From cdaf1b22faaa85a82e3f85609369433408c57504 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Thu, 8 Jul 2021 11:43:33 +0200
Subject: [PATCH] Find all transactions that precede an acknowledgement

---
 abc/past.nim           | 15 ++++++++++++---
 tests/abc/testPast.nim | 12 +++++++++++-
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/abc/past.nim b/abc/past.nim
index eaa8982..78d8422 100644
--- a/abc/past.nim
+++ b/abc/past.nim
@@ -1,11 +1,20 @@
 import ./txstore
 
-func past*(store: TxStore, txHash: TxHash, accumulator: var seq[TxHash]) =
+func past(store: TxStore, txHash: TxHash, accumulator: var seq[TxHash]) =
   if transaction =? store[txHash]:
     for (hash, _) in transaction.inputs:
       if not accumulator.contains hash:
         accumulator.add(hash)
         store.past(hash, accumulator)
 
-func past*(store: TxStore, txHash: TxHash): seq[TxHash] =
-  store.past(txHash, result)
+func past(store: TxStore, ackHash: AckHash, accumulator: var seq[TxHash]) =
+  if ack =? store[ackHash]:
+    if previous =? ack.previous:
+      store.past(previous, accumulator)
+    for txHash in ack.transactions:
+      if not accumulator.contains txHash:
+        accumulator.add(txHash)
+        store.past(txHash, accumulator)
+
+func past*(store: TxStore, hash: TxHash|AckHash): seq[TxHash] =
+  store.past(hash, result)
diff --git a/tests/abc/testPast.nim b/tests/abc/testPast.nim
index c40d85b..0dcc15b 100644
--- a/tests/abc/testPast.nim
+++ b/tests/abc/testPast.nim
@@ -3,13 +3,14 @@ import abc/past
 import ./basics
 import ./alicebob
 
-suite "Past":
+suite "Past transactions and acknowledgements":
 
   let genesis = Transaction.genesis
   let alice = PublicKey.alice
   let bob = PublicKey.bob
   let victor = PublicKey.victor
   var tx1, tx2, tx3: Transaction
+  var ack1, ack2: Ack
 
   setup:
     tx1 = !Transaction.init({genesis.hash: alice}, {bob: 100.u256}, victor)
@@ -19,6 +20,8 @@ suite "Past":
       {alice: 200.u256},
       victor
     )
+    ack1 = !Ack.init([tx1.hash, tx2.hash], victor)
+    ack2 = !Ack.init(ack1.hash, [tx3.hash], victor)
 
   test "finds all transactions that precede a transaction":
     var store = TxStore.init(genesis)
@@ -30,3 +33,10 @@ suite "Past":
   test "past is empty when transaction cannot be found":
     let store = TxStore.init(genesis)
     check store.past(tx1.hash) == []
+
+  test "finds all transactions that precede an acknowledgement":
+    var store = TxStore.init(genesis)
+    store.add(tx1, tx2, tx3)
+    store.add(ack1, ack2)
+    check store.past(ack1.hash) == [tx1.hash, genesis.hash, tx2.hash]
+    check store.past(ack2.hash) == [tx1.hash, genesis.hash, tx2.hash, tx3.hash]