Add taproot script path spend contract

lib/contracts/taproot/scriptpath_spend.rb

@@ -0,0 +1,93 @@
+# Copyright 2024 Kulpreet Singh
+#
+# This file is part of Bitcoin-DSL
+#
+# Bitcoin-DSL is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bitcoin-DSL is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bitcoin-DSL. If not, see <https://www.gnu.org/licenses/>.
+
+# frozen_string_literal: false
+
+# Generate new keys
+Bitcoin::Node::Configuration.new(network: :regtest)
+@alice = key wif: 'cNtZwU6mYnUXDJtPqfyEaRsZuNy6C5PCZHY16xbps85HvRSn9KqE'
+@bob = key wif: 'cMyDpdQkC1qRfWYNQHXawUwzEmXyFjv7PYw2EqYFRnhXhBs4bXt9'
+@carol = key wif: 'cRCuYhzDcPPCjfVZPzSiuRAsXUgivChpz5xEfeXPRAi2EDnuHymz'
+
+transition :create_input_tx do
+  # Seed alice with some coins and make coinbase spendable
+  extend_chain num_blocks: 101, to: @alice
+
+  # Get coinbase to spend using tr
+  @coinbase_tx = get_coinbase_at 2
+
+  @taproot_keypath_tx = transaction inputs: [
+                                      { tx: @coinbase_tx,
+                                        vout: 0,
+                                        script_sig: 'sig:wpkh(@alice)' }
+                                    ],
+                                    outputs: [
+                                      {
+                                        taproot: { internal_key: @bob,
+                                                   leaves: ['pk(@carol)', 'pk(@alice)'] },
+                                        amount: 49.999.sats
+                                      }
+                                    ]
+
+  broadcast @taproot_keypath_tx
+  confirm transaction: @taproot_keypath_tx
+
+  log 'Transaction with taproot output confirmed'
+end
+
+transition :spend_first_leaf do
+  @spend_taproot_output_tx = transaction inputs: [
+                                           { tx: @taproot_keypath_tx,
+                                             vout: 0,
+                                             script_sig: { leaf_index: 0, sig: 'sig:@carol' },
+                                             sighash: :all }
+                                         ],
+                                         outputs: [
+                                           { descriptor: 'wpkh(@carol)',
+                                             amount: 49.998.sats }
+                                         ]
+
+  assert_mempool_accept @spend_taproot_output_tx
+
+  broadcast @spend_taproot_output_tx
+  confirm transaction: @spend_taproot_output_tx
+
+  log 'Taproot script path transaction spent using first leaf'
+end
+
+transition :spend_second_leaf do
+  @spend_taproot_output_tx = transaction inputs: [
+                                           { tx: @taproot_keypath_tx,
+                                             vout: 0,
+                                             script_sig: { leaf_index: 1, sig: 'sig:@alice' },
+                                             sighash: :all }
+                                         ],
+                                         outputs: [
+                                           { descriptor: 'wpkh(@carol)',
+                                             amount: 49.998.sats }
+                                         ]
+
+  assert_mempool_accept @spend_taproot_output_tx
+
+  broadcast @spend_taproot_output_tx
+  confirm transaction: @spend_taproot_output_tx
+
+  log 'Taproot script path transaction spent using second leaf'
+end
+
+run_transitions :create_input_tx, :spend_first_leaf
+run_transitions :reset, :create_input_tx, :spend_second_leaf

spec/runner_spec.rb

@@ -74,5 +74,6 @@
 
   describe 'taproot transactions' do
     it_behaves_like 'script evaluation', './lib/contracts/taproot/keypath_spend.rb'
+    it_behaves_like 'script evaluation', './lib/contracts/taproot/scriptpath_spend.rb'
   end
 end