Use JSON in xban.db (#26)

This should prevent bans database from resetting with a "function has more than 65536 constants" error. Older databases should still be loaded correctly.

Also makes use of minetest.safe_file_write to avoid data corruption.

init.lua

@@ -25,6 +25,7 @@ end
 
 local ACTION = make_logger("action")
 local WARNING = make_logger("warning")
+local ERROR = make_logger("error")
 
 local unit_to_secs = {
 	s = 1, m = 60, h = 3600,
@@ -343,18 +344,12 @@ end
 
 local function save_db()
 	minetest.after(SAVE_INTERVAL, save_db)
-	local f, e = io.open(DB_FILENAME, "wt")
 	db.timestamp = os.time()
-	if f then
-		local ok, err = f:write(xban.serialize(db))
-		if not ok then
-			WARNING("Unable to save database: %s", err)
-		end
-	else
-		WARNING("Unable to save database: %s", e)
+	local contents = assert(xban.serialize_db(db))
+	local ok = minetest.safe_file_write(DB_FILENAME, contents)
+	if not ok then
+		ERROR("Unable to save database")
 	end
-	if f then f:close() end
-	return
 end
 
 local function load_db()
@@ -368,7 +363,7 @@ local function load_db()
 		WARNING("Unable to load database: %s", "Read failed")
 		return
 	end
-	local t, e2 = minetest.deserialize(cont)
+	local t, e2 = xban.deserialize_db(cont)
 	if not t then
 		WARNING("Unable to load database: %s",
 		  "Deserialization failed: "..(e2 or "unknown error"))

serialize.lua

@@ -27,5 +27,44 @@ local function my_serialize_2(t, level)
 end
 
 function xban.serialize(t)
+	minetest.log("warning", "[xban2] xban.serialize() is deprecated")
 	return "return {\n"..my_serialize_2(t, 1).."\n}"
 end
+
+-- JSON doesn't allow combined string+number keys, this function moves any
+-- number keys into an "entries" table
+function xban.serialize_db(t)
+	local res = {}
+	local entries = {}
+	for k, v in pairs(t) do
+		if type(k) == "number" then
+			entries[k] = v
+		else
+			res[k] = v
+		end
+	end
+	res.entries = entries
+	return minetest.write_json(res, true)
+end
+
+function xban.deserialize_db(s)
+	if s:sub(1, 1) ~= "{" then
+		-- Load legacy databases
+		return minetest.deserialize(s)
+	end
+
+	local res, err = minetest.parse_json(s)
+	if not res then
+		return nil, err
+	end
+
+	-- Remove all "null"s added by empty tables
+	for i, entry in ipairs(res.entries or {}) do
+		entry.names = entry.names or {}
+		entry.record = entry.record or {}
+		res[i] = entry
+	end
+	res.entries = nil
+
+	return res
+end