local isSimulator = playdate.isSimulator

-- local function keysContain(key, allowedKeys)
--     for _, allowedKey in pairs(allowedKeys) do
--         if key == allowedKey then
--             return true
--         end
--     end
--     return false
-- end

---@generic T
---@param shape T
---@param process fun(entity: T, dt: number, system: System)
---@return System | { entities: T[] }
function filteredSystem(shape, process)
    local system = tiny.processingSystem()
    local keys = {}
    for key, value in pairs(shape) do
        if type(value) ~= "table" or value.maybe == nil then
            -- ^ Don't require any Maybe types
            keys[#keys + 1] = key
        end
    end
    system.filter = tiny.requireAll(table.unpack(keys))
    if not process then
        return world:addSystem(system)
    end
    if isSimulator then
        -- local acceptableKeys = ""
        -- for _, key in ipairs(keys) do
        --     acceptableKeys = acceptableKeys .. "'" .. key .. "', "
        -- end
        -- acceptableKeys = acceptableKeys .. "]"
        function system:process(e, dt)
            -- local _e = e
            -- e = setmetatable({}, {
            --     __newindex = function()
            --         error("Do not attempt to mutate entity data!")
            --     end,
            --     __index = function(_, key)
            --         -- TODO: also assert their types
            --         assert(
            --             keysContain(key, keys),
            --             "Attempted to use key '" .. key .. "' - should be one of [ " .. acceptableKeys
            --         )
            --         return _e[key]
            --     end,
            -- })
            process(e, dt, self)
        end
    else
        function system:process(e, dt)
            process(e, dt, self)
        end
    end
    return world:addSystem(system)
end