Make FIFO accounting_method linear time

src/rp2/abstract_accounting_method.py

@@ -38,13 +38,23 @@ def __init__(
         accounting_method: "AbstractAccountingMethod",
         acquired_lot_list: List[InTransaction],
         acquired_lot_2_partial_amount: Dict[InTransaction, RP2Decimal],
-        up_to_index: int,
     ) -> None:
         self.__accounting_method: AbstractAccountingMethod = accounting_method
         self.__acquired_lot_list = acquired_lot_list
         self.__acquired_lot_2_partial_amount = acquired_lot_2_partial_amount
+        self.__up_to_index = 0
+        self.__from_index = 0
+
+    def set_up_to_index(self, up_to_index: int) -> None:
         self.__up_to_index = up_to_index
 
+    def set_from_index(self, from_index: int) -> None:
+        self.__from_index = from_index
+
+    @property
+    def from_index(self) -> int:
+        return self.__from_index
+
     def has_partial_amount(self, acquired_lot: InTransaction) -> bool:
         return acquired_lot in self.__acquired_lot_2_partial_amount
 
@@ -60,14 +70,14 @@ def clear_partial_amount(self, acquired_lot: InTransaction) -> None:
         self.set_partial_amount(acquired_lot, ZERO)
 
     def __iter__(self) -> "AccountingMethodIterator":
-        return AccountingMethodIterator(self.__acquired_lot_list, self.__up_to_index, self.__accounting_method.lot_candidates_order())
+        return AccountingMethodIterator(self.__acquired_lot_list, self.__from_index, self.__up_to_index, self.__accounting_method.lot_candidates_order())
 
 
 class AccountingMethodIterator:
-    def __init__(self, acquired_lot_list: List[InTransaction], up_to_index: int, order_type: AcquiredLotCandidatesOrder) -> None:
+    def __init__(self, acquired_lot_list: List[InTransaction], from_index: int, up_to_index: int, order_type: AcquiredLotCandidatesOrder) -> None:
         self.__acquired_lot_list = acquired_lot_list
-        self.__start_index = 0 if order_type == AcquiredLotCandidatesOrder.OLDER_TO_NEWER else up_to_index
-        self.__end_index = up_to_index if order_type == AcquiredLotCandidatesOrder.OLDER_TO_NEWER else 0
+        self.__start_index = from_index if order_type == AcquiredLotCandidatesOrder.OLDER_TO_NEWER else up_to_index
+        self.__end_index = up_to_index if order_type == AcquiredLotCandidatesOrder.OLDER_TO_NEWER else from_index
         self.__step = 1 if order_type == AcquiredLotCandidatesOrder.OLDER_TO_NEWER else -1
         self.__index = self.__start_index
         self.__order_type = order_type

src/rp2/accounting_engine.py

@@ -84,6 +84,7 @@ def type_check(cls, name: str, instance: "AccountingEngine") -> "AccountingEngin
 
     def __init__(self, years_2_methods: AVLTree[int, AbstractAccountingMethod]) -> None:
         self.__years_2_methods: AVLTree[int, AbstractAccountingMethod] = years_2_methods
+        self.__lot_candidates: AVLTree[int, AcquiredLotCandidates] = AVLTree()
         if not self.__years_2_methods:
             raise RP2RuntimeError("Internal error: no accounting method defined")
 
@@ -114,6 +115,20 @@ def initialize(
         if not self.__acquired_lot_avl.root:
             raise RP2RuntimeError("Internal error: AVL tree has no root node")
 
+        to_visit = []
+        node = self.__years_2_methods.root
+        while node is not None:
+            self.__lot_candidates.insert_node(node.key, AcquiredLotCandidates(node.value, self.__acquired_lot_list, self.__acquired_lot_2_partial_amount))
+            if node.left:
+                to_visit.append(node.left)
+            if node.right:
+                to_visit.append(node.right)
+
+            if len(to_visit) > 0:
+                node = to_visit.pop()
+            else:
+                break
+
     # AVL tree node keys have this format: <timestamp>_<internal_id>. The internal_id part is needed to disambiguate transactions
     # that have the same timestamp. Timestamp is in format "YYYYmmddHHMMSS.ffffff" and internal_id is padded right in a string of fixed
     # length (KEY_DISAMBIGUATOR_LENGTH).
@@ -189,18 +204,19 @@ def get_acquired_lot_for_taxable_event(
             if avl_result.acquired_lot != self.__acquired_lot_list[avl_result.index]:
                 raise RP2RuntimeError("Internal error: acquired_lot incongruence in accounting logic")
             method = self._get_accounting_method(taxable_event.timestamp.year)
-            lot_candidates: AcquiredLotCandidates = AcquiredLotCandidates(
-                method, self.__acquired_lot_list, self.__acquired_lot_2_partial_amount, avl_result.index
-            )
-            acquired_lot_and_amount: Optional[AcquiredLotAndAmount] = method.seek_non_exhausted_acquired_lot(
-                lot_candidates, taxable_event, new_taxable_event_amount
-            )
-            if acquired_lot_and_amount:
-                return TaxableEventAndAcquiredLot(
-                    taxable_event=taxable_event,
-                    acquired_lot=acquired_lot_and_amount.acquired_lot,
-                    taxable_event_amount=new_taxable_event_amount,
-                    acquired_lot_amount=acquired_lot_and_amount.amount,
+            lot_candidates: Optional[AcquiredLotCandidates] = self.__lot_candidates.find_max_value_less_than(taxable_event.timestamp.year)
+
+            if lot_candidates:
+                lot_candidates.set_up_to_index(avl_result.index)
+                acquired_lot_and_amount: Optional[AcquiredLotAndAmount] = method.seek_non_exhausted_acquired_lot(
+                    lot_candidates, taxable_event, new_taxable_event_amount
                 )
+                if acquired_lot_and_amount:
+                    return TaxableEventAndAcquiredLot(
+                        taxable_event=taxable_event,
+                        acquired_lot=acquired_lot_and_amount.acquired_lot,
+                        taxable_event_amount=new_taxable_event_amount,
+                        acquired_lot_amount=acquired_lot_and_amount.amount,
+                    )
 
         raise AcquiredLotsExhaustedException()

src/rp2/plugin/accounting_method/fifo.py

@@ -25,7 +25,7 @@
 from rp2.rp2_decimal import ZERO, RP2Decimal
 
 
-# FIFO plugin. See https://www.investopedia.com/terms/l/fifo.asp. This plugin uses universal application, not per-wallet application:
+# FIFO (First In, First Out) plugin. See https://www.investopedia.com/terms/l/fifo.asp. This plugin uses universal application, not per-wallet application:
 # this means there is one queue for each coin across every wallet and exchange and the accounting method is applied to each such queue.
 # More on this at https://www.forbes.com/sites/shehanchandrasekera/2020/09/17/what-crypto-taxpayers-need-to-know-about-fifo-lifo-hifo-specific-id/
 class AccountingMethod(AbstractAccountingMethod):
@@ -38,8 +38,8 @@ def seek_non_exhausted_acquired_lot(
         selected_acquired_lot_amount: RP2Decimal = ZERO
         selected_acquired_lot: Optional[InTransaction] = None
         acquired_lot: InTransaction
-        # This loop causes O(m*n) complexity, where m is the number of acquired lots and n in the number of taxable events. The taxable
-        # event loop is in the caller. Non-trivial optimizations are possible using different data structures but they need to be researched.
+        # This loop avoids O(m*n) complexity by keeping track of the index of the most recently exhausted lot.
+        # As FIFO ensures no non-exhausted lots can exist to the left of this index, this approach is O(n).
         for acquired_lot in lot_candidates:
             acquired_lot_amount: RP2Decimal = ZERO
 
@@ -48,7 +48,8 @@ def seek_non_exhausted_acquired_lot(
             elif lot_candidates.get_partial_amount(acquired_lot) > ZERO:
                 acquired_lot_amount = lot_candidates.get_partial_amount(acquired_lot)
             else:
-                # The acquired lot has zero partial amount
+                # The acquired lot has zero partial amount, so we can advance our start offset
+                lot_candidates.set_from_index(lot_candidates.from_index + 1)
                 continue
 
             selected_acquired_lot_amount = acquired_lot_amount