--[[
Type checking, vaguely inspired by Python3's typing module.
]]

local types = {}

function types.positive(arg)
	local is_number, err = types.number(arg)
	if not is_number then
		return false, err
	end
	if arg < 0 then
		return false, string.format("was not positive")
	end
	return true
end

--Basic lua types
local builtin_types = {
	"nil","boolean","number","string","table","function","coroutine","userdata"
}
for _,type_ in pairs(builtin_types) do
	types[type_] = function(arg)
		local argtype = type(arg)
		if argtype ~= type_ then
			return false, string.format("was not a %s, was a %s",type_,argtype)
		end
	end
end

function types.matches_pattern(pattern)
	return function(arg)
		local is_string, err = types.string(arg)
		if not is_string then
			return false, err
		end
		if not string.match(arg, pattern) then
			return false, string.format(
				"Expected %q to match pattern %q, but it did not.",
				arg,
				pattern
			)
		end
	end
end

function types.check(...)

end

return types