Merge pull request #30 from ovnanova/cid

working Multicodec + CID!!

config/config.exs

@@ -7,4 +7,5 @@ config :hexpds,
   plc_server: "plc.bsky-sandbox.dev",
   appview_server: "api.bsky-sandbox.dev",
   relay_server: "bgs.bsky-sandbox.dev",
-  pds_host: "pds.shreyanjain.net" # ignore pls for now
+  pds_host: "abyss.computer", # ignore pls for now
+  multicodec_csv_path: "multicodec.csv"

lib/hexpds/k256.ex

@@ -150,7 +150,7 @@ defmodule Hexpds.K256 do
         (pubkey
          |> compress()
          |> Base.decode16!(case: :lower)
-         |> Hexpds.Multicodec.encode(:"secp256k1-pub")
+         |> Hexpds.Multicodec.encode!(:"secp256k1-pub")
          |> Multibase.encode!(:base58_btc))
     end
   end

lib/hexpds/multicodec.ex

@@ -1,6 +1,77 @@
 defmodule Hexpds.Multicodec do
-  @spec encode(binary(), :"secp256k1-pub") :: binary()
-  def encode(pubkey, :"secp256k1-pub") do
-    <<0xE7, 0x01, pubkey::binary>>
+  use GenServer
+
+  def start_link(multicodec_csv \\ Application.get_env(:hexpds, :multicodec_csv_path)) do
+    GenServer.start_link(__MODULE__, multicodec_csv, name: __MODULE__)
+  end
+
+  @impl GenServer
+  def init(csv_path) do
+    {:ok, csv} = File.read(csv_path)
+    {:ok, read_csv(csv)}
+  end
+
+  @impl GenServer
+  def handle_call(:multicodec_map, _from, state) do
+    {:reply, state, state}
+  end
+
+  def read_csv(csv) do
+    csv
+    |> String.split("\n", trim: true)
+    |> Stream.map(&String.replace(&1, " ", ""))
+    |> Stream.map(&String.split(&1, ",", trim: true))
+    |> Enum.reduce(%{}, fn [name, _tag, "0x" <> code, _status], acc ->
+      Map.put(acc, String.to_atom(name), Integer.parse(code, 16) |> elem(0))
+    end)
+  end
+
+  def multicodec_map() do
+    GenServer.call(__MODULE__, :multicodec_map)
+  end
+
+  def bytes_to_codec() do
+    for {codec, bytes} <- multicodec_map(), into: %{} do
+      {bytes, codec}
+    end
+  end
+
+  def encode!(bytes, "" <> codec) do
+    <<Varint.LEB128.encode(multicodec_map()[String.to_atom(codec)])::binary, bytes::binary>>
+  end
+
+  def encode!(bytes, codec) do
+    encode!(bytes, to_string(codec))
+  end
+
+  @spec encode(binary(), String.t() | atom()) ::
+          {:error, any()} | {:ok, binary()}
+  def encode(b, c) do
+    try do
+      {:ok, encode!(b, c)}
+    catch
+      _, e -> {:error, e}
+    end
+  end
+
+  def codec_decode("" <> encoded) do
+    try do
+      with {prefix, rest} <- Varint.LEB128.decode(<<encoded::binary>>),
+           codec <- bytes_to_codec()[prefix],
+           do: {:ok, {rest, to_string(codec)}}
+    catch
+      _, e -> {:error, e}
+    end
+  end
+
+  @spec codec?(binary()) :: boolean()
+  def codec?("" <> codec) do
+    Map.has_key?(multicodec_map(), String.to_atom(codec))
+  end
+
+  def codecs do
+    multicodec_map()
+    |> Map.keys()
+    |> Enum.map(&to_string/1)
   end
 end