initial_state}
+        {:reconnect, initial_state}
       end
 
       @impl true

lib/xogmios/chain_sync/messages.ex

@@ -50,6 +50,47 @@ defmodule Xogmios.ChainSync.Messages do
     json
   end
 
+  def find_origin do
+    # For finding origin, any value can be passed as a point as long as "origin"
+    # is the first value.
+    json = ~S"""
+    {
+      "jsonrpc": "2.0",
+      "method": "findIntersection",
+      "params": {
+          "points": [
+            "origin",
+            {
+              "slot": 4492799,
+              "id": "f8084c61b6a238acec985b59310b6ecec49c0ab8352249afd7268da5cff2a457"
+            }
+          ]
+      }
+    }
+    """
+
+    validate_json!(json)
+    json
+  end
+
+  # The following are the last points (absolute slot and block id) of
+  # the previous era of each entry. The sync is done against the last
+  # point, so that the next block received is the first of the following era.
+  @era_bounds %{
+    shelley: {4_492_799, "f8084c61b6a238acec985b59310b6ecec49c0ab8352249afd7268da5cff2a457"},
+    allegra: {16_588_737, "4e9bbbb67e3ae262133d94c3da5bffce7b1127fc436e7433b87668dba34c354a"},
+    mary: {23_068_793, "4e9bbbb67e3ae262133d94c3da5bffce7b1127fc436e7433b87668dba34c354a"},
+    alonzo: {39_916_796, "e72579ff89dc9ed325b723a33624b596c08141c7bd573ecfff56a1f7229e4d09"},
+    babbage: {72_316_796, "c58a24ba8203e7629422a24d9dc68ce2ed495420bf40d9dab124373655161a20"}
+  }
+
+  def last_block_from(era_name) when is_atom(era_name) do
+    case @era_bounds[era_name] do
+      {last_slot, last_block_id} -> find_intersection(last_slot, last_block_id)
+      nil -> {:error, :unknown_block}
+    end
+  end
+
   defp validate_json!(json) do
     case Jason.decode(json) do
       {:ok, _decoded} -> :ok