chore：新的根节点

lua/lib/userdb.lua

@@ -0,0 +1,116 @@
+local META_KEY_PREFIX = "\001" .. "/"
+
+-- UserDb 缓存，使用弱引用表，不阻止垃圾回收并能自动清理
+local db_pool = setmetatable({}, { __mode = "v" })
+
+---@class WrappedUserDb: UserDb
+---@field meta_query fun(self: self, prefix: string): DbAccessor
+---@field meta_fetch fun(self: self, key: string): string|nil
+---@field meta_update fun(self: self, key: string, value: string): boolean
+---@field meta_erase fun(self: self, key: string): boolean
+---@field query_with fun(self: self, prefix: string, handler: fun(key: string, value: string))
+---@field empty fun(self: self, include_metafield?: boolean) -- 清空数据库
+
+-- 用于存放包装器对象的自定义方法
+local extends = {}
+
+--- @param key string
+--- @return string|nil
+function extends:meta_fetch(key)
+  return self._db:fetch(META_KEY_PREFIX .. key)
+end
+
+--- @param key string
+--- @param value string
+--- @return boolean
+function extends:meta_update(key, value)
+  return self._db:update(META_KEY_PREFIX .. key, value)
+end
+
+--- @param key string
+--- @return boolean
+function extends:meta_erase(key)
+  return self._db:erase(META_KEY_PREFIX .. key)
+end
+
+--- @param prefix string
+--- @return DbAccessor
+function extends:meta_query(prefix)
+  return self._db:query(META_KEY_PREFIX .. prefix)
+end
+
+function extends:query_with(prefix, handler)
+  local da = self._db:query(prefix)
+  if da then
+    for key, value in da:iter() do
+      handler(key, value)
+    end
+  end
+  da = nil
+  collectgarbage()
+end
+
+--- @param include_metafield boolean 是否也清理元数据。
+function extends:empty(include_metafield)
+  self:query_with("", function(key, _)
+    local is_metafield = key:find(META_KEY_PREFIX, 1, true) == 1
+    if include_metafield or not is_metafield then
+      self._db:erase(key)
+    end
+  end)
+end
+
+local mt = {
+  __index = function(wrapper, key)
+    -- 优先使用自定义方法
+    if extends[key] then
+      return extends[key]
+    end
+
+    -- 不是自定义方法，委托给真实的 UserDb 对象
+    local real_db = wrapper._db
+    local value = real_db[key]
+
+    if type(value) == "function" then
+      return function(_, ...)
+        return value(real_db, ...)
+      end
+    end
+
+    return value
+  end,
+}
+
+local userdb = {}
+
+--- @param db_name string
+--- @param db_class "userdb" | "plain_userdb" | nil
+--- @return WrappedUserDb
+function userdb.UserDb(db_name, db_class)
+  db_class = db_class or "userdb"
+  local key = db_name .. "." .. db_class
+
+  ---@type UserDb
+  local db = db_pool[key]
+  if not db then
+    db = UserDb(db_name, db_class)
+    db_pool[key] = db
+  end
+
+  local wrapper = {
+    _db = db,
+    _pool_key = key,
+  }
+
+  return setmetatable(wrapper, mt)
+end
+
+function userdb.LevelDb(db_name)
+  return userdb.UserDb(db_name, "userdb")
+end
+
+function userdb.TableDb(db_name)
+  return userdb.UserDb(db_name, "plain_userdb")
+end
+
+return userdb