Move coin choosing logic to own class

This contains no change in logic, but is preparation for cleanup and possible alternative strategies.
2015-11-28 14:47:08 +09:00
parent 0c20e737a9
commit e9061ea371
2 changed files with 123 additions and 76 deletions
--- a/lib/coinchooser.py
+++ b/lib/coinchooser.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python
+#
+# Electrum - lightweight Bitcoin client
+# Copyright (C) 2011 thomasv@gitorious
+#
+# This program 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.
+#
+# This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+
+from operator import itemgetter
+
+from bitcoin import MIN_RELAY_TX_FEE
+from util import NotEnoughFunds, PrintError, profiler
+from transaction import Transaction
+
+
+class CoinChooser(PrintError):
+    def __init__(self, wallet):
+        self.wallet = wallet
+
+    def fee(self, tx, fixed_fee, fee_per_kb):
+        if fixed_fee is not None:
+            return fixed_fee
+        return self.wallet.estimated_fee(tx, fee_per_kb)
+
+    def dust_threshold(self):
+        return 182 * 3 * MIN_RELAY_TX_FEE/1000
+
+    def make_tx(self, coins, outputs, change_addrs, fixed_fee, fee_per_kb):
+        '''Select unspent coins to spend to pay outputs.'''
+        amount = sum(map(lambda x: x[2], outputs))
+        total = 0
+        inputs = []
+        tx = Transaction.from_io(inputs, outputs)
+        fee = self.fee(tx, fixed_fee, fee_per_kb)
+        # add inputs, sorted by age
+        for item in coins:
+            v = item.get('value')
+            total += v
+            self.wallet.add_input_info(item)
+            tx.add_input(item)
+            # no need to estimate fee until we have reached desired amount
+            if total < amount + fee:
+                continue
+            fee = self.fee(tx, fixed_fee, fee_per_kb)
+            if total >= amount + fee:
+                break
+        else:
+            raise NotEnoughFunds()
+
+        # remove unneeded inputs.
+        removed = False
+        for item in sorted(tx.inputs, key=itemgetter('value')):
+            v = item.get('value')
+            if total - v >= amount + fee:
+                tx.inputs.remove(item)
+                total -= v
+                removed = True
+                continue
+            else:
+                break
+        if removed:
+            fee = self.fee(tx, fixed_fee, fee_per_kb)
+            for item in sorted(tx.inputs, key=itemgetter('value')):
+                v = item.get('value')
+                if total - v >= amount + fee:
+                    tx.inputs.remove(item)
+                    total -= v
+                    fee = self.fee(tx, fixed_fee, fee_per_kb)
+                    continue
+                break
+        self.print_error("using %d inputs" % len(tx.inputs))
+
+        # if change is above dust threshold, add a change output.
+        change_addr = change_addrs[0]
+        change_amount = total - (amount + fee)
+        if fixed_fee is not None and change_amount > 0:
+            tx.outputs.append(('address', change_addr, change_amount))
+        elif change_amount > self.dust_threshold():
+            tx.outputs.append(('address', change_addr, change_amount))
+            # recompute fee including change output
+            fee = self.wallet.estimated_fee(tx, fee_per_kb)
+            # remove change output
+            tx.outputs.pop()
+            # if change is still above dust threshold, re-add change output.
+            change_amount = total - (amount + fee)
+            if change_amount > self.dust_threshold():
+                tx.outputs.append(('address', change_addr, change_amount))
+                self.print_error('change', change_amount)
+            else:
+                self.print_error('not keeping dust', change_amount)
+        else:
+            self.print_error('not keeping dust', change_amount)
+
+        return tx