Revert "Removed block 212937"

This reverts commit b917da765c9406adacbb5abd261c3b6ed236ec74.

src/main/java/org/qortal/block/Block.java

@@ -1104,6 +1104,10 @@ public class Block {
 			// Create repository savepoint here so we can rollback to it after testing transactions
 			repository.setSavepoint();
 
+			if (this.blockData.getHeight() == 212937)
+				// Apply fix for block 212937 but fix will be rolled back before we exit method
+				Block212937.processFix(this);
+
 			for (Transaction transaction : this.getTransactions()) {
 				TransactionData transactionData = transaction.getTransactionData();
 
@@ -1308,6 +1312,9 @@ public class Block {
 			// Distribute block rewards, including transaction fees, before transactions processed
 			processBlockRewards();
 
+			if (this.blockData.getHeight() == 212937)
+				// Apply fix for block 212937
+				Block212937.processFix(this);
 		}
 
 		// We're about to (test-)process a batch of transactions,
@@ -1542,6 +1549,10 @@ public class Block {
 			// Invalidate expandedAccounts as they may have changed due to orphaning TRANSFER_PRIVS transactions, etc.
 			this.cachedExpandedAccounts = null;
 
+			if (this.blockData.getHeight() == 212937)
+				// Revert fix for block 212937
+				Block212937.orphanFix(this);
+
 			// Block rewards, including transaction fees, removed after transactions undone
 			orphanBlockRewards();
 

src/main/java/org/qortal/block/Block212937.java

@@ -0,0 +1,153 @@
+package org.qortal.block;
+
+import java.io.InputStream;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import javax.xml.bind.JAXBContext;
+import javax.xml.bind.JAXBException;
+import javax.xml.bind.UnmarshalException;
+import javax.xml.bind.Unmarshaller;
+import javax.xml.transform.stream.StreamSource;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.eclipse.persistence.jaxb.JAXBContextFactory;
+import org.eclipse.persistence.jaxb.UnmarshallerProperties;
+import org.qortal.data.account.AccountBalanceData;
+import org.qortal.repository.DataException;
+
+/**
+ * Block 212937
+ * <p>
+ * Somehow a node minted a version of block 212937 that contained one transaction:
+ * a PAYMENT transaction that attempted to spend more QORT than that account had as QORT balance.
+ * <p>
+ * This invalid transaction made block 212937 (rightly) invalid to several nodes,
+ * which refused to use that block.
+ * However, it seems there were no other nodes minting an alternative, valid block at that time
+ * and so the chain stalled for several nodes in the network.
+ * <p>
+ * Additionally, the invalid block 212937 affected all new installations, regardless of whether
+ * they synchronized from scratch (block 1) or used an 'official release' bootstrap.
+ * <p>
+ * After lengthy diagnosis, it was discovered that
+ * the invalid transaction seemed to rely on incorrect balances in a corrupted database.
+ * Copies of DB files containing the broken chain were also shared around, exacerbating the problem.
+ * <p>
+ * There were three options:
+ * <ol>
+ * <li>roll back the chain to last known valid block 212936 and re-mint empty blocks to current height</li>
+ * <li>keep existing chain, but apply database edits at block 212937 to allow current chain to be valid</li>
+ * <li>attempt to mint an alternative chain, retaining as many valid transactions as possible</li>
+ * </ol>
+ * <p>
+ * Option 1 was highly undesirable due to knock-on effects from wiping 700+ transactions, some of which
+ * might have affect cross-chain trades, although there were no cross-chain trade completed during
+ * the decision period.
+ * <p>
+ * Option 3 was essentially a slightly better version of option 1 and rejected for similar reasons.
+ * Attempts at option 3 also rapidly hit cumulative problems with every replacement block due to
+ * differing block timestamps making some transactions, and then even some blocks themselves, invalid.
+ * <p>
+ * This class is the implementation of option 2.
+ * <p>
+ * The change in account balances are relatively small, see <tt>block-212937-deltas.json</tt> resource
+ * for actual values. These values were obtained by exporting the <tt>AccountBalances</tt> table from
+ * both versions of the database with chain at block 212936, and then comparing. The values were also
+ * tested by syncing both databases up to block 225500, re-exporting and re-comparing.
+ * <p>
+ * The invalid block 212937 signature is: <tt>2J3GVJjv...qavh6KkQ</tt>.
+ * <p>
+ * The invalid transaction in block 212937 is:
+ * <p>
+ * <code><pre>
+   {
+      "amount" : "0.10788294",
+      "approvalStatus" : "NOT_REQUIRED",
+      "blockHeight" : 212937,
+      "creatorAddress" : "QLdw5uabviLJgRGkRiydAFmAtZzxHfNXSs",
+      "fee" : "0.00100000",
+      "recipient" : "QZi1mNHDbiLvsytxTgxDr9nhJe4pNZaWpw",
+      "reference" : "J6JukdTVuXZ3JYbHatfZzwxG2vSiZwVCPDzW5K7PsVQKRj8XZeDtqnkGCGGjaSQZ9bQMtV44ky88NnGM4YBQKU6",
+      "senderPublicKey" : "DBFfbD2M3uh4jPE5PaUcZVvNPfrrJzVB7seeEtBn5SPs",
+      "signature" : "qkitxdCEEnKt8w6wRfFixtErbXsxWE6zG2ESNhpqBdScikV1WxeA6WZTTMJVV4tCeZdBFXw3V1X5NVztv6LirWK",
+      "timestamp" : 1607863074904,
+      "txGroupId" : 0,
+      "type" : "PAYMENT"
+   }
+   </pre></code>
+ * <p>
+ * Account <tt>QLdw5uabviLJgRGkRiydAFmAtZzxHfNXSs</tt> attempted to spend <tt>0.10888294</tt> (including fees)
+ * when their QORT balance was really only <tt>0.10886665</tt>.
+ * <p>
+ * However, on the broken DB nodes, their balance
+ * seemed to be <tt>0.10890293</tt> which was sufficient to make the transaction valid.
+ */
+public final class Block212937 {
+
+	private static final Logger LOGGER = LogManager.getLogger(Block212937.class);
+	private static final String ACCOUNT_DELTAS_SOURCE = "block-212937-deltas.json";
+
+	private static final List<AccountBalanceData> accountDeltas = readAccountDeltas();
+
+	private Block212937() {
+		/* Do not instantiate */
+	}
+
+	@SuppressWarnings("unchecked")
+	private static List<AccountBalanceData> readAccountDeltas() {
+		Unmarshaller unmarshaller;
+
+		try {
+			// Create JAXB context aware of classes we need to unmarshal
+			JAXBContext jc = JAXBContextFactory.createContext(new Class[] {
+				AccountBalanceData.class
+			}, null);
+
+			// Create unmarshaller
+			unmarshaller = jc.createUnmarshaller();
+
+			// Set the unmarshaller media type to JSON
+			unmarshaller.setProperty(UnmarshallerProperties.MEDIA_TYPE, "application/json");
+
+			// Tell unmarshaller that there's no JSON root element in the JSON input
+			unmarshaller.setProperty(UnmarshallerProperties.JSON_INCLUDE_ROOT, false);
+		} catch (JAXBException e) {
+			String message = "Failed to setup unmarshaller to read block 212937 deltas";
+			LOGGER.error(message, e);
+			throw new RuntimeException(message, e);
+		}
+
+		ClassLoader classLoader = BlockChain.class.getClassLoader();
+		InputStream in = classLoader.getResourceAsStream(ACCOUNT_DELTAS_SOURCE);
+		StreamSource jsonSource = new StreamSource(in);
+
+		try  {
+			// Attempt to unmarshal JSON stream to BlockChain config
+			return (List<AccountBalanceData>) unmarshaller.unmarshal(jsonSource, AccountBalanceData.class).getValue();
+		} catch (UnmarshalException e) {
+			String message = "Failed to parse block 212937 deltas";
+			LOGGER.error(message, e);
+			throw new RuntimeException(message, e);
+		} catch (JAXBException e) {
+			String message = "Unexpected JAXB issue while processing block 212937 deltas";
+			LOGGER.error(message, e);
+			throw new RuntimeException(message, e);
+		}
+	}
+
+	public static void processFix(Block block) throws DataException {
+		block.repository.getAccountRepository().modifyAssetBalances(accountDeltas);
+	}
+
+	public static void orphanFix(Block block) throws DataException {
+		// Create inverse deltas
+		List<AccountBalanceData> inverseDeltas = accountDeltas.stream()
+				.map(delta -> new AccountBalanceData(delta.getAddress(), delta.getAssetId(), 0 - delta.getBalance()))
+				.collect(Collectors.toList());
+
+		block.repository.getAccountRepository().modifyAssetBalances(inverseDeltas);
+	}
+
+}