Bitcoin: persist authenticated Bitcoin Core balance observations

Author: mearvk

source/bitcoin/module/BitcoinBalanceObserver.java

@@ -0,0 +1,75 @@
+package bitcoin.module;
+
+import bitcoin.base.BitcoinBase;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.Statement;
+import java.time.Instant;
+
+/**
+ * Records authenticated Bitcoin Core balance observations.
+ *
+ * The value is an observation from getbalance, not an inferred wallet-file
+ * balance. Monetary storage is fixed-point satoshis.
+ */
+public final class BitcoinBalanceObserver
+{
+    private static final String TABLE = "bitcoin_balance_observations";
+
+    public void observe()
+    {
+        try (Connection conn = database.N21DataSource.get())
+        {
+            if (conn == null) return;
+            createTable(conn);
+
+            BitcoinBase rpc = new BitcoinBase(null);
+            String balanceText = rpc.get_balance();
+            long satoshis = parseSatoshis(balanceText);
+
+            String sql = "INSERT INTO " + TABLE +
+                " (wallet_name, balance_satoshis, source_method, observed_at) VALUES (?,?,?,?)";
+            try (PreparedStatement ps = conn.prepareStatement(sql))
+            {
+                ps.setString(1, "United States");
+                ps.setLong(2, satoshis);
+                ps.setString(3, "getbalance");
+                ps.setTimestamp(4, java.sql.Timestamp.from(Instant.now()));
+                ps.executeUpdate();
+            }
+        }
+        catch (Exception e)
+        {
+            exceptions.ExceptionHandler.dispatch(e);
+        }
+    }
+
+    private void createTable(final Connection conn) throws Exception
+    {
+        try (Statement st = conn.createStatement())
+        {
+            st.executeUpdate("CREATE TABLE IF NOT EXISTS " + TABLE + " (" +
+                "id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY," +
+                "wallet_name VARCHAR(128) NOT NULL," +
+                "balance_satoshis BIGINT UNSIGNED NOT NULL," +
+                "source_method VARCHAR(64) NOT NULL," +
+                "observed_at DATETIME(6) NOT NULL," +
+                "KEY ix_balance_wallet_time (wallet_name, observed_at)" +
+                ") ENGINE=InnoDB");
+        }
+    }
+
+    static long parseSatoshis(final String text)
+    {
+        if (text == null || text.isBlank()) throw new IllegalArgumentException("Bitcoin Core returned an empty balance");
+        BigDecimal btc = new BigDecimal(text.trim());
+        if (btc.signum() < 0 || btc.scale() > 8) throw new IllegalArgumentException("Invalid Bitcoin Core balance");
+        BigDecimal satoshis = btc.movePointRight(8).setScale(0, RoundingMode.UNNECESSARY);
+        if (satoshis.compareTo(BigDecimal.valueOf(Long.MAX_VALUE)) > 0)
+            throw new IllegalArgumentException("Bitcoin Core balance is too large");
+        return satoshis.longValueExact();
+    }
+}