-- mod_storage_lmdb
-- Copyright (C) 2015 Kim Alvefur
--
-- This file is MIT/X11 licensed.
-- 
-- Depends on lightningdbm
-- https://github.com/shmul/lightningdbm
--
-- luacheck: globals prosody open

local lmdb = require"lightningmdb";
local lfs = require"lfs";
local path = require"util.paths";
local serialization = require"util.serialization";
local serialize = serialization.serialize;
local deserialize = serialization.deserialize;

local drivers = {};
local provider = {};

local keyval = {};
local keyval_mt = { __index = keyval, flags = lmdb.MDB_CREATE };
drivers.keyval = keyval_mt;

function keyval:set(user, value)
	local t = self.env:txn_begin(nil, 0);
	if type(value) == "table" and next(value) == nil then
		value = nil;
	end
	if value ~= nil then
		value = serialize(value);
	end
	local ok, err;
	if value ~= nil then
		ok, err = t:put(self.db, user, value, 0);
	else
		ok, err = t:del(self.db, user, value);
	end
	if not ok then
		t:abort();
		return nil, err;
	end
	return t:commit();
end

function keyval:get(user)
	local t = self.env:txn_begin(nil, 0);
	local data, err = t:get(self.db, user, 0);
	if not data then
		t:abort();
		return nil, err;
	end
	t:commit();
	return deserialize(data);
end

function provider:init(config)
	if config.base_path then
		lfs.mkdir(config.base_path);
	end
	local env = lmdb.env_create();
	env:set_maxdbs(config.maxdbs or 20);
	local env_flags = 0;
	if config.flags then
		for flag in config.flags do
			env_flags = env_flags + assert(lmdb["MDB_"..flag:upper()], "No such flag "..flag);
		end
	end
	env:open(config.base_path or ".", env_flags, tonumber("640", 8));
	self.env = env;
end

function provider:open(store, typ)
	typ = typ or "keyval";
	local driver_mt = drivers[typ];
	if not driver_mt then
		return nil, "unsupported-store";
	end
	local env = self.env;
	local t = env:txn_begin(nil, 0);
	local db = t:dbi_open(store.."_"..typ, driver_mt.flags);
	local ok, err = t:commit();
	if not ok then
		module:log("error", "Could not open database %s_%s: %s", store, typ, tostring(err));
		return ok, err;
	end

	return setmetatable({ env = env, store = store, type = typ, db = db }, driver_mt);
end

if prosody then
	provider:init({
		base_path = path.resolve_relative_path(prosody.paths.data, module.host);
		flags = module:get_option_set("lmdb_flags", {});
		maxdbs = module:get_option_number("lmdb_maxdbs", 20);
	});

	function module.unload()
		provider.env:sync(1);
		provider.env:close();
	end

	module:provides("storage", provider);
else
	return provider;
end