From 257ecf62226b5e4ad8ad31b6281ffc6f7750882b Mon Sep 17 00:00:00 2001
From: Christian Decker <decker.christian@gmail.com>
Date: Thu, 1 Jun 2017 16:10:40 +0200
Subject: [PATCH] wallet: Helper to store/retrieve persistent vars to/from DB

Not the nicest code, but it allows us to store the bip32_max_index so
that we don't forget our addresses upon restart. We could have done
the same by retrieving the max index from our index, but then we'd
forget addresses that don't have an associated output. Conversion
to/from string is so that we can store arbitrary one off values in the
DB in the future, independent of type.
---
 lightningd/build_utxos.c |  1 +
 lightningd/lightningd.c  |  2 ++
 wallet/db.c              | 39 +++++++++++++++++++++++++++++++++++++++
 wallet/db.h              | 16 ++++++++++++++++
 wallet/db_tests.c        | 23 +++++++++++++++++++++++
 5 files changed, 81 insertions(+)

diff --git a/lightningd/build_utxos.c b/lightningd/build_utxos.c
index 0e0f41ef0..532c607bd 100644
--- a/lightningd/build_utxos.c
+++ b/lightningd/build_utxos.c
@@ -49,6 +49,7 @@ static void json_newaddr(struct command *cmd,
 	ripemd160(&p2sh, h.u.u8, sizeof(h));
 
 	ld->bip32_max_index++;
+	db_set_intvar(ld->wallet->db, "bip32_max_index", ld->bip32_max_index);
 
 	json_object_start(response, NULL);
 	json_add_string(response, "address",
diff --git a/lightningd/lightningd.c b/lightningd/lightningd.c
index 48d84d86d..cf62978c9 100644
--- a/lightningd/lightningd.c
+++ b/lightningd/lightningd.c
@@ -257,6 +257,8 @@ int main(int argc, char *argv[])
 	/* Initialize wallet, now that we are in the correct directory */
 	ld->wallet = wallet_new(ld, ld->log);
 
+	ld->bip32_max_index = db_get_intvar(ld->wallet->db, "bip32_max_index", 0);
+
 	/* Mark ourselves live. */
 	log_info(ld->log, "Hello world from %s!", version());
 
diff --git a/wallet/db.c b/wallet/db.c
index 81b3c0314..4d3223251 100644
--- a/wallet/db.c
+++ b/wallet/db.c
@@ -2,8 +2,10 @@
 
 #include "daemon/log.h"
 #include "lightningd/lightningd.h"
+
 #include <ccan/tal/str/str.h>
 #include <ccan/tal/tal.h>
+#include <inttypes.h>
 
 #define DB_FILE "lightningd.sqlite3"
 
@@ -230,3 +232,40 @@ struct db *db_setup(const tal_t *ctx)
 	}
 	return db;
 }
+
+s64 db_get_intvar(struct db *db, char *varname, s64 defval)
+{
+	int err;
+	s64 res = defval;
+	const unsigned char *stringvar;
+	sqlite3_stmt *stmt =
+	    db_query(__func__, db,
+		     "SELECT val FROM vars WHERE name='%s' LIMIT 1", varname);
+
+	if (!stmt)
+		return defval;
+
+	err = sqlite3_step(stmt);
+	if (err == SQLITE_ROW) {
+		stringvar = sqlite3_column_text(stmt, 0);
+		res = atol((const char *)stringvar);
+	}
+	sqlite3_finalize(stmt);
+	return res;
+}
+
+bool db_set_intvar(struct db *db, char *varname, s64 val)
+{
+	/* Attempt to update */
+	db_exec(__func__, db,
+		"UPDATE vars SET val='%" PRId64 "' WHERE name='%s';", val,
+		varname);
+	if (sqlite3_changes(db->sql) > 0)
+		return true;
+	else
+		return db_exec(
+		    __func__, db,
+		    "INSERT INTO vars (name, val) VALUES ('%s', '%" PRId64
+		    "');",
+		    varname, val);
+}
diff --git a/wallet/db.h b/wallet/db.h
index d0e01d6dd..3e39efe97 100644
--- a/wallet/db.h
+++ b/wallet/db.h
@@ -57,4 +57,20 @@ bool db_commit_transaction(struct db *db);
  */
 bool db_rollback_transaction(struct db *db);
 
+/**
+ * db_set_intvar - Set an integer variable in the database
+ *
+ * Utility function to store generic integer values in the
+ * database.
+ */
+bool db_set_intvar(struct db *db, char *varname, s64 val);
+
+/**
+ * db_get_intvar - Retrieve an integer variable from the database
+ *
+ * Either returns the value in the database, or @defval if
+ * the query failed or no such variable exists.
+ */
+s64 db_get_intvar(struct db *db, char *varname, s64 defval);
+
 #endif /* WALLET_DB_H */
diff --git a/wallet/db_tests.c b/wallet/db_tests.c
index 13d946f7e..0fb57d109 100644
--- a/wallet/db_tests.c
+++ b/wallet/db_tests.c
@@ -31,11 +31,34 @@ static bool test_empty_db_migrate(void)
 	return true;
 }
 
+static bool test_vars(void)
+{
+	struct db *db = create_test_db(__func__);
+	char *varname = "testvar";
+	CHECK(db);
+	CHECK(db_migrate(db));
+
+	/* Check default behavior */
+	CHECK(db_get_intvar(db, varname, 42) == 42);
+
+	/* Check setting and getting */
+	CHECK(db_set_intvar(db, varname, 1));
+	CHECK(db_get_intvar(db, varname, 42) == 1);
+
+	/* Check updating */
+	CHECK(db_set_intvar(db, varname, 2));
+	CHECK(db_get_intvar(db, varname, 42) == 2);
+
+	tal_free(db);
+	return true;
+}
+
 int main(void)
 {
 	bool ok = true;
 
 	ok &= test_empty_db_migrate();
+	ok &= test_vars();
 
 	return !ok;
 }