local unpack = table.unpack or unpack

local registry = {}
local current_namespace
local fallback_namespace

local s = {

    _COPYRIGHT = "Copyright (c) 2012 Olivine Labs, LLC.",
    _DESCRIPTION = "A simple string key/value store for i18n or any other case where you want namespaced strings.",
    _VERSION = "Say 1.3",

    set_namespace = function(self, namespace)
        current_namespace = namespace
        if not registry[current_namespace] then
            registry[current_namespace] = {}
        end
    end,

    set_fallback = function(self, namespace)
        fallback_namespace = namespace
        if not registry[fallback_namespace] then
            registry[fallback_namespace] = {}
        end
    end,

    set = function(self, key, value)
        registry[current_namespace][key] = value
    end,
}

local __meta = {
    __call = function(self, key, vars)
        if vars ~= nil and type(vars) ~= "table" then
            error(("expected parameter table to be a table, got '%s'"):format(type(vars)), 2)
        end
        vars = vars or {}

        local str = registry[current_namespace][key] or registry[fallback_namespace][key]

        if str == nil then
            return nil
        end
        str = tostring(str)
        local strings = {}

        for i = 1, vars.n or #vars do
            table.insert(strings, tostring(vars[i]))
        end

        return #strings > 0 and str:format(unpack(strings)) or str
    end,

    __index = function(self, key)
        return registry[key]
    end,
}

s:set_fallback('en')
s:set_namespace('en')

s._registry = registry

return setmetatable(s, __meta)