Add previous public key pending validation

lib/archethic/mining/pending_transaction_validation.ex

@@ -82,6 +82,7 @@ defmodule Archethic.Mining.PendingTransactionValidation do
 
     with :ok <- validate_size(tx),
          :ok <- valid_not_exists(tx),
+         :ok <- valid_previous_public_key(tx),
          :ok <- valid_previous_signature(tx),
          :ok <- validate_contract(tx),
          :ok <- validate_ownerships(tx),
@@ -128,7 +129,14 @@ defmodule Archethic.Mining.PendingTransactionValidation do
     end
   end
 
-  @spec valid_previous_signature(tx :: Transaction.t()) :: :ok | {:error, any()}
+  defp valid_previous_public_key(tx = %Transaction{address: address}) do
+    if Transaction.previous_address(tx) == address do
+      {:error, "Invalid previous public key (should be chain index - 1)"}
+    else
+      :ok
+    end
+  end
+
   defp valid_previous_signature(tx = %Transaction{}) do
     if Transaction.verify_previous_signature?(tx) do
       :ok

test/archethic/mining/pending_transaction_validation_test.exs

@@ -23,6 +23,7 @@ defmodule Archethic.Mining.PendingTransactionValidationTest do
 
   alias Archethic.TransactionChain
   alias Archethic.TransactionChain.Transaction
+  alias Archethic.TransactionChain.TransactionData
   alias Archethic.TransactionChain.TransactionData.Recipient
   alias Archethic.TransactionChain.TransactionData.Ledger
   alias Archethic.TransactionChain.TransactionData.Ownership
@@ -91,6 +92,24 @@ defmodule Archethic.Mining.PendingTransactionValidationTest do
     end
   end
 
+  describe "validate_previous_public_key" do
+    test "should return error if previous transaction address is the same address as the current transaction" do
+      {public_key, private_key} = Crypto.derive_keypair("seed", 0)
+
+      tx =
+        Transaction.new_with_keys(
+          :transfer,
+          %TransactionData{},
+          private_key,
+          public_key,
+          public_key
+        )
+
+      assert {:error, "Invalid previous public key (should be chain index - 1)"} =
+               PendingTransactionValidation.validate(tx)
+    end
+  end
+
   describe "validate_ownerships" do
     defp get_tx(ownerships) do
       TransactionFactory.create_non_valided_transaction(type: :data, ownerships: ownerships)