add transaction hash computation

lib/doc/transaction.ex

@@ -62,6 +62,35 @@ defmodule Doc.Transaction do
 
   def verif(_), do: false
 
+  @doc """
+  Compute the hash of a transaction
+
+  ## Example
+      iex> Doc.Transaction.hash(%{
+      ...> "blockstamp" => "506140-00000006174C9FD4F4088D1CD830A1B372865977DBA7ED834AE94C6767EA42C6",
+      ...> "comment" => "",
+      ...> "currency" => "g1",
+      ...> "inputs" => ["7500:0:T:05B64E84A7F6DECB91B8FAAE287676B121D9C3D3CCFD7EF57FD6F91B4B3E548C:1"],
+      ...> "issuers" => ["7HzhXCA9Cp3JQE2GpY6JJwv89fJi6FQSBtDsq657jpj3"],
+      ...> "locktime" => 0,
+      ...> "outputs" => [
+      ...>   "2500:0:SIG(6SMqmUyJ7zCzht5twiQg6ePLiQ6HfLd3shhihMbAq5av)",
+      ...>   "5000:0:SIG(7HzhXCA9Cp3JQE2GpY6JJwv89fJi6FQSBtDsq657jpj3)"
+      ...> ],
+      ...> "signatures" => [
+      ...>   "/FC7D8TMkDuUn+0MNKSbFM/4x2dIWo/cQkGIj4KKTHjcm2F900P/nC9YyWvNUQLrhwD5lIZ6v8iSGyFAVFiVAw=="
+      ...> ],
+      ...> "unlocks" => ["0:SIG(0)"],
+      ...> "version" => 10
+      ...> })
+      "BB62BC1515CC1BE35993CC05EA8702A358763C3315DCE321C4E9D5B60E2A1D6B"
+  """
+  def hash(transaction) do
+    :crypto.hash(:sha256, raw_format(transaction, true))
+    |> Base.encode16()
+    |> String.upcase()
+  end
+
   defp regex_exact_match(regex, string) do
     Regex.compile!("^#{regex}$")
     |> Regex.match?(string)
@@ -114,7 +143,7 @@ defmodule Doc.Transaction do
     raw <> "#{line}\n"
   end
 
-  defp raw_format(transaction) do
+  defp raw_format(transaction, signature \\ false) do
     # Convert to the raw format of DUBP
     """
     Version: #{transaction["version"]}
@@ -132,5 +161,10 @@ defmodule Doc.Transaction do
     |> add_line("Outputs:")
     |> add_list_entries(transaction["outputs"])
     |> add_line("Comment: #{transaction["comment"]}")
+    |> then(fn raw_without_signatures ->
+      if signature,
+        do: raw_without_signatures |> add_list_entries(transaction["signatures"]),
+        else: raw_without_signatures
+    end)
   end
 end

test/doc/transaction_test.exs

@@ -36,6 +36,26 @@ defmodule Doc.TransactionTest do
     ]
   }
 
+  @transaction_hash %{
+    "blockstamp" => "506140-00000006174C9FD4F4088D1CD830A1B372865977DBA7ED834AE94C6767EA42C6",
+    "blockstampTime" => 1_646_604_540,
+    "comment" => "",
+    "currency" => "g1",
+    "hash" => "BB62BC1515CC1BE35993CC05EA8702A358763C3315DCE321C4E9D5B60E2A1D6B",
+    "inputs" => ["7500:0:T:05B64E84A7F6DECB91B8FAAE287676B121D9C3D3CCFD7EF57FD6F91B4B3E548C:1"],
+    "issuers" => ["7HzhXCA9Cp3JQE2GpY6JJwv89fJi6FQSBtDsq657jpj3"],
+    "locktime" => 0,
+    "outputs" => [
+      "2500:0:SIG(6SMqmUyJ7zCzht5twiQg6ePLiQ6HfLd3shhihMbAq5av)",
+      "5000:0:SIG(7HzhXCA9Cp3JQE2GpY6JJwv89fJi6FQSBtDsq657jpj3)"
+    ],
+    "signatures" => [
+      "/FC7D8TMkDuUn+0MNKSbFM/4x2dIWo/cQkGIj4KKTHjcm2F900P/nC9YyWvNUQLrhwD5lIZ6v8iSGyFAVFiVAw=="
+    ],
+    "unlocks" => ["0:SIG(0)"],
+    "version" => 10
+  }
+
   def replaceKey(map, old_name, new_name) do
     {value, updated_map} = Map.pop(map, old_name)
     Map.put(updated_map, new_name, value)
@@ -96,4 +116,8 @@ defmodule Doc.TransactionTest do
              )
            )
   end
+
+  test "transaction hash" do
+    assert Doc.Transaction.hash(@transaction_hash) == @transaction_hash["hash"]
+  end
 end