[Bug] Fix nTimeSmart computation

Given the strict timestamp checks enforced with POS TimeProtocol v2
(introduced with PIVX-Project#1002: a block cannot have a timestamp earlier than
previous blocks and cannot be more than 15 seconds in the future), we
don't need the complex (and error-prone) logic of ComputeTimeSmart. We
can, instead, simply rely on the blocktime, which already ensures a
proper ordering for the transactions.

src/wallet/wallet.cpp

@@ -3323,44 +3323,21 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t>& mapKeyBirth) const
         mapKeyBirth[it->first] = it->second->GetBlockTime() - 7200; // block times can be 2h off
 }
 
+/**
+ * Update smart timestamp for a transaction being added to the wallet.
+ *
+ * Logic:
+ * - If the transaction is not yet part of a block, assign its timestamp to the current time.
+ * - Else assign its timestamp to the block time
+ */
 unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
 {
     unsigned int nTimeSmart = wtx.nTimeReceived;
     if (!wtx.hashBlock.IsNull()) {
         if (mapBlockIndex.count(wtx.hashBlock)) {
-            int64_t latestNow = wtx.nTimeReceived;
-            int64_t latestEntry = 0;
-            {
-                // Tolerate times up to the last timestamp in the wallet not more than 5 minutes into the future
-                int64_t latestTolerated = latestNow + 300;
-                TxItems txOrdered = wtxOrdered;
-                for (TxItems::reverse_iterator it = txOrdered.rbegin(); it != txOrdered.rend(); ++it) {
-                    CWalletTx* const pwtx = (*it).second.first;
-                    if (pwtx == &wtx)
-                        continue;
-                    CAccountingEntry* const pacentry = (*it).second.second;
-                    int64_t nSmartTime;
-                    if (pwtx) {
-                        nSmartTime = pwtx->nTimeSmart;
-                        if (!nSmartTime)
-                            nSmartTime = pwtx->nTimeReceived;
-                    } else
-                        nSmartTime = pacentry->nTime;
-                    if (nSmartTime <= latestTolerated) {
-                        latestEntry = nSmartTime;
-                        if (nSmartTime > latestNow)
-                            latestNow = nSmartTime;
-                        break;
-                    }
-                }
-            }
-
-            int64_t blocktime = mapBlockIndex[wtx.hashBlock]->GetBlockTime();
-            nTimeSmart = std::max(latestEntry, std::min(blocktime, latestNow));
+            nTimeSmart = mapBlockIndex[wtx.hashBlock]->GetBlockTime();
         } else
-            LogPrintf("AddToWallet() : found %s in block %s not in index\n",
-                wtx.GetHash().ToString(),
-                wtx.hashBlock.ToString());
+            LogPrintf("%s : found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), wtx.hashBlock.ToString());
     }
     return nTimeSmart;
 }

src/wallet/wallet.h

@@ -769,6 +769,10 @@ class CWalletTx : public CMerkleTx
     std::vector<std::pair<std::string, std::string> > vOrderForm;
     unsigned int fTimeReceivedIsTxTime;
     unsigned int nTimeReceived; //! time received by this node
+    /**
+     * Stable timestamp representing the block time, for a transaction included in a block,
+     * or else the time when the transaction was received if it isn't yet part of a block.
+     */
     unsigned int nTimeSmart;
     char fFromMe;
     std::string strFromAccount;