-- Basic SQL driver

-- This driver stores data as simple key-values

local ser = require "util.serialization".serialize;

local envload = require "util.envload".envload;

local deser = function(data)

	module:log("debug", "deser: %s", tostring(data));

	if not data then return nil; end

	local f = envload("return "..data, nil, {});

	if not f then return nil; end

	local s, d = pcall(f);

	if not s then return nil; end

	return d;

end;

local driver = {};

driver.__index = driver;

driver.item_table = "item";

driver.list_table = "list";

function driver:prepare(sql)

	module:log("debug", "query: %s", sql);

	local err;

	if not self.sqlcache then self.sqlcache = {}; end

	local r = self.sqlcache[sql];

	if r then return r; end

	r, err = self.connection:prepare(sql);

	if not r then error("Unable to prepare SQL statement: "..err); end

	self.sqlcache[sql] = r;

	return r;

end

function driver:load(username, host, datastore)

	local select = self:prepare("select data from "..self.item_table.." where username=? and host=? and datastore=?");

	select:execute(username, host, datastore);

	local row = select:fetch();

	return row and deser(row[1]) or nil;

end

function driver:store(username, host, datastore, data)

	if not data or next(data) == nil then

		local delete = self:prepare("delete from "..self.item_table.." where username=? and host=? and datastore=?");

		delete:execute(username, host, datastore);

		return true;

	else

		local d = self:load(username, host, datastore);

		if d then -- update

			local update = self:prepare("update "..self.item_table.." set data=? where username=? and host=? and datastore=?");

			return update:execute(ser(data), username, host, datastore);

		else -- insert

			local insert = self:prepare("insert into "..self.item_table.." values (?, ?, ?, ?)");

			return insert:execute(username, host, datastore, ser(data));

		end

	end

end

function driver:list_append(username, host, datastore, data)

	if not data then return; end

	local insert = self:prepare("insert into "..self.list_table.." values (?, ?, ?, ?)");

	return insert:execute(username, host, datastore, ser(data));

end

function driver:list_store(username, host, datastore, data)

	-- remove existing data

	local delete = self:prepare("delete from "..self.list_table.." where username=? and host=? and datastore=?");

	delete:execute(username, host, datastore);

	if data and next(data) ~= nil then

		-- add data

		for _, d in ipairs(data) do

			self:list_append(username, host, datastore, ser(d));

		end

	end

	return true;

end

function driver:list_load(username, host, datastore)

	local select = self:prepare("select data from "..self.list_table.." where username=? and host=? and datastore=?");

	select:execute(username, host, datastore);

	local r = {};

	for row in select:rows() do

		table.insert(r, deser(row[1]));

	end

	return r;

end

local _M = {};

function _M.new(dbtype, dbname, ...)

	local d = {};

	setmetatable(d, driver);

	local dbh = get_database(dbtype, dbname, ...);

	--d:set_connection(dbh);

	d.connection = dbh;

	return d;

end

return _M;