wallet: Report current blockheight as the offset to continue from

This is a big simplification, we just report the DBs current blockchain height
as the point to continue scanning, or the passed in default. No more guessing
where to continue from or whether the wallet was used and when it first saw the
light of day.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

wallet/wallet.c

@@ -767,29 +767,6 @@ void wallet_channel_stats_load(struct wallet *w,
 	stats->out_msatoshi_fulfilled = sqlite3_column_int64(stmt, 7);
 }
 
-#ifdef COMPAT_V052
-/* Upgrade of db (or initial create): do we have anything to scan for? */
-static bool wallet_ever_used(struct wallet *w)
-{
-	sqlite3_stmt *stmt;
-	bool channel_utxos;
-
-	/* If we ever handed out an address. */
-	if (db_get_intvar(w->db, "bip32_max_index", 0) != 0)
-		return true;
-
-	/* Or if they do a unilateral close, the output to us provides a UTXO. */
-	stmt = db_query(__func__, w->db,
-			"SELECT COUNT(*) FROM outputs WHERE commitment_point IS NOT NULL;");
-	int ret = sqlite3_step(stmt);
-	assert(ret == SQLITE_ROW);
-	channel_utxos = (sqlite3_column_int(stmt, 0) != 0);
-	sqlite3_finalize(stmt);
-
-	return channel_utxos;
-}
-#endif
-
 /* We want the earlier of either:
  * 1. The first channel we're still watching (it might have closed),
  * 2. The last block we scanned for UTXO (might have new incoming payments)
@@ -799,43 +776,16 @@ static bool wallet_ever_used(struct wallet *w)
  */
 u32 wallet_first_blocknum(struct wallet *w, u32 first_possible)
 {
-	int err;
-	u32 first_channel, first_utxo;
-	sqlite3_stmt *stmt =
-	    db_query(__func__, w->db,
-		     "SELECT MIN(first_blocknum) FROM channels;");
-
-	/* If we ever opened a channel, this will give us the first block. */
-	err = sqlite3_step(stmt);
-	if (err == SQLITE_ROW && sqlite3_column_type(stmt, 0) != SQLITE_NULL)
-		first_channel = sqlite3_column_int(stmt, 0);
-	else
-		first_channel = UINT32_MAX;
-	sqlite3_finalize(stmt);
-
-#ifdef COMPAT_V052
-	/* This field was missing in older databases. */
-	first_utxo = db_get_intvar(w->db, "last_processed_block", 0);
-	if (first_utxo == 0) {
-		/* Don't know?  New db, or upgraded. */
-		if (wallet_ever_used(w))
-			/* Be conservative */
-			first_utxo = first_possible;
-		else
-			first_utxo = UINT32_MAX;
-	}
-#else
-	first_utxo = db_get_intvar(w->db, "last_processed_block", UINT32_MAX);
-#endif
-
-	/* Never go below the start of the Lightning Network */
-	if (first_utxo < first_possible)
-		first_utxo = first_possible;
+	u32 blockheight;
+	sqlite3_stmt *stmt = db_prepare(w->db, "SELECT MAX(height) FROM blocks;");
 
-	if (first_utxo < first_channel)
-		return first_utxo;
-	else
-		return first_channel;
+	/* If we ever processed a block we'll get the latest block in the chain */
+	if (sqlite3_step(stmt) == SQLITE_ROW && sqlite3_column_type(stmt, 0) != SQLITE_NULL) {
+		blockheight = sqlite3_column_int(stmt, 0);
+		sqlite3_finalize(stmt);
+		return blockheight;
+	} else
+		return first_possible;
 }
 
 static void wallet_channel_config_insert(struct wallet *w,